Measurements and correlations of frictional pressure drop of TiO2/R123 flow boiling inside a horizontal smooth tube

Nanorefrigerant is one kind of nanofluids. It is the mixture of nanoparticles with refrigerants. It has better heat transfer performance than traditional refrigerants. Recently, some researches have been done about nanorefrigerants. Most of them are related to thermal conductivity of these fluids. Viscosity also deserves as much consideration as thermal conductivity. Pumping power and pressure drop depend on viscosity. In this paper, the volumetric and temperature effects over viscosity of TiO2/R123 nanorefrigerants have been studied. Numerical conditions include temperature from 300 to 325 K, nanoparticle concentrations from 0.5% up to 2%, mass fluxes from 150 to 200 kg m− 2 s− 1, inlet vapor qualities from 0.2 to 0.7 and diameter of tube from 6 to 10 mm. The effect of pressure drop with the increase of viscosity has also been investigated. Based on the analysis it is found that viscosity of nanorefrigerant increased accordingly with the increase of nanoparticle volume concentrations and decreases with the increment of temperature. Furthermore, pressure drop augmented significantly with the intensification of volume concentrations and vapor quality. Therefore, low volume concentrations of nanorefrigerant are suggested for better performance of a refrigeration system.