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1
Ma, Bao Ji, Yu Quan Zhu und Xiao Li Jin. „Heat Source and Heat Partition Models in ELID Grinding“. Advanced Materials Research 328-330 (September 2011): 115–19. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.115.
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Based on the feature of the ELID grinding, heat production mechanism in the ELID grinding was analyzed and a heat source model was given. Heat partition among work-piece, grinding wheel and electrolyte was discussed and a heat partition model was established. And numerical investigation was down. The results indicated that heat in ELID grinding was mainly produced by interaction between grit and work piece. Partition of the heat among work piece, grinding wheel and electrolyte was function of position. Electrolyte and grinding wheel take away the most heat produced in ELID grinding.
2
Kik, Tomasz. „Heat Source Models in Numerical Simulations of Laser Welding“. Materials 13, Nr. 11 (10.06.2020): 2653. http://dx.doi.org/10.3390/ma13112653.
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The article presents new possibilities for modifying heat source models in numerical simulations of laser welding processes conducted using VisualWeld (SYSWELD) software. Due to the different power distributions and shapes of a laser beams, it was necessary to propose a modification of heat source models and methods of defining the heat introduced into a welded material in the case of simulations of welding processes using solid-state and high-power diode lasers. A solution was proposed in the form of modification of predefined heat source models in the case of simulations of welding processes using solid-state disc lasers and high-power diode lasers (HPDL). Based on the results of metallographic tests and the acquisition of thermal cycles of real laser welding processes, the process of calibration and validation of the proposed models of heat sources depending on the type of device used as well as the obtained shapes of fusion beads was carried out. The purpose and assumptions of this approach towards creating heat sources were also reported, comparing exemplary stresses and cumulative plastic strain distributions for the calculation variant using a standard and modified heat source model.
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Mirkoohi, Elham, Daniel E. Seivers, Hamid Garmestani und Steven Y. Liang. „Heat Source Modeling in Selective Laser Melting“. Materials 12, Nr. 13 (26.06.2019): 2052. http://dx.doi.org/10.3390/ma12132052.
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Selective laser melting (SLM) is an emerging additive manufacturing (AM) technology for metals. Intricate three-dimensional parts can be generated from the powder bed by selectively melting the desired location of the powders. The process is repeated for each layer until the part is built. The necessary heat is provided by a laser. Temperature magnitude and history during SLM directly determine the molten pool dimensions, thermal stress, residual stress, balling effect, and dimensional accuracy. Laser-matter interaction is a crucial physical phenomenon in the SLM process. In this paper, five different heat source models are introduced to predict the three-dimensional temperature field analytically. These models are known as steady state moving point heat source, transient moving point heat source, semi-elliptical moving heat source, double elliptical moving heat source, and uniform moving heat source. The analytical temperature model for all of the heat source models is solved using three-dimensional differential equations of heat conduction with different approaches. The steady state and transient moving heat source are solved using a separation of variables approach. However, the rest of the models are solved by employing Green’s functions. Due to the high temperature in the presence of the laser, the temperature gradient is usually high which has a substantial impact on thermal material properties. Consequently, the temperature field is predicted by considering the temperature sensitivity thermal material properties. Moreover, due to the repeated heating and cooling, the part usually undergoes several melting and solidification cycles, and this physical phenomenon is considered by modifying the heat capacity using latent heat of melting. Furthermore, the multi-layer aspect of the metal AM process is considered by incorporating the temperature history from the previous layer since the interaction of the layers have an impact on heat transfer mechanisms. The proposed temperature field models based on different heat source approaches are validated using experimental measurement of melt pool geometry from independent experimentations. A detailed explanation of the comparison of models is also provided. Moreover, the effect of process parameters on the balling effect is also discussed.
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Alexeev, Anton, Grigory Onushkin, Jean-Paul Linnartz und Genevieve Martin. „Multiple Heat Source Thermal Modeling and Transient Analysis of LEDs“. Energies 12, Nr. 10 (15.05.2019): 1860. http://dx.doi.org/10.3390/en12101860.
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Thermal transient testing is widely used for LED characterization, derivation of compact models, and calibration of 3D finite element models. The traditional analysis of transient thermal measurements yields a thermal model for a single heat source. However, it appears that secondary heat sources are typically present in LED packages and significantly limit the model’s precision. In this paper, we reveal inaccuracies of thermal transient measurements interpretation associated with the secondary heat sources related to the light trapped in an optical encapsulant and phosphor light conversion losses. We show that both have a significant impact on the transient response for mid-power LED packages. We present a novel methodology of a derivation and calibration of thermal models for LEDs with multiple heat sources. It can be applied not only to monochromatic LEDs but particularly also to LEDs with phosphor light conversion. The methodology enables a separate characterization of the primary pn junction thermal power source and the secondary heat sources in an LED package.
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Mei, Viung C. „Heat Transfer of Buried Pipe for Heat Pump Application“. Journal of Solar Energy Engineering 113, Nr. 1 (01.02.1991): 51–55. http://dx.doi.org/10.1115/1.2929951.
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It is generally felt that the application of line source theory for ground coil design usually resulted in excessive overdesign. It was anticipated that in order for the ground coil heat pump systems to be economically competitive with other residential heating and cooling systems, ground coil overdesign had to be kept to a minimum. A new ground coil model was derived, which based on energy balance rather than the traditional line source theory. It was aimed to more accurately predict the operation of ground coils. It is the intention of this study to compare this ground coil model with models based on line source theory, a simple line source model and a modified line source model, by using them to simulate the same field test data for both summer and winter ground coil operations. The results indicated that for winter coil operation, the new model predicted the coil liquid exit temperature less than 2°C maximum deviation from the measured values, with an average deviation less than 1°C. The modified line source model had an average deviation of more than 1.5°C. For summer operation, all models underpredicted the measured soil temperatures because the effect of thermal backfill material was not included in the models. The new model still predicted the test results better than the other two models. However, when the effect of sand thermal backfill was included in the new model, which was not easy for the other two models, the calculated soil temperatures were almost identical to the test results.
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Patel, Anand Kumar, und Pankaj Mishra. „“OPTIMIZATION OF GROUND SOURCE HEAT PUMP:A REVIEW”“. SMART MOVES JOURNAL IJOSCIENCE 4, Nr. 6 (26.06.2018): 9. http://dx.doi.org/10.24113/ijo-science.v4i6.146.
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To effectively exploit the heat capacity of the soil a heat-exchanger system has to be constructed. Usually an array of buried pipes running along the length of the building, a nearby field or buried vertically into the ground is utilized. A circulating fluid (water or air) is used in summer to extract heat from the hot environment of the building and dump it into the ground and vice versa in winter. A heat pump may also be coupled to the ground heat exchanger to increase its efficiency. In the literature several calculation models are found for ground heat exchangers. One-dimensional models were devised in the first stages of the system study which were replaced by two- dimensional models during the nineties and three-dimensional systems during the recent years. The present study are further refined and can accept any type of grid geometry that may give greater detail of the temperature variation around the pipes and in the ground.
