Experimental Evaluation of Double Air Pass Solar Collector in Humid Tropical Environment

Abstract

The present work was focused on the experimental investigation of a double air pass solar collector which was designed and constructed at the Laboratory of Energetic and Thermal Applied of the National School of Agro-Industrial Sciences of the University of Ngaoundere. It consists of a double glazed cover with a surface of 0.47 m², an absorbent plate and a layer of thermal insulation. It allows simultaneous circulation and the same flow direction of the working fluid (air) on both side of the absorber. The experimental tests were conducted outdoor, in natural environment of Ngaoundéré city, during one month period, from 4 to 30 of April, between 9:00 am and 5:00 pm, local time. The research aim was to characterize, on one hand, the local weather conditions (solar radiation, ambient temperature, relative humidity and wind velocity), and on the other hand the collector performance. The solar collector was permanently oriented towards the South and tilted by 45° with respect to the horizontal plane. The analysis of the temperature profiles of different components of the collector showed that the maximum temperature was reached at 2:30 pm, when solar radiation was 1217 W/m² and they were 73.9°C, 61.7°C and 44.7°C for absorber, inner glass and outer glass, respectively. As concerning the outlet temperature of the heat transfer fluid, the analysis of the results shows that it goes up to 58.4°C and 52.2°C, while thermal efficiency was as high as 47.81% and 65.57% when the air flow velocities were setup at 0.5 m/s and 1.5 m/s, respectively.