Dissertations / Theses on the topic 'Enthalpy'
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Hilding, Emil. "Enthalpy Based Boost Pressure Control." Thesis, Linköpings universitet, Fordonssystem, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-70682.
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A turbo system is driven by the excess energy in the exhaust gases. As a result, variation in exhaust temperature cause variations in boost pressure. By using the information about the available exhaust energy in the turbo controller directly through a feedforward controller, an unexpected variation in turbo boost can be avoided. A model based controller is developed that calculates the desired turbine power from the boost pressure reference and then, by observing the available exhaust energy, controls the generated turbine power to match the desired power. A Mean Value Engine Model has been used to make simulation with the developed controller implemented. Steps between different boost pressure references are used to evaluate controller performance. Tests in a car have also been made to make sure the simulation results are consistent in a real environment.Turbosystem drivs av överskottsenergin i motorns avgaser. Dettainnebär att temperaturvariationer i avgaserna orsakar variationer igenererad turbineffekt och därmed ökat laddtryck från turbosystemet.Används informationen om den tillgängliga energin i avgaserna när manstyr turbinen så kan man motverka oväntade laddtrycksförändringar. Idenna rapport har en modellbaserad turboregulator med en framkopplingsom beräknar en önskad turbineffekt från givet referenstryckutvecklats. Sedan tas en styrsignal fram till turbinen som, genom attanvända informationen om den observerade energin i avgaserna, matcharden önskade turbineffekten. En model av en medelvärdesmotor haranvänds för att validera prestandan i regulatorn via stegsvar mellanolika referenstryck. Det har även utförts tester i bil för att avgöraom resultatet blir detsamma under verkliga förhållanden.
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Vine, David Mark. "Enthalpy measurement and equations of state." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292496.
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Koester, Sebastian Markus [Verfasser]. "Membrane-based Enthalpy Exchangers / Sebastian Markus Koester." Aachen : Shaker, 2017. http://d-nb.info/1138177334/34.
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Armani, Silvia. "High-enthalpy geothermal reservoir model calibration using PEST." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13293/.
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The main purpose of this thesis work is focused on the use of PEST (Parameter Estimation) to calibrate numerical models of High Enthalpy Geothermal Reservoirs (HEGR). PEST is a parameter estimation and analysis of the uncertainties of complex numerical models tool, that can be instructed to work with a standalone simulator. So, the T2Well-EWASG was used as coupled wellbore-reservoir simulator for multiphase-multicomponent HEGR. The idea of this thesis work is that the possibility to implement some automation degrees in the wellbore-reservoir model calibration task would improve substantially the Reservoir Engineers work. To become familiar with PEST, it has been necessary a preliminary training to learn how to manage its input files, its keywords, and the utility programs having the function of verifying the correctness and consistency of the created files. Then, one of the examples of PEST manual (which Fortran source code is supplied) was reproduced and analyzed, and subsequently modified. In particular, starting from this example, a simple linear model with two free parameters, some changes have been performed: "fixing" a parameter to inhibit its change during the calibration; reading a more complex model output file respect to the original example; inserting dummy data that should not be processed and instructing PEST to consider only the data of interest; changing the model adding parameters to be calibrated, and including them in the analysis changing the PEST inputs files. Finally, these skills were applied to use PEST with T2Well-EWASG to calibrate a numerical model, relative to a real HEGR, previously calibrated via a trial and error approach in a PhD thesis work. Among the real data used there were also short production-tests done in a geothermal field located in the Dominica Commonwealth.
The preliminary results show that the PEST-T2Well-EWASG calibration system works fine, and that it is a useful tool that can improve the work of reservoir engineering.
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Jeong, Dahai. "Laboratory Measurements of the Moist Enthalpy Transfer Coefficient." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_theses/145.
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The enthalpy (sensible and latent heat) exchange processes within the surface layers at an air-water interface have been examined in 15-m wind-wave tunnel at the University of Miami. Measurements yielded 72 mean values of fluxes and bulk variables in the wind speed (referred to 10 m) range form 0.6 to 39 m/s, covering a full range of aerodynamic conditions from smooth to fully rough. Meteorological variables and bulk enthalpy transfer coefficients, measured at 0.2-m height, were adjusted to neutral stratification and 10-m height following the Monin-Obukhov similarity approach. The ratio of the bulk coefficients of enthalpy and momentum was estimated to evaluate Emanuel's (1995) hypothesis. Indirect "Calorimetric" measurements gave reliable estimates of enthalpy flux from the air-water interface, but the moisture gained in the lower air from evaporation of spray over the rough water remained uncertain, stressing the need for flux measurements along with simultaneous spray data to quantify spray's contribution to the turbulent air-water enthalpy fluxes.
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Hamilton, Christianne Rhea. "Design of Test Sections for a High Enthalpy Wind Tunnel." MSSTATE, 2003. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04082003-114126/.
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This document describes the design of a supersonic and a subsonic test section for a high enthalpy wind tunnel. A streamline is tracked through a supersonic test section using the method of characteristics. The specifics of the design program and the design techniques are illustrated for the supersonic section. The section of the paper dealing with the subsonic nozzle has a greatly diverse nature. This section details the inlet and exhaust restrictions and construction elements for the entire low speed system. The system is currently being set up for testing with the subsonic section, and the supersonic will eventually follow.
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Koester, Sebastian Verfasser], Matthias [Akademischer Betreuer] [Wessling, and Eric [Akademischer Betreuer] Favre. "Membrane-based enthalpy exchangers / Sebastian Koester ; Matthias Weßling, Eric Favre." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1169657559/34.
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Koester, Sebastian Markus [Verfasser], Matthias [Akademischer Betreuer] Wessling, and Eric [Akademischer Betreuer] Favre. "Membrane-based enthalpy exchangers / Sebastian Koester ; Matthias Weßling, Eric Favre." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://nbn-resolving.de/urn:nbn:de:101:1-2018102306195201006883.
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Bell, Michael M. "Air-sea enthalpy and momentum exchange at major hurricane wind speeds." Monterey, Calif. : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/dissert/2010/Jun/10Jun%5FBell%5FPhD.pdf.
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Dissertation (Ph.D. in Meteorology)--Naval Postgraduate School, June 2010.Dissertation supervisor: Montgomery, Michael. "June 2010." Description based on title screen as viewed on July 14, 2010. Author(s) subject terms: Air-sea interaction, tropical cyclones, surface fluxes, drag coefficient, CBLAST. Includes bibliographical references (p. 125-131). Also available in print.
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Ottosson, Jenny. "Enthalpy and Entropy in Enzyme Catalysis : A Study of Lipase Enantioselectivity." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3216.
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Zhang, Rongpeng. "Dynamic Optimization of Integrated Active - Passive Strategies for Building Enthalpy Control." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/404.
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The building sector has become the largest consumer of end use energy in the world, exceeding both the industry and the transportation sectors. Extensive types of energy saving techniques have been developed in the past two decades to mitigate the impact of buildings on the environment. Instead of the conventional active building environmental control approaches that solely rely on the mechanical air conditioning systems, increasing attention is given to the passive and mixed-mode approaches in buildings. This thesis aims to explore the integration of passive cooling approaches and active air conditioning approaches with different dehumidification features, by making effective use of the information on: 1) various dynamic response properties of the building system and mechanical plants, 2) diverse variations of the building boundary conditions over the whole operation process, 3) coupling effect and synergistic influence of the key operational parameters, and 4) numerous parameter conflicts in the integrated active-passive operation. These issues make the proposed integration a complex multifaceted process operation problem. In order to deal with these challenges, a systematic approach is developed by integrating a number of advanced building/system physical models and implementing well established advanced dynamic optimization algorithms. Firstly, a reduced-order model development and calibration framework is presented to generate differential-algebraic equations (DAE) based physical building models, by coupling with the high-order building energy simulations (i.e., EnergyPlus) and implementing MLE+ co-simulation programs in the Matlab platform. The reduced-order building model can describe the dynamic building thermal behaviors and address substantial time delay effects intrinsic in the building heat transfer and moisture migration. A calibration procedure is developed to balance the modelling complexity and the simulation accuracy. By making use of the advanced modeling and simulation features of EnergyPlus, the developed computational platform is able to handle real buildings with various geometric configurations, and offers the potential to cooperate with the dominant commercial building modeling software existing in the current AEC industry. Secondly, the physical model for the active air conditioning systems is developed, which is the other critical part for the dynamic optimization. By introducing and integrating a number of sub-models developed for specific building components, the model is able to specify the dynamic hygrothermal behavior and energy performance of the system under various operating conditions. Two representative air conditioning systems are investigated as the study cases: variable air volume systems (VAV) with mechanical dehumidification, and the desiccant wheel system (DW) with chemical dehumidification. The control variables and constraints representing the system operational characteristics are specified for the dynamic optimization. Thirdly, the integrated active-passive operations are formulated as dynamic optimization problems based on the above building and system physical models. The simultaneous collocation method is used in the solution algorithm to discretize the state and control variables, translating the optimization formulation into a nonlinear program (NLP). After collocation, the translated NLP problems for the daily integrated VAV/DW operation for a case zone have 1605/2181 variables, 1485/2037 equality constraints and 280/248 inequality constraints, respectively. It is found that IPOPT is able to provide the optimal solution within minutes using an 8-core 64-bit desktop, which illustrates the efficiency of the problem formulation. The case study results indicate that the approach can effectively improve the energy performance of the integrated active-passive operations, while maintaining acceptable indoor thermal comfort. Compared to the conventional local control strategies, the optimized strategies lead to remarkable energy saving percentages in different climate conditions: 29.77~48.76% for VAV and 27.85~41.33% for DW. The energy saving is contributed by the improvement of both the passive strategies (around 33%) and active strategies (around 67%). It is found that the thermal comfort constraint defined in the optimization also affects the energy saving. The total optimal energy consumption drops by around 3% if the value of the predicted percentage dissatisfied (PPD) limit is increased by one unit between 5~15%. It is also found that the fitted periodic weather data can lead to similar operation strategies in the dynamic optimization as the realistic data, and therefore can be a reasonable alternative when the more detailed realistic weather data is not available. The method described in the thesis can be generalized to supervise the operation design of building systems with different configurations.
