Dissertations / Theses: 'Fluid flow; Combustion; Heat transfer'

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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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Kedukodi, Sandeep. "Numerical Analysis of Flow and Heat Transfer through a Lean Premixed Swirl Stabilized Combustor Nozzle." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77393.

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While the gas turbine research community is continuously pursuing development of higher cyclic efficiency designs by increasing the combustor firing temperatures and thermally resistant turbine vane / blade materials, a simultaneous effort to reduce the emission levels of high temperature driven thermal NOX also needs to be addressed. Lean premixed combustion has been found as one of the solutions to these objectives. However, since less amount of air is available for backside cooling of liner walls, it becomes very important to characterize the convective heat transfer that occurs on the inside wall of the combustor liners. These studies were explored using laboratory scale experiments as well as numerical approaches for several inlet flow conditions under both non-reacting and reacting flows. These studies may be expected to provide valuable insights for the industrial design communities towards identifying thermal hot spot locations as well as in quantifying the heat transfer magnitude, thus aiding in effective designs of the liner walls. Lean premixed gas turbine combustor flows involve strongly coupled interactions between several aspects of physics such as the degree of swirl imparted by the inlet fuel nozzle, premixing of the fuel and incoming air, lean premixed combustion within the combustor domain, the interaction of swirling flow with combustion driven heat release resulting in flow dilation, the resulting pressure fluctuations leading to thermo-acoustic instabilities there by creating a feedback loop with incoming reactants resulting in flow instabilities leading to flame lift off, flame extinction etc. Hence understanding combustion driven swirling flow in combustors continues to be a topic of intense research. In the present study, numerical predictions of swirl driven combustor flows were analyzed for a specific swirl number of an industrial fuel nozzle (swirler) using a commercial computational fluid dynamics tool and compared against in-house experimental data. The latter data was obtained from a newly developed test rig at Applied Propulsion and Power Laboratory (APPL) at Virginia Tech. The simulations were performed and investigated for several flow Reynolds numbers under non-reacting condition using various two equation turbulence models as well as a scale resolving model. The work was also extended to reacting flow modeling (using a partially premixed model) for a specific Reynolds number. These efforts were carried out in order investigate the flow behavior and also characterize convective heat transfer along the combustor wall (liner). Additionally, several parametric studies were performed towards investigating the effect of combustor geometry on swirling flow and liner hear transfer; and also to investigate the effect of inlet swirl on the jet impingement location along the liner wall under both non-reacting as well as reacting conditions. The numerical results show detailed comparison against experiments for swirling flow profiles within the combustor under reacting conditions indicating a good reliability of steady state modeling approaches for reacting conditions; however, the limitations of steady state RANS turbulence models were observed for non-reacting swirling flow conditions, where the flow profiles deviate from experimental observations in the central recirculation region. Also, the numerical comparison of liner wall heat transfer characteristics against experiments showed a sensitivity to Reynolds numbers. These studies offer to provide preliminary insights of RANS predictions based on commercial CFD tools in predicting swirling, non-reacting and reacting flow and heat transfer. They can be extended to reacting flow heat transfer studies in future and also may be upgraded to unsteady LES predictions to complement future experimental observations conducted at the in-house test facility.
Ph. D.

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Shinde, Pradeep R. "Investigation of Low Reynolds Number Flow and Heat Transfer of Louvered Surfaces." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3038.

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This study focuses on the investigation of flow behavior at low Reynolds numbers by the experimental and numerical performance testing of micro-channel heat exchangers. An experimental study of the heat transfers and pressure drop of compact heat exchangers with louvered fins and flat tubes was conducted within a low air-side Reynolds number range of 20 < ReLp < 225. Using an existing low-speed wind tunnel, 26 sample heat exchangers of corrugated louver fin type, were tested. New correlations for Colburn j and Fanning friction f factor have been developed in terms of non-dimensional parameters. Within the investigated parameter ranges, it seems that both the j and f factors are better represented by two correlations in two flow regimes (one for ReLp = 20 – 80 and one for ReLp = 80 – 200) than a single regime correlation in the power-law format. The results support the conclusion that airflow and heat transfer at very low Reynolds numbers behaves differently from that at higher Reynolds numbers. The effect of the geometrical parameters on the heat exchanger performance was investigated. The numerical investigation was conducted for further understanding of the flow behavior at the range of experimentally tested Reynolds number. Ten different heat exchanger geometries with varied geometrical parameters obtained for the experimental studies were considered for the numerical investigation. The variations in the louver angle were the basis of the selection. The heat transfer and pressure drop performance was numerically investigated and the effect of the geometrical parameters was evaluated. Numerical results were compared against the experimental results. From the comparison, it is found that the current numerical viscous laminar models do not reflect experimentally observed transitional two regime flow behavior from fin directed to the louver directed at very low Reynolds number ranging from 20 to 200. The flow distribution through the fin and the louver region was quantified in terms of flow efficiency. The flow regime change was observed at very low Reynolds number similar to the experimental observations. However, the effect of two regime flow change does not reflect on the thermal hydraulic performance of numerical models. New correlations for the flow efficiency � have developed in terms of non-dimensional parameters.

