Theoretical and experimental investigation of a novel hybrid heat-pipe solar collector

This article describes a novel flat plate heat-pipe solar collector, namely, the hybrid heat-pipe solar collector. An analytical model has been developed to calculate the collector efficiency as well as simulate the heat transfer processes occurring in the collector. The effects of heat pipes/absorber, top cover, flue gas channel geometry, and flue gas temperature and flow rate, on the collector efficiency were investigated based on three modes of operation, i.e., solar only operation, solar/exhaust gas combined, and solar, exhaust gas and boiler combined. Experimental testing of the collector was also carried out for each of these modes of operation under real climatic conditions. The results were used to estimate the efficiency of the collector and determine the relation between the efficiency and general external parameter. The modeling and experimental results were compared and a correlation factor was used to modify the theoretical predictions. It was found that the efficiency of the collector was increased by about 20-30% compared to a conventional flat-plate heat pipe solar collector.