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Ogden, David D. "Enthalpy of Vaporization of Hypersaline Brine from 230 to 280 bar." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1515061054240954.
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Lutz, Andrew. "Experimental Investigation And Analysis Of High-Enthalpy Nitrogen Flow Over Graphite." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/361.
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The high-enthalpy flow generated by hypersonic vehicles traveling within the Earth's atmosphere inherently delivers an elevated heat flux to the vehicle surface. In addition to conductive heating, the liberated energy generated by various exothermic chemical reactions occurring at the vehicle surface further augment the total heat load. Quantifying the rates at which these reactions take place is imperative and remains a significant challenge as developers attempt to design the next generation of thermal protection systems.
This study focused on nitrogen recombination and carbon nitridation, as these reactions are ubiquitous to the most aggressive atmospheric re-entry trajectories in which carbon-based ablative heat shields are conventionally employed. The 30-kW inductively coupled plasma torch located within the Plasma Diagnostics and Test Laboratory at the University of Vermont was used to produce high-enthalpy nitrogen plasma flow, which sufficiently simulated the various in-flight heat flux processes. A combination of optical-based techniques, including spontaneous emission spectroscopy and laser induced fluorescence were utilized to study the free jet and the interaction of the flow with samples constructed from POCO graphite.
Emission measurements within the free stream indicated that the nitrogen flow was in non-equilibrium due to the inverse predissociation of ground state nitrogen atoms into the v = 13 vibrational level of the molecular nitrogen electronic B-state. The degree of non-equilibrium was quantified by determining the overpopulation of ground state nitrogen with respect to equilibrium and its effects were considered throughout the analysis.
Results obtained through emission spectroscopy and laser induced fluorescence confirmed that the graphite material behaved as a catalytic surface that actively promoted nitrogen recombination. Additionally, the calculated carbon nitridation rate was several orders less efficient, although its effect on the sample surface erosion was evident in the sample mass loss measurements.
Subsequently, an independent set of heat flux measurements performed over materials of varying catalycities further supported the data obtained with optical diagnostics. Furthermore, the heat flux results yielded the surface accommodation factor of graphite for the nitrogen recombination rate and indicated that the surface was slightly less than fully-accommodating.
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Hirst, Catherine Mary. "The geothermal potential of low enthalpy deep sedimentary basins in the UK." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/11979/.
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Low enthalpy geothermal resources located within deep Permian and post-Permian sedimentary basins across the UK are estimated to contain at least 300 EJ (x1018 J) of heat, sufficient if fully developed to supply all heating needs in the UK for the next century. The geothermal heat estimate is based on data held within the Geothermal Catalogue (Busby, 2010). A source of deep well data not included in the Geothermal Catalogue is held by the oil and gas industry; access to this data has allowed new geothermal research to be undertaken to re-evaluate and constrain an existing geothermal resource (the Cheshire Basin), and to evaluate a previously un-quantified resource (the East Midlands). These areas were determined based on the availability of oil and gas well data. Data relating to the East Midlands indicate the total available extractable heat from produced oil and co-produced water located in Carboniferous sediments totals 2.64 MWt. In the Welton Field water from non-oil bearing horizons are factored in; the extractable heat increases from 0.91 MWt to 1.6 MWt. The Cheshire Basin uses the offshore East Irish Sea Basin as an analogue to better constrain the aquifer properties of the Triassic Sherwood Sandstone Group (SSG) and Permian Collyhurst Sandstone Group (CS). It also assesses the connectivity of these Groups across the basin. The Helsby Sandstone Formation (part of the SSG) will likely exhibit a minimum transmissivity of 4.26 D m alone. Data for the CS were inconclusive due to diverging porosity trends between the basins; transmissivity could be on average 0.13 D m or 3.85 D m with resulting flow rates of 47.7 m3 d-1 or 1431 m3 d-1. Factoring in reservoir stimulation is deemed necessary if the CS is to be targeted. The connectivity of the basin is restricted by large N-S orientated largely cemented faults, restricting flow in an E W orientation. In addition the connectivity is further affected by facies heterogeneity and diagenesis; this increases tortuosity that may be advantageous in a geothermal context. The work is pertinent given the UK’s commitment to the Kyoto Protocol and Renewable Energy Directive. Geothermal technologies are low CO2 emitters, are non-intermittent, unobtrusive, do not attract large emission-based taxes, have long (~25 year) lifespans and have minimal post-use clean up costs. The uptake of geothermal resource within the UK still remains low, however, indicating barriers to uptake exist. Technical barriers (i.e. those relating to drilling of the well, geology, flow rates and temperature) are not limiting uptake. Non-technical barriers relating to lack of risk insurance schemes and longer payback times owing to the relative value of hot water versus petroleum are identified as restricting factors to the uptake of geothermal resources. Geothermal energy development in the UK is still in its infancy and work such as this only strengthens the case for investment. The potential for geothermal resource exploitation to offset the conventional energy consumed to produce heat is sizeable; no other renewable technology has the capacity to deliver heat that low enthalpy geothermal offers.
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Mondragon, Camacho Ricardo. "Non-physical enthalpy method for phase change modelling in the solidification process." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/nonphysical-enthalpy-method-for-phase-change-modelling-in-the-solidification-process(2ab7597c-eaaa-44d8-abb8-0bf49e413c76).html.
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This research is concerned with the development of a mathematical approach for energy and mass transport in solidification modelling involving a control volume (CV) technique and finite element method (FEM) and incorporating non-physical variables in its solution. The former technique is used to determine an equivalent capacitance to describe energy transport whilst the latter technique provides temperatures over the material domain. The numerical solution of the transport equations is achieved by the introduction of two concepts, i.e. weighted transport equations and non-physical variables. The main aim is to establish equivalent transport equations that allow exact temporal integration and describe the behaviour of non-physical variables to replace the original governing transport equations. The variables defined are non-physical in the sense that they are dependent on the velocity of the moving CV. This dependence is a consequence of constructing transport equations that do not include flux integrals. The form of the transport equations facilitate the construction of a FEM formulation that is applicable to heat and mass transport problems and caters for singularities arising from phase-change, which can prove difficult to model. However, applying the non-physical enthalpy method (NEM) any singularity involved in the solidification process is precisely identified and annihilated.
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Rai, G. "Enthalpy effects in ionic liquids and mixing schemes in aqueous Ionic systems." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2012. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2404.
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Meritt, Ryan James. "A Study of Direct Measuring Skin Friction Gages for High Enthalpy Flow Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76783.
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This study concerns the design, analysis, and initial testing of a novel skin friction gage for applications in three-dimensional, high-speed, high-enthalpy flows. Design conditions required favorable gage performance in the Arc-Heated Facilities at Arnold Engineering Development Center. Flow conditions are expected to be at Mach 3.4, with convective heat properties of h= 1,500 W/(m°·K) (264 Btu/(hr·ft°·°R)) and T_aw= 3,900 K (7,000 °R). The wall shear stress is expected to be as high as τ_w= 2,750 Pa (0.40 psi) with a correlating coefficient of skin friction value around C_f= 0.0035. Through finite element model and analytical analyses, a generic gage design is predicted to remain fully functional and within reasonable factors of safety for short duration tests. The deflection of the sensing head does not exceed 0.025 mm (0.0001 in). Surfaces exposed to the flow reach a maximum temperatures of 960 K (1,720 °R) and the region near the sensitive electronic components experience a negligible rise in temperature after a one second test run.
The gage is a direct-measuring, non-nulling design in a cantilever beam arrangement. The sensing head is flush with the surrounding surface of the wall and is separated by a small gap, approximately 0.127 mm (0.005 in). A dual-axis, semi-conductor strain gage unit measures the strain in the beam resulting from the shear stress experienced by the head due to the flow. The gage design incorporates a unique bellows system as a shroud to contain the oil filling and protect the strain gages. Oil filling provides dynamic and thermal damping while eliminating uniform pressure loading. An active water-cooling system is routed externally around the housing in order to control the temperature of the gage system and electronic components. Each gage is wired in a full-bridge Wheatstone configuration and is calibrated for temperature compensation to minimize temperature effects.
Design verification was conducted in the Virginia Tech Hypersonic Tunnel. The gage was tested in well-documented Mach 3.0, cold and hot flow environments. The tunnel provided stagnation temperatures and pressures of up to T₀= 655 K (1,180 °R) and P₀= 1,020 kPa (148 psi) respectively. The local wall temperatures ranged from T_w= 292 to 320 K (525 to 576 °R). The skin friction coefficient measurements were between 0.00118 and 0.00134 with an uncertainty of less than 5%. Results were shown to be repeatable and in good concurrence with analytical predictions.
The design concept of the gage proved to be very sound in heated, supersonic flow. When it worked, it did so very effectively. Unfortunately, the implementation of the concept is still not robust enough for routine use. The strain gage units in general were often unstable and proved to be insufficiently reliable. The detailed gage design as built was subject to many potential sources of assembly misalignment and machining tolerances, and was susceptible to pre-loading. Further recommendations are provided for a better implementation of this design concept to make a fully functional gage test ready for Arnold Engineering Development Center.Master of Science
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Staton, JoAnna Christen II. "Heat and Mass Transfer Characteristics of Desiccant Polymers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/9785.
