Modeling and performance evaluation of a small solar parabolic trough collector (PTC) for possible purification of drained water

Abstract

Small-scale solar thermal contaminated water purification is a promising green energy based decentralized process especially for rural area. The present work describes thermal performance estimation of a Parabolic Trough Collector (PTC) suitable for contaminated water purification. Contaminated drain water is pressurized through a slow sand filter and PTC with glass cover enclosing a copper tube. The diameter of the copper tube was estimated as 26 mm and that of the glass cover was 50 mm. The rim angle and width of the parabola were 60° and 1.2 m respectively. The PTC focal length, concentration ratio, overall heat loss coefficient was 493.4 mm, 13.93 and 7.39 W/m2K respectively. The maximum modeled and experimental thermal efficiency were about 60% and 55% respectively. Around water flow rate of 0.002 kg/s and solar radiation 750 W/m2, both water temperature and useful heat gain were maximum. The exergetic efficiency of the system increases with the increase of inlet temperature of water for different solar intensity. The solar purified water had all other parameters within acceptable limit except residual chlorine (0.24 mg/L).