Numerical investigation of efficiency and economic analysis of an evacuated U-tube solar collector with different nanofluids

In this paper, an evacuated U-tube tube solar collector (EUSC) was designed and simulated numerically. The thermal performance of the EUSC was analyzed under different operating conditions. In order to enhance the heat transfer efficiency and also collector efficiency, higher thermal conductivity working fluids were used. Ag, ZnO and MgO nanoparticles in 30%:70% (by volume) ethylene glycol-pure water (EG-PW) mixture and different nanoparticle volumetric concentrations were used as working fluids. The highest collector efficiency is found at 68.7% for 4.0vol% Ag/EG-PW nanofluid which is 26.7% higher than EG-PW. Furthermore, using nanofluids in solar collectors helps to reduce the coal usage with CO2 and SO2 generation. The maximum values of reduction of coal usage and CO2 and SO2 generation are 855.5kg, 2241.4kg and 7.2kg per year, respectively, when 30 solar collectors are installed with using 4.0vol% Ag/EG-PW nanofluid. These findings reveal that the using of solar energy comprehensively is more beneficial for health of earth.