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Jin, T., und G. Q. Cai. „Analytical Thermal Models of Oblique Moving Heat Source for Deep Grinding and Cutting“. Journal of Manufacturing Science and Engineering 123, Nr. 2 (01.03.2000): 185–90. http://dx.doi.org/10.1115/1.1343458.
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Three related analytical thermal models of plane heat source moving obliquely along the surface of a semi-infinite solid are presented. The temperature distribution of grinding zone under deep-cut conditions is investigated with these models. It is proposed that the oblique angle of the heat source plane to its moving direction has an essential influence on the grinding zone temperature rise and its distribution of high efficiency deep grinding (HEDG). Compared with that in creep-feed grinding, HEDG has a different form of heat flux distribution in grinding zone and should be treated with different thermal models. The temperature distribution at the shear zone of orthogonal cutting is also briefly discussed with the thermal models. The models developed in the paper provide a more rational and integrated analytical basis for dealing with the heat transfer problems of inclined moving heat sources.
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Al Hamahmy, Mohamed I., und Ibrahim Deiab. „Review and analysis of heat source models for additive manufacturing“. International Journal of Advanced Manufacturing Technology 106, Nr. 3-4 (06.12.2019): 1223–38. http://dx.doi.org/10.1007/s00170-019-04371-0.
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9
Zhan, Xiaohong, Qi Zhang, Qibing Wang, Jie Chen, Hongbing Liu und Yanhong Wei. „Numerical simulation of flow field in the Invar alloy laser–MIG hybrid welding pool based on different heat source models“. International Journal of Numerical Methods for Heat & Fluid Flow 28, Nr. 4 (03.04.2018): 909–26. http://dx.doi.org/10.1108/hff-02-2017-0069.
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Purpose The purpose of this paper is to establish a three-dimensional flow field model of the Invar alloy laser–metal inert gas (laser–MIG) hybrid welding process to investigate the influence of different heat sources between different layers and to analyze the flow field based on the two different heat source models for the multilayer welding. Design/methodology/approach The Invar steel plates with 19.5 mm thickness are welded into three layers’ seam using the hybrid laser–MIG welding technology. The flow field based on different heat source models is studied and then used to investigate the influence of different heat sources in different layers during the laser–MIG hybrid welding process. The simulation results of flow field using two different heat source models are compared with experiments. Findings The flow field simulations results show that using the Gaussian rotating body heat source model to simulate the temperature field is more consistent with the experiment of the hybrid laser–MIG welding where its flow field between different layers better reflects the characteristics of the hybrid laser–MIG welding. Originality/value The findings will be useful in the study of a variety of thick-plate laser–MIG hybrid welding process fluid flows.
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Zhang, Chao, Xiao Dan Zhao und Guang Hui Zhou. „The Numerical Simulation of the Solar-Air Dual-Source Heat Pump System“. Applied Mechanics and Materials 138-139 (November 2011): 305–9. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.305.
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The heat pump technology which is as an effective energy-saving technology has attracted more and more attentions. A novel solar-air dual-source heat pump system which could synchronously use two heat sources has been provided. In this paper, the mathematical model of the new heat pump system has been built and the calculation accuracy of the mathematical model has been proved. Based on a novel solar-air dual-source heat pump system, the mathematical models of the thermophysical parameters of working fluids, compressor, capillary, condenser, evaporator, and heat pump system have been established. The distribution parameter method has been adopted in the mathematical models of condenser and evaporator. Three operation modes of the novel solar-air dual-source heat pump system have been simulated. The simulated results and the experimental results have been compared. The experiments of the novel solar-air dual-source heat pump system have been accomplished in the constant temperature and humidity laboratory. The compared results show that the error is less than 10%.
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Maksimov, Vyacheslav I., Tatiana A. Nagornova und Nikolai I. Kurilenko. „Verification of Conjugate Heat Transfer Models in a Closed Volume with Radiative Heat Source“. MATEC Web of Conferences 72 (2016): 01061. http://dx.doi.org/10.1051/matecconf/20167201061.
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12
Muzychka, Y. S., und M. M. Yovanovich. „Thermal Resistance Models for Non-Circular Moving Heat Sources on a Half Space“. Journal of Heat Transfer 123, Nr. 4 (08.01.2001): 624–32. http://dx.doi.org/10.1115/1.1370516.
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Solutions to stationary and moving heat sources on a half space are reviewed for rectangular and elliptic contacts. The effects of shape, heat flux distribution, and orientation with respect to the direction of motion are examined. The dimensionless thermal resistance is shown to be a weak function of heat source shape if the square root of contact area is used as a characteristic length scale. Simple expressions are developed for calculating total thermal resistances of non-circular moving heat sources by combining asymptotic solutions for large and small values of the Peclet number. Both uniform and parabolic heat flux distributions are examined. A model is developed for predicting average or maximum flash temperatures of real sliding contacts. Comparisons of the proposed model are made with numerical solutions for two cases involving non-circular contacts.
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Clain, Fernanda Mazuco, Paulo Roberto de Freitas Teixeira und Douglas Bezerra de Araújo. „Two Heat Source Models to Simulate Welding Processes with Magnetic Deflection“. Soldagem & Inspeção 22, Nr. 1 (März 2017): 99–113. http://dx.doi.org/10.1590/0104-9224/si2201.10.
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Abstract The technique of weaving by magnetic arc deflection was developed a few years ago to enable the oscillation of the weld pool, thus, causing grain refinement and improving the properties on the welded joint. This paper aims to propose two heat source models that include effects of magnetic arc deflection on a bead-on-plate GTAW process in numerical simulations by using the finite element method. Two cases are studied. In the first case, non-deflected arc and straigth magnectic deflected arc along the torch movement are carried out and compared to numerical simulations. Temperatures at three different points on the backside of the plates (two away from the welding center line and one in its center) and weld pools of SAE 1020 3.2 mm and 6 mm thick steel plates are analyzed. Results obtained by numerical simulations are close to the experimental ones. In the second case, welding with weaving (frequency of 1Hz) on 3 mm thick steel plates is analyzed. The bead width and its visual presentation are compared to experimental results, which show good agreement with both proposed models.
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Yang, Lian, Yong Hong Huang und Liu Zhang. „Study on Engineering Construction with Three-Dimensional Heat Transfer Modeling for Double U-Tube Heat Exchangers in Ground-Source Heat Pump Systems“. Advanced Materials Research 700 (Mai 2013): 231–34. http://dx.doi.org/10.4028/www.scientific.net/amr.700.231.