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Desiccant-enhanced air conditioning equipment has exhibited both the capability to improve humidity control and the potential to save energy costs by lowering the latent energy requirement of the supply air stream. The resulting increasing popularity of desiccant-enhanced air conditioning systems has sparked new interest in the search for a better, more efficient desiccant material. The ultimate goal of this research was to develop a material that, when applied to an existing air-to-air heat exchanger, would achieve the necessary heat and mass transfer in a single process, thus transforming a sensible heat exchanger into a total enthalpy exchanger.
This study focuses on the development and determination of appropriate polymeric desiccant materials for use in different heat and mass transfer applications. Various candidate materials were initially studied. It was decided that polyvinyl alcohol best met the pre-determined selection criteria. After the focus material was chosen, numerical models representing two heat and mass transfer applications were created. One-dimensional numerical models were developed for the performance studies of a rotary wheel total enthalpy exchanger. A two-dimensional numerical model was developed for the performance studies of a fixed plate total enthalpy exchanger as well. Material characterization tests were performed to collect material property information required by the numerical models.
Sensible, latent, and total efficiencies gathered from both the rotary wheel total enthalpy exchanger and the fixed plate total enthalpy exchanger models indicate potential uses for some candidate polyvinyl alcohol materials.Master of Science
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Orondo, Peter Omondi. "A theoretical analysis of interstitial hydrogen : pressure-composition-temperature, chemical potential, enthalpy and entropy." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78547.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 371-373).
We provide a first principles analysis of the physics and thermodynamics of interstitial hydrogen in metal. By utilizing recent advances in Density Functional Theory (DFT) to get state energies of the metal-hydrogen system, we are able to model the absorption process fairly accurately. A connection to experiment is made via Pressure-Composition-Temperature (PCT) isotherms, and thermodynamic molar quantities. In the model, we understand the excess entropy of absorbed hydrogen in terms of the change in its accessible microstates. A connection is also made between the entropy and electronic states of interstitial hydrogen. However, our model indicates that this connection is too small to account for experimental results. Therefore, a conclusion is made that the entropy of absorbed hydrogen is mostly (non-ideal) configurational in nature. To model the latter in a manner consistent with experiment, we have explored a new model that posits a weak binding between clusters of hydrogen atoms at neighboring sites. We have developed a formulation and fitted the results to experimental data. We find a least squares fitting of the model to the entropy and enthalpy results in model parameters which seem physically reasonable. The resulting model appears to provide a natural physical explanation for the dependence of the excess entropy on loading.
by Peter Omondi Orondo.
Ph.D.
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Meritt, Ryan James. "Skin Friction Sensor Design Methodology and Validation for High-Speed, High-Enthalpy Flow Applications." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54569.
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This investigation concerns the design, build, and testing of a new class of skin friction sensor capable of performing favorably in high-speed, high-enthalpy flow conditions, such as that found in atmospheric re-entry vehicles, scramjets, jet engines, material testing, and industrial processes. Fully understanding and optimizing these complex flows requires an understanding of aerodynamic properties at high enthalpies, which, in turn, requires numerical and analytical modeling as well as reliable diagnostic instrumentation. Skin friction is a key quantity in assessing the overall flight and engine performance, and also plays an important role in identifying and correcting problem areas.
The sensor design is founded on a direct-measuring, cantilever arrangement. The design incorporates two fundamental types of materials in regards to thermal conductivity and voltage resistivity properties. The non-conducting material distinction greatly deters the effect of heat soak and prevents EMI transmission throughout the sensor. Four custom fabricated metal-foil strain gauges are arranged in a Wheatstone bridge configuration to increase sensitivity and to provide further compensation for sensitivity effects. The sensor is actively cooled via a copper water channel to minimize the temperature gradient across the electronic systems. The design offers a unique immunity to many of the interfering influences found in complex, high-speed, high-enthalpy flows that would otherwise overshadow the desired wall shear measurement.
The need to develop an encompassing design methodology was recognized and became a principal focus of this research effort. The sensor design was developed through a refined, multi-disciplinary approach. Concepts were matured through an extensive and iterative program of evolving key performance parameters. Extensive use of finite element analysis (FEA) was critical to the design and analysis of the sensor. A software package was developed to utilize the powerful advantage of FEA methods and optimization techniques over the traditional trial and error methods.
Each sensor endured a thorough series of calibrations designed to systematically evaluate individual aspects of its functionality in static, dynamic, pressure, and thermal responses. Bench-test facilities at Virginia Tech (VT) and Air Force Research Laboratory (AFRL) further characterized the design vibrational effects and electromagnetic interference countermeasure effectiveness. Through iterations of past designs, sources of error have been identified, controlled, and minimized. The total uncertainty of the skin friction sensor measurement capability was determined to be ±8.7% at 95% confidence and remained fairly independent of each test facility.
A rigorous, multi-step approach was developed to systematically test the skin friction sensor in various facilities, where flow enthalpy and run duration were progressively increased. Initial validation testing was conducted at the VT Hypersonic Tunnel. Testing at AFRL was first performed in the RC-19 facility under high-temperature, mixing flow conditions. Final testing was conducted under simulated scramjet flight conditions in the AFRL RC-18 facility. Performance of the skin friction sensors was thoroughly analyzed across all three facilities. The flow stagnation enthalpies upward of 1053 kJ/kg (453 Btu/lbm) were tested. A nominal Mach 2.0 to 3.0 flow speed range was studied and stagnation pressure ranged from 172 to 995 kPa (25 to 144 psia). Wall shear was measured between 94 and 750 Pa (1.96 and 15.7 psf). Multiple entries were conducted at each condition with good repeatability at ±5% variation. The sensor was also able to clearly indicate the transient flow conditions of a full scramjet combustion operability cycle to include shock train movement and backflow along the isolator wall. The measured experimental wall shear data demonstrated good agreement with simple, flat-plate analytical estimations and historic data (where available). Numerical CFD predictions of the scramjet flow path gave favorable results for steady cold and hot flow conditions, but had to be refined to handle the various fueling injection schemes with burning in the downstream combustor and surface roughness models. In comparing CFD wall shear predictions to the experimental measurements, in a few cases, the sensor measurement was adversely affected by shock and complex flow interaction. This made comparisons difficult for these cases. The sensor maintained full functionality under sustained high-enthalpy conditions. No degradation in performance was noted over the course of the tests.
This dissertation research and development program has proven successful in advancing the development of a skin friction sensor for applications in high-speed, high-enthalpy flows. The sensor was systematically tested in relevant, high-fidelity laboratory environments to demonstrate its technology readiness and to successfully achieve a technology readiness level (TRL) 6 milestone. The instrumentation technology is currently being transitioned from laboratory development to the end users in the hypersonic test community.Ph. D.
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Taguta, Jestos. "The relationship between enthalpy of immersion, and its derived wettability parameters, to flotation response." Doctoral thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/30541.
