Дисертації з теми "Fluid flow and heat transfer"
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1
Mala, Gh Mohiuddin. "Heat transfer and fluid flow in microchannels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/NQ39562.pdf.
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2
Beale, Steven Brydon. "Fluid flow and heat transfer in tube banks." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8103.
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3
Tian, Jing. "Fluid flow and heat transfer in woven textiles." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615243.
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Matys, Paul. "Fluid flow and heat transfer in continuous casting processes." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28504.
Повний текст джерелаАнотація:
A three-dimensional finite difference code was developed to simulate fluid flow and heat transfer phenomena in continuous casting processes.
The mathematical model describes steady state transport phenomena in a three dimensional solution domain that involves: turbulent fluid flow, natural and forced convection, conduction, release of latent heat at the solidus surface, and tracing of unknown location of liquid/solid interface.
The governing differential equations are discretized using a finite volume method and a hybrid central, upwind differencing scheme. A fully three-dimensional ADI-like iterative procedure is used to solve the discretized algebraic equations for each dependent variable. The whole system of interlinked equations is solved by the SIMPLE algorithm.
The developed computer code was used for parametric studies of continuous casting of aluminum. The results were compared against available experimental data. This numerical simulation enhances understanding of the fluid flow and heat transfer phenomena in continuous casting processes and can be used as a tool to optimize technologies for continuous casting of metals.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
5
Janakiraman, S. V. "Fluid flow and heat transfer in transonic turbine cascades." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06112009-063614/.
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6
McPhail, Stephen John. "Single-phase fluid flow and heat transfer in microtubes." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-36182.
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7
Jagannatha, Deepak. "Heat transfer and fluid flow characteristics of synthetic jets." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2437.
Повний текст джерелаАнотація:
This thesis presents a fundamental research investigation that examines the thermal and fluid flow behaviour of a special pulsating fluid jet mechanism called synthetic jet. It is envisaged that this novel heat transfer enhancement strategy can be developed for high-performance heat sinks in electronic cooling applications.The study considers a unique arrangement of a periodic jet induced by diaphragm motion within a cavity and mounted on a confined flow channel with a heated wall upon which the jet impingement occurs. The operation of this jet mechanism is examined as two special cases for unravelling its parametric influences. In Case (a), the jet impingement is analysed in a channel with stagnant fluid permitting clear view of the pure synthetic jet process and its controlling variables. In Case (b), jet impingement is considered with fluid flow in the channel to establish the nature of synthetic jet and cross-flow interaction.The unsteady flow of this jet mechanism is simulated as a time-dependant two-dimensional numerical model with air as the working fluid. The current model considers a solution domain in its entirety, comprising the confined flow regions of the jet impinging surface, the cavity and the orifice. With a User Defined Function (UDF), the model accounts for the bulk fluid temperature variations during jet operation, which has been grossly ignored in all published work. Overcoming previous modelling limitations, the current simulation includes flow turbulence for realistic representation of pulsed jet characteristics and cross-flow interference.Computations are performed with applicable boundary conditions to obtain the heat transfer and fluid flow characteristics of the synthetic jet along with cross-flow interaction for the diaphragm amplitude ranging from 0.5 mm to 2 mm and the diaphragm frequency varying from 250 Hz to 1000 Hz. The numerical simulation yields stable solutions and aptly predicts the sequential formation of synthetic jet and its intrinsic vortex shedding process while accurately portraying the flow within the cavity.It is identified that the diaphragm amplitude primarily determines the jet velocity while the diaphragm frequency governs the rate of vortex ejection and the fluid circulation in the vicinity of the heater. The synthetic jet thermal performance is improved with high amplitude that gives rise to stronger jet impingement and reduced bulk fluid temperature arising from high frequency leading to better fluid circulation. The fluid flow in the channel or cross flow drags the jet downstream affecting jet’s ability to reach the heated wall. The relative strengths of jet velocity and channel flow determine the combined thermal performance. The fluid compressibility is seen to have insignificant effect on the synthetic jet behaviour within the examined range of parameters. As for geometrical parameters, reduced orifice width increases jet velocity improving heat transfer rates while the optima is identified for the heater -to- orifice distance within 6 to 10 times the orifice width.Results conclusively show that in a stagnant fluid medium, the proposed synthetic jet mechanism delivers 40 percent higher heat transfer rates than an equivalent continuous jet. It also thermally outperforms pure natural convection at the heated channel wall by up to 120 times within the parametric range. Under cross-flow conditions, the synthetic jet can provide 2-fold improvement in heat transfer compared to an equivalent continuous jet. By adding this synthetic jet mechanism to a flow channel, the overall thermal performance of the hybrid system is enhanced up to about 18 times the pure forced convection heat transfer rates in a channel without this jet mechanism.The observed outstanding thermal performance of the pulsed jet-cross flow hybrid mechanism surpasses the heat removal potential of current conventional techniques for electronic component cooling. It operates with a unique ability of not causing flow pressure drop increases and not requiring additional fluid circuits, which are recognised as key advantages that set this method apart from other techniques. Thus, the proposed synthetic jet-cross flow hybrid mechanism is envisaged to be potentially regarded as an outstanding thermal enhancement strategy in the development of heat sinks for future high-capacity electronic cooling needs.
8
Mihic, Stefan Dragoljub. "CFD Investigation of Metalworking Fluid Flow and Heat Transfer in Grinding." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302189719.
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Ettrich, Jörg [Verfasser]. "Fluid Flow and Heat Transfer in Cellular Solids / Jörg Ettrich." Karlsruhe : KIT Scientific Publishing, 2014. http://www.ksp.kit.edu.
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Kent, Russell Malcolm. "Modelling fluid flow and heat transfer in some volcanic systems." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306912.
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11
Kim, Tongbeum. "Fluid-flow and heat-transfer in a lattice-frame material." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616470.
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Iverson, Jared M. "Computational fluid dynamics validation of buoyant turbulent flow heat transfer." Thesis, Utah State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1550153.