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Liewkongsataporn, Wichit. "A numerical study of pulse-combustor jet impingement heat transfer." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22651.

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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.
Committee Co-Chair: Ahrens, Fred; Committee Co-Chair: Patterson, Tim; Committee Member: Aidun, Cyrus; Committee Member: Empie, Jeff; Committee Member: Frederick, Jim.

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Zhang, Huaibao. "HIGH TEMPERATURE FLOW SOLVER FOR AEROTHERMODYNAMICS PROBLEMS." UKnowledge, 2015. https://uknowledge.uky.edu/me_etds/64.

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A weakly ionized hypersonic flow solver for the simulation of reentry flow is firstly developed at the University of Kentucky. This code is the fluid dynamics module of known as Kentucky Aerothermodynamics and Thermal Response System (KATS). The solver uses a second-order finite volume approach to solve the laminar Navier– Stokes equations, species mass conservation and energy balance equations for flow in chemical and thermal non-equilibrium state, and a fully implicit first-order backward Euler method for the time integration. The hypersonic flow solver is then extended to account for very low Mach number flow using the preconditioning and switch of the convective flux scheme to AUSM family. Additionally, a multi-species preconditioner is developed. The following part of this work involves the coupling of a free flow and a porous medium flow. A new set of equation system for both free flows and porous media flows is constructed, which includes a Darcy–Brinkmann equation for momentum, mass conservation, and energy balance equation. The volume-average technique is used to evaluate the physical properties in the governing equations. Instead of imposing interface boundary conditions, this work aims to couple the free/porous problem through flux balance, therefore, flow behaviors at the interface are satisfied implicitly.

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Nelson, Lauren May. "Rayleigh Flow of Two-Phase Nitrous Oxide as a Hybrid Rocket Nozzle Coolant." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/284.

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The Mechanical Engineering Department at California Polytechnic State University in San Luis Obispo currently maintains a lab-scale hybrid rocket motor for which nitrous oxide is utilized as the oxidizer in the combustion system. Because of its availability, the same two-phase (gas and liquid) nitrous oxide that is used in the combustion system is also routed around the throat of the hybrid rocket’s converging-diverging nozzle as a coolant. While this coolant system has proven effective empirically in previous tests, the physics behind the flow of the two-phase mixture is largely unexplained. This thesis provides a method for predicting some of its behavior by modeling it using the classic gas dynamics scenarios of Rayleigh and Fanno flows which refer to one-dimensional, compressible, inviscid flow in a constant area duct with heat addition and friction. The two-phase model produced utilizes a separated phase with interface exchange model for predicting whether or not dryout occurs. The Shah correlation is used to predict heat transfer coefficients in the nucleate boiling regime. The homogeneous flow model is utilized to predict pressure drop. It is proposed that a Dittus-Boelter based correlation much like that of Groeneveld be developed for modeling heat transfer coefficients upon the collection of sufficient data. Data was collected from a series of tests on the hybrid rocket nozzle to validate this model. The tests were first run for the simplified case of an ideal gas (helium) coolant to verify the experimental setup and promote confidence in subsequent two-phase experimental results. The results of these tests showed good agreement with a combined Rayleigh-Fanno model with a few exceptions including: (1) reduced experimental gas pressure and temperature in the annulus entrance and exit regions compared to the model and (2) reduced experimentally measured copper temperatures uniformly through the annulus. These discrepancies are likely explained by the geometry of the flowpath and location of the copper thermocouples respectively. Next, a series of two-phase cooled experiments were run. Similar trends were seen to the helium experiment with regards to entrance and exit regions. The two-phase Rayleigh homogeneous flow model underpredicted pressure drop presumably due to the inviscid assumption. Ambiguity was observed in the fluid temperature measurements but the trend seemed to suggest that mild thermal non-equilibrium existed. In both cases, the dryout model predicted that mist flow (a post-CHF regime) occurred over most of the annulus. Several modifications should be implemented in future endeavors. These include: (1) collecting more data to produce a heat transfer coefficient correlation specific to the nitrous oxide system of interest, (2) accounting for thermal non-equilibrium, (3) accounting for entrance and exit effects, and (4) developing a two-phase Fanno model.

