**8. Comparison between cryogenic and refrigeration system using isobutane as refrigerant**

From the description of the cryogenic refrigeration system (CRS), it visible that,


However, this study focused on the importance, properties, challenges, limitations, and refrigerants' applications in the domestic refrigeration system. The refrigeration system's heat transfer fluid (refrigerant) determines the overall performance of the system. More so, the refrigerant serves as the heat transfer medium, while the refrigerant type enables the prediction of a suitable refrigerant to be used in the vapor compression refrigeration system. This work's case study is an ideal system using isobutane (R600a) and hydrofluorocarbon (R134a) as refrigerants. And comparisons were carried out to investigate their performance characteristics.

### **8.1 Solubility/miscibility of lubricant**

The heat transfer within the heat exchanger (H.E) of the refrigeration system is enhanced by the lubricant type used in the process. However, the solubility of the

working fluid in the lubricant improves the heat transfer due to a reduction in the oil's viscosity, which increases the oil fluidity and reduces the negative impact of the heat transfer within the heat exchanger [21]. Therefore, the newly manufactured lubricant is recommended to operate a refrigeration system that uses hydrofluoroolefins, hydrocarbon, and hydrofluorocarbon blend as working fluid is polyol-ester (POE) oil. It possessed better lubricating properties than conventional oils. Thus, the refrigerant effect becomes more visible on the heat transfer rate within the vapor compression refrigeration system as the appropriate lubricant is charged into the compressor [71].
