Cascade Refrigeration System:

Figure 12 (a) is a schematic representation of a cascade refrigeration system along its T-S diagram .A cascade refrigeration system may be considered to be corresponding to two independent vapour-compression systems connected together in such a way that the evaporator of the high-temperature system becomes the condenser of the low-temperature system. Though, the working media of the two of these systems are separated from each other. Therefore this allows the use of different refrigerants functioning at different temperature ranges to attain the desired influence, which would otherwise; ought to be attained through a single refrigerant functioning at a bigger operating pressure range. Therefore, we may make use of appropriate refrigerants at the higher & lower pressure ranges to derive greatest benefit.

 (a) Schematic illustration of                                                     (b) T-s plot of

Multistage Evaporator System                                        Multistage Evaporator System

There are several industrial & medical applications that necessitate the use of the cascade refrigeration system. One such instance is the storage of blood in blood banks. Blood require temperatures as low as - 80 ⁰C for proper storage.