Dynamic simulation and control of dual-evaporator compression refrigeration systems

The need for refrigeration cooling at two different sub-ambient temperature levels is an important problem in some processes. A modern grocery store is an extremely important global example in which there is a need for a moderate temperature heat sink (5 °C) to keep food cool but also a need for a significantly colder heat sink (− 20 °C) for frozen food products. If the two temperatures are not too different, a single refrigerant can be used. The compression refrigeration configuration then consists of two compressors operating in parallel, a single condenser, a single refrigerant liquid surge drum and multiple evaporators. Liquid refrigerant at high pressure is split into a large number of parallel streams to feed individual evaporators in the cooling and freezing compartments. This paper studies how this multi-variable interacting dynamic system can be modeled and controlled using simple conventional controllers.