Improving the performance of refrigeration systems by using nanofluids: A comprehensive review

In view of energy security and environmental concern, the performance of refrigeration system needs to be improved, which can be done by modifying either the systems or the properties of primary and secondary working fluids. Recently, the nanofluids or hybrid nanofluids have gained interest in many engineering fields due to its excellent thermophysical properties, which can be easily used in refrigeration and air conditioning systems by many roles for performance improvement. This review summarizes the researches on preparation and characterization of nanofluids, various thermophysical and electrical properties (density, heat capacity, viscosity, thermal conductivity, surface tension, electrical conductivity, freezing characteristics, etc.) of nanofluids. Applications of nanofluids in the refrigeration systems as refrigerant, lubricant and secondary fluid are well-grouped and discussed. Finally, the challenges and opportunities for future research are identified, which will be useful for the newcomers and manufacturers in this field.