A two-stage refrigeration system for a supermarket using heat recovery and natural refrigerants

The cooling demand of a supermarket is split into two systems operating at different temperature levels corresponding to low temperature frozen food, and high temperature chilled food storage. This paper describes a proposed system in which high temperature cooling is provided by a screw compressor driven by a gas engine, and low temperature cooling is provided by waste heat from the gas engine. A jet-pump refrigeration system is most suitable for driving the low temperature cooling system. A COP of 1.0 could be achieved for the jet-pump sub-cycle, which is high because the jet-pump discharges to an intermediate pressure. Secondary fluids transfer the coolth to the display cabinets so allowing the cooling plant to be housed in purpose built machine rooms, enabling hydrocarbon refrigerants to be used and minimising flammability risks.