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Since 1995, research has been going on in different aspects of nanofluids. Most of them are related to thermal conductivity and heat transfer properties of nanofluids based on water or ethylene glycol. Nanorefrigerants are one kind of promising nanofluids that based on refrigerants. Hear transfer and pressure drop characteristics of nanorefrigerants must be determined before putting into application. The objectives of this study are to determine the heat transfer and pressure drop characteristics of Al2O3-R141b nanorefrigerants for different volume concentrations. The experimental conditions include: constant mass flux of 100 kgm-2s-1, vapor qualities from 0.2 to 0.7, temperature at 25 °C and 0.078535 MPa pressure. Based on the analysis it was found that both heat transfer and pressure drop characteristics increased with the enhancement of nanoparticle volume concentrations. Therefore, an optimum concentration of nanoparticles with refrigerants (compromising the heat transfer performance and pressure drop characteristics) can improve the performance of a refrigeration system as to increase the energy efficiency and cooling capacity.
Mahbubul et al. (Tue,) studied this question.