Cascade refrigeration system with inverse Brayton cycle on the cold side

The cold store refrigeration system proposed herein features a cascade configuration which has a vapour compression cycle as the top cycle and an inverse Brayton as the bottom cycle. The cold store air is used as working fluid in the Brayton cycle. Therefore, the cold side heat exchanger (that would be the evaporator in a vapour compression cycle) is replaced by a cold air inlet. Frost formation inside the cold store, as well as the heat load due to the air circulation fan, are hence eliminated. On the other hand, the Brayton cycle has lower efficiency when compared to vapour compression cycles. This gap may be reduced once the temperature range is lowered by the cascade configuration. The top vapour compression cycle may also refrigerate the loading dock. This paper describes a first screening of the relevant design parameters for an overall system optimization.