Повний текст джерелаАнотація:
Computational fluid dynamics (CFD) is commonly implemented in industry to perform fluid-flow and heat-transfer analysis and design. Turbulence model studies in literature show that fluid flows influenced by buoyancy still pose a significant challenge to modeling. The Experimental Fluid Dynamics Laboratory at Utah State University constructed a rotatable buoyancy wind tunnel to perform particle image velocimetry experiments for the validation of CFD turbulence models pertaining to buoyant heat-transfer flows. This study validated RANS turbulence models implemented within the general purpose CFD software STAR-CCM+, including the k – ε models: realizable two-layer, standard two-layer, standard low-Re, v2 – f, the k- ω models from Wilcox and Menter, and the Reynolds stress transport and Spalart - Allmaras models. The turbulence models were validated against experimental heat flux and velocity data in mixed and forced convection flows at mixed convection ratios in the range of 0.1 ≤ Gr/Re2 ≤ 0.8. The k- εε standard low-Re turbulence model was found most capable overall of predicting the fluid velocity and heat flux of the mixed convection flows, while mixed results were obtained for forced convection.
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Iverson, Jared M. "Computational Fluid Dynamics Validation of Buoyant Turbulent Flow Heat Transfer." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2025.
Повний текст джерелаАнотація:
Computational fluid dynamics (CFD) is commonly used to visualize and understand complicated fluid flow and heat transfer in many industries. It is imperative to validate the CFD computer models in order to avoid costly design choices where experimentation cannot be used to ratify the predictions of computer models. Assessments of CFD computer models in the literature conclude that significant errors occur in computer model predictions of fluid flow influenced by buoyancy forces.
The Experimental Fluid Dynamics Laboratory at Utah State University constructed a wind tunnel with which to perform experiments on buoyancy induced fluid flow. The experiments measured the heat transfer and fluid velocity occurring in the buoyant flows to be used to validate computer models. Additional experimental measurements at the inlet and around the walls from each experiment allowed the computer models to simulate the fluid flow with realistic boundary conditions.For this study, four experiments were performed, including two cases where the buoy- ancy influence was significant, and two where it was not. For each set of two cases, one experiment was performed where the heat transfer occurred from a wall of the wind tunnel held at constant temperature and in the other experiment the wall temperature fluctuated axially.
This study used the experimental data to validate computer models available in the general purpose CFD software STAR-CCM+, including the k − ε models: realizable two- layer, standard two-layer, standard low-Re, v2 − f, the k − ω models from Wilcox and Menter, and the Reynolds stress transport and Spalart–Allmaras models. The k − ε stan- dard low-Re model was found most capable overall of predicting the fluid flow and heat transfer that occurred in the flows where the buoyancy influence was significant. For the experimental cases where the buoyancy influence was less significant, the validation results were inconsistent.
14
Kuan, Wai Keat. "Experimental study of flow boiling heat transfer and critical heat flux in microchannels /." Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/1887.
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15
Gebart, Rikard. "Analysis of heat transfer and fluid flow in the resin transfer moulding process." Doctoral thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26582.
Повний текст джерелаАнотація:
This thesis contains an analysis of fluid flow and heat transfer problems in the resin transfer moulding (RTM) process for manufacturing of polymer based fibre composites and it consists of five separate papers. The permeability of unidirectional fabrics, that are often used in advanced composites, is considered in Paper A and a theory for the permeability dependence on the micro geometry is developed. The theory is based on lubrication theory for narrow gaps which is motivated by the fact that most of the flow resistance comes from a small region where the fibres are closest to each other. Despite this limitation the results agree excellently with numerical results. 'Me best performance of the theory is expected at high fibre volume fractions (Vf) but the dependence on Vf is surprisingly good even at as low values as 0.3. Although the theory is formulated for an idealised geometry it can be used to predict the variation of the anisotropic permeability tensor with fibre volume fraction in real fabrics after fitting of three model parameters. Paper B is a study of the influence from different process parameters on the void content in the laminate. The void content is shown to be reduced strongly by an applied vacuum during mould filling. The main mechanism for void formation appears to be mechanical entrapment at the flow front. The voids are convected by the flow so that their concentration is highest close to the flow front. Microscopy investigation of the bubbles show that they are of two basic types, large spherical bubbles in the interstices between fibre bundles and smaller cylindrical bubbles inside the fibre bundles. The positive influence of vacuum compared to no vacuum can be explained as a combined effect of an increased mobility due to larger volume changes during mould filling and compression by the increased pressure during cure. In Paper C a comparison is made between the mould filling times for different injection strategies. The possible alternatives for a normal laminate are point injection, edge injection and peripheral injection. Theoretical results are derived that can be used to estimate the mould filling time with the different alternatives. In addition, fundamental theoretical results are derived from the governing equations showing the scaling of the mould filling time with the process parameters. This analysis also shows that the flow front motion during mould filling is only a function of the anisotropy of the reinforcement and the location of the gates. Paper D presents an analysis of the non-uniform flow at the flow front during impregnation of a stack of fabrics consisting of layers with different flow resistance. A detailed derivation of the theory and an analytical solution to the equations are presented in an addendum to Paper D. The theoretical model is compared with experimental results and is found to describe the experiment qualitatively well. The resulting permeability of a stack of different fabrics is derived from the basic equations and is found to be a weighted average of the permeability in the individual layers. This result is compared with experiments with different stacking sequences and it is found that the stacking sequence has no influence on the resulting permeability as expected from the theory. Experimental results in excellent agreement with Darcy's law are also presented for the case with radial flow and with unidirectional flow. Finally, Paper E is a theoretical study of the curing behaviour of thick laminates. A general solution independent of the cure kinetic model is derived. The solution is valid for low exothermal peak temperatures and it is characterised by two dimensionless numbers. The first parameter is the ratio between the time scales for the reaction and for heat conduction, the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The general solution is specialised to a second order autocatalytic cure model so that the results can be compared to numerical results. The agreement between the numerical and the analytical solution is excellent for small exothermal peak temperatures, as expected. The particular model used also serves as an example of the additional dimensionless parameters that are introduced by a specific kinetic model.Godkänd; 1993; 20070426 (ysko)
16
Seyedein, Seyed Hossein. "Simulation of fluid flow and heat transfer in impingement flows of various configurations." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69587.