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The wettability of mineral surfaces plays an important role in the flotation process. A wettable mineral is hydrophilic while a non-wettable mineral is hydrophobic. In the flotation process, sufficiently hydrophobic particles are collected by rising air bubbles and they report to the concentrate. On the other hand, hydrophilic particles do not attach to the air bubbles and they report to the tailings. Some of the conventional methods used to characterise mineral surface wettability include contact angle, inverse gas chromatography (iGC), time of flight secondary ion mass spectrometry (ToF-SIMS) and induction time measurements. The measurement of contact angles on flat, smooth and ideal surfaces is relatively simple, straight forward and well-described, but the measurement of powder contact angles is not so straight forward. The iGC technique is a gas phase technique while ToF-SIMS exposes the particles under high vacuum compared to an aqueous environment in real flotation systems. This thesis has investigated the use of the enthalpy of immersion as an indicator of the wettability of mineral surfaces. The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a reliable means of determining the wettability of solid surfaces, it has found only limited applications in flotation research where wettability of mineral ores is a key variable. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. The Washburn method and a microflotation system were used to measure the corresponding powder contact angles and the flotation responses of the same minerals respectively. Two mineral systems were investigated in this study, viz: different pure minerals in their natural form as well as collector-coated sulphide minerals. Furthermore, to assess whether the enthalpy of immersion is able to differentiate between the amounts of minerals of different wettabilities in a mineral mixture, a synthetic ore comprising of different proportions of a sulphide mineral (realgar) and a silicate gangue mineral(albite) was also investigated. The surface energetics of different minerals and the synthetic ore were also characterised by measuring the enthalpies of immersion in different probe liquids and applying the van Oss-Chaudhury-Good (VOCG) model. The VOCG model is reported to give consistent results in terms of surface energetics of surfaces. It has been found that the enthalpy of immersion technique was capable of distinguishing differences in the wettabilities of different minerals and these differences were explained in terms of the solid state properties of the minerals. The enthalpy of immersion method was also able to assess the changes in the surface chemical properties of the galena and realgar surfaces resulting from collector adsorption. The magnitude of the enthalpy of immersion was inversely related to the surface coverage of potassium amyl xanthate on both galena and realgar. The enthalpy of immersion measurements correlated well with powder contact angle measurements, but, most importantly, the enthalpy of immersion measurements were found to be more reproducible and sensitive than the contact angle measurements. It has also been shown that the enthalpy of immersion is a more widely applicable measure of the hydrophobicity of mineral particles typical of those used in the flotation process as opposed to the contact angle. It is therefore concluded that the enthalpy of immersion is a superior indicator of the extent to which minerals are hydrophobic or hydrophilic either in their natural form or after treatment with a collector. Furthermore, it was found that there was a strong inverse relationship between the enthalpy of immersion of the minerals studied and their flotation response. The strong inverse relationship has potential to be used in pulp phase flotation models, although this was not the focus of this thesis. In addition, a value, termed the critical enthalpy of immersion (CEI), was observed above which no flotation occurred. The CEI was in the region of -200 mJ/m². At values less exothermic than the CEI, the flotation response was found to be inversely related to the enthalpy of immersion. At values more exothermic, viz. more negative, than the CEI, no flotation occurs. The significance of this finding is that for any mineral whose flotation behaviour is unknown, the measurement of the enthalpy of immersion appears to be able to predict the flotation response of the mineral. The variance in the inverse relationship between enthalpy of immersion and rate of flotation was reduced when the data was normalized with respect to particle density which was the only variable in the flotation studies in terms of particle-bubble encounter efficiency. These results have shown that the enthalpy of immersion is an excellent indicator of both the natural mineral hydrophobicity and of the extent to which collectors render a mineral hydrophobic. The relative strength of the acid-base sites was shown to depend on the mineral type. The surface energetics obtained in this study were consistent with the hydrophobichydrophilic nature of these minerals. The basic, polar components as well as the total surface energy decreased in the following order: silicates > metallic sulphide minerals and talc. It was observed that the higher the total surface energy, the lower the hydrophobicity of the mineral. The acid-base characteristics of the minerals, measured by solution calorimetry, can give a detailed insight into the surface energies of different mineral types and may be useful in optimising processing strategies. Using the surface energetics, two important parameters were calculated, viz: the interfacial free energy of interaction between mineral particles and bubbles immersed in water (∆Gpwb) as well as the work of adhesion for water (Wadh). Interestingly, and not surprisingly, the trends in both of these parameters coincided with the trend in the enthalpies of immersion of the different minerals in water. Critical values of ∆Gpwb and Wadh parameters in the region of 200 mJ/m² and 320 mJ/m² respectively were observed above which no flotation occurs. At values less than the critical values, both parameters were inversely related to the flotation response. The enthalpy of immersion was able to differentiate between the amounts of minerals of different wettabilities in a mineral mixture. The enthalpy of immersion became increasingly exothermic as the percentage of albite in the realgar-albite mixtures increased. The experimentally determined enthalpies of immersion in water were in excellent agreement with the weighted enthalpies of immersion for the realgar-albite mixtures. The weighted enthalpies of immersion of the synthetic ore were calculated based on the specific surface areas of both realgar and albite. Therefore, it is possible to calculate the enthalpy of immersion of a synthetic ore (mineral mixtures) from the knowledge of the proportion and the enthalpy of immersion in water of the individual minerals comprising the synthetic ore. The surface energetics of the synthetic ore showed that there is a relationship between the mass recovery and the calculated relative surface polarity, based on the individual polar and total surface energies. As the relative surface polarity increases, there is a significant decrease in the mass recovery after a relative surface polarity of about 0.4. Thus, the enthalpy of immersion has the potential to be used to predict the wettability and the floatability potential of mineral mixtures. It is proposed that this work should be extended to other mineral mixtures, with careful measurement and calculation of the surface energetics of these mixtures. Thus, this work presents an opportunity for further study to investigate the use of the enthalpy of immersion to characterise the wettability of real ores.
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Grubbs, Laura Michelle Sprunger. "Characterization of Novel Solvents and Absorbents for Chemical Separations." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc67989/.
Full textAbstract:
Predictive methods have been employed to characterize chemical separation mediums including solvents and absorbents. These studies included creating Abraham solvation parameter models for room-temperature ionic liquids (RTILs) utilizing novel ion-specific and group contribution methodologies, polydimethyl siloxane (PDMS) utilizing standard methodology, and the micelles cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) utilizing a combined experimental setup methodology with indicator variables. These predictive models allows for the characterization of both standard and new chemicals for use in chemical separations including gas chromatography (GC), solid phase microextraction (SPME), and micellar electrokinetic chromatography (MEKC). Gas-to-RTIL and water-to-RTIL predictive models were created with a standard deviation of 0.112 and 0.139 log units, respectively, for the ion-specific model and with a standard deviation of 0.155 and 0.177 log units, respectively, for the group contribution fragment method. Enthalpy of solvation for solutes dissolved into ionic liquids predictive models were created with ion-specific coefficients to within standard deviations of 1.7 kJ/mol. These models allow for the characterization of studied ionic liquids as well as prediction of solute-solvent properties of previously unstudied ionic liquids. Predictive models were created for the logarithm of solute's gas-to-fiber sorption and water-to-fiber sorption coefficient for polydimethyl siloxane for wet and dry conditions. These models were created to standard deviations of 0.198 and 0.122 logunits for gas-to-PDMS wet and dry, respectively, as well as 0.164 and 0.134 log units for water-to-PDMS wet and dry, respectively. These models are particularly useful in solid phase microextraction separations. Micelles were studied to create predictive models of the measured micelle-water partition coefficient as well as models of measured MEKC chromatographic retention factors for CTAB and SDS. The resultant predictive models were created with standard deviations of 0.190 log units for the logarithm of the mole fraction concentration of water-to-CTAB, 0.171 log units for the combined logarithms of both the mole fraction concentration of water-to-CTAB and measured MEKC chromatographic retention factors for CTAB, and 0.153 log units for the combined logarithms of both the mole fraction concentration of water-to-SDS and measured MEKC chromatographic retention factors for SDS.
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Thomas, Daniel. "Thermodynamische und kinetische Untersuchungen im System Lithium-Silicium." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-159680.
Full textAbstract:
Die vorliegende Dissertation stellt die experimentelle Bestimmung von grundlegenden thermodynamischen und kinetischen Stoffdaten im System Lithium-Silicium vor. Ausgehend von der Synthese qualitativ hochwertiger Lithiumsilicide wurden Wärmekapazitäten über einen großen Temperaturbereich (2-873 K) bestimmt, die aufgrund der Ergebnisse bei tiefen Temperaturen die Ermittlung weiterer Parameter wie beispielsweise der Standardentropien bzw. der Bildungsentropien der Lithiumsilicide ermöglichte. Die Eigenschaft der Silicide, mit Wasserstoff Verbindungen einzugehen, führte zudem zur Ausdehnung der Untersuchungen auf das System Li-Si-H. Aus der Erweiterung resultierte neben der formalkinetischen Beschreibung ablaufender Gleichgewichtsreaktionen die Bestimmung von Bildungsenthalpien der Silicide. Auf Grundlage der experimentell bestimmten Stoffgrößen (Cp, S°, ∆BH°), die für theoretische und praxisrelevante Berechnungen sehr verlässliche Stoffdaten darstellen, wurden thermodynamische Modellierungen im stofflichen System durchgeführt.
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Simmons, Russell. "Direct Simulation Monte Carlo modelling of surface catalytic events in high enthalpy rarefied gas flows." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318865.
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Salemi, Leonardo da Costa, and Leonardo da Costa Salemi. "Numerical Investigation of Hypersonic Conical Boundary-Layer Stability Including High-Enthalpy and Three-Dimensional Effects." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621854.
Full textAbstract:
The spatial stability of hypersonic conical boundary layers is investigated utilizing different numerical techniques. First, the development and verification of a Linearized Compressible Navier-Stokes solver (LinCS) is presented, followed by an investigation of different effects that affect the stability of the flow in free-flight/ground tests, such as: high-enthalpy effects, wall-temperature ratio, and three-dimensionality (i.e. angle-of-attack). A temporally/spatially high-order of accuracy parallelized Linearized Compressible Navier-Stokes solver in disturbance formulation was developed, verified and employed in stability investigations. Herein, the solver was applied and verified against LST, PSE and DNS, for different hypersonic boundary-layer flows over several geometries (e.g. flat plate - M=5.35 & 10; straight cone - M=5.32, 6 & 7.95; flared cone - M=6; straight cone at AoA = 6 deg - M=6). The stability of a high-enthalpy flow was investigated utilizing LST, LinCS and DNS of the experiments performed for a 5 deg sharp cone in the T5 tunnel at Caltech. The results from axisymmetric and 3D wave-packet investigations in the linear, weakly, and strongly nonlinear regimes using DNS are presented. High-order spectral analysis was employed in order to elucidate the presence of nonlinear couplings, and the fundamental breakdown of second mode waves was investigated using parametric studies. The three-dimensionality of the flow over the Purdue 7 deg sharp cone at M=6 and AoA =6 deg was also investigated. The development of the crossflow instability was investigated utilizing suction/blowing at the wall in the LinCS/DNS framework. Results show good agreement with previous computational investigations, and that the proper basic flow computation/formation of the vortices is very sensitive to grid resolution.
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Mellors, Linda Jane 1974. "Development of a realistic in vitro model for studying the energetics of cardiac papillary muscles." Monash University, Dept. of Physiology, 2001. http://arrow.monash.edu.au/hdl/1959.1/9196.
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Peshek, Timothy John. "Studies in the Growth and Properties of ZnGeN2 and the Thermochemistry of GaN." online version, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=case1207231457.
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Yu, Hongtao. "Water in Protein Cavities: Free Energy, Entropy, Enthalpy, and its Influences on Protein Structure and Flexibility." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/341.