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Psimas, Michael J. "Experimental and numerical investigation of heat and mass transfer due to pulse combustor jet impingement." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33863.

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Under certain circumstances pulse combustors have been shown to improve both heat transfer and drying rate when compared to steady flow impingement. Despite this potential, there have been few investigations into the use of pulse combustor driven impingement jets for industrial drying applications. The research presented here utilized experimental and numerical techniques to study the heat transfer characteristics of these types of oscillating jets when impinging on solid surfaces and the heat and mass transfer when drying porous media. The numerical methods were extensively validated using laboratory heat flux and drying data, as well as correlations from literature. As a result, the numerical techniques and methods that were developed and employed in this work were found to be well suited for the current application. It was found that the pulsating flows yielded elevated heat and mass transfer compared to similar steady flow jets. However, the numerical simulations were used to analyze not just the heat flux or drying, but also the details of the fluid flow in the impingement zone that resulted in said heat and mass transport. It was found that the key mechanisms of the enhanced transfer were the vortices produced by the oscillating flow. The characteristics of these vortices such as the size, strength, location, duration, and temperature, determined the extent of the improvement. The effects of five parameters were studied: the velocity amplitude ratio, oscillation frequency, the time-averaged bulk fluid velocity at the tailpipe exit, the hydraulic diameter of the tailpipe, and the impingement surface velocity. Analysis of the resulting fluid flow revealed three distinct flow types as characterized by the vortices in the impingement zone, each with unique heat transfer characteristics. These flow types were: a single strong vortex that dissipated before the start of the next oscillation cycle, a single persistent vortex that remained relatively strong at the end of the cycle, and a strong primary vortex coupled with a short-lived, weaker secondary vortex. It was found that the range over which each flow type was observed could be classified into distinct flow regimes. The secondary vortex and persistent vortex regimes were found to enhance heat transfer. Subsequently, transition criteria dividing these regimes were formed based on dimensionless parameters. The critical dimensionless parameters appeared to be the Strouhal number, a modified Strouhal number, the Reynolds number, the velocity amplitude ratio, and the H/Dh ratio. Further study would be required to determine if these parameters offer similar significance for other configurations.

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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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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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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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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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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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Matys, Paul. "Fluid flow and heat transfer in continuous casting processes." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28504.

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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

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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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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.

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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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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." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2025.

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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.

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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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Luo, Xi. "Study of Periodical Flow Heat Transfer in an Internal Combustion Engine." Thesis, Wayne State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10637206.

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In-cylinder heat transfer is one of the most critical physical behaviors which has a direct influence on engine out emission and thermal efficiency for IC engine. In-cylinder wall temperature has to be precisely controlled to achieve high efficiency and low emission. However, this cannot be done without knowing gas-to-wall heat flux. This study reports on the development of a technique suitable for engine in-cylinder surface temperature measurement, as the traditional method is “hard to reach.” A laser induced phosphorescence technique was used to study in-cylinder wall temperature effects on engine out unburned hydrocarbons during the engine transitional period (warm up). A linear correlation was found between the cylinder wall surface temperature and the unburned hydrocarbons at mediate and high charge densities. At low charge density, no clear correlation was observed because of miss-fire events. A new auto background correction infrared (IR) diagnostic was developed to measure the instantaneous in-cylinder surface temperature at 0.1 CAD resolution. A numerical mechanism was designed to suppress relatively low-frequency background noise and provide an accurate in-cylinder surface temperature measurements with an error of less than 1.4% inside the IC engine. In addition, a proposed optical coating reduced time delay errors by 50% compared to more conventional thermocouple techniques. A new cycle-averaged Re_s number was developed for an IC engine to capture the characteristics of engine flow. Comparison and scaling between different engine flow parameters are available by matching the averaged Re_s number. From experimental results, the engine flow motion was classified as intermittently turbulent, and it is different from the original fully developed turbulent assumption, which has previously been used in almost all engine simulations. The intermittent turbulence could have a great impact on engine heat transfer because of the transitional turbulence effect. Engine 3D CFD model further proves the existence of transitional turbulence flow. A new multi zone heat transfer model is proposed for IC engines only. The model includes pressure work effects and improved heat transfer prediction compared to the standard Law of the wall model.

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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.

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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)

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Maier, Andreas. "Geometric parameters influencing IC engine inlet valve flow and heat transfer." Thesis, University of Sunderland, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298001.

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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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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.

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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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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.

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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.

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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/.

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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.

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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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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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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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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.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O 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.

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31

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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32

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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33

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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34

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.

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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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35

Levy, Jean-Francois. "Prediction of flow, combustion and heat transfer in coal fired cement kilns." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46886.

