Thermo-hydraulic performance analyses of water based CuO-SiO2 hybrid nanofluid flow in a horizontal straight tube

This study presents a numerical investigation of volume fraction effect of water based hybrid CuO-SiO2 nanofluid in a horizontal tube on thermal performance. Uniform heat flux was applied onto the outer surface of the test tube. Fully developed turbulent flow was ensured with adjusting solution domain. k-epsilon turbulent model was chosen to simulate turbulent flow, and analyses were implemented for Reynolds number ranging from 10,000 to 50,000. The nanofluid flow was assumed as single phase, and properties of nanoparticles and water are concerned as independent in temperature. Thermo-physical properties of nanofluid were calculated with commonly used equations and correlations in literature. Nanoparticle volume fractions in water were employed as 5, 4, 3, and 2% in which each volume fraction is different value of CuO and SiO2. As a result, since CuO is more effective thermal properties than SiO2, it is observed that greater volume fraction of CuO than SiO2 shows better heat transfer performance. Moreover, the highest Nusselt number is obtained for 1%CuO-4%SiO2 water based nanofluid for Reynolds number of 50,000. However, due to better hydraulic properties of SiO2 than CuO, the higher volume fraction of SiO2 compared to CuO, the higher thermo-hydraulic performance was obtained.