Full textAbstract:
Complexes of the antibiotics novobiocin and clorobiocin with DNA gyrase are illustrative of the importance of bound water to binding thermodynamics. Mutants resistantto novobiocin as well as those with a decreased affinity for novobiocin over clorobiocinboth involve a less favorable entropy of binding, which more than compensates for amore favorable enthalpy, and additional water molecules at the proteinligandinterface.Free energy, enthalpy, and entropy for these water molecules were calculated by thermodynamicintegration computer simulations. The calculations show that addition of thewater molecules is entropically unfavorable, with values that are comparable to the measuredentropy differences. The free energies and entropies correlate with the change inthe number of hydrogen bonds due to the addition of water molecules.To examine the wide variety of cavities available to water molecules inside proteins,a model of the protein cavities is developed with the local environment treated at atomicdetail and the nonlocal environment treated approximately. The cavities are then changedto vary in size and in the number of hydrogen bonds available to a water molecule insidethe cavity. The free energy, entropy, and enthalpy change for the transfer of a watermolecule to the cavity from the bulk liquid is calculated from thermodynamic integration.The results of the model are close to those of similar cavities calculated using the fullprotein and solvent environment. As the number of hydrogen bonds resulting from theaddition of the water molecule increases, the free energy decreases, as the enthalpic gainof making a hydrogen bond outweighs the entropic cost. Changing the volume of thecavity has a smaller effect on the thermodynamics. Once the hydrogen bond contributionis taken into account, the volume dependence on free energy, entropy, and enthalpy issmall and roughly the same for a hydrophobic cavity as a hydrophilic cavity.The influences of bound water on protein structure and influences are also evaluatedby performing molecular dynamics simulation for proteins with and without boundwater. Four proteins are simulated, the wildtypebovine pancreatic trypsin inhibitor(BPTI), the wildtypehen egg white lysozyme (HEWL), and two variants of the wildtypeStaphylococcal nuclease (SNase), PHS and PHS/V66E. The simulation reveals that allthese four proteins suffer structural changes upon the removing of bound water molecules,as indicating by their increased RMSD values with respect to the crystal structures. Threeout of the four proteins, BPTI, HEWL, and the PHS mutant of SNase have increased flexibility,while no apparent flexibility change is seen in the PHS/V66E variant of SNase.
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Smith, Theodore Brooke. "Development and Ground Testing of Direct Measuring Skin Friction Gages for High Enthalpy Supersonic Flight Tests." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29351.
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A series of direct-measuring skin friction gages were developed for a high-speed, high-temperature environment of the turbulent boundary layer in flows such as that in supersonic combustion ramjet (scramjet) engines, with a progression from free-jet ground tests to a design for an actual hypersonic scramjet-integrated flight vehicle. The designs were non-nulling, with a sensing head that was flush with the model wall and surrounded by a small gap. Thus, the shear force due to the flow along the wall deflects the head, inducing a measurable strain. Strain gages were used to detect the strain. The gages were statically calibrated using a direct force method. The designs were verified by testing in a well-documented Mach 2.4 cold flow. Results of the cold-flow tests were repeatable and within 15% of the value of Cf estimated from simple theory. The first gage design incorporated a cantilever beam with semiconductor strain gages to sense the shear on the floating head. Cooling water was routed both internally and around the external housing in order to control the temperature of the strain gages. This first gage was installed and tested in a rocket-based-combined-cycle (RBCC) engine model operating in the scramjet mode. The free-jet facility provided a Mach 6.4 flow with P0 = 1350 psia (9310 kPa) and T0 = 2800 °R (1555 °K). Local wall temperatures were measured between 850 and 900 °R (472-500 °K). Output from the RBCC scramjet tests was reasonable and repeatable. A second skin friction gage was designed for and tested in a wind tunnel model of the Hyper-X flight vehicle scramjet engine. These unsuccessful tests revealed the need for a radically different skin friction gage design. The third and final skin friction gage was specifically developed to be installed on the Hyper-X flight vehicle. Rather than the cantilever beam and semiconductor strain gages, the third skin friction gage made use of a flexure ring and metal foil strain gages to sense the shear. The water-cooling and oil-fill used on the previous skin friction sensors were eliminated. It was qualified for flight through a rigorous series of environmental tests, including pressure, temperature, vibration, and heat flux tests. Finally, the third skin friction gage was tested in the Hyper-X Engine Model (HXEM), a full-scale-partial-width wind tunnel model of the flight vehicle engine. These tests were conducted at Mach 6.5 enthalpy with P0 = 555 psia (3827 kPa) and h0 = 900 Btu/lbm in a freejet facility. The successful testing in the wind tunnel scramjet model provided the final verification of the gage before installation in the flight vehicle engine. The development, testing, and results of all three skin friction gages are discussed.Ph. D.
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Chadwick, Kenneth Michael. "An actively cooled floating element skin friction balance for direct measurement in high enthalpy supersonic flows." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134703/.
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Moosbrugger, John C. "Numerical computation of metal/mold boundary heat flux in sand castings using a finite element enthalpy model." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/16365.
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Maza, William Antonio. "Reaction Enthalpy and Volume Profiles for Excited State Reactions Involving Electron Transfer and Proton-Coupled Electron Transfer." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4539.
Full textAbstract:
Electron transfer, ET, and proton-coupled electron transfer, PCET, reactions are central to biological reactions involving catalysis, energy conversion and energy storage. The movement of electrons and protons in either a sequential or concerted manner are coupled in a series of elementary reaction steps in respiration and photosynthesis to harvest and convert energy consumed in foodstuffs or by absorption of light into high energy chemi-cal bonds in the form of ATP. These electron transfer processes may be modulated by conformational dynamics within the protein matrix or at the protein-protein interface, the energetics of which are still not well understood. Photoacoustic calorimetry is an estab-lished method of obtaining time-resolved reaction enthalpy and volume changes on the nanosecond to microsecond timescale. Photoacoustic calorimetry is used here to probe 1) the energetics and volume changes for ET between the self-assembled anionic uroporphy-rin:cytochrome c complex and the role of the observed volume changes in modulating ET within the complex, 2) the enthalpy and volume change for the excited state PCET reac-tion of a tyramine functionalized ruthenium(II) bis-(2,2'-bipyridine)(4-carboxy-4'-methyl-2,2'-bipyrine) meant to be a model for the tyrosine PCET chemistry carried out by cyto-chrome c oxidase and photosystem II, 3) the enthalpy and volume changes related to car-bon monoxide and tryptophan migration in heme tryptophan catabolic enzyme indoleam-ine 2,3-dioxygenase.
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TADDIA, GLENDA. "Low Enthalpy Geothermal Open Loop Heat Pumps: a suitable tool for thermal energy supply in urban areas." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2617565.
Full textAbstract:
Geothermal heat pumps represent an interesting technology that is expected to
contribute significantly to the reduction of primary energy use for heating and
cooling and meet the targets set by the European Union. Additional benefits of this
technology are related to the integration with discontinuous energy resources, in
particular wind, combining heat and power.
The replacement of conventional heating systems such as boilers, with heat pump
systems allows the de-localization of emissions of micropollutants from urban
centers to the sites in which thermal power stations are operating. This also
enhances emissions monitoring and control. Furthermore, the use of distributed
production systems based on the use of renewable sources reduces also CO2
emissions. (Lo Russo et al., 2011)
In this general context, the increasing implementation in several areas of the world
of the open-loop groundwater heat pumps technology which discharge into the
aquifer for cooling and heating buildings could potentially cause, even in the short
term, a significant environmental impact associated with thermal interference with
groundwater, particularly in the shallow aquifers.
The discharge of water at different temperatures compared to baseline (warmer in
summer and colder in winter) poses a number of problems in relation to the
potential functionality of many existing situations of use of the groundwater
(drinking water wells, agricultural, industrial, etc.). In addition, there may be cases
of interference between systems, especially in the more densely urbanized. This
means that the alteration of the temperature of the groundwater determined by a
plant may affect the installations located downstream, with significant alterations
of the performances of the systems themselves. These issues highlight how it is
crucial for the compatible development of the technology of groundwater heat
pumps discharging into aquifers that it shall be a fair assessment and technically
effective both for cooling and heating plants and pumping and injection systems in
ground.
The current legislation related to withdrawals and discharges into aquifers design a
framework suitable for the protection of groundwater and permit to decide the
3
best configuration of the plant with a case by case approach. Appropriate
specialized hydrogeological investigations should be performed for the
characterization of the main hydrogeological parameters of the subsoil at the
considered site.
In this thesis some important aspects related to the development of open-loop heat
pumps have been explored in a typical urban contest (Torino city, NW Italy).
The results of the work have allowed to define several fundamental aspects in order
to optimize the design choices of GroundWater Heat Pump (GWHP) systems.
After a general description of the low enthalpy geothermal heat pumps
technologies (Chapter 1), the analysis and comparison of the current hydrogeology
problems in urban area are described, considering the impact of groundwater heat
pump system in a urban contest (Chapter 2). Urban and industrial development can
impose major stresses on groundwater resources. The conceptual model for the
groundwater flow system, the schematization of the aquifer boundaries and the
estimation of basic hydrogeological parameters are among the main issues which
should be investigated in the development of open-loop heat pumps plants. In
particular, some characteristics of urban elements require particular attention if
compared to less anthropized areas.
In Chapter 3 the geological and hydro-stratigraphical characteristics of the Torino
test site have been described. This chapter includes a complete description of the
GWHP system plant and monitoring system that has been installed in the
Politecnico di Torino and the illustration of the fundamentals of the numerical
modelling we performed using a specific commercial code (FEFLOW® Diersch,
2010).
In Chapter 4 the relative significance of the different subsurface parameters that
mostly characterize the developed thermal plume is determined through a detailed
sensitivity analysis under different simulation conditions. In Chapter 5 we explore
the importance of the compliance between real and simulated variable input flow
data (discharge and injection temperatures) to obtain reliable simulation results.
