INCREASED SOLAR COLLECTOR'S EFFICIENCY WITH REVERSED-PASS AIR FLOW SYSTEM

Abstract

The thermal performance of a solar heat collector in which the air path is reversed to flow beneath the absorber plate after passing over it was studied. This type of system is referred to by the authors as the Reversed-Pass Air Flow Collector. Under the same operating conditions (gas flow rate & tilt angle), the rise in air temperature, ΔT, was found to be 10 to 40% higher than that obtained with single-pass air flow (without reversing) system depending upon the prevailing weather conditions. The local heat transfer coefficient from the top surface of the absorber plate was calculated for both types of flow systems and was found to be almost equal. The increased rise in temperature, ΔT, with the reversed-pass air flow system led to an increase in the thermal efficiency of the solar collector. On comparing the two air flow systems, it was noticed that with reversed-pass air flow systems the air is heated at the entrance region, over the absorber's top surface and during the reversed flow from the absorber...