Повний текст джерелаАнотація:
Results of numerical simulation of two-dimensional flow field and heat transfer impingement due to laminar and turbulent single as well as multiple slot jets discharging normally into a confined channel are presented. Both low-Reynolds and high-Reynolds number versions of $k - epsilon$ models were used to model the turbulent jet flow. A control volume-based finite difference method was employed to solve the governing mass, momentum, turbulent kinetic energy, turbulent kinetic energy dissipation rate and energy equations in the turbulent impinging jet cases. A separate program was written based on a body-fitted coordinate system to predict the transport characteristics of multiple laminar jets impinging on a plate surface with an inclined upper confinement surface. The parameters studied include: the jet Reynolds number, nozzle-to-impingement surface spacing and for the inclined confinement surface cases, the angle of inclination of the upper surface. From the low-Reynolds number model studied it was found that models presented by Lam-Bremhorst and Launder-Sharma to be applicable to single turbulent jet impingement heat transfer predictions. Inclination of the confined surface so as to accelerate the exhaust flow was found to level the Nusselt number distribution on the impingement surface.
17
Mouslim, Abderrazzak. "Tests of Fluid-to-Fluid Scaling Laws for Supercritical Heat Transfer." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38912.
Повний текст джерелаАнотація:
A comparison of available fluid-to-fluid scaling laws for scaling convective heat transfer at supercritical pressures showed that the ones suggested by Zahlan, Groeneveld and Tavoularis (ZGT) have some advantages. The applicability of the ZGT laws was tested for pairs of fluids including carbon dioxide, water or Refrigerant R134a. The conditions of previous measurements taken in the Supercritical University of Ottawa Loop with CO2 flowing vertically upwards in an electrically heated tube with 8 mm ID were scaled to equivalent conditions in R134a and new measurements of the heat transfer coefficient (HTC) were taken in the same tube using the latter fluid. The inlet pressure was 1.13 times the critical pressure (4.06 MPa), the mass flux was in the range from 212 kg/m^2 s to 1609 kg/m^2 s, the heat flux was in the range from 2 kW/m^2 to 137 kW/m^2, and the inlet temperature was in the range from 62 ℃ to 105 ℃. The HTC at equivalent conditions in water was also determined with the use of transcritical look-up tables. Average and linearly varying corrections to the ZGT scaling laws were derived by statistical analysis for each pair of fluids under NHT or DHT conditions. Such corrections reduced the standard deviation of the scaling error but did not eliminate the presence of large errors under many sets of conditions. As expected, scaling errors were in general larger for DHT than NHT conditions. The present results did not reveal any systematic and correctable dependence of the scaling error upon the mass flux or heat flux but showed that scaling errors became particularly large as the bulk temperature T_b approached the pseudocritical temperature T_pc. In conclusion, the ZGT scaling laws appear to be fairly accurate for the three pairs of fluids considered in the liquid-like region with T_b/T_pc ≤ 0.94 and possibly in the gas-like region with T_b/T_pc ≥ 1.02, whereas outside this range scaling errors could be significant. It was also found that the ZGT scaling laws do not scale accurately the onset of DHT in different fluids.
18
Chen, Li-Kwen. "Unsteady flow and heat transfer in periodic complex geometries for the transitional flow regime." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Chen_09007dcc804bed71.pdf.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references.
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Sridharan, Harini. "COUPLED DYNAMICS OF HEAT TRANSFER AND FLUID FLOW IN SHEAR RHEOMETRY." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597346164780318.
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20
Rizvi, Syed Mahdi Abbas. "Prediction of flow, combustion and heat transfer in pulverised coal flames." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/8946.
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Carapanayotis, Achilles E. "Modeling of fluid flow and heat transfer processes in an engine." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5228.
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22
Liu, Qingyun. "COUPLING HEAT TRANSFER AND FLUID FLOW SOLVERS FOR MULTI-DISCIPLINARY SIMULATIONS." MSSTATE, 2003. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11122003-165044/.
Повний текст джерелаАнотація:
The purpose of this study is to build, test, validate, and implement two heat transfer models, and couple them to an existing fluid flow solver, which can then be used for simulating multi-disciplinary problems. The first model is for heat conduction computations, the other one is a quasi-one-dimensional cooling channel model for water-cooled jacket structural analysis. The first model employs the integral, conservative form of the thermal energy equation, which is discretized by means of a finite-volume numerical scheme. A special algorithm is developed at the interface between the solid and fluid regions, in order to keep the heat flux consistent. The properties of the solid region materials can be temperature dependent, and different materials can be used in different parts of the domains, thanks to a multi-block gridding strategy. The cooling channel flow model is developed by using uasi-one-dimensional conservation laws of mass, momentum, and energy, taking into account the effects of heat transfer and friction. It is possible to have phase changes in the channel, and a mixture model is applied, which allows two phases to be present, as long as they move at the same bulk velocity and vapor quality does not exceed relatively small values. The coupling process of both models (with the fluid solver and with each other) is handled within the Loci system, and is detailed in this study. A hot-air nozzle wall problem is simulated, and the computed results are validated with available experimental data. Finally, a more complex case involving the water-cooled nozzle of a Rocket Based Combined Cycle(RBCC) gaseous oxygen/gaseous hydrogen thruster is simulated, which involves all three models, fully coupled. The calculated temperatures in the nozzle wall and at the cooling channel outlet compare favorably with experimental data.
23
Ong, C.-L. "Computation of fluid flow and heat transfer in rotating disc-systems." Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233697.
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CARVALHO, MARCIO DA SILVEIRA. "HEAT TRANSFER IN NON-NEWTONIAN FLUID FLOW THROUGH AN ABRUPT HIRING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19071@1.
