Experimental analysis of a dual-functional solar collector working in air heating mode

Flat plate solar collectors are widely utilized for water or air heating throughout the world. But both the water collector and air collector may be left unused occasionally. In this paper, a new designed solar collector that can work for water or air heating is proposed. Different from the conventional solar water heater, the air flow through the up and down channel of the dual-functional solar collector in air heating mode. A test rig has been set up to evaluate the thermal performance of collector working in air heating mode. The thermal efficiency under different flow rate and air inlet temperature was tested. The result shows that the efficiency varies from 44.5% to 62.3% with different flow rate and the typical efficiency at zero reduced temperature is 51.9% under flow rate of 0.025 kg/s. The dual-function solar collector can operate efficiently in air heating mode under variable conditions.