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There are many ground source heat pumps in engineering construction application. However, Research on heat exchanger models of single-hole buried vertical ground source heat pump mostly focuses on single U-tube ground heat exchangers other than double U-tube ones in China currently. Compared with single U-tubes, double U-tubes have the heat transfer particularity of asymmetry. Therefore, the use of the traditional single tube models would have large error in the simulation of the actual double U-tube heat exchangers. This paper frames a three-dimensional heat transfer model for the vertical single-hole buried double u-tube heat exchanger in a ground source heat pump system. The model considers the performance of U-bube material and uses a dual coordinate system and makes the control elemental volumes superimposed.
15
Karkhin, V. A., A. Pittner, C. Schwenk und M. Rethmeier. „Simulation of inverse heat conduction problems in fusion welding with extended analytical heat source models“. Frontiers of Materials Science 5, Nr. 2 (Juni 2011): 119–25. http://dx.doi.org/10.1007/s11706-011-0137-1.
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Kapjor, Andrej, Peter Durcansky und Martin Vantuch. „Effect of Heat Source Placement on Natural Convection from Cylindrical Surfaces“. Energies 13, Nr. 17 (21.08.2020): 4334. http://dx.doi.org/10.3390/en13174334.
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Placement of heat source can play a significant role in final heat output, or heat source effectivity. Because of this, there is a need to analyze thermal fields of the heat exchange system by natural convection, where the description by criterion equations is desired, as the net heat output from tubes can be quantified. Based on known theoretical models, numerical methods were adapted to calculate the heat output with natural air flow around tubes, where mathematical models were used to describe the heat transfer more precisely. After validation of heat transfer coefficients, the effect of wall and heat source placement was studied, and the Coanda effect was also observed. The heat source placement also has an effect at the boundary layer, which can change and therefore affect the overall heat transfer process. The optimal wall-to-cylinder distance for an array of horizontal cylinders near a wall was also expressed as a function of the Rayleigh number and number of cylinders in the array.
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Shuja, S. Z., B. S. Yilbas und Z. Ayar. „Laser pulse heating and phase change process: A comparison of volumetric heat source models“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, Nr. 8 (28.12.2009): 1697–706. http://dx.doi.org/10.1243/09544062jmes1730.
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In the laser heating process, irradiated energy is absorbed on the surface skin of the substrate material. This results in excess computational efforts due to grid arrangement in the irradiated region and the remaining region in the solution domain due to the fine grid spacing in the irradiated region. However, consideration of the surface heat source minimizes this problem, since it does not require fine grid spacing in the skin of the surface. In the present study, laser heating and phase change in the irradiated region are modelled. The laser heating situation is modelled after considering the volumetric heat source incorporating an absorption process (Beer—Lambert's Law) and the surface heat source model. The temperature distribution, melt layer, and solid—liquid zone (mushy zone) formed in the heated region are predicted for the volumetric and surface heat source heating models. This study is extended to include the influence of spatial distribution of the laser pulse on temperature rise and phase change processes. It is found that the surface heat source model predicts higher values of temperature than those corresponding to the volumetric heat source in the surface vicinity. As the depth increases, temperature distributions predicted from both models become almost identical. In addition, the melt layer thickness and mushy zone predicted from both models are almost identical.
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Ortega, Alfonso, und Shankar Ramanathan. „On the Use of Point Source Solutions for Forced Air Cooling of Electronic Components—Part I: Thermal Wake Models for Rectangular Heat Sources“. Journal of Electronic Packaging 125, Nr. 2 (01.06.2003): 226–34. http://dx.doi.org/10.1115/1.1569506.
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Analytical solutions are presented for the temperature field that arises from the application of a source of heat on an adiabatic plate or board when the fluid is represented as a uniform flow with an effective turbulent diffusivity, i.e., the so-called UFED flow model. Solutions are summarized for a point source, a one-dimensional strip source, and a rectangular source of heat. The ability to superpose the individual kernel solutions to obtain the temperature field due to multiple sources is demonstrated. The point source solution reveals that the N−1 law commonly observed for the centerline thermal wake decay for three-dimensional arrays is predicted by the point source solution for the UFED model. Examination of the solution for rectangular sources shows that the thermal wake approaches the point source behavior downstream from the source, suggesting a new scaling for the far thermal wake based on the total component power and a length scale given by ε/U. The new scaling successfully collapses the thermal wake for several sizes of components and provides a fundamental basis for experimental observations previously made for arrays of three-dimensional components.
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Chen, J., C. S. Wu und M. A. Chen. „Improvement of welding heat source models for TIG-MIG hybrid welding process“. Journal of Manufacturing Processes 16, Nr. 4 (Oktober 2014): 485–93. http://dx.doi.org/10.1016/j.jmapro.2014.06.002.
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Durcansky, Peter. „COMPARISON OF MATHEMATICAL MODELS FOR HEAT EXCHANGERS OF UNCONVENTIONAL CHP UNITS“. Acta Polytechnica 55, Nr. 4 (31.08.2015): 223. http://dx.doi.org/10.14311/ap.2015.55.0223.
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An unconventional CHP unit with a hot air engine is designed as the primary energy source with fuel in the form of biomass. The heat source is a furnace designed for combustion of biomass, whether in the form of wood logs or pellets. The transport of energy generated by the biomass combustion to the working medium of a hot-air engine is ensured by a special heat exchanger connected to this resource. The correct operation of the hot-air engine is largely dependent on an appropriate design of the exchanger. The paper deals with the calculation of the heat exchanger for the applications<br />mentioned, using criterion equations, and based on CFD simulations.
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Huang, Y., und S. Y. Liang. „Modelling of the cutting temperature distribution under the tool flank wear effect“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 217, Nr. 11 (01.11.2003): 1195–208. http://dx.doi.org/10.1243/095440603771665232.
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The understanding of cutting temperature distribution at the presence of tool wear can aid in addressing important metal cutting issues such as part surface integrity, tool life and dimensional tolerance under practical operating conditions. The effect of tool wear on the cutting temperature distribution was first modelled by Chao and Trigger and there have been very few followers since. In Chao's model, the primary heat source was assumed to have no effect on the workpiece temperature rise and the chip temperature rise was treated as a bulk quantity. This paper analytically quantifies the tool wear effect by taking into account the contributions of the primary heat source and considering the distribution of chip temperature rise. On the chip side, the primary shear zone is modelled as a uniform moving oblique band heat source and the secondary shear zone as a non-uniform moving band heat source within a semi-infinite medium. On the tool side, the effects of both the secondary and the rubbing heat sources are modelled as non-uniform static rectangular heat sources within a semi-infinite medium. For the workpiece side, the study models the primary shear zone as a uniform moving oblique band heat source and the rubbing heat source as a non-uniform moving band heat source within a semi-infinite medium. The proposed model is verified based on the published experimental data in the orthogonal cutting of Armco iron. Furthermore, a comparison case is presented on the temperature variation with respect to cutting speed, feed rate and flank wear length.
