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Hagen-Poiseuille law Hagen-Rubens relation, between electrical and optical constants, Hall Taylor, N S, Halogenated hydrocarbons: Handley and Heggs equation for fixed bed pressure drop, Hankinson and Thomson method, for liquid density: Hardening (precipative) of stainless steels, Hardwick, R, Harris, D, Hausen equation for developing laminar flow, Hays, G F Headers in shell-and-tube heat exchangers, Heads, in heat exchangers: Heat and mass transfer: Heat exchanger design, introduction, Heat exchangers: Heat of vaporisation (see Enthalpy of vaporisation), of pure substances Heat pipes: Heat pumping, relation to heat exchanger network design, Heat storage (see Regenerators and thermal energy storage) entropy generation in, Heat transfer: Heat transfer coefficient: Heat transfer media, Heat transfer salt, Heat transfer regimes: Heat of vaporization, Heated cavity reflectometer, Heating media, for reboilers, Heavy water, physical properties of, Heggs, P J, Helical coils of circular cross section: Helical coils of rectangular cross section, Helical inserts, for enhancement of heat transfer in boiling, Helium: Helmholtz reciprocity principle, in radiative heat transfer, Henry, J A R, Henry-Fauske model, for critical two-phase flow, Henry's law, for partial pressure, Heptadecane: Heptadecene: Heptane: 1-Heptanol: 1-Heptene: Herman, K W, Hermes, C L L, Heterogeneous conveyance in horizontal pipes, Heterogeneous nucleation in boiling, Hewitt, G F Hexachloroethane (Refrigerant 116): Hexacyclopentane, superheated vapor properties, Hexadecane: Hexadecene: 1,5-Hexadiene: Hexagonal cells, in free convection, Hexamethylbenzene: Hexane: Hexanoic acid: 1-Hexanol: 1-Hexene: Hexylbenzene: Hexylcyclohexane: Hexylcyclopentane, Hicks equation, for fixed-bed pressure drop, High pressure closures, ASME VIII code guidance for, High-chrome steels, thermal and mechanical properties, High-finned tubes, correlations for single-phase heat transfer in flow over, Hills, P D Hohlraum cavity,
Introduction
Holdup, in liquid-liquid flow, Holland, guide to national practice for mechanical design of heat exchangers, Homogeneous condensation (fog formation), Homogeneous model: Homogeneous nucleation: Honeycombs: Hopkins, D, Horizontal condensers: Horizontal cylinders: Horizontal layers, of fluid, free convection heat transfer in, Horizontal pipes: Horizontal shell-side evaporator, Horizontal surfaces: Horizontal thermosiphon reboilers: Horizontal tube-side evaporator, Horizontal tubes: Hottel's rule, in absorption of radiation by gases, Hsu criterion, for onset of nucleate boiling, Hybrid cooling towers, Hydraulic conveyance: Hydraulic expansion, of tubes into tube sheets in shell-and-tube heat exchangers, Hydraulic turbine, lost work in, Hydraulic resistance, in flow of supercritical fluids, Hydraulically smooth surface, Hydrazine: Hydrocarbons: Hydrodynamic entrance length, in single-phase flow in ducts, Hydrogen: Hydrogen bromide: Hydrogen chloride: Hydrogen cyanide: Hydrogen fluoride: Hydrogen iodide: Hydrogen peroxide: Hydrogen sulfide: Hydrostatic testing of shell-and-tube heat exchangers, Hysteresis:

Index

HEDH
A B C D E F G H
Hagen-Poiseuille law Hagen-Rubens relation, between electrical and optical constants, Hall Taylor, N S, Halogenated hydrocarbons: Handley and Heggs equation for fixed bed pressure drop, Hankinson and Thomson method, for liquid density: Hardening (precipative) of stainless steels, Hardwick, R, Harris, D, Hausen equation for developing laminar flow, Hays, G F Headers in shell-and-tube heat exchangers, Heads, in heat exchangers: Heat and mass transfer: Heat exchanger design, introduction, Heat exchangers: Heat of vaporisation (see Enthalpy of vaporisation), of pure substances Heat pipes: Heat pumping, relation to heat exchanger network design, Heat storage (see Regenerators and thermal energy storage) entropy generation in, Heat transfer: Heat transfer coefficient: Heat transfer media, Heat transfer salt, Heat transfer regimes: Heat of vaporization, Heated cavity reflectometer, Heating media, for reboilers, Heavy water, physical properties of, Heggs, P J, Helical coils of circular cross section: Helical coils of rectangular cross section, Helical inserts, for enhancement of heat transfer in boiling, Helium: Helmholtz reciprocity principle, in radiative heat transfer, Henry, J A R, Henry-Fauske model, for critical two-phase flow, Henry's law, for partial pressure, Heptadecane: Heptadecene: Heptane: 1-Heptanol: 1-Heptene: Herman, K W, Hermes, C L L, Heterogeneous conveyance in horizontal pipes, Heterogeneous nucleation in boiling, Hewitt, G F Hexachloroethane (Refrigerant 116): Hexacyclopentane, superheated vapor properties, Hexadecane: Hexadecene: 1,5-Hexadiene: Hexagonal cells, in free convection, Hexamethylbenzene: Hexane: Hexanoic acid: 1-Hexanol: 1-Hexene: Hexylbenzene: Hexylcyclohexane: Hexylcyclopentane, Hicks equation, for fixed-bed pressure drop, High pressure closures, ASME VIII code guidance for, High-chrome steels, thermal and mechanical properties, High-finned tubes, correlations for single-phase heat transfer in flow over, Hills, P D Hohlraum cavity,
Introduction
Holdup, in liquid-liquid flow, Holland, guide to national practice for mechanical design of heat exchangers, Homogeneous condensation (fog formation), Homogeneous model: Homogeneous nucleation: Honeycombs: Hopkins, D, Horizontal condensers: Horizontal cylinders: Horizontal layers, of fluid, free convection heat transfer in, Horizontal pipes: Horizontal shell-side evaporator, Horizontal surfaces: Horizontal thermosiphon reboilers: Horizontal tube-side evaporator, Horizontal tubes: Hottel's rule, in absorption of radiation by gases, Hsu criterion, for onset of nucleate boiling, Hybrid cooling towers, Hydraulic conveyance: Hydraulic expansion, of tubes into tube sheets in shell-and-tube heat exchangers, Hydraulic turbine, lost work in, Hydraulic resistance, in flow of supercritical fluids, Hydraulically smooth surface, Hydrazine: Hydrocarbons: Hydrodynamic entrance length, in single-phase flow in ducts, Hydrogen: Hydrogen bromide: Hydrogen chloride: Hydrogen cyanide: Hydrogen fluoride: Hydrogen iodide: Hydrogen peroxide: Hydrogen sulfide: Hydrostatic testing of shell-and-tube heat exchangers, Hysteresis:
I J K L M N O P Q R S T U V W X Y Z
H Hohlraum cavity,
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Introduction

DOI 10.1615/hedhme.a.000204

2.9.1 Introduction

D. K. Edwards

A. Radiation heat transfer in thermal design

When does one consider radiation heat transfer, and when does one not? One does not consider radiation inside of a fluid that is highly opaque to the source spectrum. In a fluid such as water, the radiation is merely a contributor to what we know as thermal conductivity. Similarly, one docs not consider radiation inside a fluid that is perfectly transparent to the source spectrum. If there is no physical mechanism by which the fluid can absorb energy from radiation passing through it, then it follows from thermodynamics that it cannot emit radiation either, and it cannot be either heated or cooled by radiation. Such a fluid is said to be diathermanous. The walls surrounding such a fluid, however, may exchange heat radiation, but only if they are not isothermal. Thus one does not ordinarily consider radiation within the passages of a heat exchanger containing oil, water, or air. The first two are opaque. The last is diathermanous.

When two walls at different temperatures are in view of each other or one wall is in view of a participating medium (one neither opaque not diathermanous), the radiation heat flux (W/m2) tends to be high when ΔCsT 4 is high, where Cs is the Stefan-Boltzmann constant, 5.6697 × 10–8 W/m2 K4. When ΔT is small compared to the absolute temperature level, ΔCsT 4 can be written 4CsTm3ΔT, where Tm is the mean temperature level. At 300 K, the value for 4CsTm3 is slightly over 6 W/m2 K, on the same order as a natural-convection heat transfer coefficient. At Tm = 2,000 K, the value is nearly 300 times greater. From such a value, 1,800 W/m2 K, one can see why radiation contributes to film-boiling heat transfer. Radiation is important when temperatures are high, distances are large (because convective heat transfer coefficients go as passage size D as D–1/5 for turbulent flow or D–1 for laminar flow), or under vacuum conditions when convective heat transfer coefficients are low because of the low fluid density.

B. Thermodynamic surfaces and surface systems

The thermal designer needs to know surface heat fluxes adjacent to the interface between phases. When one phase is highly opaque and the other is not, the opaque surface system concept is used. Figure 1 depicts a surface system. The s surface lies just outside the highly opaque phase: the u surface lies just within it. The m surface lies sufficiently below the phase interface so that (1) no radiation crossing the s and u surfaces is transmitted to the m surface, and (2) the radiation flux crossing the m surface is given by the radiation-diffusion equation and is included with the conduction. For no flow through the surfaces and negligible transient heat storage in the mass between the m and u surfaces, one has

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