Rohsenow W., Hartnett J., Young Cho. Handbook of Heat Transfer (776121), страница 4
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Boiling15.1Introduction / 15.1General Considerations / 15.1Manifestations of Boiling Heat Transfer / 15.2Stucture of This Chapter / 15.2Phase Equilibrium / 15.3Single-Component Systems / 15.3Multicomponent Systems / 15.5Nucleation and Bubble Growth / 15.6Equilibrium of a Bubble / 15.6Homogeneous Nucleation / 15.7Heterogeneous Nucleation / 15.9Bubble Growth / 15.18Bubble Release Diameter and Frequency / 15.26PoolBoiling / 15.30Pool Boiling Heat Transfer Before the Critical Heat Flux Limit / 15.31The Critical Heat Flux Limit in Pool Boiling / 15.56Heat Transfer Beyond the Critical Heat Flux Limit in Pool Boiling / 15.66Cross Flow Boiling / 15.75Heat Transfer Below the Critical Heat Flux Limit in Cross Flow Boiling / 15.77Critical Heat Flux in Cross Flow Boiling / 15.81Heat Transfer Beyond the Critical Heat Flux Limit in Cross Flow Boiling / 15.83Forced Convective Boiling in Channels / 15.84Heat Transfer Below the Critical Heat Flux Limit in Forced Convective Boiling in Channels / 15.89Critical Heat Flux in Forced Convective Boiling in Channels / 15.112Heat Transfer Beyond the Critical Heat Flux Limit in Forced ConvectiveBoiling in Channels / 15.132Thin Film Heat Transfer / 15.137Evaporating Liquid Films: Laminar Flow / 15.138Evaporating Liquid Films: Turbulent Flow / 15.140Evaporating Liquid Films: Multicomponent Mixtures / 15.140Evaporating Liquid Films with Nucleate Boiling / 15.141Heat Transfer to a Nonevaporating (Subcooled) Falling Liquid Film / 15.141Film Breakdown / 15.142Rewetting of Hot Surfaces / 15.143Nomenclature / 15.145References / 15.152Chapter 16.
Measurement of Temperature and Heat TransferIntroduction / 16.1Temperature Measurement / 16.2Basic Concepts and Definitions / 16.2Standards and Temperature Scales / 16.3Sensors / 16.8Local Temperature Measurement / 16.51Calibration of Thermometers and Assurance of Measurements / 16.5416.1xivCONTENTSHeat Flux Measurement / 16.58Basic Principles / 16.58Methods / 16.59Thermal Resistance Gauges / 16.60Measurement by Analogy / 16.64Introduction / 16.64Sublimation Technique / 16.65Electrochemical Technique / 16.66Acknowledgments / 16.68Nomenclature / 16.68List of Abbreviations / 16.71References / 16.7117.1Chapter 17. Heat ExchangersIntroduction / 17.1Classification of Heat Exchangers / 17.2Shell-and-Tube Exchangers / 17.2Newer Designs of Shell-and-Tube Exchangers / 17.14Compact Heat Exchangers / 17.15Exchanger Heat Transfer and Pressure Drop Analysis / 17.25Heat Transfer Analysis / 17.27The e-NTU, P-NTU, and MTD Methods / 17.30Fin Efficiency and Extended Surface Efficiency / 17.34Extensions of the Basic Recuperator Thermal Design Theory / 17.47e-NTUo and A-FI Methods for Regenerators / 17.55Single-Phase Pressure Drop Analysis / 17.62Single-Phase Surface Basic Heat Transfer and Flow Friction CharacteristicsExperimental Methods / 17.69Analytical Solutions / 17.
76Experimental Correlations / 17.84Influence of Temperature-Dependent Fluid Properties / 17.88Influence of Superimposed Free Convection / 17.89Two-Phase Heat Transfer and Pressure Drop Correlations / 17.89Flow Patterns / 17.89Two-Phase Pressure Drop Correlations / 17.95Heat Transfer Correlations for Condensation / 17.97Heat Transfer Correlations for Boiling / 17.103Thermal Design for Single-Phase Heat Exchangers / 17.105Exchanger Design Methodology / 17.105Extended Surface Heat Exchangers / 17.105Shell-and-Tube Heat Exchangers / 17.111Thermal Design for Two-Phase Heat Exchangers / 17.120Condensers / 17.120Vaporizers / 17.125Flow-Induced Vibration / 17.127Tube Vibration / 17.127Acoustic Vibrations / 17.128Design Guidelines for Vibration Mitigation / 17.136Flow Maldistribution / 17.136Geometry-Induced Flow Maldistribution / 17.136Flow Maldistribution Induced by Operating Conditions / 17.141Mitigation of Flow Maldistribution / 17.145Fouling and Corrosion / 17.146Fouling / 17.147Corrosion / 17.152Concluding Remarks / 17.153Nomenclature / 17.154References / 17.16217.66CONTENTSChapter 18.
