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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
E-type shells in shell-and-tube heat exchangers: Ebert and Panchal equation, for crude oil fouling, Eckert number, Eddy viscosity: Eddy diffusivity, of heat, Edge, D, Edwards, D K EEC code for thermal design of heat exchangers, Effective diffusivity, Effective thermal conductivity of fixed beds, Effective tube length in shell-and-tube heat exchangers, Effectiveness of a heat exchanger: Efficiency of fins, Eicosane: Eicosene: Ejectors, in flash distillation plant, EJMA (Expansion Joint Manufacturers Association), standards for expansion bellows Elastic properties of solids: El-Dessouky, H, Electrical enhancement processes, in heat transfer augmentation, Electric fields, effect on properties of rheologically complex materials, Electric fields, in augmentation of condensation, Electrical process heater, specification of, Electrokinetics, for heat transfer augmentation in microfluidic systems, Electromagnetic theory of radiation, Electrostatic fields in augmentation of heat transfer, Elements: Elhadidy relation between heat and momentum transfer, Embedding methods for radiative heat transfer in nonisothermal gases, Embittlement, of stainless steels, Emission of thermal radiation, in solids, Emissivity: Emitting media, interaction phenomena with, Emulsions, viscosity of, EN13445 (European Pressure Vessel Codes), design of heat exchangers to, Enclosures:
annuli, free convective heat transfer in: horizontal, concentric spheres, free convective heat transfer in, free convection heat transfer in, when heated from below, honeycombs, free convective heat transfer in, horizontal cylinders, free convective heat transfer inside, inclined, free convective heat transfer in, rectangular, free convective heat transfer in, when heated from the sides, flow patterns in,
Free Convection in Layers and Enclosures
large aspect ratios, with local heating, low aspect ratios,
Energy equation: Energy recovery, maximum, in heat exchanger network design, Enhanced surfaces, fouling in, Enhancement devices: Enlargements in pipes: Enthalpy: Entrainment in annular gas-liquid flow Entrance effects in heat and mass transfer: Entrance lengths, hydrodynamic in pipe flow, Entrance losses for tube inlet in shell-and-tube heat exchanger, Entry losses in plate heat exchangers, Entropy generation and minimisation Environmental impact, of fouling, Eotvos number: Epstein, N, Epstein matrix, for fouling, Equalizing rings, for expansion bellows, Equilibrium interphase: Equilibrium vapor nucleus, Equivalent sand roughness, Ergun equation, for pressure drop in fixed beds ESDU correlations: Esters: Ethane: Ethanol: Ethers: Ethyl acetate: Ethylacetylene: Ethylacrylate: Ethylamine: Ethylbenzene: Ethyl benzoate: Ethyl butanoate: Ethylcyclohexane: Ethylcyclopentane: Ethyl formate: Ethylene: Ethylene diamine: Ethylene glycol: Ethylene oxide: Ethylmercaptan: 1-Ethylnaphthalene: 2-Ethylnaphthalene: Ethyl proprionate: Ethyl propylether: Ettouney, H, Euler number: Eutectic mixtures, condensation of forming immiscible liquids, Evaporation: Evaporative crystallisers, Evaporators: Exergy, definition of, Exergy analysis, Exit losses for tubes in shell-and-tube exchanger, Expansion bellows, for shell-and-tube heat exchangers: EJMA (Expansion Joint Manufacturers Association), standards for Expansion joints, mechanical design of: Expansion of tubes into tube sheets: Expansion turbine, lost work in, Explosively clad plate, Explosive welding of tubes into tube sheets Explosive expansion joints, Extended surfaces (see also Fins) Externally induced convection, in kettle reboilers, Extinction coefficient, Extinction efficiency, Eyring fluid (non-Newtonian),