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Gangar, Nikunj, Sandro Macchietto und Christos N. Markides. „Recovery and Utilization of Low-Grade Waste Heat in the Oil-Refining Industry Using Heat Engines and Heat Pumps: An International Technoeconomic Comparison“. Energies 13, Nr. 10 (18.05.2020): 2560. http://dx.doi.org/10.3390/en13102560.
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We assess the technoeconomic feasibility of onsite electricity and steam generation from recovered low-grade thermal energy in oil refineries using organic Rankine cycle (ORC) engines and mechanical vapour compression (MVC) heat pumps in various countries. The efficiencies of 34 ORC and 20 MVC current commercial systems are regressed against modified theoretical models. The resulting theoretical relations predict the thermal efficiency of commercial ORC engines within 4–5% and the coefficient of performance (COP) of commercial MVC heat pumps within 10–15%, on average. Using these models, the economic viability of ORC engines and MVC heat pumps is then assessed for 19 refinery streams as a function of heat source and sink temperatures, and the available stream thermal energy, for gas and electricity prices in selected countries. Results show that: (i) conversion to electrical power with ORC engines is, in general, economically feasible for heat-source temperatures >70 °C, however with high sensitivity to energy prices; and (ii) steam generation in MVC heat pumps, even more sensitive to energy prices, is in some cases not economical under any conditions—it is only viable with high gas/low electricity prices, for large heat sources (>2 MW) and higher temperatures (>140 °C). In countries and conditions with positive economics, payback periods down to two years are found for both technologies.
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PATEL, L. K., und LAKSHMI S. DESAI. „PLANE SYMMETRIC VISCOUS-FLUID COSMOLOGICAL MODELS WITH HEAT FLUX“. International Journal of Modern Physics D 03, Nr. 03 (September 1994): 639–45. http://dx.doi.org/10.1142/s0218271894000770.
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A class of nonstatic inhomogeneous plane-symmetric solutions of Einstein field equations is obtained. The source for these solutions is a viscous fluid with heat flow. The fluid flow is irrotational and it has nonzero expansion, shear and acceleration. All these solutions have a big-bang singularity. The matter-free limit of the solutions is the well-known Kasner vacuum solution. Some physical features of the solutions are briefly discussed.
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Dhinakaran, V., N. Siva Shanmugam und K. Sankaranarayanasamy. „Some studies on temperature field during plasma arc welding of thin titanium alloy sheets using parabolic Gaussian heat source model“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, Nr. 4 (08.08.2016): 695–711. http://dx.doi.org/10.1177/0954406215623574.
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In this paper, a new volumetric heat source model is developed for predicting the weld bead geometry during plasma arc welding of thin sheets of titanium alloy. Numerical simulations are carried out with the proposed parabolic Gaussian heat source (PGHS) model and already prevailing familiar heat source models namely, conical heat source and modified conical heat source, using finite element package COMSOL. The temperature-dependent material properties for Ti–6Al–4V alloy are considered for performing numerical calculations, which tend to influence the temperature fields while computing. Besides, the effect of trailing gas shielding, latent heat, and radiative and convective heat transfer are taken into account while performing the transient thermal analysis which significantly alters the sensitivity and accuracy of the model. Experimental trials on thin titanium alloy sheets are carried out to enable the validation of the proposed PGHS model. Subsequently, the outcome reveals that the PGHS model is capable and proved its high degree of efficiency in predicting the weld bead geometry more accurately than the existing heat source models. The distribution of heat intensity along the thickness of thin sheet is observed to be parabolic as predicted by the proposed model. The prediction appears to have a good correlation with the experimental result and it is clearly perceptible that the parabolic shape is more reliable and yields greater accuracy of the proposed heat source model.
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Gang, Wenjie, und Jinbo Wang. „Predictive ANN models of ground heat exchanger for the control of hybrid ground source heat pump systems“. Applied Energy 112 (Dezember 2013): 1146–53. http://dx.doi.org/10.1016/j.apenergy.2012.12.031.
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Obeid, Obeid, Giulio Alfano und Hamid Bahai. „Analysis of the Temperature Evolution during Lined Pipe Welding“. Advanced Materials Research 1016 (August 2014): 753–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.753.
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A numerical analysis of thermal phenomena occurring during lined-pipe welding is presented in this paper. Numerical models of surfaces and volumetric heat sources were used to predict the time evolution of the temperature field both in a corrosion-resistance-alloy (CRA) liner, made of SUS304 stainless steel (SS), and for the single-pass girth welding of a carbon-manganese (C-Mn) steel pipe. Using the finite-element code ABAQUS, three-dimensional non-liner heat-transfer analyses was carried out to simulate the gas-tungsten-arc (GTA) welding process used in liner welding and the metal-inert-gas (MIG) welding process consumed in C-Mn steel backing welding. FORTRAN user subroutines were coded to implement the movable welding heat source and heat transfer coefficient models. The thermal history was numerically computed at locations where circumferential angles from the welding start/atop position are 90°, 180° and 270° with respect to axial distances from the weld centerline (WC). Keywords: Finite element analysis FEA, CRA Liner, C-Mn steel backing, Heat source, Thermal history.
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Simon, F., J. Ordoñez, T. A. Reddy, A. Girard und T. Muneer. „Developing multiple regression models from the manufacturer's ground-source heat pump catalogue data“. Renewable Energy 95 (September 2016): 413–21. http://dx.doi.org/10.1016/j.renene.2016.04.045.
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Li, Kuan-Ming, und Steven Y. Liang. „Modeling of Cutting Temperature in Near Dry Machining“. Journal of Manufacturing Science and Engineering 128, Nr. 2 (13.10.2005): 416–24. http://dx.doi.org/10.1115/1.2162907.
