Abstract: INTRODUCTION Vector and Tensor Notations Fundamental Concepts and Definitions Eulerian and Lagrangian Descriptions Properties of a System Conductive Heat Transfer Convective Heat Transfer Radiation Heat Transfer Phase Change Heat Transfer Conservation of Energy Problems CONDUCTION HEAT TRANSFER Introduction One-Dimensional Heat Conduction Thermal and Contact Resistances Fins and Extended Surfaces Multidimensional Heat Conduction Graphical Solution Methods Analytical Methods Transient Heat Conduction Combined Transient and Spatial Effects References Problems CONVECTIVE HEAT TRANSFER Introduction Convection Governing Equations Velocity and Thermal Boundary Layers External Forced Convection Internal Forced Convection Free Convection Second Law of Thermodynamics Turbulence Modelling References Problems RADIATIVE HEAT TRANSFER Introduction Fundamental Processes and Equations Radiation Exchange Between Surfaces Thermal Radiation in Enclosures with Diffuse Gray Surfaces Solar Energy References Problems PHASE CHANGE HEAT TRANSFER Introduction Processes of Phase Change Mixture and Two-Fluid Formulations Interface Tracking References Problems GAS (VAPOR) - LIQUID SYSTEMS Introduction Boiling Heat Transfer Condensation Heat Transfer Devices with Vapor - Liquid Phase Change References Problems GAS - SOLID (PARTICLE) SYSTEMS Introduction Classification of Gas - Solid Flows Dynamics of Gas - Solid Flows Fluidized Beds References Problems LIQUID - SOLID SYSTEMS Introduction One-Dimensional Solidification and Melting Phase Change with Convection Phase Change with Coupled Heat and Mass Transfer Problems in Other Geometries Multi-Dimensional Solidification and Melting Dynamics of Liquid - Solid Flows Applications References Problems GAS -LIQUID - SOLID SYSTEMS Introduction Droplet Flows with Phase Change Gas Flows with Solidification and Melting Chemically Reacting Systems Multiphase Byproducts of Reacting Flows References Problems HEAT EXCHANGERS Introduction Tubular Heat Exchangers Cross-Flow and Shell-and-Tube Heat Exchangers Effectiveness - NTU Method of Analysis Condensers and Evaporators References Problems COMPUTATIONAL HEAT TRANSFER Finite Difference Methods Weighted Residual Methods Finite Element Method Hybrid Methods Numerical Methods for Other Applications Accuracy and Efficiency Improvements References Problems APPENDICES INDEX

Abstract: The performance correlations for the effectiveness of heat and moisture transfer processes in an enthalpy exchanger with membrane cores are presented. The physical phenomena relevant to the heat and moisture transfer in these devices have been used to develop a novel set of correlations based on the relevant dimensionless parameters. The total enthalpy effectiveness can be calculated from sensible effectiveness, latent effectiveness, and the ratio of latent to sensible energy differences across the unit. Studies show that the sensible effectiveness is a function of NTU, the number of transfer units for heat; while the latent effectiveness is a function ofNTUL, the number of transfer units for moisture. The relations between NTUL and NTU are derived and studied with the proper separation of moisture resistance for membranes. This newly developed dimensionless parameter, NTUL, is to summarize the sorption characteristics of membrane material, the exchanger configurations, as well as the operating conditions. A number of experimental results on an enthalpy exchanger with novel hydrophilic membrane cores has been used to valid these correlations. @DOI: 10.1115/1.1469524#

Abstract: An experimental study for air-side thermal-hydraulic performance of brazed aluminum heat exchangers under dehumidifying conditions has been performed. For 30 samples of louvered fin heat exchangers with different geometrical parameters, the heat transfer and pressure drop characteristics for wet surface were evaluated. The test was conducted for air-side Reynolds number in the range of 80–300 and tube-side water flow rate of 320 kg/h. The dry- and wet-bulb temperatures of the inlet air for heat exchangers were 27 and 19 °C, respectively and the inlet water temperature was 6 °C. The air-side thermal performance data for cooling and dehumidifying conditions were analyzed using effectiveness- NTU method for cross-flow heat exchanger with both fluids unmixed. The test results are reported, compared with those for the dry surface heat exchangers, in terms of sensible j factor and friction factor f , as functions of Reynolds number based on louver pitch. The correlations for j and f factors are developed within rms errors of ±16.9 and ±13.6%, respectively.

Abstract: This article presents a study on heat transfer in condensation of pure and mixtures of hydrocarbons in a compact welded plate heat exchanger. Three pure fluids (pentane, butane, and propane) and two mixtures (butane + propane) have been used. The operating pressure ranges from 1.5 to 18 bar. For pure fluids, two heat transfer mechanisms have been identified. For low Reynolds numbers, the condensation occurs almost filmwise and the heat transfer coefficient decreases with increasing Reynolds number. For higher values of the Reynolds number, the heat transfer coefficient increases gently. The transition between the two regimes is between Re = 100 and 1,000 and depends on the operating conditions. For mixtures, the behavior is different. For low Reynolds numbers, mass transfer affects heat transfer and reduces the heat transfer coefficient by a factor of up to 4. Correlations for filmwise and in-tube condensation do not predict the results accurately, and a specific correlation is proposed for pure fluid condensation. For mixtures, the condensation curve method does not allow mass transfer effects to be taken into account, and more work is required to establish an accurate predictive model.

