Experimental investigations on direct absorption solar flat plate collector using Al2O3 nanofluid. (21st November 2021) - Khatri, Rahul
Solar flat plate collectors have lower thermal conversion efficiencies due to high thermal losses and lower heat transfer. Direct absorption solar collector (DASC) works on the concept of volumetric absorption, i.e., solar energy will be absorbed by a thin layer of fluid flowing over a flat surface. The glass plate with reflective surface was used as base for fluid film formation and experimental investigations were carried out with water and Al2 O3 nanofluid. Nanoparticles of size 20 nm were used to prepare nanofluid with ultrasonic mixers. Three flow rates, i.e., 2, 3 and 4 lpm were worked out with water and 0.001%, 0.005%, and 0.01% volume concentrations of nanofluid. Improvement in efficiency of the collector with nanofluid was recorded when compared with water as a working fluid. Optimal flow rate of 2 lpm recorded better thermal efficiencies for water and nanofluids both. Higher efficiencies were recorded with 0.01% volume concentration of nanofluid when compared with water, 0.001% and 0.005%. For constant mass flow of 2 lpm, the maximum efficiency improvement, i.e., 13% was achieved with 0.01% volume concentration of nanoparticles compared with water. Maximum single pass temperature difference of 2.7°C and 4.5°C was achieved for water and 0.01% nanofluid, respectively.