A low carbon, low TEWI refrigeration system design

This paper describes an engineering solution to the problem of designing a large direct expansion system suitable for use in supermarkets which can run efficiently on environmentally benign refrigerants and has thus a low total equivalent warming impact value. The system is designed in order to allow the adoption of alternative refrigerants and is based on energy saving criteria. It is predicted to be economically competitive when compared with existing technologies. Some of the desirable features include lowered condensing temperature, sub-cooling of liquid refrigerant, raised evaporator temperature, reduced amount of refrigerant circulating, circulating velocities reduced to the minimum required for oil return and suppression of vapour formation in the liquid lines. Such a system is predicted to save up to 26% of the energy used by the best existing systems to meet a given refrigeration load, using typical UK annual climatic data. The refrigerant inventory is reduced and consequently so are losses. Such a system can also run on common refrigerants such as R404A or R410A whilst still achieving good savings on running costs.