Evaporators Performance

Condenser performance should be expressed as evaporating effect to enable matching with compressor and evaporator performance. Condenser evaporating effect is the refrigeration capacity of an evaporator served by a particular condenser. It is the function of the cycle, evaporating temperature, and the compressor. The evaporating effect could be calculated from the heat-rejection ratio qc / e -... 

The diagram of the evaporator performance is shown in the Fig. 11-97. The character of the curvature of the hues (variable heat-transfer rate) indicates that the evaporator is coohng air. Influences of the flow rate of cooled fluid are also shown in this diagram i.e., higher flow rate will increase heat transfer. The same effect could be shown... 

Evaporator performance is rated on the basis of steam economy— kilograms of solvent evaporated per kilogram of steam used. Heat is... 

The preliminary investigation showed that lower pressures result in significantly higher heat fluxes. It s possible to approaeh 50 W/em while maintaining the wall temperature below 85 °C with little optimization. A more eomprehensive parameterization study will be addressed such as pore size, geometry, and other effeets as the limits of graphite foam evaporator performance [34-35]. 

Key issues in both cases are efficient heat transfer to the samples to achieve good evaporation performance, and resistance against the chemicals usually encountered in organic synthesis. 

Energy economy and evaporative capacity are the major measures of evaporator performance. When evaporating water with steam, the economy is nearly always less than 1.0 for single-effect evaporators, but in multiple-effect evaporators it is considerably greater. Other performance variables to be considered include product quality, product losses, and decrease in performance as scaling, salting, or fouling occurs. 

Nearly every supplier of evaporation equipment and systems maintains a pilot plant facility where, for a fee, different evaporation schemes can be set up. Data obtained from several days of testing on small laboratory or pilot plant units can be good predictors of evaporator performance, and these data are very helpful in the scaling-up calculations for production-sized installations. Samplers obtained from the test work can be used to check the mass balances, concentrations, and product quality. Serious operational problems like foaming, plugging, and fouling can occur in even short pilot plant tests and can point to the need for alternative evaporator types or modified designs. 

Tests are conducted to determine capacity, heat transfer rates, steam economy, product losses, and cleaning cycles. Practically all the criteria of evaporator performance are obtained from differences between test measurements. Errors can result when measuring flow rates, temperatures and pressures, concentrations, and steam quality. Factors which can have a great effect on performance include dilution, vent losses, heat losses, and physical properties of fluids. 

The results of experiments conducted to determine the magnitude of lead contamination from the air are shown in Table XXI. In these experiments, 500 ml of 6 N hydrochloric acid was taken to dryness in the various environments in the time period listed in the table. The evaporations performed in the ordinary-air laboratory were in a Transite hood recently coated with Tygon paint (C8). 

Make efficient use of the available energy. This may take several forms. Evaporator performance often is rated on the basis of steam economy-pounds of solvent evaporated per pound of steam used. Heat is required to raise the feed temperature from its initial value to that of the boiling liquid, to provide the energy required to separate liquid solvent from the feed, and to vaporize the solvent. 

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