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Near dry machining refers to the condition of applying cutting fluid at relatively low flow rates, on the order of 2-100ml∕h, as opposed to the conventional way of using either a large quantity, typically of about 10l∕min, as in wet machining; or no fluid at all, as in dry machining. One important expectation of applying fluids is to control the cutting temperature, which is an important parameter for tool life and part dimensional accuracy in machining processes. In this context, the understanding of cutting temperature variation corresponding to the near dry cooling and lubrication is of interest. This paper models the temperature distributions in the cutting zone under through-the-tool near dry cooling condition. The heat source method is implemented to estimate the cutting temperatures on the tool-chip interface and the tool-workpiece interface. For the temperature rise in the chip, the effects of the primary heat source and the secondary heat source were modeled as moving heat sources. For the temperature rise in the tool, the effects of the secondary heat source, the heat loss due to cooling, and the rubbing heat source due to the tool flank wear, were modeled as stationary heat sources. For the temperature rise in the workpiece, the primary heat source, the heat loss due to cooling, and the rubbing heat source due to the tool flank wear were modeled as moving heat sources. The model describes the dual effects of air-oil mixture in near dry machining in terms of the reduction of cutting temperature through the cooling effect, as well as the reduction of heat generation through the lubricating effect. To pursue model calibration and validation, embedded thermocouple temperature measurement in cutting medium carbon steels with uncoated carbide insets were carried out. The model predictions and experimental measurements show reasonable agreement and results suggest that the combination of the cooling and the lubricating effects in near dry machining reduces the cutting temperatures on the tool-chip interface by about 8% with respect to dry machining. Moreover, the cutting speed remains a dominant factor in cutting temperature compared with the feed and the depth of cut in near dry machining processes.
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Hoffmann, H., H. Nieto, R. Jensen, R. Guzinski, P. Zarco-Tejada und T. Friborg. „Estimating evaporation with thermal UAV data and two-source energy balance models“. Hydrology and Earth System Sciences 20, Nr. 2 (12.02.2016): 697–713. http://dx.doi.org/10.5194/hess-20-697-2016.
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Abstract. Estimating evaporation is important when managing water resources and cultivating crops. Evaporation can be estimated using land surface heat flux models and remotely sensed land surface temperatures (LST), which have recently become obtainable in very high resolution using lightweight thermal cameras and Unmanned Aerial Vehicles (UAVs). In this study a thermal camera was mounted on a UAV and applied into the field of heat fluxes and hydrology by concatenating thermal images into mosaics of LST and using these as input for the two-source energy balance (TSEB) modelling scheme. Thermal images are obtained with a fixed-wing UAV overflying a barley field in western Denmark during the growing season of 2014 and a spatial resolution of 0.20 m is obtained in final LST mosaics. Two models are used: the original TSEB model (TSEB-PT) and a dual-temperature-difference (DTD) model. In contrast to the TSEB-PT model, the DTD model accounts for the bias that is likely present in remotely sensed LST. TSEB-PT and DTD have already been well tested, however only during sunny weather conditions and with satellite images serving as thermal input. The aim of this study is to assess whether a lightweight thermal camera mounted on a UAV is able to provide data of sufficient quality to constitute as model input and thus attain accurate and high spatial and temporal resolution surface energy heat fluxes, with special focus on latent heat flux (evaporation). Furthermore, this study evaluates the performance of the TSEB scheme during cloudy and overcast weather conditions, which is feasible due to the low data retrieval altitude (due to low UAV flying altitude) compared to satellite thermal data that are only available during clear-sky conditions. TSEB-PT and DTD fluxes are compared and validated against eddy covariance measurements and the comparison shows that both TSEB-PT and DTD simulations are in good agreement with eddy covariance measurements, with DTD obtaining the best results. The DTD model provides results comparable to studies estimating evaporation with similar experimental setups, but with LST retrieved from satellites instead of a UAV. Further, systematic irrigation patterns on the barley field provide confidence in the veracity of the spatially distributed evaporation revealed by model output maps. Lastly, this study outlines and discusses the thermal UAV image processing that results in mosaics suited for model input. This study shows that the UAV platform and the lightweight thermal camera provide high spatial and temporal resolution data valid for model input and for other potential applications requiring high-resolution and consistent LST.
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Jokisch, Torsten, Nikolay Doynov, Ralf Ossenbrink und Vesselin Georgiev Michailov. „Heat source model for electron beam welding of nickel-based superalloys“. Materials Testing 63, Nr. 1 (01.01.2021): 17–28. http://dx.doi.org/10.1515/mt-2020-0002.
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Abstract An adapted heat source model is developed for transient thermal numerical analysis of electron beam welded nickel-based alloy with increased susceptibility to hot cracking. The model enables the consideration of heat redistribution due to beam deflection phenomena. The modeling concept is validated by the appropriate theoretical models and in addition, experimental studies especially performed for this purpose. Special attention is given to the calibration of heat source model parameters. The calibration procedure is based on a statistical approach involving a combination of novel analytical solutions and quasi-steady state finite element models. The model parameter field is statistically analyzed, and a prediction algorithm is developed using optimization algorithms from the six sigma theory. The reliability and practicability of the model is demonstrated by validation weldments. The work is dedicated to precisely calculating the temperature field in the high temperature region around the weld pool and thus to provide a more detailed explanation of the formation of hot cracks when welding turbine materials commonly used in industry and aircraft constructions.
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Piña-Ortiz, A., J. F. Hinojosa, J. P. Xamán und J. M. A. Navarro. „Test of turbulence models for heat transfer within a ventilated cavity with and without an internal heat source“. International Communications in Heat and Mass Transfer 94 (Mai 2018): 106–14. http://dx.doi.org/10.1016/j.icheatmasstransfer.2018.03.021.
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Joy, Stuart L., und José L. Chávez. „Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area“. Atmosphere 12, Nr. 2 (21.02.2021): 281. http://dx.doi.org/10.3390/atmos12020281.
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Eddy covariance (EC) systems are being used to measure sensible heat (H) and latent heat (LE) fluxes in order to determine crop water use or evapotranspiration (ET). The reliability of EC measurements depends on meeting certain meteorological assumptions; the most important of such are horizontal homogeneity, stationarity, and non-advective conditions. Over heterogeneous surfaces, the spatial context of the measurement must be known in order to properly interpret the magnitude of the heat flux measurement results. Over the past decades, there has been a proliferation of ‘heat flux source area’ (i.e., footprint) modeling studies, but only a few have explored the accuracy of the models over heterogeneous agricultural land. A composite ET estimate was created by using the estimated footprint weights for an EC system in the upwind corner of four fields and separate ET estimates from each of these fields. Three analytical footprint models were evaluated by comparing the composite ET to the measured ET. All three models performed consistently well, with an average mean bias error (MBE) of about −0.03 mm h−1 (−4.4%) and root mean square error (RMSE) of 0.09 mm h−1 (10.9%). The same three footprint models were then used to adjust the EC-measured ET to account for the fraction of the footprint that extended beyond the field of interest. The effectiveness of the footprint adjustment was determined by comparing the adjusted ET estimates with the lysimetric ET measurements from within the same field. This correction decreased the absolute hourly ET MBE by 8%, and the RMSE by 1%.