Повний текст джерелаАнотація:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO trabalho analisa a transferência de calor no escoamento de fluidos não-newtonianos através de uma contração abrupta circular de razão 4:1, com temperatura prescrita nas paredes sólidas. O escoamento de fluidos elásticos nesta geometria apresenta uma região de recirculação bem maior que no caso de fluidos Newtonianos. Esta alteração no padrão do escoamento altera significativamente o processo de transferência de calor. O escoamento representa uma boa modelagem do processo de extrusão de líquidos poliméricos. Resolvem-se as equações de conservação de momentum e energia desacopladamente, já que foi adotadas a hipótese de não variação das propriedades do fluido com a temperatura. A relação tensão – taxa de deformação foi feita através de dois modelos constitutivos, Newtoniano generalizado e Maxwell convectado. A hipótese de escoamento lento não foi adotada, como é usualmente feito na literatura da área. Deste modo, analisa-se separadamente a influencia dos efeitos elásticos e inerciais. As equações diferenciais foram integradas numericamente pelo método dos volumes finitos e o aclopamento velocidade\ pressão foi feito através do algoritmo SIMPLE. Pelos resultados obtidos, observa-se a importância da modelagem não newtoniana e da inclusão dos termos inerciais no estudo do escoamento e da transferência de calor no processo de extrusão de polímeros.
It is well known that the flow of a non-Newtonian fluid through a sudden contraction exhibits a vortex in the corner region bigger than the one observed in the corresponding flow of a Newtonian Fluid. This change of pattern of the flow affects significantly the heat transfer at the wall. It was investigated the case og a a 4:1 circular contraction, with uniform temperature distrubuition at the solid walls. This problem represents a first approach for the analysis of the polymeric liquids extrusion process. The flow and temperature field have been obtained from the numerical integration of the conservation equations. To account for the flow dependence of the stress tensor, a generalized Newtonian model and a convected Maxwell model have been employed. The creeping flow hypothesis has not been adopted, so it was possible to analyse the elastic effects and the inertial effects separately. The nuemerical solution have been obtained via a finite-volume method. The results show the importance of the non-Newtonian modeling and of the inclusion of inertial terms in the study of the flow and beat transfer in the polymeric liquids extrusion process.
25
O'Hare, Lynne. "Continuum simulation of fluid flow and heat transfer in gas microsystems." Thesis, University of Strathclyde, 2008. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=11811.
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Kim, Sung Jin. "Interfacial interactions in heat transfer and fluid flow through porous media /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487675687171761.
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Hosler, Carrie E. "Fluid flow, heat, and mass transfer of barite mineralization in Missouri /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421142.
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Dai, Zhenhui. "Experimental study of fluid flow and heat transfer in tortuous microchannels." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/11596.
Повний текст джерелаАнотація:
Tortuous microchannels have attracted increasing interest due to great potential to enhance fluid mixing and heat transfer. While the fluid flow and heat transfer in wavy microchannels have been studied extensively in a numerical fashion, experimental studies are very limited due to the technical difficulties of making accurate measurements in micro-scale flows. This thesis provides insights into thermohydraulics of tortuous microchannels by developing experimental techniques and performing systematic visualisation and heat transfer experiments. The detailed flow patterns (including Dean vortices) and transition behaviours in wavy channels are successfully identified using Micro-Particle Image Velocimetry (micro-PIV) and 3D reconstruction techniques. Conjugate heat transfer simulations are carried out to understand the complex thermal behaviour present in the current experimental design and to validate and compare with experimental results. The impact of tortuous geometry on flow and heat transfer in microchannels is studied systematically. The high quality experimental data provide a new perspective on flow behaviour and heat transfer performance in wavy microchannels. In addition, the stackability of channels on a plate is considered. The zigzag pathways are found to provide the greatest heat transfer intensification based on a plate structure. A significant component of the research in this thesis has been the development of experimental techniques to measure local heat transfer rates in microchannels. A two-dye laser induced fluorescence (LIF) technique using temperature sensitive particles (TSPs) is developed with promising characteristics for local temperature measurement and the capability for simultaneous measurement of temperature and velocity fields in microscale systems. The advanced experimental techniques developed in this thesis provide important tools for the investigation of thermohydraulics of various micro-devices in the field of engineering.
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Khan, Waqar. "Modeling of Fluid Flow and Heat Transfer for Optimization of Pin-Fin Heat Sinks." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/947.
Повний текст джерелаАнотація:
In this study, an entropy generation minimization procedure is employed to optimize the overall performance (thermal and hydrodynamic) of isolated fin geometries and pin-fin heat sinks. This allows the combined effects of thermal resistance and pressure drop to be assessed simultaneously as the heat sink interacts with the surrounding flow field. New general expressions for the entropy generation rate are developed using mass, energy, and entropy balances over an appropriate control volume. The formulation for the dimensionless entropy generation rate is obtained in terms of fin geometry, longitudinal and transverse pitches, pin-fin aspect ratio, thermal conductivity, arrangement of pin-fins, Reynolds and Prandtl numbers. It is shown that the entropy generation rate depends on two main performance parameters, i. e. , thermal resistance and the pressure drop, which in turn depend on the average heat transfer and friction coefficients. These coefficients can be taken from fluid flow and heat transfer models. An extensive literature survey reveals that no comprehensive analytical model for any one of them exists that can be used for a wide range of Reynolds number, Prandtl number, longitudinal and transverse pitches, and thermal conductivity. This study is one of the first attempts to develop analytical models for the fluid flow and heat transfer from single pins (circular and elliptical) with and without blockage as well as pin-fin arrays (in-line and staggered). These models can be used for the entire laminar flow range, longitudinal and transverse pitches, any material (from plastic composites to copper), and any fluid having Prandtl numbers (≥0. 71). In developing these models, it is assumed that the flow is steady, laminar, and fully developed. Furthermore, the heat sink is fully shrouded and the thermophysical properties are taken to be temperature independent. Using an energy balance over the same control volume, the average heat transfer coefficient for the heat sink is also developed, which is a function of the heat sink material, fluid properties, fin geometry, pin-fin arrangement, and longitudinal and transverse pitches. The hydrodynamic and thermal analyses of both in-line and staggered pin-fin heat sinks are performed using parametric variation of each design variable including pin diameter, pin height, approach velocity, number of pin-fins, and thermal conductivity of the material. The present analytical results for single pins (circular and elliptical) and pin-fin-arrays are in good agreement with the existing experimental/numerical data obtained by other investigators. It is shown that the present models of heat transfer and pressure drop can be applied for a wide range of Reynolds and Prandtl numbers, longitudinal and transverse pitches, aspect ratios, and thermal conductivity. Furthermore, selected numerical simulations for a single circular cylinder and in-line pin-fin heat sink are also carried out to validate the present analytical models. Results of present numerical simulations are also found to be in good agreement.
