Refrigeration evaporators

Refrigeration evaporators could be classified according to the method of feed as either direc t (diy) expansion or flooded (hquid... 

The dried ether solution contains about 30 g (65%) of monoperphthalic acid and is approx. 0.26 to 0.28 M. It may be used directly for oxidation reactions (cf. Chapter 1, Section IV), or stored under refrigeration. Evaporation of the ether under reduced pressure (no heat) affords the crystalline product, mp 110° (dec). 

Refrigeration load of process cooling 35 MM Btu/hr Refrigeration evaporating temperature — 13°F Temperature of process fluid —10°F... 

Refrigerant evaporating temperature Consider the 25MM Btu/hr —40°F independently as a simple two-stage system. Thus, condensing at +120°F... 

Example 35.6 An air cooling coil extracts 45 kW sensible heat with air entering at 24°C and leaving at 18°C, with the refrigerant evaporating at 11°C. Estimate the cooling capacity at 95, 90 and 85% mass air flow. 

A block diagram helps us to visualize the thermodynamic processes. The liquid refrigerant evaporates at constant temperature as it absorbs heat from the contents of the refrigerator, which are at a different constant temperature. 

Pressure level. The choice of pressure level for the mixed refrigerant evaporation affects the temperature difference between the process cooling curve and refrigerant evaporation curve. Increasing the overall temperature difference will increase the refrigeration power requirements. 

Estimate the power required to reject 1 MW of cooling duty to cooling water with a return temperature of 40°C. Assume A Tmin = 5°C for the refrigeration evaporator and Arml = 10°C for the condenser. Suggest suitable refrigeration fluids for these two duties using Figure 24.35. 

A vapor-compression refrigeration system is conventional except that a countercurrent exchanger is installed to subcool the liquid from the condenser by heat exchange with the v stream from the evaporator. The minimum temperature difference for heat transfer is 10(°F). Amm is the refrigerant, evaporating at 22(°F) and condensing at 80(°F). The heat load on the evapo is 2,000(Btu)(s) . If the compressor efficiency is 75 percent, what is the power requirement ... 

The crystallization process is normally controlled through a variation of flow rate, refrigerant evaporation temperature, or by changing the layout of the intermediate worker unit and cooling cylinders according to the oil blends used. 

The Linde liquefaction process, which depends solely on throttling expansion, is shown in Fig. 9.6. After compression, the gas is precooled to ambient temperature. It may be even further cooled by refrigeration. The lower the temperature of the gas entering the throttle valve, the greater the fraction of gas that is liquefied. For example, a refrigerant evaporating in the cooler at 233.15 K (—40°C) provides a lower temperature at the valve than if water at 294.15 K (21°C) is the cooling medium. 

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