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Zhang, Jun Jie, Ling Hong Xu, Heng Min und Ling Yun Wang. „Effect of a Cumulative Cold and Heat Load Ratio on Hybrid Ground-Source Heat Pump System Performance Parameters“. Advanced Materials Research 1092-1093 (März 2015): 26–35. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.26.
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The imbalance in cold and heat load in large public buildings located in a cooling-dominated areas is apparent. To explore the effect of a cumulative cold and heat load ratio (CCHLR) on the performance parameters of the hybrid ground-source heat pump system (HGSHPS) of large public buildings, this study selects a Wuhan office building as the simulation object. When this model is considered as the prototype, five other building models whose CCHLR interval is relatively uniform can be developed. The full-year dynamic loads of the six models were calculated with Designer’s Simulation Toolkits. The 20-year simulation of the six HGSHPS models was conducted with TRNSYS. Then, the performance parameters of the HGSHPS model under different CCHLR values were studied and compared. These parameters included the average soil temperature, exiting fluid temperature (ExFT) of the ground heat exchanger (GHE), average energy efficiency ratio, and specific energy consumption (the electrical energy required to obtain per kilowatt cooling or heating capacity) of the heat pump system. Simulation results indicated that with the increase in CCHLR, the average soil temperature rapidly increases, the ExFT of the GHE increases to a value that is considerably higher than the suggested standard, and the specific energy consumption of the system increases.
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Liu, Jie, und Y. Kevin Chou. „Cutting Tool Temperature Analysis in Heat-Pipe Assisted Composite Machining“. Journal of Manufacturing Science and Engineering 129, Nr. 5 (08.04.2007): 902–10. http://dx.doi.org/10.1115/1.2752528.
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Machining of advanced materials, such as composite, encounters high cutting temperatures and rapid tool wear because of the abrasive nature of the reinforcement phases in the workpiece materials. Ultrahard coatings, such as chemical vapor deposition diamond, have been used for machining such advanced materials. Wear of diamond-coated tools is characterized by catastrophic coating failure, plausibly due to the high stress developed at the coating-substrate interface at high temperatures because of very different elastic moduli and thermal expansion coefficients. Temperature reductions, therefore, may delay the onset of the coating failure and offer tool life extension. In this study, a passive heat-dissipation device, the heat pipe, has been incorporated in composite machining. Though it is intuitive that heat transfer enhanced by the heat pipe may reduce tool temperatures, the heat pipe will likely increase heat partitioning into the tool at the rake face, and complicate the temperature reduction effectiveness. A combined experimental, analytical, and numerical approach was used to investigate the heat-pipe effects on cutting tool temperatures. A machining experiment was conducted and the heat-source characteristics were analyzed using cutting mechanics. With the heat sources as input, cutting tool temperatures in machining, without or with a heat pipe, were analyzed using finite element simulations. The simulations encompass a 3-D model of a cutting tool system and a 2-D chip model. The heat flux over the rake-face contact area was used in both models with an unknown heat partition coefficient, determined by matching the average temperature at the tool-chip contact from the two models. Cutting tool temperatures were also measured in machining using thermocouples. The simulation results agree reasonably with the experiment. The model was used to evaluate how the heat pipe modifies the heat transport in a cutting tool system. Applying heat-pipe cooling inevitably increases the heat flux into the tool because of the enhanced heat dissipation. However, the heat pipe is still able to reduce the tool-chip contact temperatures, though not dramatically at current settings. The parametric study using the finite element analysis (FEA) models shows that the cooling efficiency decreases as the cutting speed and feed increase, because of the increased heat flux and heat-source area. In addition, increasing the heat-pipe volume and decreasing the heat-pipe distance to the heat source enhances the heat-pipe cooling effectiveness.
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Pert, G. J. „Models of laser-plasma ablation“. Journal of Plasma Physics 35, Nr. 1 (Februar 1986): 43–74. http://dx.doi.org/10.1017/s0022377800011132.
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Dimensional analysis is used to predict the functional relationships amongst the characteristic variables of the ablation of a cold dense fluid by an imposed external heat source. From these relations, self-similar limiting forms are identified and evaluated. Numerical simulation is used to investigate the interpolation between these limits. Self-similar forms generalizing well-known existing solutions of relevance to laser-plasma are demonstrated and include a general proof of Nemchinov's hypothesis for the heating of small targets of limited mass.
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Sebarchievici, Calin. „Performance assessment between a ground coupled and air source heat pump used for domestic hot water preparation“. E3S Web of Conferences 111 (2019): 06075. http://dx.doi.org/10.1051/e3sconf/201911106075.
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A ground-coupled heat pump system (GCHP) and an air source heat pump (ASHP) driven by photovoltaic panels are used to provide domestic hot preparation for a NZEB house. The experimental measurements are used to test both the heat pump models in the same conditions of water temperature and volume of domestic hot water. A comparative analysis of the two heat pumps for domestic hot water preparation is performed. In addition, using the software TRNSYS (Transient Systems Simulation), two numerical simulation models of thermal and electrical energy consumption in DHW mode are developed. Finally, the simulations obtained using TRNSYS software are analysed and compared to the experimental data.
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Yi, Sung-Chul. „Heat Transfer of a Smoldering Flammable Substrate. Part 1. Development of a Theoretical Model for the Heat Transfer of a Smoldering Substrate“. Journal of Fire Sciences 15, Nr. 6 (November 1997): 462–80. http://dx.doi.org/10.1177/073490419701500603.
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Part 1 of this two part paper describes the development of a theo retical model for the interaction of the moving heat source and a solid substrate when they are in contact. For purposes of the model the substrate is assumed to act as a continuum and the Fourier equation for transient, three-dimensional conduction is solved using Laplace and Fourier transformations. Unlike most previous models, this model shows the explicit relations between the properties of the heat source and those of the substrate. Since the size, shape and speed of the heat source impact the ignition of substrate, considerable attention is devoted to evaluating these parameters. Results are presented which show the effects of the size, shape and speed of the heat source of the substrate.
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Yaagoubi, Hanane, Hamid Abouchadi und Mourad Taha Janan. „Simulation of the Heat Laser of the Selective Laser Sintering Process of the Polyamide12“. E3S Web of Conferences 297 (2021): 01050. http://dx.doi.org/10.1051/e3sconf/202129701050.
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Laser sintering sintering is one of the most widely used 3D printing technologies, in which it transforms 3D models into authentic parts with generally excellent workmanship, the test today is to ensure the unmatched nature of the item produced, therefore hypothetically to understand and predict the thermal history in this process, the thermal models must be exact and fair, In this article, the consideration will be focused on the different models of heat flux diffusion, in the bibliography, some formulas Numbers that describe the transport of the heat source out of the powder bed have been found. A comparison between its laser source models will be established. The re-modeling takes place in MATLAB using the parameters of polyamide12.
