Thermocompressors Types

Figure 8.16. Some types of evaporators, (a) Horizontal tube, (b) Calandria type, (c) Thermocompressor evaporator, (d) Long tube vertical, (e) Falling film, (f) Forced circulation evaporator-crystallizer, (g) Three types of Oslo/Krystal circulating liquid evaporator-crystallizers.

When a compression evaporator of any type is designed, the designer must provide adequate heat transfer surface in fact, he may want to provide more surface than required to compensate for reduced heat transfer as fouling occurs. If there is inadequate surface to transfer heat available after compression, the design compression ratio will be exceeded. Under these conditions a thermocompressor may become unstable and "backfire" and the mechanical compressor may require more energy than provided. Generally, it is wise to be on the safe side and provide extra heat transfer surface for compression evaporators. 

The thermocompressor design is very similar to that of steam jet ejectors used for producing vacuum. The standard types of ejectors used for thermal compression are shown in Figure 18-2. Each ejector consists of three basic... 

Thermocompressors can be of two basic types fixed nozzle types or units with a reguiating spindle. Fixed-nozzle thermocompressors are more efficieni and are used when the thermocompressor can be operated under steady-loac conditions. Thermocompressors with regulating spindles are designed for use when performance approaches critical conditions and changes in suction loac and suction and discharge pressures are expected. 

The construction of a multiple-nozzle fixed-orifice thermocompressor is the same as that of the single nozzle unit, except that it employs several steam nozzles as shown In Figure 18-2(c). The usuai configuration has one nozzle on center with the remaining nozzles equally spaced peripherally around it. This type of unit can be used for both critical and noncritical applications. Its characteristic performance curve is similar to that of a single nozzle fixed orifice unit. 

---