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Bakaraju, Omkareshwar Rao. "Heat Transfer in Electroosmotic Flow of Power-Law Fluids in Micro-Channel." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1263337731.
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Kota, Siva Kumar k. "Analysis of Heat Transfer Enhancement in Channel Flow through Flow-Induced Vibration." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062854/.
Повний текст джерелаАнотація:
In this research, an elastic cylinder that utilized vortex-induced vibration (VIV) was applied to improve convective heat transfer rates by disrupting the thermal boundary layer. Rigid and elastic cylinders were placed across a fluid channel. Vortex shedding around the cylinder led to the periodic vibration of the cylinder. As a result, the flow-structure interaction (FSI) increased the disruption of the thermal boundary layer, and therefore, improved the mixing process at the boundary. This study aims to improve convective heat transfer rate by increasing the perturbation in the fluid flow. A three-dimensional numerical model was constructed to simulate the effects of different flow channel geometries, including a channel with a stationary rigid cylinder, a channel with a elastic cylinder, a channel with two elastic cylinders of the same diameter, and a channel with two elastic cylinders of different diameters. Through the numerical simulations, the channel maximum wall temperature was found to be reduced by approximately 10% with a stationary cylinder and by around 17% when introducing an elastic cylinder in the channel compared with the channel without the cylinder. Channels with two-cylinder conditions were also studied in the current research. The additional cylinder with the same diameter in the fluid channel only reduced the surface wall temperature by 3% compared to the channel without any cylinders because the volume of the second cylinder could occupy some space, and therefore, reduce the effect of the convective heat transfer. By reducing the diameter of the second cylinder by 25% increased the effect of the convection heat transfer and reduced the maximum wall temperature by around 15%. Compared to the channel with no cylinder, the introduction of cylinders into the channel flow was found to increase the average Nusselt number by 55% with the insertion of a stationary rigid cylinder, by 85% with the insertion of an elastic cylinder, by 58% with the insertion of two cylinders of the same diameter, and by approximately 70% with the insertion of two cylinders of different diameters (the second cylinder having the smaller diameter). Furthermore, it was also found that the maximum local Nusselt number could be enhanced by around 200%-400% at the entrance of the fluid channel by using the elastic cylinders compared to the channel without cylinders.
32
Karabay, Hasan. "Flow and heat transfer in cover-plate pre-swirl rotor-stator system." Thesis, University of Bath, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242797.
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33
Malin, Michael Ronald. "Turbulence modelling for flow and heat transfer in jets, wakes and plumes." Thesis, University of London, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287796.
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34
Gerace, Salvadore. "A MODEL INTEGRATED MESHLESS SOLVER (MIMS) FOR FLUID FLOW AND HEAT TRANSFER." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2371.
Повний текст джерелаАнотація:
Numerical methods for solving partial differential equations are commonplace in the engineering community and their popularity can be attributed to the rapid performance improvement of modern workstations and desktop computers. The ubiquity of computer technology has allowed all areas of engineering to have access to detailed thermal, stress, and fluid flow analysis packages capable of performing complex studies of current and future designs. The rapid pace of computer development, however, has begun to outstrip efforts to reduce analysis overhead. As such, most commercially available software packages are now limited by the human effort required to prepare, develop, and initialize the necessary computational models. Primarily due to the mesh-based analysis methods utilized in these software packages, the dependence on model preparation greatly limits the accessibility of these analysis tools. In response, the so-called meshless or mesh-free methods have seen considerable interest as they promise to greatly reduce the necessary human interaction during model setup. However, despite the success of these methods in areas demanding high degrees of model adaptability (such as crack growth, multi-phase flow, and solid friction), meshless methods have yet to gain notoriety as a viable alternative to more traditional solution approaches in general solution domains. Although this may be due (at least in part) to the relative youth of the techniques, another potential cause is the lack of focus on developing robust methodologies. The failure to approach development from a practical perspective has prevented researchers from obtaining commercially relevant meshless methodologies which reach the full potential of the approach. The primary goal of this research is to present a novel meshless approach called MIMS (Model Integrated Meshless Solver) which establishes the method as a generalized solution technique capable of competing with more traditional PDE methodologies (such as the finite element and finite volume methods). This was accomplished by developing a robust meshless technique as well as a comprehensive model generation procedure. By closely integrating the model generation process into the overall solution methodology, the presented techniques are able to fully exploit the strengths of the meshless approach to achieve levels of automation, stability, and accuracy currently unseen in the area of engineering analysis. Specifically, MIMS implements a blended meshless solution approach which utilizes a variety of shape functions to obtain a stable and accurate iteration process. This solution approach is then integrated with a newly developed, highly adaptive model generation process which employs a quaternary triangular surface discretization for the boundary, a binary-subdivision discretization for the interior, and a unique shadow layer discretization for near-boundary regions. Together, these discretization techniques are able to achieve directionally independent, automatic refinement of the underlying model, allowing the method to generate accurate solutions without need for intermediate human involvement. In addition, by coupling the model generation with the solution process, the presented method is able to address the issue of ill-constructed geometric input (small features, poorly formed faces, etc.) to provide an intuitive, yet powerful approach to solving modern engineering analysis problems.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
35
Castiglia, Davide. "Fluid flow and heat transfer in unconventional tube bundle arrangements in crossflow." Thesis, King's College London (University of London), 2002. https://kclpure.kcl.ac.uk/portal/en/theses/fluid-flow-and-heat-transfer-in-unconventional-tube-bundle-arrangements-in-crossflow(19f17b5f-6ea1-4f6c-9168-8e809d2495f7).html.
