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Lamella heat exchangers, Laminar flow: Laminar flow control, of boundary layers, Lancaster, J F, Langelier index for water quality, Large eddy simulation, in prediction of turbulent boundary layers, Laws for turbulent flows: Layers of fluid, free convection heat transfer in, Le Fevre equations for free convective heat transfer, Leakage between streams, in shell-and-tube heat exchangers Leakage effects, on heat transfer and pressure drop in shell-and-tube heat exchangers, Leaks, in heat exchanger, sealing by explosive welding, Lebedev, M E, Lee and Kesler equation, for vapour pressure, L-footed fins, Lessing rings, characteristic of, as packings for fixed beds,
Fixed Beds
Li equation, for critical temperature of mixtures, Lienhard and Dhir analysis of critical heat flux in pool boiling, Lienhard and Eichhorn criterion, for transition in critical heat flux mechanism in crossflow over single tube, Lift force: Liley, P E, Limb, D, Limpet coils: Linnhoff, B, Liquefaction, exergy analysis of, Liquid fluidized beds, Liquid fuels, properties of, Liquid hold-up, Liquid-liquid-gas flow, Liquid-liquid flow, Liquid metals: Liquid sheets, in direct contact heat transfer, Liquid-solid interfaces, fouling at, Liquids: Lister, D H, Local conditions hypothesis, for critical heat flux in flow boiling, Lockhart and Martinelli correlations: Lodge's rubberlike liquid (non-Newtonian), Logarithmic law region, Logarithmic mean temperature difference Longitudinal flow and heat transfer in tube banks, Long-tube vertical evaporator, Loss coefficient, Lost work in unit operations/exergy analysis, Louvered fins, in plate fin exchangers, Low-alloy steels: Low-finned tubes: Low-nickel steels, Lubricants, physical properties: Lucas methods

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A B C D E F G H I J K L
Lamella heat exchangers, Laminar flow: Laminar flow control, of boundary layers, Lancaster, J F, Langelier index for water quality, Large eddy simulation, in prediction of turbulent boundary layers, Laws for turbulent flows: Layers of fluid, free convection heat transfer in, Le Fevre equations for free convective heat transfer, Leakage between streams, in shell-and-tube heat exchangers Leakage effects, on heat transfer and pressure drop in shell-and-tube heat exchangers, Leaks, in heat exchanger, sealing by explosive welding, Lebedev, M E, Lee and Kesler equation, for vapour pressure, L-footed fins, Lessing rings, characteristic of, as packings for fixed beds,
Fixed Beds
Li equation, for critical temperature of mixtures, Lienhard and Dhir analysis of critical heat flux in pool boiling, Lienhard and Eichhorn criterion, for transition in critical heat flux mechanism in crossflow over single tube, Lift force: Liley, P E, Limb, D, Limpet coils: Linnhoff, B, Liquefaction, exergy analysis of, Liquid fluidized beds, Liquid fuels, properties of, Liquid hold-up, Liquid-liquid-gas flow, Liquid-liquid flow, Liquid metals: Liquid sheets, in direct contact heat transfer, Liquid-solid interfaces, fouling at, Liquids: Lister, D H, Local conditions hypothesis, for critical heat flux in flow boiling, Lockhart and Martinelli correlations: Lodge's rubberlike liquid (non-Newtonian), Logarithmic law region, Logarithmic mean temperature difference Longitudinal flow and heat transfer in tube banks, Long-tube vertical evaporator, Loss coefficient, Lost work in unit operations/exergy analysis, Louvered fins, in plate fin exchangers, Low-alloy steels: Low-finned tubes: Low-nickel steels, Lubricants, physical properties: Lucas methods
M N O P Q R S T U V W X Y Z
L Lessing rings, characteristic of, as packings for fixed beds,
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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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