Abstract: Jet-refrigeration cycles seem to provide an interesting solution to the increasing interest in environment protection and the need for energy saving due to their low plant costs, reliability and possibility to use water as operating fluid. A steam/steam ejector cycle refrigerator is investigated introducing a two-stage ejector with annular primary at the second stage. The steady_state refrigerator, exchanging heat with the water streams at inlet fixed temperatures at the three shell and tube heat exchangers, evaporator, condenser and generator, is considered as an open system. Heat transfer irreversibilities in the heat exchangers and external friction losses in the water streams are considered, ignoring the internal pressure drop of the vapor. A simulation program numerically searches the maximum COP at given external inlet fluid temperatures as a function of mass flows, dimensions and temperature differences in the heat exchangers. The code gives the ejector and heat exchangers design parameters.

Abstract: A waste heat source (100) is used to heat a high temperature heat transfer fluid which is used to heat an absorption heat transfer machine (10) having a generator (20), an absorber (30), a condenser (40), and an evaporator (50) operatively connected together. The high temperature heat transfer fluid can also be used to heat a load (190) such as a room space or a process. The waste heat source (100) can also be used to heat an intermediate heat transfer fluid, which can be used to heat a second load (175) such as a space, a process, or an absorption heat transfer machine. Novel flow control devices (70, 60) for controlling the flow of weak sluution from generator (20) to absorber (30) or of refrigerant from condenser (40) to evaporator (50), respectively, are also described.

Abstract: A distillation column with the possibility of heat exchange on every tray (a fully diabatic column) is optimized in the sense of minimizing its total entropy production. This entropy production counts the interior losses due to heat and mass flow as well as the entropy generated in the heat exchangers. It is observed that the optimal heating distribution, i.e. the heat exchange required on each tray, is essentially the same for all trays in the stripping and rectification sections, respectively. This makes a column design with consecutive interior heat exchanger and only one exterior supply for each of the two sections very appealing. The result is only slightly dependent on the heat transfer law considered. In the limit of an infinite number of trays even this column with resistance to transfer of heat becomes reversible.

Abstract: Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540–550, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10056

Abstract: This paper studies the use of fins with embedded wave-type vortex generators to enhance heat transfer in fin-tube heat exchangers. An infrared thermovision is used to visualize the temperature distribution on the surface of a scaled-up plain fin and upon fins with embedded vortex generators. Numerical methods are used to investigate the conjugate heat transfer and to perform a 3-D turbulence analysis of the heat transfer and fluid flow associated with wave-type vortex generators embedded fins. The current results indicate that heat transfer and friction losses are strongly dependent on the geometric parameters of the vortex generators. This study identifies a maximum improvement of 120% in the local heat transfer coefficient and an improvement of 18.5% in the average heat transfer coefficient. Furthermore, it is found that a reduction in fin area of approximately 18-20% may be obtained if vortex generators embedded fins are used in place of plain fins. Finally, it is noted that the magnitude of the attain...

Abstract: A method of modeling a heat exchanger is disclosed and comprises assigning input temperatures, assumed output temperatures, and a set of flow rates, inputting the parameters into a set of equations arranged to calculate a heat transfer coefficient, inputting parameters into a second set of equations arranged to calculate output temperatures, substituting actual output temperatures for the assumed output temperatures, and again calculating the heat transfer cooefficient. The new heat transfer coefficient is then used to obtain revised actual output temperatures, and the initial actual output temperatures and the revised actual output temperatures are compared to determine whether they differ by less than a desired variance. If not, a new iteration is performed until the output temperatures converge.

Abstract: This paper reports on experiments to evaluate the effectiveness of delta-wing vortex generators applied to fin-and-tube heat exchangers. For air flowing at Reynolds numbers from about 700 to 2300, Colburn j and friction factor f data are obtained for a conventional refrigerator evaporator with and without a single row of delta-wing vortex generators placed at the inlet face of the test heat exchanger. Colburn j factor enhancements up to 31% over the baseline were obtained, without any pressure-drop penalties. The data confirm the promise for this method of heat transfer augmentation in plain-fin-and-tube heat exchanger applications, and provide a basis for improving heat exchanger performance.

Abstract: The performance optimization of an irreversible simple Brayton refrigerator coupled to constant-temperature heat reservoirs is carried out by taking the cooling load density, i.e., the ratio of cooling load to the maximum specific volume in the cycle, as the optimization objective using finite-time thermodynamics (FTT) or entropy generation minimization (EGM) in this paper. The analytical formulae about the relations between cooling load density and pressure ratio, as well as between coefficient of performance (COP) and pressure ratio are derived with the heat resistance losses in the hot- and cold-side heat exchangers, and the irreversible compression and expansion losses in the compressor and expander. The influences of the effectiveness of the heat exchangers, the temperature ratio of the reservoirs, and the efficiencies of the compressor and expander on the cooling load density versus COP are provided by numerical examples. The cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, and searching the optimum distribution of heat conductance of the hot- and cold-side heat exchangers for the fixed total heat exchanger inventory. The influences of some design parameters, including the effectiveness of the heat exchangers between the working fluid and heat reservoirs, the efficiencies of compressor and expander, the temperature ratio of heat reservoirs, on the maximum cooling load density, the optimum heat conductance distribution and the optimum pressure ratio are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander, and the hot- and cold-side heat exchangers.