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36
Lucente, Carlin Miller. "COMPUTATIONAL ANALYSES FOR FLUID FLOW AND HEAT TRANSFER IN DIFFERENT CURVED GEOMETRIES." Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1337176681.
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37
Foong, Andrew Jun Li. "Heat transfer and fluid flow characteristics of microchannels with internal longitudinal fins." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/360.
Повний текст джерелаАнотація:
Electronic components generate large amount of heat during their operation, which requires to be dissipated. Over the past decade, internal heat generation levels have exponentially increased due to the compact packaging of high-powered microelectronic circuitry in modern devices. The efficient removal of this internally generated heat from microelectronic components is a critical design consideration for enabling optimum performance, and improving the operational reliability of modern high-performance electronic devices. Traditional cooling techniques such as fan-cooled heat sinks are grossly inadequate, and impose severe limits on product design, and hence cannot be used for cooling modern electronic components. Microchannel based cooling systems are highly popular due to its high surface area to volume ratio, and are identified as a highly viable practical alternative for meeting the current and future cooling needs of advanced electronic components. There are several methods to enhance the heat transfer performance of a microchannel. One of the single-phase heat transfer enhancement methods is to provide internal fins in a microchannel. The internal fins provide an increase in the surface area for heat transfer, and under certain conditions, alter the internal flow to provide an enhancement in heat transfer as compared to a microchannel without internal fins.In this thesis, a numerical study is performed to investigate the heat transfer and fluid flow characteristics of microchannels with four longitudinal internal fins. The simulations are carried out in the presence of a hydrodynamically fully developed, thermally developing laminar flow. Constant heat flux boundary conditions are assumed on the external walls of the microchannel. A range of channel aspect ratios covering square and rectangular cross-sectioned microchannels, with four internal longitudinal fins of various heights and thicknesses are considered in the modeling. Results of the velocity and temperature distribution are analysed in detail, to examine the effects of fin height and thickness on the heat transfer and fluid flow characteristics of the microchannels. Based on the range of parameters analysed, an optimum fin geometry that provides the maximum heat transfer rate is obtained from the analysis. The result of the optimum fin geometry is also obtained using the thermal resistance method of analysis. A thermodynamic analysis based on the entropy generation minimization method is carried out by estimating the irreversibility due to both heat transfer and fluid friction, in order to obtain the an optimum fin geometry. The optimum fin geometry obtained from the above methods are further compared, and is found to be similar. The comprehensive study carried out in this thesis provide more physical insight, and useful results on the heat and fluid flow characteristics of this potential single-phase passive heat transfer enhancement technique.
38
Steinke, Mark E. "Single-phase liquid flow and heat transfer in plain and enhanced silicon microchannels /." Link to online version, 2005. http://hdl.handle.net/1850/999.
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39
Ali, Rashid. "Phase Change Phenomena During Fluid Flow in Microchannels." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26796.
Повний текст джерелаАнотація:
Phase change phenomena of a fluid flowing in a micro channel may be exploited to make the heat exchangers more compact and energy efficient. Compact heat exchangers offer several advantages such as light weight, low cost, energy efficiency, capability of removing high heat fluxes and charge reduction are a few to mention. Phase change phenomena in macro or conventional channels have been investigated since long but in case of micro channels, fewer studies of phase change have been conducted and underlying phenomena during two-phase flow in micro channels are not yet fully understood. It is clear from the literature that the two-phase flow models developed for conventional channels do not perform well when extrapolated to micro scale. In the current thesis, the experimental flow boiling results for micro channels are reported. Experiments were conducted in circular, stainless steel and quartz tubes in both horizontal and vertical orientations. The internal diameters of steel tubes tested were 1.70 mm, 1.224 mm and the diameter of quartz tube tested was 0.781 mm. The quartz tube was coated with a thin, electrically conductive, transparent layer of Indium-Tin-Oxide (ITO) making simultaneous heating and visualization possible. Test tubes were heated electrically using DC power supply. Two refrigerants R134a and R245fa were used as working fluids during the tests. Experiments were conducted at a wide variety of operating conditions. Flow visualization results obtained with quartz tube clearly showed the presence of confinement effects and consequently an early transition to annular flow for micro channels. Several flow pattern images were captured during flow boiling of R134a in quartz tube. Flow patterns recorded during the experiments were presented in the form of Reynolds number versus vapour quality and superficial liquid velocity versus superficial gas velocity plots. Experimental flow pattern maps so obtained were also compared with the other flow pattern maps available in the literature showing a poor agreement. Flow boiling heat transfer results for quartz and steel tubes indicate that the heat transfer coefficient increases with heat flux and system pressure but is independent on mass flux and vapour quality. Experimental flow boiling heat transfer coefficient results were compared with those obtained using different correlations from the literature. Heat transfer experiments with steel tubes were continued up to dryout condition and it was observed that dryout conditions always started close to the exit of the tube. The dryout heat flux increased with mass flux and decreased with exit vapour quality. The dryout data were compared with some well known CHF correlations available in the literature. Two-phase frictional pressure drop for the quartz tube was also obtained under different operating conditions. As expected, two-phase frictional pressure drop increased with mass flux and exit vapour quality.QC 20101206
40
Yang, Tianliang, and 楊天亮. "Multiplicity and stability of flow and heat transfer in rotating curved ducts." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242571.
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41
Lloyd, S. "Fluid flow and heat transfer characteristics in the entrance regions of circular pipes." Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370795.
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42
Amin, Norsarahaida. "Oscillation-induced mean flows and heat transfer." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329339.
