A One-dimensional Analysis and Optimum Air Flow Rate of a Triple-Pass Solar Air Heater

Renewable energy conversion of solar energy to hot air is a feasible and sustainable solution in the trend of energy saving and environmental protection. In this work, a 1D mathematical model is reported and solved using the control volume method to investigate the distribution of seven temperatures in the triple pass flat plate solar air heater (SAH). A compact solver for predicting local temperatures of a multiple-pass SAH has been rarely found in the open literature. The collector parameters are fixed while the mass velocity of the air is varied from 0.0121 to 0.07246 kg/m
²
-s. The results of temperature distribution analysis show that the absorber plate temperature reaches a maximum in the center of the plate which is different from that of a double pass solar air collector. When the air flow rate is large, the upper glass is no longer able to transfer heat to the air, so the efficiency of the triple pass collector decreases. It is concluded the pertinent air flow rate of 0.04 kg/m
²
-s to obtain the highest effective efficiency of 64%. The present study is expected to develop multi-parametric study and apply finned, baffled or ribbed air channels.