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Ding, Li Bin, Jin Yun Pu und Kai Ren. „Analysis of Thermal Radiation Models for Large Open Pool Fire on Ship Deck“. Applied Mechanics and Materials 470 (Dezember 2013): 259–62. http://dx.doi.org/10.4028/www.scientific.net/amm.470.259.
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Three radiation models are discussed in the present paper. The heat fluxes vary considerably between different methods. In all models, fluxes vary highly on the position of nearing the flame and are almost identical on the far away position. Heat fluxes calculated from point source model is less than other two models, and Shokri-Beyler model is highest. Shokri-Beyler method is most applicable at heat fluxes greater than 5 KW/m2 and recommended in engineering design, and Mudan model is not applicable for calculating the heat flux nearing the flame.
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Qin, Yan Ding, Yan Ling Tian und Da Wei Zhang. „Thermal Modeling and Analysis for Grinding Operation“. Key Engineering Materials 426-427 (Januar 2010): 624–28. http://dx.doi.org/10.4028/www.scientific.net/kem.426-427.624.
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This paper focuses on the effects of heat source profiles during thermal analysis of grinding. Three different models of heat source, namely triangular model, parabolic model and elliptic model, have been suggested and their numeric formulas are provided. These models take into account of the variation of heat flux along the contact zone, so as to improve the accuracy of numeric results. Finite Element Analysis (FEA) is utilized to investigate the temperature distributions under different thermal models and the effects of two profile parameters (η and ξ). The result is a) peak temperature decreases as η increases and the location of peak value moves backwards simultaneously; b) peak temperature decreases as ξ increases and the location of peak value moves forwards simultaneously.
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Blumenthal, Ralf S., Arun K. Tangirala, RI Sujith und Wolfgang Polifke. „A systems perspective on non-normality in low-order thermoacoustic models: Full norms, semi-norms and transient growth“. International Journal of Spray and Combustion Dynamics 9, Nr. 1 (08.07.2016): 19–43. http://dx.doi.org/10.1177/1756827716652474.
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Non-normal transient growth of energy is a feature encountered in many physical systems. Its observation is intimately related to the norm used to describe the system dynamics. For a multi-physics problem such as thermoacoustics, where a heat source is in feedback with acoustic waves and a flow field, the appropriate metric is an ongoing matter of debate. Adopting a systemic perspective, it is argued in the present paper that an energy norm is, in principle, a matter of choice, but one that is critically tied to the dynamics described by the system model. To illustrate our arguments, it is shown that different norms exhibit the non-normal dynamics of thermoacoustic systems differently, but that this difference is fully explicable by the energy flux and source terms related to the formulation of the model. The non-normal dynamics as such is unaffected by the choice of norm, and transient growth merely results from a maximization of the flux and source terms governing the energy balance associated with the specific model formulation. Investigating transient growth for arbitrary energy norms requires the capability to handle semi-norm optimization problems. In the present study, we propose an approach to do so using the singular value decomposition. Non-normal transient growth around a stable fix point is then investigated for a low-order model of a simple thermoacoustic configuration of a premixed flame enclosed in a duct with non-zero mean temperature jump and bulk mean flow. The corresponding optimal mode shapes and pertinent parameters leading to transient growth are identified and discussed. For transient growth resulting from the interaction of the flame with the acoustic field, it is found that heat sources with a fast response lead to more transient growth than slow heat sources, because the system can bear a larger source term before becoming linearly unstable. Furthermore, the amount of transient energy growth does not increase monotonically with the amplitude of the initial perturbation of the flame.
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Hocine, Samy, Helena Van Swygenhoven und Steven Van Petegem. „Verification of selective laser melting heat source models with operando X-ray diffraction data“. Additive Manufacturing 37 (Januar 2021): 101747. http://dx.doi.org/10.1016/j.addma.2020.101747.
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Fleischer, Christian Etienne. „A data processing approach with built-in spatial resolution reduction methods to construct energy system models“. Open Research Europe 1 (19.04.2021): 36. http://dx.doi.org/10.12688/openreseurope.13420.1.
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Introduction: Data processing is a crucial step in energy system modelling which prepares input data from various sources into a format needed to formulate a model. Multiple open-source web-hosted databases offer pre-processed input data within the European context. However, the number of documented open-source data processing workflows that allow for the construction of energy system models with specified spatial resolution reduction methods is still limited. Methods: This paper presents a novel data processing approach to construct sector-coupled energy system models for European countries while maximising the use of existing web-hosted pre-processed data. Three power and heat optimisation models of Germany were constructed using different spatial resolution reduction methods. Results: Significant variation in generation, transmission and storage capacity of electricity were observed between the optimisation results of the energy system models. The results of the model that used administrative state boundaries to define regions were found to be sensitive to the omission of solar rooftop photovoltaic availability. Conclusions: This paper uses the proposed data processing approach to demonstrate the importance of spatial context when building and analysing power and heat optimisation models.
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Piekarska, W. „Numerical and Experimental Study of Phase Transformations in Welding Processes / Badania Numeryczne I Doświadczalne Przemian Fazowych W Procesach Spawania“. Archives of Metallurgy and Materials 60, Nr. 4 (01.12.2015): 2559–68. http://dx.doi.org/10.1515/amm-2015-0414.
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The paper concerns the mathematical and numerical modeling of phase transformations in solid state occurring during welding. The analysis of the influence of heating rate, cooling rate and maximum temperatures of thermal cycles on the kinetics of phase transformations is presented. On the basis of literature data and experimental studies the evaluation of classic mathematical and numerical models of phase transformation is presented with respect to the advanced methods of welding by using a high speed and a high power heat source. The prediction of the structure composition in laser welded butt-joint made of S460 steel is performed, where phase transformations are calculated on the basis of modified numerical models. Temperature distributions are determined as well as the shape and size of fusion zone and heat affected zone (HAZ). Temperature field is obtained by the solution of transient heat transfer equation with convective term and external volumetric heat source taken into account. Latent heat of fusion, evaporation and heats generated during phase transformations in solid state are considered in the numerical algorithm due to the large temperature range present in analyzed process. Results of the numerical prediction of structure composition in HAZ are presented in this work. Obtained results of computer simulations are compared to experimental research performered on the laser welded joint.
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Ni, Na. „Thermodynamic Features and Design of Solar-Air Source Composite Heating System“. International Journal of Heat and Technology 38, Nr. 4 (31.12.2020): 967–75. http://dx.doi.org/10.18280/ijht.380424.