In the following Chapter (6) we explore the potential alternative to Finite Element
Modeling (FEM) tools in the spatial and temporal prediction of the thermal plume
development by considering the use of Artificial Neural Networks (ANNs). Finally, in
4
Chapter 7, we consider the potential alternatives to traditional vertical drilled wells
to disperse the thermal energy in the aquifer comparing such technology with the
alternative use of gabions draining.
The results highlighted some important aspects that should be considered in the
modeling of the open-loop heat pumps that are summarized in the Conclusions.
The research individuated some important aspects and reached important results
but, as clearly highlighted, several aspects of the analysis of these kind of
technology should be further investigated by research and practical monitoring
observations in the future. However, even taking into account all the limitations of
the open-loop heat pumps technology, we believe that these systems represent one
of the most promising potential clean energy source especially in the urban areas
under transformation in order to reach the important goal of greenhouse-gas
emission reduction of the future Smart liveable Cities.
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Jain, Akash. "Estimation of Melting Points of Organic Compounds." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1303%5F1%5Fm.pdf&type=application/pdf.
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Brett, Richard Curtis. "Kimberlitic olivine." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/4459.
Full textAbstract:
Kimberlite hosts two populations of olivine that are distinguished on the basis of grain size and morphology; the populations are commonly described genetically as xenocrysts and phenocrysts. Recent studies of zoning patterns in kimberlitic olivine phenocrysts have cast doubt on the actual origins of the smaller olivine crystals. Here, we elucidate the nature and origins of the textural and chemical zonation that characterize both populations of olivine. Specifically, we show that both olivine-I and olivine-II feature chemically distinct overgrowths resulting from magmatic crystallization on pre-existing olivine xenocrysts. These results suggest that the total volume of olivine crystallized during transport is substantially lower (≤5%) than commonly assumed (e.g. ~25%), and that crystallization is dominantly heterogeneous. This reduces estimates of the Mg# in primitive kimberlite melt to more closely reconcile with measured phenocryst compositions.
Several additional textures are observed in olivine, and include: sealed cracks, healed cracks, phases trapping in cracks, rounded grains, overgrowths and phase trapping in overgrowths. These features record processes that operate in kimberlite during ascent, and from these features we create a summary model for kimberlite ascent:
• Olivine is incorporated into kimberlitic melts at great depths as peridotitic mantle xenoliths.
• Shortly after the incorporation of these xenocrysts the tensile strength of the crystals within xenoliths is reached at a minimum of 20 km from its source. Disaggregation of mantle xenoliths producing xenocrysts is facilitated by expansion of the minerals within the xenoliths.
• The void space produced by the failure of the crystals is filled with melt and crystals consisting of primary carbonate (high-Sr), chromite and spinel crystals. The carbonate later crystallizes to produce sealed fractures.
• Subsequent decompression causes cracks that are smaller than the sealed cracks and are preserved as healed cracks that crosscut sealed cracks.
• Mechanical rounding of the xenocrysts post-dates, and/or occurs contemporaneously with decompression events that cause cracking.
• Saturation of olivine produces rounded overgrowths on large xenocrysts, euhedral overgrowths on smaller xenocrysts, and a volumetrically minor population of olivine phenocrysts. Olivine growth traps fluid, solid and melt inclusions.
Calculations based on these relationships suggest that the melt saturates with olivine at a maximum depth of 20 km and a minimum depth of 7 km.
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Sanderson, Simon R. "Shock wave interaction in hypervelocity flow /." Web site:, 1995. http://etd.caltech.edu/etd/available/etd-11092004-094744/.
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Rini, Pietro. "Analysis of differential diffusion phenomena in high enthalpy flows, with application to thermal protection material testing in ICP facilities." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210893.
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This thesis presents the derivation of the theory leading to the determination of the governing equations of chemically reacting flows under local thermodynamic equilibrium, which rigorously takes into account effects of elemental (de)mixing. As a result, new transport coefficients appear in the equations allowing a quantitative predictions and helping to gain deeper insight into the physics of chemically reacting flows at and near local equilibrium. These transport coefficients have been computed for both air and carbon dioxide mixtures allowing the application of this theory to both Earth and Mars entry problems in the framework of the methodology for the determination of the catalytic activity of Thermal Protections Systems (TPS) materials.Firstly, we analyze the influence of elemental fraction variations on the computation of thermochemical equilibrium flows for both air and carbon dioxide mixtures. To this end, the equilibrium computations are compared with several chemical regimes to better analyze the influence of chemistry on wall heat flux and to observe the elemental fractions behavior along a stagnation line. The results of several computations are presented to highlight the effects of elemental demixing on the stagnation point heat flux and chemical equilibrium composition for air and carbon dioxide mixtures. Moreover, in the chemical nonequilibrium computations, the characteristic time of chemistry is artificially decreased and in the limit the chemical equilibrium regime, with variable elemental fractions, is achieved. Then, we apply the closed form of the equations governing the behavior of local thermodynamic equilibrium flows, accounting for the variation in local elemental concentrations in a rigorous manner, to simulate heat and mass transfer in CO2/N2 mixtures. This allows for the analysis of the boundary layer near the stagnation point of a hypersonic vehicle entering the true Martian atmosphere. The results obtained using this formulation are compared with those obtained using a previous form of the equations where the diffusive fluxes of elements are computed as a linear combination of the species diffusive fluxes. This not only validates the new formulation but also highlights its advantages with respect to the previous one :by using and analyzing the full set of equilibrium transport coefficients we arrive at a deep understanding of the mass and heat transfer for a CO2/N2 mixture.
Secondly, we present and analyze detailed numerical simulations of high-pressure inductively coupled air plasma flows both in the torch and in the test chamber using two different mathematical formulations: an extended chemical non-equilibrium formalism including finite rate chemistry and a form of the equations valid in the limit of local thermodynamic equilibrium and accounting for the demixing of chemical elements. Simulations at various operating pressures indicate that significant demixing of oxygen and nitrogen occurs, regardless of the degree of nonequilibrium in the plasma. As the operating pressure is increased, chemistry becomes increasingly fast and the nonequilibrium results correctly approach the results obtained assuming local thermodynamic equilibrium, supporting the validity of the proposed local equilibrium formulation. A similar analysis is conducted for CO2 plasma flows, showing the importance of elemental diffusion on the plasma behavior in the VKI plasmatron torch.
Thirdly, the extension of numerical tools developed at the von Karman Institute, required within the methodology for the determination of catalycity properties for thermal protection system materials, has been completed for CO2 flows. Non equilibrium stagnation line computations have been performed for several outer edge conditions in order to analyze the influence of the chemical models for bulk reactions. Moreover, wall surface reactions have been examined, and the importance of several recombination processes has been discussed. This analysis has revealed the limits of the model currently used, leading to the proposal of an alternative approach for the description of the flow-surface interaction. Finally the effects of outer edge elemental fractions on the heat flux map is analyzed, showing the need to add them to the list of parameters of the methodology currently used to determine catalycity properties of thermal protection materials.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
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Shpotyuk, M., O. Shpotyuk, and V. Balitska. "Unified configuration-enthalpy model describing optical response originated from physical ageing and high-energy irradiation in chalcogenide glasses." Thesis, Book of Abstract of 5th International Co ference on the Physics of Optical Materials and Devices, 2018. http://hdl.handle.net/123456789/5001.
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Hany, Cindy. "Développement de méthodes thermiques pour la caractérisation de réactions chimiques en microfluidique." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13936/document.
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Ce travail porte sur le développement de nouvelles méthodes de mesure permettant la caractérisation de réactions chimiques très exothermiques dans des conditions de sécurité. Pour cela, nous souhaitons combiner l’analyse thermique des réactions et la technologie microfluidique. L’utilisation de la microfluidique rend possible l’utilisation de très faibles volumes réactionnels limitant ainsi tout risque lié à la dangerosité des réactions explosives. Le premier appareil développé est un microcalorimètre qui mesure le flux de chaleur global dégagé lors d’un écoulement co-courant ou gouttes. Plusieurs paramètres peuvent être déterminés : enthalpie de mélange et de réaction, concentration par dosage calorimétrique et cinétique. Le deuxième dispositif consiste à mesurer le champ de température du milliréacteur isopéribolique à l’aide d’une caméra InfraRouge et ainsi de suivre localement l’évolution de la réaction pour déterminer les paramètres thermocinétiquesThis work deals with the development of new measurement methods in order to characterize high exothermic chemical reactions in safe conditions. Thus, we combine thermal analysis with microfluidic technology. The use of microfluidics allows to manipulate a very small amount of product safely. First, we have developed a microcalorimeter to measure the global heat flux produced in co-flow or droplet-flow configurations. Several parameters can be determined: reaction and mixing enthalpy, concentrations by calorimetric titration and kinetics. The second method uses an InfraRed camera to measure the temperature field of the isoperibolic millireactor. Then, the local evolution of the reaction is estimated by thermal processing. From such inverse methods, the thermokinetic parameters can be determined
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Lee, Matthew Colin John. "Correlations between MO Eigenvectors and the Thermochemistry of Simple Organic Molecules, Related to Empirical Bond Additivity Schemes." The University of Waikato, 2008. http://hdl.handle.net/10289/2623.
