Example Evaporator with Variable Heat Exchanging Surface

4 Example Evaporator with Variable Heat Exchanging Surface 

The evaporator shown in Fig. 3.14, is a suitable process which can be used to demonstrate the basic principles of interaction between energy and mass balances. This will be worked out further in a subsequent chapter. In this chapter the environmental diagram will be developed. This diagram is almost similar to the one used earlier in this chapter, however, the behavior is strongly different. 

The process concerns an evaporator that evaporates a liquid and discharges the vapor to a vapor system. In the evaporator a heat exchanger is mounted from the top to the bottom, as shown in Fig. 3.14. This implies that the heat-exchanging surface will depend on the liquid level. The heat required for the evaporation is delivered by condensing steam. 

The purpose of the model is to investigate the behavior of the liquid level and vapor flow to changes in process throughput. The behavior of the level is important in order to know whether it is sufficiently self-regulating. The behavior of the vapor flow can be compared to an evaporator with fixed heat exchanging surface. 

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