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43
Cole, Brian D. "Transient performance of parallel-flow and cross-flow direct transfer type heat exchangers with a step temperature change on the minimum capacity rate fluid stream. /." Online version of thesis, 1995. http://hdl.handle.net/1850/11924.
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44
Solnørdal, Christopher Baard. "Modelling of fluid flow and heat transfer in decaying swirl through a heated annulus /." Connect to thesis, 1992. http://eprints.unimelb.edu.au/archive/00001478.
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45
Parise, Ronald J. "A heat transfer and fluid flow model for the drawing of optical fibers." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/18221.
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46
Paniagua, Sánchez Leslye. "Three-dimensional numerical simulation of fluid flow and heat transfer in fin-and-tube heat exchangers at different flow regimes." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277561.
Повний текст джерелаАнотація:
This thesis aims at unifying two distinct branches of work within the Heat Transfer Technological Center (CTTC). On one side, extensive experimental work has been done during the past years by the researchers of the laboratory. This experimental work has been complemented with numerical models for the calculation of fin and tube heat exchangers thermal and fluid dynamic behavior. Such numerical models can be referred to as fast numerical tool which can be used for industrial rating and design purposes. On the other hand, the scientists working at the research center have successfully developed a general purpose multi-physics Computational Fluid Dynamics (CFD) code (TermoFluids). This high performance CFD solver has been extensively used by the co-workers of the group mainly to predict complex flows of great academic interest.
The idea of bringing together this two branches, comes from the necessity of a reliable numerical platform with detailed local data of the flow and heat transfer on diverse heat exchanger applications. Being able to use local heat transfer coefficients as an input on the rating and design tool will lead to affordable and accurate prediction of industrial devices performance, by which the center can propose enhanced alternatives to its industrial partners. To accomplish these goals, several contributions have been made to the existing TermoFluids software which is in continuous evolution in order to meet the competitive requirements. The most significant problematics to adequately attack this problem are analyzed and quite interesting recommendations are given. Some of the challenging arising issues involve the generation of suitable and affordable meshes, the implementation and validation of three dimensional periodic boundary condition and coupling of different domains with important adjustments for the study of cases with different flow physics like time steps and thermal development.
Turbulence is present in most of engineering flows, and refrigeration evaporator heat exchangers are not an exception. The presence of many tubes (acting like bluff bodies for the flow) arranged in different configurations and the fact that the flow is also confined by fins, create complex three dimensional flow features that have usually turbulent or transition to turbulent regime. Therefore, three dimensional turbulent forced convection in a matrix of wall-bounded pins is analyzed. Large Eddy Simulations (LES) are performed in order to assess the performance of three different subgrid-scale models, namely WALE, QR and VMS. The Reynolds numbers of the study were set to 3000, 10000 and 30000. Some of the main results included are the pressure coefficient around the cylinders, the averaged Nusselt number at the endwalls and vorticity of the flow.
The final part of the thesis is devoted to study the three dimensional fluid flow and conjugated heat transfer parameters encountered in a plate fin and tube heat exchanger used for no-frost refrigeration. The numerical code and post processing tools are validated with a very similar but smaller case of a heat exchanger with two rows of tubes at low Reynolds for which experimental data is available. The next analysis presented is a typical configuration for no-frost evaporators with double fin spacing (for which very few numerical data is reported in the scientific literature). Conjugated convective heat transfer in the flow field and heat conduction in the fins are coupled and considered. The influence of some geometrical and flow regime parameters is analyzed for design purposes. In conclusion, the implementations and general contributions of the present thesis together with the previous existent multi-physics computational code, has proved to be capable to perform successful top edge three dimensional simulations of the flow features and heat transfer mechanisms observed on heat exchanger devices.Esta tesis tiene como objetivo unificar dos ramas de trabajo dentro del Centro Tecnológico de Transferencia de Calor (CTTC). Por un lado, se ha realizado un amplio trabajo experimental durante los últimos años. Este trabajo experimental se ha complementado con modelos numéricos para el estudio de intercambiadores de calor de tipo aleta-tubo. Tales modelos numéricos pueden considerarse una herramienta numérica de bajo coste empleada con propósitos de diseño principalmente. Por otro lado, los científicos que trabajan en el centro han desarrollado con éxito un código de Dinámica de Fluidos Computacionales (TermoFluids). Este código de alto rendimiento ha sido ampliamente utilizado principalmente para predecir flujos complejos de gran interés académico. La idea de unir a estas dos ramas, proviene de la necesidad de una plataforma numérica fiable con datos locales propios del flujo y de la transferencia de calor en diversas aplicaciones de intercambiadores de calor. Ser capaz de generar coeficientes locales de transferencia de calor para abastecer con datos propios los modelos existentes de bajo coste, permitirá la correcta predicción del rendimiento de dichos dispositivos. Para lograr estos objetivos, se han hecho varias contribuciones al código TermoFluids que está en continua evolución. Algunas de las mayores cuestiones que se plantean implican la generación de mallas adecuadas y asequibles, la implementación y validación de la condición de contorno periódica tridimensional y el acoplamiento de los diferentes dominios para el estudio de casos con diferentes comportamientos físicos, como desarrollo transitorio e inercia térmica. La turbulencia está presente en la mayoría de los flujos de ingeniería, y los intercambiadores de calor de evaporadores para refrigeración no son una excepción. La presencia de muchos tubos (que actúan como obstáculos para el fluido) colocados en diferentes configuraciones y el hecho de que el flujo también está confinado por aletas, crean características de flujo tridimensionales complejas que tienen generalmente régimen turbulento o en transición. Por lo tanto, se analiza la convección forzada turbulenta en una matriz de pines delimitados por paredes. simulando las grandes escalas de turbulencia y modelando las pequeñas (LES) con el fin de evaluar el desempeño de los tres modelos seleccionados, a saber WALE, QR y VMS. Los números de Reynolds establecidos para el estudio son 3000, 10000 y 30000. Algunos de los principales resultados que se incluyen son el coeficiente de presión alrededor los cilindros, el número de Nusselt promedio en las paredes y la vorticidad del flujo. La parte final de la tesis se dedica a estudiar el flujo tridimensional y los parámetros de transferencia de calor encontrados en un intercambiador de calor de tipo aleta-tubo utilizado para la refrigeración doméstica en equipos de 'no-escarcha'. Las implementaciones del código y el postproceso numéricos se validan en un caso muy similar para un intercambiador de calor con dos filas de tubos a bajos Reynolds para el cual se dispone de datos experimentales. El siguiente análisis que se presenta es una configuración típica para evaporadores 'no-escarcha' con paso de aleta doble (para el que se tiene muy poca información numérica en la literatura). Se considera el acoplamiento conjugado de la transferencia de calor convectiva entre fluido y sólido y conductiva dentro de la aleta. La influencia de algunos parámetros geométricos y de régimen de flujo se analizan con propósitos de diseño. En conclusión, las contribuciones generales de esta tesis junto con el código computacional ya existente, ha demostrado ser capaz de realizar con éxito simulaciones tridimensionales para predecir las características del flujo y los mecanismos responsables de la transferencia de calor en intercambiadores de calor de tipo aleta-tubo
47
Ettrich, Jörg [Verfasser], and B. [Akademischer Betreuer] Nestler. "Fluid Flow and Heat Transfer in Cellular Solids / Jörg Ettrich. Betreuer: B. Nestler." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1053704038/34.