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36

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/.

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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.

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37

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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38

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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39

Nakamura, Masamichi, and Kazuhiro Yamamoto. "Simulation on Flow and Heat Transfer in Diesel Particulate Filter." ASME (American Society of Mechanical Engineers), 2011. http://hdl.handle.net/2237/19976.

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40

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.

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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

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41

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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42

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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43

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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44

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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45

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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46

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.

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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

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47

Mayo, David Earl Jr. "The Effect of Combustor Exit to Nozzle Guide Vane Platform Misalignment on Heat Transfer over an Axisymmetric Endwall at Transonic Conditions." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78110.

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This paper presents details of an experimental and computational investigation on the effect of misalignment between the combustor exit and nozzle guide vane endwall on the heat transfer distribution across an axisymmetric converging endwall. The axisymmetric converging endwall investigated was representative of that found on the shroud side of a first stage turbine nozzle section. The experiment was conducted at a nominal exit M of 0.85 and exit Re 1.5 x 10⁶ with an inlet turbulence intensity of 16%. The experiment was conducted in a blowdown transonic linear cascade wind tunnel. Two different inlet configurations were investigated. The first configuration, Case I, was representative of a combustor exit aligned to the nozzle platform, with a gap located at the interface of the tow components. The second configuration, Case II, the endwall platform was offset in the span-wise direction to create a backward facing step at the inlet. This step is representative of a misalignment between the combustor exit and the NGV platform. An infrared camera was used to capture the temperature history on the endwall, from which the endwall heat transfer distribution was determined. A numerical study was also conducted by solving RANS equations using ANSYS Fluent v.15. The numerical results provided insight into the passage flow field which explained the observed heat transfer characteristics. Case I showed the typical characteristics of transonic vane cascade flow, such as the separation line, saddle point, and horseshoe vortices. The presence of a gap at the combustor-nozzle interface facilitated the formation of a separated flow which propagated through the passage. This flow feature caused the passage vortex reattach to the SS vane at 0.44 x/C. The addition of the platform misalignment in Case II caused the flow reattachment region to occur near the vane LE plane. The separated flow which formed at the inlet step, merged with the recirculation region on the endwall platform, forming two counter-rotating auxiliary vortices. These vortices significantly delayed migration of the passage vortex, causing it to reattach on the SS vane at 0.85 x/C. These two flow features also had a significant effect on the endwall heat transfer characteristics. The heat transfer levels on the endwall platform, from -0.50 to +0.50 Cx relative to the vane LE, had an average increase of ~40%. However, downstream of the vane mid-passage, the heat transfer levels showed no appreciable heat transfer augmentation due to flow acceleration through the passage throat.
Master of Science

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48

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.

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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

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49

Gokaltun, Seckin. "Lattice Boltzmann Method for Flow and Heat Transfer in Microgeometries." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/64.

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Recent technological developments have made it possible to design various microdevices where fluid flow and heat transfer are involved. For the proper design of such systems, the governing physics needs to be investigated. Due to the difficulty to study complex geometries in micro scales using experimental techniques, computational tools are developed to analyze and simulate flow and heat transfer in microgeometries. However, conventional numerical methods using the Navier-Stokes equations fail to predict some aspects of microflows such as nonlinear pressure distribution, increase mass flow rate, slip flow and temperature jump at the solid boundaries. This necessitates the development of new computational methods which depend on the kinetic theory that are both accurate and computationally efficient. In this study, lattice Boltzmann method (LBM) was used to investigate the flow and heat transfer in micro sized geometries. The LBM depends on the Boltzmann equation which is valid in the whole rarefaction regime that can be observed in micro flows. Results were obtained for isothermal channel flows at Knudsen numbers higher than 0.01 at different pressure ratios. LBM solutions for micro-Couette and micro-Poiseuille flow were found to be in good agreement with the analytical solutions valid in the slip flow regime (0.01 < Kn < 0.1) and direct simulation Monte Carlo solutions that are valid in the transition regime (0.1 < Kn < 10) for pressure distribution and velocity field. The isothermal LBM was further extended to simulate flows including heat transfer. The method was first validated for continuum channel flows with and without constrictions by comparing the thermal LBM results against accurate solutions obtained from analytical equations and finite element method. Finally, the capability of thermal LBM was improved by adding the effect of rarefaction and the method was used to analyze the behavior of gas flow in microchannels. The major finding of this research is that, the newly developed particle-based method described here can be used as an alternative numerical tool in order to study non-continuum effects observed in micro-electro-mechanical-systems (MEMS).

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50

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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Dissertations / Theses on the topic 'Fluid flow; Combustion; Heat transfer'

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