Experimental performance evaluation and comparative analyses of heat pipe and direct flow augmented solar collectors

Experimental performance evaluation and comparative analyses of two different types of internal concentrator augmented solar collectors; the evacuated tube heat pipe solar collector array with either an evacuated or non-evacuated direct flow or heat pipe internal concentrator augmented collectors based on heat extraction methods are presented in this paper. To effectively analysis and compare these systems under similar operating conditions, experimental results are presented in the form of temperature response (inlet and outlet temperature increase, outlet and inlet temperature differential, mean temperature differential at the start and end of the experimental test periods), heat flow rates and collection efficiency plotted against experimental test time. This analytical method shows the merits and demerits of each solar collector operating under variable conditions and indicates the best application area for each system. The evacuated and non-evacuated heat pipe augmented concentrators proved to be better options for medium temperature applications due to higher temperature response, lower heat losses and higher collection efficiencies.