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The article widely reviewed the variation of the heat transfer characteristics and fluid flow of various nanofluids based on physical and chemical parameters like velocity, geometry, viscosity, friction factor, and pressure drop. It also shed light on the stability of these nanofluids in various conditions. The article mainly focuses on the effects on Reynolds number and Nusselt number, thermal changes in the environment and the cooling solution used for nanofluids, and the dependency of concentration of nanoparticles in the working fluid. Apart from this, it also discusses the geometry in which the fluid is kept and the motion or forces it experiences and simulations to observe and analyse the flow of fluid and heat through these nanofluids. Also, this article presents the improvement in the pool boiling heat transfer rates through nanofluids with twisted tapes and corrugated patterns such as corrugated double-tube exchangers. This article concluded with the results obtained from experimental analysis and numerical methods. According to the study, as nanofluids get bigger, their velocity increases. When particle size is increased from 10 nm to 100 nm, the alumina-water nanofluid’s velocity rises by 22.22%. For Al2O3/water nanofluid with a particle size of 10 nm, the rate of expansion in wall shear stress when concentration is raised from 0% to 5% is 75%. The geometry of the tubes affects the properties of heat transport. When a triangular tube having a twisted tape is utilized in the system, the Nusselt number is enhanced by 34.7% and 52.5% in turbulent and laminar flow respectively.

In this paper viability of the Nano-refrigerants as a replacement for conventional coolants in bringing down energy consumption and thereby contribute to the green economy has been reviewed. The influence of the % of nanoparticle concentration in thermal conductivity, heat transfer characteristics, and system performance in a refrigeration system is analysed. In this paper, the use of MHD and NEPCM were also discussed and reviewed for their useful impact in the field of nano refrigeration. Review analysis indicated that the maximum coefficient of performance, i.e., 18.75% of enhancement, was observed when the TiO2 nanoparticle was added to the R134a refrigerant. Whereas in the case of the power consumption, Al2O3/R134a gives a 27% reduction in power consumption compared to the conventional fluids. Energy-saving of Al2O3/R134a nano-refrigerant is more than 5 times and 80% more efficient compared to R134a/CuO. Similarly, Al2O3/R134a is 50% more efficient than R134a/SiO2 and 3.4% more efficient than R134a/TiO2. However, R134a/TiO2 exhibited a 54.7% increment in the value of COP compared to R134a/Al2O3. Also, R134a/TiO2 displayed 60% and 35.2% of increment in COP in contrast to R134a/CuO, R134a/SiO2 respectively. The analysis recommends R134a/TiO2 as the best nano-refrigerant as its COP is the highest of all with the energy savings on par with the Al2O3/R134a.