No abstract

Optimal thermo-physical properties of nanofluids provide an opportunity to overcome energy associated difficulties, in addition to providing new alternatives to catch, store and exchange of energy. A significant reduction in energy consumption is possible by improving the performance of a heat exchanger circuit, and may in part alleviate current energy related challenging issues such as global warming, climate change, and the fuel crisis. The objective of this work is to gain an insight into the overall stability of nanofluids with respect to pH, zeta potential, particle size distribution, and its effect on viscosity and thermal conductivity. For the purpose of this study two nanofluids were selected (water based alumina and copper oxide). Various nanoparticles concentrations as well as anionic surfactants (sodium dodecylbenzene sulfonate) were investigated for their stability, viscosity as well as thermal conductivity. The results clearly showed that nanofluid stability has a strong relation with viscosity and thermal conductivity. The stability of the nanofluid was found to be improved with a decrease in viscosity and an increase in thermal conductivity.

No abstract

No abstract

No abstract

No abstract

a b s t r a c tNowadays, nanofluids are being considered as an efficient heat transfer fluid in various thermal applications. Refrigerant-based nanofluids, termed as ''nanorefrigerants'', have the potential to improve the heat transfer performances of refrigeration and air-conditioning systems. This study analyzed the thermophysical properties and their effects on the coefficient of performance (COP) resulted by addition of 5 vol.% Al 2 O 3 nanoparticles into R-134a refrigerant at temperatures of 283-308 K. The analysis has been done for a uniform mass flux through a horizontal smooth tube using established correlations.The results indicate that the thermal conductivity, dynamic viscosity, and density of Al 2 O 3 /R-134a nanorefrigerant increased about 28.58%, 13.68%, and 11%, respectively compared to the base refrigerant (R-134a) for the same temperature. On the other hand, specific heat of nanorefrigerant is slightly lower than that of R-134a. Moreover, Al 2 O 3 /R-134a nanorefrigerant shows the highest COP of 15%, 3.2%, and 2.6% for thermal conductivity, density, and specific heat, respectively compared to R-134a refrigerant. Therefore, application of nanoparticles in refrigeration and air-conditioning systems is promising to improve the performances of the systems.

No abstract