EFFECT OF PACKING MATERIAL AND ITS GEOMETRY ON THE PERFORMANCE OF PACKED BED COLLECTOR

Abstract

It has been well established that packed bed solar collectors perform better as compared to conventional collectors. Results of performance studies on packed bed solar collector are available in literature in which different operating conditions have been considered which make it difficult to compare their performance accurately. Considering this comparative study of performance of solar collector with different packing elements has been made in the present work. Experimental investigations on solar collector packed with iron chips, wire mesh, gravels and glass balls for the same set of operating parameter have been done on a single setup to study the effect of packing material and its geometry on the thermal efficiency of packed bed collector. It is observed that iron chips packed collector is identified as the best packing materials out of the materials selected for study leading to thermal efficiency of 76.21% for the mass flow rate of 0.035 kg/s and porosity of 0.945, which is 69.58% higher as compared to smooth collector. Thermal efficiency of wire mesh packed collector for similar operating conditions is found to be 74.26% which is 65.24% higher than smooth collector. In low porosity range gravel packed collector is found to perform better as compared to glass ball packing. Effect of mass flow rate on the effective efficiency has also been conducted for various packing elements used in the present study. Based on the experimental results, plots have been drawn for efficiency against temperature rise parameters for different packing elements which can be used by the designer for choosing the correct value of mass flow rate for the specific temperature rise application.