Numerical simulation of heat transfer in a parabolic solar coleector absorber tube using two-phase method

Parabolic solar collector, use highly reflective materials to collect and concentrate the heat energy from solar radiation. The thermal efficiency of the solar collectors increases by using nanofluid. It is necessary to consider some thermal properties of nanofluid and operating parameters to reach maximum efficiency. This article presents the heat transfer of a nanofluid in the absorber tube of a parabolic collector with non-uniform heat flux on the wall. Two types of nanofluids were utilised and prepared TiO2-Syltherm 800 and Al2O3-water with 1.0%, 2.0%, 3.0%, and 4.0% nanoparticle volume fractions are used as working fluids. Reynolds number is between 10,000 and 80,000. Comparing the Nusselt number of TiO2-Syltherm 800 and Al2O3-water nanofluid demonstrated that the nanofluid has better thermal performance than the base fluid. The highest percentage increase in Nusselt number of TiO2-Syltherm 800 and Al2O3-water compared to their base fluid is 66% and 57%, respectively. The highest increase in Nusselt number is related to TiO2-Siltherm 800 nanofluid. at Reynolds 10000 and concentration of 4%. In this case, the Performance evaluation criterion, PEC, is 2.93. For both nanofluids, PEC increases with increasing concentration. With increasing Reynolds number, PEC decreases for TiO2-Siltherm 800 and increases for Al2O3-water nanofluid.