1.1.2. Cascaded refrigeration cycle

Cascade cycles are usually applied in two cases [8]: (1) when the temperature range between condensation and evaporation cannot be covered by any single refrigerant and (2) when use of a single refrigerant cycle consumes more work than a cascade cycle.

Cascaded cycles are composed of two or more refrigeration cycles, where each cycle employs a different refrigerant. The low temperature cycle and a high temperature cycle, as shown in Figure 1(b), are connected to each other through a heat exchanger, which acts as an evaporator

Figure 1. (a) Simple vapor-compression cycle; (b) cascade refrigeration cycle.

for the high temperature cycle and a condenser for the low temperature cycle. The partition temperature, which is the temperature of the evaporator of the upper cycle, is an important design parameter. It influences the total shaft work requirement of the cycle as will be seen in Section 1.2.1.
