Operator transfer

Heat transfer operations. Heat transfer fluids other than steam... 

R. Krishna and R. Taylor iu N. P. Chemetisiuoff, ed.. Handbook for Heat and Mass Transfer Operations, Vol. 2, Gulf Publishing Corporation, Houston, Tex., 1986. 

R. E. Treybal, Mass Transfer Operations, 3rd ed. McGraw Hill, New York, 1980. 

Gas-Cycle Systems. In principle, any permanent gas can be used for the closed gas-cycle refrigeration system however, the prevailing gas that is used is air. In the gas-cycle system operating on the Brayton cycle, all of the heat-transfer operations involve only sensible heat of the gas. Efficiencies are low because of the large volume of gas that must be handled for a relatively small refrigera tion effect. The advantage of air is that it is safe and inexpensive. 

Heat transfer and mass transfer occur simultaneously whenever a transfer operation involves a change in phase or a chemical reaction. Of these two situations, only the first is considered herein because in reacting systems the complications of chemical reaction mechanisms and pathways are usually primary (see HeaT-EXCHANGETECHNOLOGy). Even in processes involving phase changes, design is frequendy based on the heat-transfer process alone mass transfer is presumed to add no compHcations. But in fact mass transfer effects do influence and can even limit the process rate. 

Taylor and Krishna, Multicomponent Mass Transfer, Wiley, 1993. Toumie, Laguerie, and Couderc, Chem. Engr. Sd., 34, 1247 (1979). Treybal, Mass Transfer Operations, 3d ed., McGraw-Hill, 1980. 

A pseudo-convective heat-transfer operation is one in which the heating gas (generally air) is passed over a bed of solids. Its nse is almost exchisively limited to drying operations (see Sec. 12, tray and shelf dryers). The operation, sometimes termed direct, is more aldu to the coudnctive mechanism. For this operation, Tsao and Wheelock [Chem. Eng., 74(13), 201 (1967)] predict the heat-transfer coefficient when radiative and conductive effects are absent by... 

Gas-hquid contac ting systems are utilized for transferring mass, heat, and momentum between the phases, subject to constraints of physical and chemical equihbrium. Process equipment for such systems is designed to achieve the appropriate transfer operations with a minimum expenditure of energy and capital investment. 

All these processes are, in common, liquid-gas mass-transfer operations and thus require similar treatment from the aspects of phase equilibrium and kinetics of mass transfer. The fluid-dynamic analysis ofthe eqmpment utihzed for the transfer also is similar for many types of liquid-gas process systems. 

To design deep-bed contactors for mass-transfer operations, one must have, in general, predictive methods for the following design parameters ... 

The power for agitation of two-phase mixtures in vessels such as these is given by the cuiwes in Fig. 15-23. At low levels of power input, the dispersed phase holdup in the vessel ((j)/ ) can be less than the value in the feed (( )df) it will approach the value in the feed as the agitation is increased. Treybal Mass Transfer Operations, 3d ed., McGraw-HiU, New York, 1980) gives the following correlations for estimation of the dispersed phase holdup based on power and physical properties for disc flat-blade turbines ... 

FK . 15-22 Uqiiid agitation by a disc flat blade turbine in the presence of a gas-liquid interface a) without wall baffles, (h) with wall baffles, and (c) in full vessels without a gas-bqiiid interface (continuous flow) and without baffles. [Couitesy Treyhal, Mass Transfer Operations, 3rd ed., p. 148, McGraw-Hill, NY,... 

SOURCE Treyhal, Mass Transfer Operations, 3ded., p. 152, McGraw-Hill, NY, 1963. 

Location of Transfer Stations Whenever possible, transfer stations should be located (1) as near as possible to the weighted center of the individual solid-waste-produciion ares to be served, (2) within easy access of major arterial highways as well as near secondary or supplemental means of transportation, (3) where there will be a minimum of pubhc and environmental objection to the transfer operations, and (4) where construction and operation will be most economical. Additionally, if the transfer-station site is to be used for processing operations involving material recovery and/or energy production, the requirements for those operations must be considered. 

In any mass transfer operation, the compositions of the liquid and vapor phases are assumed to follow the relationship illustrated by the column operating line. This line represents the overall calculated profile down the column however, the composition on each individual square foot of a particular column cross-section may vary from that represented by the operating line. These variations are the result of deviations in the hydraulic flow rates of the vapor and liquid phases, as well as incomplete mixing of the phases across the entire column. 

An AC corona discharge in the throat leads to a cloud of charged droplets whose large momentum allows very long travel distances. Multiple devices for eliminating static discharges in powder silos have been tested [41] but the tests did not address typical flow rates for large capacity, dense phase pneumatic transfer operations. 

Mass transfer operations (in which a material is transferred across a phase boundary or interface)... 

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