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Facing the huge energy consumption of buildings, it is highly practical to study every aspect of energy-saving technologies for heating and cooling devices. Solar thermal technology and air/water source heat pump are two popular energy-saving technologies, which could be combined into a composite heating system with good energy-saving effect and efficiency. This paper constructs a solar-air source composite heating system, analyzes its thermodynamic features, and builds up the corresponding thermodynamic model. In addition, the authors modeled the daytime and nighttime heat balances, as well as the monthly cumulative heat supply for the constructed system. Finally, a dual-tank composite heating system was designed with independent heat supply/storage. The proposed models and system were proved valid and scientific through experiments.
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Chávez, JoséL, Christopher M. U. Neale, Lawrence E. Hipps, John H. Prueger und William P. Kustas. „Comparing Aircraft-Based Remotely Sensed Energy Balance Fluxes with Eddy Covariance Tower Data Using Heat Flux Source Area Functions“. Journal of Hydrometeorology 6, Nr. 6 (01.12.2005): 923–40. http://dx.doi.org/10.1175/jhm467.1.
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Abstract In an effort to better evaluate distributed airborne remotely sensed sensible and latent heat flux estimates, two heat flux source area (footprint) models were applied to the imagery, and their pixel weighting/integrating functionality was investigated through statistical analysis. Soil heat flux and sensible heat flux models were calibrated. The latent heat flux was determined as a residual from the energy balance equation. The resulting raster images were integrated using the 2D footprints and were compared to eddy covariance energy balance flux measurements. The results show latent heat flux estimates (adjusted for closure) with errors of (mean ± std dev) −9.2 ± 39.4 W m−2, sensible heat flux estimate errors of 9.4 ± 28.3 W m−2, net radiation error of −4.8 ± 20.7 W m−2, and soil heat flux error of −0.5 ± 24.5 W m−2. This good agreement with measured values indicates that the adopted methodology for estimating the energy balance components, using high-resolution airborne multispectral imagery, is appropriate for modeling latent heat fluxes. The method worked well for the unstable atmospheric conditions of the study. The footprint weighting/integration models tested indicate that they perform better than simple pixel averages upwind from the flux stations. In particular the flux source area model (footprint) seemed to better integrate the resulting heat flux image pixels. It is suggested that future studies test the methodology for heterogeneous surfaces under stable atmospheric conditions.
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Xu, Jie, Xiao Lei Jia, Yu Fan, Zhi Sun, An Min Liu und Chong Hao Zhang. „A Comparison of 3D and Axi-Symmetric Models in Pipe Welding Simulation Process“. Applied Mechanics and Materials 529 (Juni 2014): 277–81. http://dx.doi.org/10.4028/www.scientific.net/amm.529.277.
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In this paper, a detailed comparison of axi-symmetric and 3D pipe finite element models was carried out under the condition of same welding simulation parameters. Results showed that axi-symmetric model share similar residual stress distribution with 3D model in the condition of same heat source shape parameters. However, the stress values of the two concerned models were different. Meanwhile the scale of welding pool for 3D model was almost twice bigger than that of axi-symmetric model. Both welding experiment and simulation results of 3D model showed that peak temperature of welding pool along the welding path increased during the welding process, and welding pool width and depth also increased with the moving of heat source.
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Szász, Cs. „Air-source heat pump LabView-based model development for NZEB applications“. International Review of Applied Sciences and Engineering 5, Nr. 1 (01.06.2014): 59–66. http://dx.doi.org/10.1556/irase.5.2014.1.8.
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Abstract A net zero-energy building (NZEB) is considered as a resident or commercial building where the energy needs are covered by using locally available renewable energy sources and technologies. Various types of heat pumps are widely used energy conversion systems for NZEB strategies implementation. This paper is focused on the development of a novel LabView-based model for an air-source heat pump system that absorbs heat from outside air and releases it inside the building as domestic hot water supply or room's space heating by using hot water-filled fan-coils. In the first research steps the mathematical background of the considered heat pump system has been developed. Then the LabView-based software implementation of the air-source heat pump and entire heating circuit model is unfolded and presented. The result is a versatile and powerful graphical software toolkit, suitable to simulate the complex heating, ventilation and air-conditioning processes in net-zero energy buildings and to perform energy balance performance evaluations. Beside the elaborated mathematical models, a concrete software implementation example and measurement data is provided in the paper. Last but not least, the proposed original model offers a feasible solution for future developments and research in NZEB applications modeling and simulation purposes.
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Rochalski, Damian, Dariusz Golański und Jacek Szulc. „Verification of the welding heat source models in arc welding and hybrid plasma-MAG welding processes based on temperature field tests“. Welding Technology Review 92, Nr. 5 (03.08.2020): 25–35. http://dx.doi.org/10.26628/wtr.v92i5.1117.
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Hybrid welding processes belong to a new group of welding varieties that most often combine two classic welding methods, such as laser welding with MIG/MAG welding or plasma welding with MAG welding. Modeling of welding stresses in this type of welding requires the definition of a new type of heat source model that combines a concentrated stream of energy with a classic heat source, which occurs in an electric arc. The paper presents the results of temperature field modeling in conventional MAG welding and hybrid plasma-MAG welding. In the first case, the heat source model described by Goldak was used, and in the second case, the Goldak model was combined with the developed rectangular heat source model with a homogeneous distribution. The temperature distributions obtained from the simulations were verified by spot temperature measurements during welding with thermocouples. A fairly good agreement of the numerical analysis results with the temperature measurements for MAG welding was obtained, while in the case of hybrid welding the discrepancies between the modeling and temperature measurements were greater. The results were discussed, indicating potential causes and factors influencing the obtained test results.
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HASSANPOUR, SAEID, und AHMAD SABOONCHI. „VALIDATION OF LOCAL THERMAL EQUILIBRIUM ASSUMPTION IN A VASCULAR TISSUE DURING INTERSTITIAL HYPERTHERMIA TREATMENT“. Journal of Mechanics in Medicine and Biology 17, Nr. 05 (12.07.2017): 1750087. http://dx.doi.org/10.1142/s0219519417500877.
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In this paper, the validity of local thermal equilibrium assumption in a tissue-like porous medium is investigated numerically, with an interstitial heat source. The study is based on comparison between two three-equation local thermal nonequilibrium (LTNE) model and one-equation local thermal equilibrium (LTE) model. The LTNE model is validated by an steady-state 1D analytical solution which is presented for first time. The presented results indicate the small temperature difference between fluid and solid phases in heat-affected region, which leads to considerable errors in prediction of tissue thermal behavior. According to records, increasing perfusion rate or intensity of heat source increases the differences between LTE and LTNE models. It is found that in a counter-current vascular tissue if the perfusion rate of blood into tissue becomes higher, the prediction error of LTE model will be more considerable. Moreover, the higher the intensity of heat source is, the greater the difference between LTE and LTNE models is. These findings could be extended to heat transfer modeling of actual tissue during various interstitial hyperthermia treatments.