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48
Kim, Man-Woong. "Effect of transverse convex surface curvature on turbulent fluid flow and heat transfer." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10183.
Повний текст джерелаАнотація:
The effect of transverse convex surface curvature on turbulent boundary layer flow and heat transfer over circular cylinders, and on fully developed turbulent flow and heat transfer in concentric annular ducts with smooth surfaces are studied both analytically and experimentally. The analytical results are obtained through a turbulence model based on the variable von Karman's constants, $\rm\kappa\sb{i}$, proposed for the first time in the present study. A computer program is developed for calculation of the desired momentum and thermal characteristics. A numerical calculation using the standard k-$\varepsilon$ turbulence model, with a modified procedure is also carried out. It is assumed that the thermodynamic fluid properties are independent of temperature. An experimental study is conducted to study the effect of the transverse convex surface curvature of the core tubes both on fully developed turbulent flows and heat transfer in concentric annular ducts. Air is used as the working fluid. Three annuli having different radii of the inner cores, R$\rm\sb{i}$ = 3.98 mm, 8.57 mm, and 16.7 mm, with a fixed radius ratio of $\alpha$ = 0.3, are used over a range of the Reynolds number between about 20,000 and 60,000. The inner cores are heated electrically to provide constant heat fluxes throughout the test sections and are instrumented for the temperature and power measurements. The outer tubes are insulated to minimize the leakage of heat. In the case of the experimental study for turbulent boundary layer flows and heat transfer on circular cylinders, the experimental data of Willmarth et al. (31) and Kim and Lee (45, 46) are recompiled for the present study. It is seen that both the friction coefficient and heat transfer increase with decreasing value of the inner core radius of concentric annuli and the radius of circular cylinders, R$\rm\sb{i}$ It is concluded that, while the effect of transverse concave curvature on fluid flow and heat transfer is negligible, that of transverse convex curvature is rather significant.
49
Lin, Xiang Wen. "Numerical study of unsteady heat transfer and fluid flow over a bluff body." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341453.
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50
Zhang, Qing Jun. "CFD simulations of fluid flow and heat transfer in a model milk vat." Thesis, University of Canterbury. Chemical and Process Engineering, 1998. http://hdl.handle.net/10092/6887.
Повний текст джерелаАнотація:
To ensure that raw milk quality is maintained during storage, milk needs to be chilled and kept at a certain temperature. To prevent the milk from creaming and to provide uniform temperature distribution, the milk needs to be smoothly stirred. Thus the milk storage process combines heat transfer and fluid flow.
This work is part of a project studying the optimisation of the design and operation of farm milk vats used for storing milk awaiting collection on New Zealand dairy farms. It concentrates on CFD simulations of the fluid flow and heat transfer in an unbaffled agitated model milk vats, In previous experimental work, fresh tap water was used instead of milk, as a medium to minimise costs and heat transfer coefficients were measured for the heating process, instead of cooling. The CFD simulations in this work were also performed for heating instead of cooling of the fluid in the vat to permit comparison with available experimental results. The geometry simulated was that of the experimental milk vat in the laboratory, being a one-third linear scale model of a commercial vat.
Computational Fluid Dynamics (CFD) package, CFX4.1, was used to solve the three-dimensional fluid flow and heat transfer in the milk vat. The impeller boundaries were directly simulated using the rotating reference frame.
The solution accuracy has been numerically examined using a set of different sized grids and two turbulence models, the k-ε model and the DS model. It was found that the DS model gave better prediction than the k-ε model, but required excessive computing time. Balancing the simulation results and the available computing facility, the k-ε model in conjunction with the rotating reference frame fixed on the impeller has been employed in this work.
The simulated impeller rotational speed ranged from 18 rpm up to 117 rpm, with the corresponding Reynolds number of about 20,000 to 144,000 resulting fully turbulent flow. The simulations of fluid flow for the batch operation mode show that the higher the impeller speed, the stronger the circulation flow is, and therefore the larger the impeller pumping capacity. However, both the pumping number and the circulation number are almost independent of the impeller speed.
To provide a steady state heat transfer process, a cooling liquid stream was introduced to the milk vat directly. This was defined as the continuous operation mode. The incoming liquid affects the discharge flow produced by the impeller, and therefore the circulation flow, but this effect is not significant at the high Reynolds numbers.
The predicted heat transfer coefficients were compared with the available experimental data. The comparison shows that the k-ε model in conjunction with heat transfer can give a reasonable prediction of the heat transfer coefficients in the range of Reynolds number simulated.