Abstract: One of the most versatile types of heat exchanger used on process plants is the plate heat exchanger (PHE). It has principle advantages over other heat exchangers in that plates can be added and/or removed easily in order to change the area available for heat transfer and therefore its overall performance. The reason for changing the amount of heat transfer area may be down to a new duty requirement or non-replacement of damaged plates after maintenance. The following paper shows how the operation of a two stream PHE can be approximated after the plate rearrangement has been made, using the existing PHE performance data. This calculation is, therefore, one purely of rating with the assumptions that the overall mass flow rates do not change with the new configuration and that truly counter-current flow is achieved.

Abstract: In this paper, an experimental set up is established to investigate the behavior of the heat exchanger with multi-components mixtures based on a real mixture refrigeration system. Two tube-in-tube heat exchangers with different configurations are tested extensively with different mixtures operating at three typical temperature ranges, such as 80 K–100 K, 120 K–150 K, and 180 K–200 K temperature ranges. The two heat exchangers are fabricated specially to be able to measure the temperatures and pressures distributions. With the measurement of the mixture compositions, temperatures, and pressures, the thermodynamic and hydraulic behaviors of the two heat exchangers are studied extensively. Finally, the heat transfer characteristics are obtained, which is useful in future design of the mixture refrigeration system.

Abstract: The performance optimization of an endoreversible air refrigerator with variable-temperature heat reservoirs is carried out by taking the cooling load density, i.e. the ratio of cooling load density to the maximum specific volume in the cycle, as the optimization objective in this paper. The analytical relations of cooling load, cooling load density and coefficient of performance are derived with the heat resistance losses in the hot- and cold-side heat exchangers. The maximum cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot- and cold-side heat exchangers for the fixed total heat exchanger inventory, and the heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the heat capacitance rate of the working fluid, the inlet temperature ratio of heat reservoirs and the total heat exchanger inventory on the maximum cooling load density, the optimum heat conductance distribution, the optimum pressure ratio and the heat capacity rate matching between the working fluid and the heat reservoirs are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander and the hot- and cold-side heat exchangers. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract: An optimization method for determining the best configuration(s) of gasketed plate heat exchangers is presented. The objective is to select the configuration(s) with the minimum heat transfer area that still satisfies constraints on the number of channels, the pressure drop of both fluids, the channel flow velocities and the exchanger thermal effectiveness. The configuration of the exchanger is defined by six parameters, which are as follows: the number of channels, the numbers of passes on each side, the fluid locations, the feed positions and the type of flow in the channels. The resulting configuration optimization problem is formulated as the minimization of the exchanger heat transfer area and a screening procedure is proposed for its solution. In this procedure, subsets of constraints are successively applied to eliminate infeasible and nonoptimal solutions. Examples show that the optimization method is able to successfully determine a set of optimal configurations with a minimum number of exchanger evaluations. Approximately 5 % of the pressure drop and channel velocity calculations and 1 % of the thermal simulations are required for the solution.

Abstract: A mathematical model of heat and mass transfer in a high-temperature heat pipe is formulated. Numerical simulation of heat and mass transfer processes is given. The fields of velocities, pressures, temperatures, and other parameters of the heat pipe are obtained. The obtained results may be used in designing thermal mode control systems and in analyzing the efficiency of high-temperature heat pipes.

Abstract: The single-phase flow and thermal performance of a double pipe heat exchanger are examined by experimental methods. The working fluid is water at atmospheric pressure. Temperature measurements at the inlet and outlet of the two streams and also at an intermediate point half way between the inlet and outlet is made, using copper-constantan thermocouple wires. Mass flow rates for each stream are also measured using calibrated rotameters. Heat is supplied to the inner tube stream by an immersion heater. The overall heat transfer coefficients are inferred from the measured data. The heat transfer coefficient of the inner tube flow (circular cross section) is calculated using the standard correlations. The heat transfer coefficient of the outer tube flow (annular cross section) is then deduced. Higher heat transfer coefficients are reported in the laminar flow regime in comparison to the predictions of standard correlations for straight and smooth tubes. The reasons for this discrepancy are identified and discussed. Experimental errors in measuring temperatures and mass flow rates are studied and their effects on the heat transfer coefficients are estimated. Experimental results for the range of operating conditions used in this work show that the outer tube side heat transfer coefficients are smaller than the inner side heat transfer coefficients by a factor of almost 1.5 and 3.4 in counter flow and parallel flow arrangements, respectively. The agreement with predictions is very good for the counter flow arrangement, but not very good for the parallel flow arrangement.