Heat Transfer Applications

These equations are applied in the simulation example CHROMDIFF to the case of a two-component separation with linear equilibrium. The situation of a non-linear equilibrium is considered as an exercise in the example. 

The simulation program CHROMPLATE uses the plate model for the same column conditions as the simulation model CHROMDIFF. The results obtained are very similar in the two approaches, but the stagewise model is much faster to calculate. 

With high concentrations, heat effects in the chromatographic column may be important. This would require the simultaneous application of an energy balance and the introduction of a term reflecting the influence of temperature on the adsorption equilibrium. 

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G. Y. Eastman and D. M. Ernst, The Heat Pipe, A Unique and Versatile Devicefor Heat Transfer Applications, RCA, Lancaster, Pa., 1966. 

Heat-Transfer Applications Heat-transfer analogs of common mass-transfer terms are ... 

Apparatus for testing materials for heat-transfer applications is shown in Fig. 28-4. Here the sample is at a higher temperature than the bulk solution. 

Aluminum and Alloys Aluminum and its alloys are made in practically all the forms in which metals are produced, including castings. Thermal conductivity of aluminum is 60 percent of that of pure copper, and unalloyed aluminum is used in many heat-transfer applications. Its high electrical conductivity makes aluminum popular in electrical apphcations. Aluminum is one of the most workable of metals, and it is usually joined by inert-gas-shielded arc-welding techniques. 

In heat transfer applications, this jacket is considered a helical coil if certain factors are used for calculating outside film coefficients. The equivalent heat transfer diameter, D, for a rectangular cross-section is equal to 4 w (w being the width of the annular space). Velocities are calculated from the actual cross-section of the flow area, pw (p being die pitch of die spiral baffle), and die effective mass flowrate W dirough die passage. The effective mass flowrate is approximately 60% of die total mass flowrate of die jacket. 

Colburn j-factor = Used in heat-transfer applications. 

Mean radiant temperature The average temperature of the six surfaces of a cubicle enclosure, used in thermal comfort work and in other heat-transfer applications. It is the sum of all the surface areas multiplied by the temperature of the surface divided by the total surface area. 

Ax,BEL, D. Heat Transfer Applications in Process Engineering (Noyes, New York, 1984). 

It is important to add heat transfer scale-up considerations to the scale-up approach for liquid parenteral solutions as heat transfer applications may play a considerable role in preparation of these products. For heat transfer applications, constant horsepower per unit volume is used to achieve approximately similar heat transfer coefficients for the same type of impeller. This approach is a close approximation since the effect of horsepower on the heat transfer coefficient (ho) is relatively small ... 

Approximately 1 kg of biphenyl per 100 kg of benzene is produced (6). Because of the large scale, HDA operations provide an ample source of crude biphenyl from which a technical grade of 93—97% purity can be obtained by distillation (35). Zone refining or other crystallization techniques are required to further refine this by-product biphenyl to the >99.9% purity required for heat-transfer applications. 

Reliable estimates of annual production of biphenyl in the United States are difficult to obtain. The 1990 figure is probably on the order of 16 million kg /yr of which about half is derived from hydrodealkylation sources. About 10% of the biphenyl derived from HDA sources is consumed, as 93—95% grade, in textile dye carrier applications. The remainder is used for alkylation or upgraded to >99.9% grades for heat-transfer purposes. Essentially all of the high purity biphenyl produced by dehydrocondensation of benzene is used as alkylation feedstock or is utilized directly in heat-transfer applications. 

Biphenyl, terphenyl, and their alkyl or hydrogenated derivatives generally serve markets where price and performance, rather than composition, is the customer s primary concern. Performance standards for heat-transfer applications are usually set by the fluid supplier. The biphenyl—diphenyl oxide eutectic (26.5% biphenyl, 73.5% DPO) represents a special case. This composition has become a widely recognized standard vapor-phase heat-transfer medium. It is sold throughout the world under various trademarks. In the United States, Dow (Dowtherm A) and Monsanto (Therminol VP-1) are the primary suppliers. Alkylated biphenyls and partially hydrogenated terphenyls serving the dielectric and carbonless copy paper dye solvent markets likewise are sold primarily on the basis of price and performance characteristics jointly agreed on by producer and user. 

Terphenyls in heat-transfer applications are used in relatively smaller quantities with negligible release to the environment. They are sufficiently biodegradable so as not to constitute an environmental threat (56,57). Some properties important for environmental considerations are summarized in Table 7. 

Monsanto Chemical Company Oils. Monsanto Chemical Co. manufactures two oils for heat-transfer applications. Therminol HFP is a solvent refined paraffinic oil Therminol XP is a dear white mineral oil essentially identical to Multitherm PG-1 and Paratherm NF. 

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