Enhancement of Heat Transfer Characteristics in an Absorber Tube of a Solar-Based Energy System Using Nanofluids

In this present paper, nanoparticles are dispersed into a base fluid, their effect on the thermophysical properties and overall heat transfer coefficient of the fluid inside a circular tube representing an absorber tube of a Parabolic Trough Solar Collector (PTSC) is studied. Different models are used to predict the effective density, specific heat capacity, viscosity and thermal conductivity of the nanofluids. For the analytical analysis, Alumina (Al₂O₃), Copper (Cu) and Single Wall Carbon Nanotubes (SWCNT) nanoparticles are dispersed into Therminol VP-1 oil. The resulting nanofluids are compared in terms of their thermophysical properties, their convective heat transfer characteristics and their overall heat transfer coefficient. Moreover, the effect on increasing the volume fraction on the properties and the heat transfer coefficient is studied. The computational analysis results show that the thermal conductivity increases with the increase of the volume fraction. In addition Therminol/SWCNT showed the highest thermal conductivity enhancement of 98% for a volume fraction of 3%. Further, the overall heat transfer coefficient increases with the increase of volume fraction, and Therminol/SWCNT showed the highest enhancement with 72% compared to Al₂O₃/Therminol and Cu/Therminol that showed an enhancement of 29% and 43% respectively.