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Wadekar, V Wagner equation, for vapour pressure, Wake, Coles law of the, Wall layer transmissivity, Wall temperature: Wallis correlations: Wallis criterion, for transition from stratified to annular flow, applications in condensation, Walz' method, for laminar boundary layers, Waste heat boilers, Waste water, fouling by, Water: Watertube boiler, Wavelengths, of blackbody radiation, Waves, interfacial, effect on film condensation on vertical surface, Wavy fins, in plate fin exchangers, Webb, D R Webb, R L Weber, M, Weber number, Weil, C J Welded channel head, in shell-and tube heat exchanger, Welded fins: Welded plate exchangers: Welding: Welds: Wentz and Thodos equation, for fixed-bed pressure drop,
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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
Wadekar, V Wagner equation, for vapour pressure, Wake, Coles law of the, Wall layer transmissivity, Wall temperature: Wallis correlations: Wallis criterion, for transition from stratified to annular flow, applications in condensation, Walz' method, for laminar boundary layers, Waste heat boilers, Waste water, fouling by, Water: Watertube boiler, Wavelengths, of blackbody radiation, Waves, interfacial, effect on film condensation on vertical surface, Wavy fins, in plate fin exchangers, Webb, D R Webb, R L Weber, M, Weber number, Weil, C J Welded channel head, in shell-and tube heat exchanger, Welded fins: Welded plate exchangers: Welding: Welds: Wentz and Thodos equation, for fixed-bed pressure drop,
Fixed Beds
Wet-bulb temperature, Wettability, of surface, effect on pool boiling, Whalley and Hewitt correlations: White-Metzner model, for non-Newtonian fluid, Wicks, for heat pipes: Wilday, A J Wildsmith, G, Wills-Johnson flow stream analysis method for segmentally baffled shell-and-tube heat exchangers, Wilson, D I Window zone, in shell-and-tube heat exchangers: Winter, H H, Wire matrix inserts, in heat exchangers, Wirth, K E, Wispy annular flow, regions of occurrence of, Work (in exergy analysis) Working fluid, selection of for heat pipe,
X Y Z
W Wentz and Thodos equation, for fixed-bed pressure drop,
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Fixed Beds

DOI 10.1615/hedhme.a.000147

2.2.5 Fixed beds

P. J. Heggs

The structural properties of fixed beds have been extensively reviewed by Haughey and Beveridge (1969). Two categories of fixed bed exist: regular and random packed. Regular packings provide complete control of bed voidage and surface area, but assembly is expensive. Regular packings are used, however, in thermal regenerators, checkerwork in high-temperature stoves in the glass and steel industries, and metallic matrix arrangements in the Ljungstrom rotary regenerators used in the power generation industry. In all these situations the pressure drop across the fixed bed must be small.

Random packings are found in a wide range of industrial operations: adsorption, catalysis, combustion, filtration, separation, and solid-fluid contacting in general. They are formed by the haphazard positioning of particles to provide a bed and the average bed properties are largely dependent on the mode of assembly (Debbas and Rumpf, 1966). The geometrical shape of fixed beds is normally cylindrical with the flow of the fluid parallel to the axis of the cylinder, however radial flow through annular beds is also used, when low pressure drop restrictions are specified. Only an infinitely sized bed is wholly random, but this is closely approached when the ratios of the container diameter (D) or diameters (Di and D0) and container length L to the particle diameter (d) are greater than 10 (Ridgway and Tarbuck, 1967). Random beds are simple in design, assembly is cheap, and construction is rugged.

Fixed beds are normally characterized by the specific surface area of the bed SB and the mean fractional voidage of the bed, εm. The latter is defined as the free volume of the bed divided by the volume of the bed, that is,

\[\label{eq1} \varepsilon_{m}=\dfrac{bed\;volume - packing\;volume}{bed\;volume}\tag{1}\]

and the specific surface area of the bed is strictly dependent on the value of the mean bed voidage, εm. The specific surface area of the particles S is defined as the surface area of the particles divided by the volume of the particles. For a sphere,

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