Index

HEDH
A B C D E
E-type shells in shell-and-tube heat exchangers: Ebert and Panchal equation, for crude oil fouling, Eckert number, Eddy viscosity: Eddy diffusivity, of heat, Edge, D, Edwards, D K EEC code for thermal design of heat exchangers, Effective diffusivity, Effective thermal conductivity of fixed beds, Effective tube length in shell-and-tube heat exchangers, Effectiveness of a heat exchanger: Efficiency of fins, Eicosane: Eicosene: Ejectors, in flash distillation plant, EJMA (Expansion Joint Manufacturers Association), standards for expansion bellows Elastic properties of solids: El-Dessouky, H, Electrical enhancement processes, in heat transfer augmentation, Electric fields, effect on properties of rheologically complex materials, Electric fields, in augmentation of condensation, Electrical process heater, specification of, Electrokinetics, for heat transfer augmentation in microfluidic systems, Electromagnetic theory of radiation, Electrostatic fields in augmentation of heat transfer, Elements: Elhadidy relation between heat and momentum transfer, Embedding methods for radiative heat transfer in nonisothermal gases, Embittlement, of stainless steels, Emission of thermal radiation, in solids, Emissivity: Emitting media, interaction phenomena with, Emulsions, viscosity of, EN13445 (European Pressure Vessel Codes), design of heat exchangers to, Enclosures:
annuli, free convective heat transfer in: horizontal, concentric spheres, free convective heat transfer in, free convection heat transfer in, when heated from below, honeycombs, free convective heat transfer in, horizontal cylinders, free convective heat transfer inside, inclined, free convective heat transfer in, rectangular, free convective heat transfer in, when heated from the sides, flow patterns in,
Free Convection in Layers and Enclosures
large aspect ratios, with local heating, low aspect ratios,
Energy equation: Energy recovery, maximum, in heat exchanger network design, Enhanced surfaces, fouling in, Enhancement devices: Enlargements in pipes: Enthalpy: Entrainment in annular gas-liquid flow Entrance effects in heat and mass transfer: Entrance lengths, hydrodynamic in pipe flow, Entrance losses for tube inlet in shell-and-tube heat exchanger, Entry losses in plate heat exchangers, Entropy generation and minimisation Environmental impact, of fouling, Eotvos number: Epstein, N, Epstein matrix, for fouling, Equalizing rings, for expansion bellows, Equilibrium interphase: Equilibrium vapor nucleus, Equivalent sand roughness, Ergun equation, for pressure drop in fixed beds ESDU correlations: Esters: Ethane: Ethanol: Ethers: Ethyl acetate: Ethylacetylene: Ethylacrylate: Ethylamine: Ethylbenzene: Ethyl benzoate: Ethyl butanoate: Ethylcyclohexane: Ethylcyclopentane: Ethyl formate: Ethylene: Ethylene diamine: Ethylene glycol: Ethylene oxide: Ethylmercaptan: 1-Ethylnaphthalene: 2-Ethylnaphthalene: Ethyl proprionate: Ethyl propylether: Ettouney, H, Euler number: Eutectic mixtures, condensation of forming immiscible liquids, Evaporation: Evaporative crystallisers, Evaporators: Exergy, definition of, Exergy analysis, Exit losses for tubes in shell-and-tube exchanger, Expansion bellows, for shell-and-tube heat exchangers: EJMA (Expansion Joint Manufacturers Association), standards for Expansion joints, mechanical design of: Expansion of tubes into tube sheets: Expansion turbine, lost work in, Explosively clad plate, Explosive welding of tubes into tube sheets Explosive expansion joints, Extended surfaces (see also Fins) Externally induced convection, in kettle reboilers, Extinction coefficient, Extinction efficiency, Eyring fluid (non-Newtonian),
F G H I J K L M N O P Q R S T U V W X Y Z
E Enclosures: flow patterns in,
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Free Convection in Layers and Enclosures

DOI 10.1615/hedhme.a.000175

2.5 SINGLE-PHASE CONVECTIVE HEAT TRANSFER
2.5.8 Free convection in layers and enclosures

S. W. Churchill

Natural convection occurs in enclosures as a result of gradients in density, which are in turn due to variations in temperature or concentration. The rate of heat transfer is usually characterized by a Nusselt number as a function of a Rayleigh number, the Prandtl number, the geometry, and the boundary and initial conditions. The Nusselt and Rayleigh numbers are ordinarily based on the external temperature difference and the dimension of the enclosure in the direction of heat transfer, with some exceptions as noted below. The other variables in these groups are defined as in Section 174.

Catton (1978) provides a recent, comprehensive, and interpretive review of natural convection in enclosures. Ostrach (1972 and 1975) discusses cylindrical and rectangular enclosures in somewhat greater detail. Koschmieder (1974) has reviewed Bénard-type convection and Buchberg et al. (1976) applications of natural convection in solar collectors. Churchill and Ozoe (n.d.) have utilized theoretical and experimental results for asymptotic conditions to develop correlating equations for heat transfer in rectangular and cylindrical enclosures for a wide range of conditions with special attention to the effect of the angles of inclination and rotation.

In this section a description of the fluid motion is provided and correlations are recommended for heat transfer for conditions of primary practical importance. Referral to the references cited herein and in the above reviews is suggested for derivations and further details.

Experimental results for natural convection in enclosures are generally less accurate than for forced convection owing to difficulty in repressing and evaluating the heat fluxes through and along the nonisothermal walls. As a consequence, discrepancies between various sets of data are not completely resolved. Also, the time scale of experiments, particularly with liquids, is sometimes insufficient to attain the true stationary state.

Theoretical results are limited in accuracy and scope owing to the inherent three dimensionality of the velocity and temperature fields in all enclosures with two or three finite dimensions. This three dimensionality affects the transitions from one mode of circulation to another. If one or the other aspect ratio is near unity, the three dimensionality affects the rates of circulation and heat transfer significantly. Even so, the many two- dimensional and the few three-dimensional solutions provide a useful basis for the interpretation, correlation, and extrapolation of the experimental values.

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