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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
Absorbing media, interaction phenomena in, Absorption of thermal radiation: Absorption coefficient, Absorption spectra in gases, Absorptivity: Acentric factor: Acetaldehyde: Acetic acid: Acetic anhydride: Acetone: Acetonitrile: Acetophenone: Acetylene: Acetylenes Ackerman correction factor in condensation, Acoustic methods, for fouling mitigation, Acoustic vibration of heat exchangers, Acrolein: Acrylic acid: Active systems for augmentation of heat transfer: Additives: Adiabatic flows, compressible, in duct, Admiralty brass, Advanced models for furnaces, Agitated beds, heat transfer to, Agitated vessels, Ahmad scaling method for critical heat flux in flow boiling of nonaqueous fluids, Air: Air-activated gravity conveyor, Air-cooled heat exchangers: Air preheaters, fouling in, Albedo for single scatter in radiation, Alcohols: Aldehydes: Aldred, D L, Allyl alcohol: Allyl chloride (-chloropropane) Alternating direction (ADR) method, for solution of implicit finite difference equations, Aluminum, spectral characteristics of anodized surfaces, Aluminum alloys, thermal and mechanical properties, Aluminium brass, Ambrose-Walton corresponding states method, for vapour pressure, Amides: Amines: Ammonia: tert-Amyl alcohol: Analogy between heat and mass and momentum transfer Analytical solution of groups, for calculation of thermodynamic Anelasticity, Angled tubes, use in increasing flooding rate in reflux condensation, Aniline: Anisotropy of elastic properties, Annular distributor in shell-and-tube heat exchangers, Annular ducts:
critical heat flux in flow in, forced convective heat transfer in single phase flow: free convective heat transfer in closed-end: horizontal,
Free Convection in Layers and Enclosures vertical (heated on vertical curved surfaces),
heat transfer to liquid metals in, single phase flow and pressure drop in, with rotating inner surface
Annular (radial) fins, efficiency Annular flow (gas-liquid): Annular flow (liquid-liquid), Annular flow (liquid-liquid-gas), Anti-foulants, Antoine equation, for vapour pressure, Aqueous solutions, as heat transfer media, Arc welding of tubes into tube sheets: Archimedes number, Area of tube outside surface in shell-and-tube heat exchangers: Argon: Arithmetic mean temperature difference, definition, Armstrong, Robert C Aromatics: ASME VIII code, for mechanical design of shell-and-tube heat exchangers: Assisted convection: Attachment, of fouling layers, Augmentation of heat transfer Austenitic stainless steels, Average phase velocity in multiphase flows, Axial flow reboilers, Axial wire attachments, for augmentation of condensation, Azeotropes, condensation of

Index

HEDH
A
Absorbing media, interaction phenomena in, Absorption of thermal radiation: Absorption coefficient, Absorption spectra in gases, Absorptivity: Acentric factor: Acetaldehyde: Acetic acid: Acetic anhydride: Acetone: Acetonitrile: Acetophenone: Acetylene: Acetylenes Ackerman correction factor in condensation, Acoustic methods, for fouling mitigation, Acoustic vibration of heat exchangers, Acrolein: Acrylic acid: Active systems for augmentation of heat transfer: Additives: Adiabatic flows, compressible, in duct, Admiralty brass, Advanced models for furnaces, Agitated beds, heat transfer to, Agitated vessels, Ahmad scaling method for critical heat flux in flow boiling of nonaqueous fluids, Air: Air-activated gravity conveyor, Air-cooled heat exchangers: Air preheaters, fouling in, Albedo for single scatter in radiation, Alcohols: Aldehydes: Aldred, D L, Allyl alcohol: Allyl chloride (-chloropropane) Alternating direction (ADR) method, for solution of implicit finite difference equations, Aluminum, spectral characteristics of anodized surfaces, Aluminum alloys, thermal and mechanical properties, Aluminium brass, Ambrose-Walton corresponding states method, for vapour pressure, Amides: Amines: Ammonia: tert-Amyl alcohol: Analogy between heat and mass and momentum transfer Analytical solution of groups, for calculation of thermodynamic Anelasticity, Angled tubes, use in increasing flooding rate in reflux condensation, Aniline: Anisotropy of elastic properties, Annular distributor in shell-and-tube heat exchangers, Annular ducts:
critical heat flux in flow in, forced convective heat transfer in single phase flow: free convective heat transfer in closed-end: horizontal,
Free Convection in Layers and Enclosures vertical (heated on vertical curved surfaces),
heat transfer to liquid metals in, single phase flow and pressure drop in, with rotating inner surface
Annular (radial) fins, efficiency Annular flow (gas-liquid): Annular flow (liquid-liquid), Annular flow (liquid-liquid-gas), Anti-foulants, Antoine equation, for vapour pressure, Aqueous solutions, as heat transfer media, Arc welding of tubes into tube sheets: Archimedes number, Area of tube outside surface in shell-and-tube heat exchangers: Argon: Arithmetic mean temperature difference, definition, Armstrong, Robert C Aromatics: ASME VIII code, for mechanical design of shell-and-tube heat exchangers: Assisted convection: Attachment, of fouling layers, Augmentation of heat transfer Austenitic stainless steels, Average phase velocity in multiphase flows, Axial flow reboilers, Axial wire attachments, for augmentation of condensation, Azeotropes, condensation of
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
A Annular ducts: free convective heat transfer in closed-end: horizontal,
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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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