Solid-Liquid Heat Exchange

Finite Bi heat transfer solutions corresponding to the infinite Bi mass transfer solutions listed for continuous countercurrent leaching are available. In these solutions a/, corresponds to a, to r, 7 s to T or y/M, and Tx to X at corresponding locations in the leaching system. When either Bi or Bi is finite the equations used to predict g, and Q are more complex than thi listed in Tables 10.8-1, 10.13-1, and 10.13-2. For example, for spherical particles when a 1.0 (the usual case) and Bi is finite. 

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Decontamination of the atmospheres. Aerosols, excess CO or hazardous gases, e.g, diborane,or valuable compounds contained in gases can be recovered as liquid or frozen out as solid by heat exchange with the cold circulating gas from the Norelco refrigerator. This is illustrated in Figure 11. 

Heat transfer by nucleate boiling is an important mechanism in the vaporization of liqmds. It occurs in the vaporization of liquids in kettle-type and natural-circulation reboilers commonly usea in the process industries. High rates of heat transfer per unit of area (heat flux) are obtained as a result of bubble formation at the liquid-solid interface rather than from mechanical devices external to the heat exchanger. There are available several expressions from which reasonable values of the film coefficients may be obtained. 

Moving-Bed Type This concept uses a single-pass tube bundle in a vertical shell with the dividea solids flowing by gravity in the tubes. It is little used for sohds. A major difficulty in divided-sohds apphcations is the problem of charging and discharging with uniformity. A second is poor heat-transfer rates. Because of these hmita-tions, this tube-bundle type is not the workhorse for solids that it is for liquid and gas-phase heat exchange. 

A heat exchanger is a device that transfers heat from one medium to another the medium may be a solid, liquid, or gas. Some of the most complex engineering design problems relate to heat exchangers. 

Where heat transfer is taking place at the saturation temperature of a fluid, evaporation or condensation (mass transfer) will occur at the interface, depending on the direction of heat flow. In such cases, the convective heat transfer of the fluid is accompanied by conduction at the surface to or from a thin layer in the liquid state. Since the latent heat and density of fluids are much greater than the sensible heat and density of the vapour, the rates of heat transfer are considerably higher. The process can be improved by shaping the heat exchanger face (where this is a solid) to improve the drainage of condensate or the escape of bubbles of vapour. The total heat transfer will be the sum of the two components. 

Flocculation or clarification processes are solids-liquid separation techniques used to remove suspended solids and colloidal particles such as clays and organic debris from water, leaving it clear and bright. Certain chemicals used (such as alums) also exhibit partial dealkaliz-ing properties, which can be important given that the principal alkaline impurity removed is calcium bicarbonate—the major contributory cause of boiler and heat exchanger scales (present in scales as carbonate), although closely followed by phosphate. 

Tucker, G. and Heydon, G Trans.I.Chem.E. 76 Part C (1998) 208. Food particle residence time measurement for the design of commercial tubular heat exchangers suitable for processing suspensions of solids im liquids,... 

Direct-contact heat exchangers should be considered whenever the process stream and coolant are compatible. The equipment used is basically simple and cheap, and is suitable for use with heavily fouling fluids and with liquids containing solids spray chambers, spray columns, and plate and packed columns are used. 

Improvement of heat transfer using mass transfer, which is convection. Convection only occurs in the liquid phase and therefore only acts when heat is transferred to the PCM. When heat is extracted, the solid phase forms at the heat exchanging surface. 

Slurry reactors may take on several physical forms they may be simple stirred autoclaves they may be simple vessels fitted with an external pump to recirculate the liquid and suspended solids through an external heat exchanger or they may resemble a bubble-tray rectifying... 

Paraformaldehyde, 2 623 22 123 Paraformaldehyde solids, 22 119 para-hydrogen, 23 759, 760—761, 764 vapor pressure of, 23 764 Parainfluenza vaccine, 25 498 Paraldehyde, 2 103 Parallax errors, in liquid-in-glass thermometers, 24 465 Parallel-counterflow exchanger, heat-exchanger effectiveness for, 23 255 Parallel flow heat exchangers heat-exchanger effectiveness for,... 

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