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A bondingness term is further developed to aid in heat of formation (ΔfHº) calculations for C, N, O and S containing molecules. Bondingness originated from qualitative investigations into the antibonding effect in the occupied MOs of ethane. Previous work used a single parameter for bondingness to calculate ΔfHº in an alkane homologous series using an additivity scheme. This work modifies the bondingness algorithm and uses the term to parameterise a test group of 345 molecules consisting of 17 subgroups that include alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, amides, diazenes, nitriles, nitroalkanes, nitrates, thiols and benzenoids. Comparing experimental with calculated ΔfHº values, a standard deviation for the residuals of 6.3 kJ mol 1 can be achieved using bondingness with a simple steric repulsion term (SSR) in a bond additivity scheme, and a standard deviation of 5.2 kJ mol 1 can be achieved using a Lennard-Jones potential. The method is compared with the group method of Pedley, which for a slightly smaller set of 338 molecules, a subset of the test set of 345 molecules, gives a standard deviation of 7.0 kJ mol 1. Bondingness, along with SSR or a Lennard-Jones potential, is parameterised in the lowest level of ab initio (HF-SCF) or semiempirical quantum chemical calculations. It therefore may be useful in determining the ΔfHº values for the largest molecules that are amenable to quantum chemical calculation. As part of our analysis we calculated the difference between the lowest energy conformer and the average energy of a mixture populated with higher energy conformers. This is the difference between the experimental ΔfHº value and the ΔfHº calculated for a single conformer. Example calculations which we have followed are given by Dale and Eliel et al.. Dale calculates the energy difference for molecules as large as hexane using relative energies based on the number of 1,4 gauche interactions. We have updated these values with constant increments ascertained by Klauda et al. as well as ab initio MP2 cc-pVDZ relative energies and have included calculations for heptane and octane.
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Gudavalli, Ravi Krishna. "Effect of pH and temperature on the carbonate promoted dissolution of sodium meta-autunite." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/773.
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Release of uranium from Na-autunite, an artificial mineral created as a result of polyphosphate injection in the subsurface at the DOE Hanford Site, takes place during slow dissolution of the mineral structure. Stability information of the uranyl-phosphate phases is limited to conditions involving pH, temperature, and a few aqueous organic materials. The carbonate ion, which creates very strong complexes with uranium, is the predominant ion in the groundwater composition.
The polyphosphate technology with the formation of autunite was identified as the most feasible remediation strategy to sequester uranium in contaminated groundwater and soil in situ. The objectives of the experimental work were (i) to quantify the effect of bicarbonate on the stability of synthetic sodium meta-autunite created as a result of uranium stabilization through polyphosphate injection, (ii) calculate the kinetic rate law parameters of the uranium release from Na-autunite during dissolution, and (iii) to compare the process parameters with those obtained for natural calcium meta-autunite.
Experiments were conducted using SPTF apparatus, which consists of syringe pumps for controlling flow rate, Teflon reactors and a heating/cooling system. 0.25 grams of synthetic Na-autunite was placed in the reactor and buffer solutions with varying bicarbonate concentrations (0.0005 to 0.003 M) at different pH (6 - 11) were pumped through the reactors. Experiments were conducted at four different temperatures in the range of 5 - 60oC.
It was concluded that the rate of release of uranium from synthetic Na-autunite is directly correlated to the bicarbonate concentration. The rate of release of uranium increased from 1.90 x 10-12 at pH 6 to 2.64 x 10-10 (mol m-2 s-1) at pH 11 at 23oC over the bicarbonate concentration range tested. The activation energy values were invariant with the change in the bicarbonate concentration; however, pH is shown to influence the activation energy values. Uranyl hydroxides and uranyl carbonates complexes helped accelerate the dissolution of autunite mineral.
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Alamaro, Moshe 1948. "Wind wave tank for experimental investigation of momentum and enthalpy transfer from the ocean surface at high wind speed." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/51587.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.Includes bibliographical references (leaves 77-79).
Thermodynamic analysis and numerical modeling of hurricane intensity has shown that its is controlled by the enthalpy transfer from the ocean surface and by drag. Direct measurements of drag, evaporation, and sensible heat transfer are not easily performed on the high seas. Therefore, a wind wave tank has been constructed in which a few aspects of a tropical storm are simulated. The air velocity inside the annular tank is comparable to that of hurricane. However, the three dimensionality of the tank obscures the quantitative comparison between experiments and actual conditions over the surface of the ocean at high wind speeds. The design of the wind wave tank and the initial experiments create a foundation for future and more comprehensive experimental programs. This thesis focuses mainly on the design and engineering of the tank, and on the fluid mechanics of the rotational flow in the tank. It also provides preliminary experimental data on the drag at high wind speeds obtained by using spindown experiments.
by Moshe Alamaro.
S.M.
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Shpotyuk, Oleh, Valentina Balitska, and Mykhaylo Shpotyuk. "On the phenomenological identity of radiation-induced effects in glassy chalcogenides under a prism of unified configuration-enthalpy model." Thesis, Seventh International Conference on radiation in various fields of research. Herceg Novi, Montenegro. June 10-14, 2019. P.207, 2019. http://hdl.handle.net/123456789/5789.
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CASASSO, ALESSANDRO. "Low enthalpy geothermal systems: coupled flow and heat transport modelling of the long-term performances of Borehole Heat Exchangers." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2496975.
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The Ground Source Heat Pump (GSHP) is a promising technology for the heating and cooling of buildings with renewable energy sources. Borehole Heat Exchangers, in which heat is exchanged by circulating a heat carrier fluid into a pipe closed loop, are the most used typology. The energy performances of these plants depend from the properties of the BHE and of the soil. In this work, the operation of BHE for a period of 30 years has been simulated, using a finite-element subsurface flow and heat transport modelling code (FEFLOW). The relative influence of each BHE, hydrogeological and thermal soil property has been investigated, running a set of simulations and analyzing the resulting fluid temperatures in the closed loop to estimate the heat pump energy consumption. Comparing the results, we observe that the length is the most important BHE property, and it should be optimized in order to minimize the overall expense (installation and maintenance); also the pipe distance, the grout heat conductivity and the properties of the heat carrier fluid play an important role. The soil heat conductivity heavily influences the resulting fluid temperatures, and in-situ tests should be carried to predict the plant operation accurately. The presence of subsurface flow enhances the heat transfer in the subsoil, improving the heat pump performances. The heat dispersivity spatial dependence is still unknown, and this causes a strong uncertainty in the prediction of BHE operation in presence of groundwater flow.
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Gomes, Filho João Soares. "Tela de sombreamento e pintura em telhados de modelos reduzidos de galpões avícolas /." Jaboticabal : [s.n.], 2010. http://hdl.handle.net/11449/104944.
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Resumo: Quatro experimentos foram conduzidos para avaliar o efeito do sombreamento artificial e da pintura dos telhados na melhoria do conforto térmico de modelos reduzidos simulando galpões avícolas. Em todos os experimentos foram utilizadas coberturas com telha de fibrocimento, novas, sem cimento amianto, com 4,0mm de espessura. O Experimento 1 foi realizado na Universidade Estadual do Maranhão (UEMA), câmpus de São Luís, onde foram testados cinco tipos de coberturas: 1- sem tela, sem pintura (STSP - controle); 2- com tela a 0,05m de altura da telha, sem pintura (CT5SP); 3- com tela a 0,05m de altura da telha, com pintura (CT5CP); 4- com tela a 0,08m de altura da telha, sem pintura (CT8SP) e 5- com tela a 0,08m de altura da telha, com pintura (CT8CP). Foram determinados o Índice de Temperatura de Globo Negro e Umidade (ITGU), a Carga Térmica de Radiação (CTR) e a Entalpia Específica (H). As colheitas das variáveis meteorológicas (temperaturas de globo negro, de bulbo seco, de bulbo úmido e velocidade do vento) foram realizadas durante 12 dias experimentais (04 a 15 de nov. de 2009) às 10:00, 12:00, 14:00 e 16:00 horas. O tipo de cobertura CT5SP foi o que apresentou os melhores valores para ITGUcorr (79,81) e H (78,84 KJ.Kg-1 de ar seco). O melhor resultado para CTRcorr foi apresentado pelo tratamento CT5CP (480,12 W.m-2). O Experimento 2 foi realizado na Universidade Estadual Paulista (UNESP), câmpus de Jaboticabal, onde foram testados os mesmos tipos de coberturas do Experimento 1. As colheitas e registro das variáveis meteorológicas foram realizadas por 40 dias (13 de fev. a 24 de mar. de 2010), nos mesmos horários do Experimento 1. O tipo cobertura que proporcionou menor resultado para o ITGU (83,86) e H (86,41 KJ.Kg-1 de ar seco) foi o CT8CP. A menor CTR (549,52 W.m-2) foi verificada na cobertura CT5CP. O Experimento 3 objetivou verificar o efeito de dois tipos de telas... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: Four experiments were conducted to assess the effect of shading and painting of roofs improving thermal comfort in reduced models of poultry houses. In all the experiments were used with roofing cement tile, new, no asbestos cement, with 4.0 mm thick. The first experiment was conducted at the Universidade Estadual do Maranhão (UEMA), campus of São Luís, where were tested five types of coverage: 1 - no shading, no paint (STSP - control), 2 - with shading 0.05 m in height tile, unpainted (CT5SP) 3 - with shading 0.05 m in height tile with painting (CT5CP) 4 - with shading 0.08 m in height tile, unpainted (CT8SP) and 5 - with shading 0.08 m height of the tile with painting (CT8CP). Were evaluated the index of black globe temperature and humidity (BGTHI), the Heat Load (HL) and the specific enthalpy (H). The readings of meteorological variables (black globe temperature, dry bulb, wet bulb temperatures and wind speed) were measured during 12 experimental days (from nov. 4th to 15th, 2009) at 10:00, 12:00, 14: 00 and 16:00 hours. The type of coverage CT5SP had the lowest values for BGTHI (79,81) and H (78,84 KJ.Kg-1 dry air). The best result for CTRcorr (480,12 W.m-2) was presented by treatment CT5CP. The second experiment was conducted at Universidade Estadual Paulista (UNESP), campus of Jaboticabal, where were tested the same types of coverages of Experiment 1. The collection and recording of meteorological variables were performed for 40 days (from feb. 13th to 24th, 2010), at the same times of Experiment 1. The type coverage that provided smaller results for the BGTHI (83,86) and H (86,41 KJ.Kg-1 dry air) was CT8CP. The lower HL (549,52 W.m-2) was verified with the coverage CT5CP. The third experiment aimed at assessing the effect of two types of shading screens (50 and 80%) on the thermal comfort... (Complete abstract click electronic access below)
Orientador: Renato Luís Furlan
Coorientador: Adhemar Pitelli Milani
Banca: Euclides Braga Malheiros
Banca: José Eduardo Pitelli Turco
Banca: Iran José Oliveira da Silva
Banca: Francisca Neide Costa
Doutor
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Galvão, Alessandro Cazonatto. "Estudo experimental da entalpia molar em excesso de soluções liquidas binarias contendo 1-pentanol ou 1-hexanol e acetonitrila a diferentes temperaturas e pressão atmosferica e correlação atraves dos modelos PFP e ERAS." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267152.
