**7. Cryogenic refrigeration cooling system**

Cryogenic refrigeration generates low temperatures far below the average temperature produced by a simple vapor compression refrigeration system. It is used to determine temperature range from 150°C to 273°C, and the gases associated with cryogenic are Nitrogen (N2), Oxygen (O2), Helium (He), and Hydrogen (H2), which boiled below 150°C, while other refrigerants have their boiling point above 150°C. In Engineering, the role of cryogenic includes electronics, rocket propulsion system, food preservation, nuclear engineering application, mechanical design, and biological application. Furthermore, the cryogenic approach of producing low temperature is used for commercial application and this achievable by different methods such as cascade refrigeration and multistage compressor [67, 68].

### **7.1 Cascade refrigeration**

This system was first introduced in 1877 by Pictet, where he used for the liquefaction of oxygen (O2). There are two or three vapor compression systems involved, and for it to generate low temperature, various kinds of refrigerants were employed at the different circuits. It has application in medical and industrial systems, and one typical example is the preservation of blood in the blood bank because blood requires a temperature as low as 80°C [69].