Heat Transfer in Materials ProcessingIntroduction / 18.1Heat Transfer Fundamentals Relevant to Materials Processing / 18.2Conduction HeatTransfer / 18.2Conduction Heat Transfer in Beam-Irradiated Materials / 18.2Conduction Heat Transfer with Thermomechanical Effects I 18.9Single-Phase Convective Heat Transfer I 18.12Two-Phase Convective Heat Transfer / 18.26Radiation Heat Transfer I 18.35System-Level Thermal Phenomena / 18.43Heating of a Load Inside Industrial Furnaces / 18.43Quenching / 18.51Processing of Several Advanced Materials / 18.57Concluding Remarks / 18.61Nomenclature / 18.61References / 18.65Index follows Chapter 18xv18.1CHAPTER 1BASIC CONCEPTSOF HEAT TRANSFERY. I. ChoDrexel UniversityE.
N. GanicUniversity of SarajevoJ. P. HartnettUniversity of Illinois, ChicagoW. M. RohsenowMassachusetts Institute of TechnologyHEAT TRANSFER MECHANISMSHeat is defined as energy transferred by virtue of a temperature difference. It flows fromregions of higher temperature to regions of lower temperature. It is customary to refer to different types of heat transfer mechanisms as modes. The basic modes of heat transfer are conduction, radiation, and convection.ConductionConduction is the transfer of heat from one part of a body at a higher temperature to anotherpart of the same body at a lower temperature, or from one body at a higher temperature toanother body in physical contact with it at a lower temperature.
The conduction process takesplace at the molecular level and involves the transfer of energy from the more energeticmolecules to those with a lower energy level. This can be easily visualized within gases, wherewe note that the average kinetic energy of molecules in the higher-temperature regions isgreater than that of those in the lower-temperature regions.
The more energetic molecules,being in constant and random motion, periodically collide with molecules of a lower energylevel and exchange energy and momentum. In this manner there is a continuous transportof energy from the high-temperature regions to those of lower temperature. In liquids themolecules are more closely spaced than in gases, but the molecular energy exchange processis qualitatively similar to that in gases.
In solids that are nonconductors of electricity (dielectrics), heat is conducted by lattice waves caused by atomic motion. In solids that are good1.11.2CHAPTER ONEconductors of electricity, this lattice vibration mechanism is only a small contribution to theenergy transfer process, the principal contribution being that due to the motion of free electrons, which move in a similar way to molecules in a gas.At the macroscopic level the heat flux (i.e., the heat transfer rate per unit area normal tothe direction of heat flow) q" is proportional to the temperature gradient:q"=-kdTdx(1.1)where the proportionality constant k is a transport property known as the thermal conductivity and is a characteristic of the material.
The minus sign is a consequence of the fact that heatis transferred in the direction of decreasing temperature. Equation 1.1 is the one-dimensionalform of Fourier's law of heat conduction. Recognizing that the heat flux is a vector quantity,we can write a more general statement of Fourier's law (i.e., the conduction rate equation) asq" = - k VT(1.2)where V is the three-dimensional del operator and T is the scalar temperature field. FromEq. 1.2 it is seen that the heat flux vector q" actually represents a current of heat (thermalenergy) that flows in the direction of the steepest temperature gradient.If we consider a one-dimensional heat flow along the x direction in the plane wall shownin Fig. 1.1a, direct application of Eq.
1.1 can be made, and then integration yieldskAq=~(T2 - T1)(1.3)where the thermal conductivity is considered constant, Ax is the wall thickness, and T1 and T2are the wall-face temperatures. Note that q/A = q", where q is the heat transfer rate throughan area A. Equation 1.3 can be written in the form7"2- Taq - Ax/kAT 2 - T1-Rth-thermal potential differencethermal resistance(1.4)where zLv,/kA assumes the role of a thermal resistance Rth.
T h e relation of Eq. 1.4 is quite likeOhm's law in electric circuit theory. The equivalent electric circuit for this case is shown inFig. 1.1b.The electrical analogy may be used to solve more complex problems involving both seriesand parallel resistances. Typical problems and their analogous electric circuits are given in many heat transfer textbooks [1--4].In treating conduction problems it is often convenient tointroduce another property that is related to the thermalAconductivity, namely, the thermal diffusivity (x,F-Temperatureprofileq(x -TI~~x(a)T2qT~AxkA(b)FIGURE 1.1 One-dimensional heat conductionthrough a plane wall (a) and electric analog (b).kpc(1.5)where p is the density and cv is the specific heat at constantpressure.As mentioned above, heat transfer will occur wheneverthere exists a temperature difference in a medium. Similarly,whenever there exists a difference in the concentration ordensity of some chemical species in a mixture, mass transfermust occur.
Hence, just as a temperature gradient constitutesthe driving potential for heat transfer, the existence of a concentration gradient for some species in a mixture providesthe driving potential for transport of that species. Therefore,BASIC CONCEPTS OF HEAT TRANSFER1.3the term mass transfer describes the relative motion of species in a mixture due to the presence of concentration gradients.Since the same physical mechanism is associated with heat transfer by conduction (i.e.,heat diffusion) and mass transfer by diffusion, the corresponding rate equations are of thesame form.
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