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Orientador: Artur Zaghini FrancesconiDissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-04T22:34:23Z (GMT). No. of bitstreams: 1 Galvao_AlessandroCazonatto_M.pdf: 4286598 bytes, checksum: 5343225ecef9d45c563d1805d234599e (MD5) Previous issue date: 2005
Resumo: Resumo: Este trabalho compreende o estudo experimetal da entalpia molar em excesso em função da composição de soluções líquidas binárias contendo 1-pentanol + acetonitrila e 1- hexanol + acctonitrila às temperaturas de 288,15, 298,15, 313,15 e 323,15K e pressão atmosférica. O método experimental utilizado para determinação da entalpia molar em excesso foi a calorimetria. O ponto de partida foi a determinação experimental do efeito térmico provocado na solução pela mistura de dois reagentes puros. Os modelos ERAS e PFP foram ampliados na tentativa de correlacionar os dados experimentais. Todas as soluções estudadas apresentaram curvas com formato aproximadamente parabólico e valores positivos para entalpia molar em excesso em função da fração molar. Os resultados de entalpia molar em excesso aumentam com o aumento da temperatura e com o aumento da cadeia carbônica do álcool. Os modelos PFP e ERAS foram capazes de correlacionar satisfatoriamente os dados experimentais de entalpia molar em excesso. Utilizou-se alguns conceitos da teoria de forças intermoleculares na tentativa de analisar o comportamento dos dados experimentais e dos modelos matemáticos
Abstract: Abstract: This work is focused on the experimental study of the excess molar enthalpy as a functions of composition of binary liquid solutions containing 1-pentanol + acetonitrile and 1- hexanol + acetonitrile for 288,15, 298,15, 313,15 and 323,15K and atmospheric pressure. The excess molar enthalpy was calculated using colorimetric method. To accomplish this purpose the starting point was calculated using calorimetric method. To accomplish this purpose, the starting point was the experimental measure of the thermal effect that arises when a mixture of two pure components take place. This solution models PFP and ERAS were applied with the attempt of correlating the experimental data. All the studied system showed values of excess molar enthalpy increase with the temperature and with the number of carbons in the alkanol chain. Both models, ERAS and PFP, were able to describe the main features of the solutions and to correlate the experimental data of the excess molar enthalpy. Some concepts of molecular forces were applied as an attempt of analyzing the behaviour of the experimental data and the mathematical models
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química
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McCune-Sanders, William J. "An Autothermal, Representative Scale Test Of Compost Heat Potential Using Geostatistical Analysis." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/841.
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Composting has been practiced for thousands of years as a way of stabilizing and recycling organic matter into useful soil amendments. Thermophilic compost releases significant amounts of heat at temperatures (~140 °F) that are useful for environmental heating or process water. This heat has been taken advantage of in various ways throughout history, but development of a widely adopted technology remains elusive.
The biggest barrier to adoption of compost heat recovery (CHR) systems is projecting accurate, attractive economic returns. The cost of transfer equipment is significant, and with variability in composting substrates and methods, it is difficult to predict the power and quality of heat a proposed system would produce. While the ultimate heat release may be calculated with standard techniques, the dynamics of compost temperature and thermal power are less understood. As heat yield is one of many goals, better understanding of compost’s thermal dynamics is important for CHR optimization. This research addresses the issue by developing a field test that measures heat release and temperature across a representative-scale compost volume.
The compost test vessel was built from common construction materials and insulated enough to be self-heating in cold weather. A 4’ x 4’ x 4’ cube of 2” foam insulation panels held 1.812 cubic yards of active compost, intermittently aerated at ~35 CFM. Data from 84 temperature sensors, and one pressure sensor at the blower, was logged at 1-minute intervals for a period of 35 days. Spatial temperature fields were estimated by Kriging, and used to calculate conductive heat loss and compost volume temperature over time. Enthalpy loss was calculated using the blower pressure curve, temperature data and humidity assumptions.
The compost exhibited wide variation in temperature and heat flow over time, and less horizontal symmetry than expected. The results are dynamic and best viewed graphically. Enthalpy loss varied with adjustments to the aeration cycle, ranging from 100 to 550 W (60-minute average rates), while conductive losses were in the range of 75 W. Peak sustained thermal output was around 600 W (500 W by aeration) from days 11-13 with about 0.6 yd3 of compost in the thermophilic zone; however, this cooled the compost significantly. Aeration was then reduced, and the compost temperature recovered, with 50% - 90% of the compost volume above 130 °F from days 14-23; during this period, total heat loss was around 150 - 200 W with aeration loss around 60-100 W.
The test was successful in producing hot compost and building temperature field and heat loss models. However representative aeration rates cooled a large amount of the compost volume as cool air was drawn into the vessel. Aeration rate reduction accomplished desired compost temperatures, but resulted in low enthalpy extraction rate and temperature. Future work will address this issue with the ability to recirculate air through the compost.
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Shields, Bradley J. "Single-Phase Turbulent Enthalpy Transport." 2014. https://scholarworks.umass.edu/masters_theses_2/113.
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Vapor generation is central to the flow dynamics within fuel injector nozzles. Because the degree of atomization affects engine emissions and spray characteristics, quantification of phase change within diesel fuel injectors is a topic of design interest. Within the nozzle, the large pressure gradient between the upstream and downstream plena induce large velocities, creating separation and further pressure drop at the inlet corner. When local pressure in the throat drops below the fluid vapor pressure, phase change can occur with sufficient time. At the elevated temperatures present in diesel engines, this process can be dependent upon the degree of superheat, motivating the modeling of heat transfer from the wall.
By modeling cavitation and flash boiling phenomena as a departure from equilibrium conditions, the HRMFoam model accurately reproduces canonical adiabatic flows. An experimentally determined relaxation time controls the rate at which vapor is generated, and includes model constants tuned for water and a diesel fuel surrogate. The model is shown to perform well for several benchmark experimental cases, including the work of Reitz, Lichtarowicz, and Nurick.
With the implementation of the Farve-averaged energy equation, the present work examines and validates the transport of enthalpy through the fixed heat flux and fixed wall temperature boundary conditions. The pipe heat transfer experiments of Boelter and Allen are replicated using the kEpsilon, Realizable kEpsilon, and Spalart-Allmaras models. With proper turbulence model selection, Allen's heat transfer coefficient data is reproduced within 2.9%. Best-case bulk temperature rise prediction is within 0.05%. Boelter's bulk temperature rise is reproduced within 16.7%. Turbulent diffusivity is shown to determine radial enthalpy distribution.
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Stiesch, Gunnar. "Performance of rotary enthalpy exchangers." 1994. http://catalog.hathitrust.org/api/volumes/oclc/33070177.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1994.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 140-143).
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Belmont, Erica Lynn. "Controlling parameters of excess enthalpy combustion." Thesis, 2014. http://hdl.handle.net/2152/24814.
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Excess enthalpy combustion utilizes heat recirculation, in which heat is transferred from hot products to cold reactants to effectively preheat the reactants, in order to achieve improved combustion performance through the extension of flammability limits and increased burning rate. This research examines the effect of key parameters in excess enthalpy combustion on combustion stability, fuel conversion, and product species production through experimental and numerical investigation. Operating condition parameters that are studied include inlet reactant equivalence ratio and inlet velocity, and reactor geometry parameters that are studied include reactor channel height and length. Premixed reactants, including gaseous and liquid fuels, are investigated at rich and lean conditions. The examination of liquid fuels and the ability of a reactor to support rich and lean combustion of both gaseous and liquid fuels is a significant demonstration of a reactor’s flexibility for practical applications. This research experimentally and numerically examines excess enthalpy combustion in a counter-flow reactor. First, the counter-flow reactor, previously used for thermal partial oxidation of gaseous hydrocarbon fuels, is used in experiments to reform a liquid hydrocarbon fuel, heptane, to syngas. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and product composition is explored. Second, lean combustion is demonstrated through experiments in the same counter-flow reactor previously used in reforming studies. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. An analytical model, previously developed for rich combustion, is adapted to qualitatively predict the behavior of the counter-flow reactor in response to changes in lean operating conditions. Third, lean combustion in the counter-flow reactor is further studied by examining the combustion of increasingly complex gaseous and liquid fuels. Again, the effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. Fourth and finally, a computational scaling study examines the impact of counter-flow reactor channel geometry on combustion stability, temperature increase above adiabatic values, heat recirculation, and fuel and product species conversion efficiency.text