Comparative Performance Analysis of Stainless-Steel Tube and Glass Coated Copper Tube Receiver in Parabolic Trough Collectors for Enhanced Thermal Efficiency

Renewable energy is the most promising energy-saving and environmentally friendly option. The concentrating type solar collector like parabolic trough collectors can be utilized for solar thermal energy collection due to low cost and high-temperature output. The paper is an experimental study of a solar parabolic trough collector with manual sun tracking. A parabolic trough with an area of 2.5´1.75 m² was constructed for the present study. A highly polished aluminum sheet for concentrating the reflecting sunlight to the focal line contains the receiver tube. The parabolic trough was tracked at regular interval of one hour concerning the sun position and focused the sunlight into the receiver tube to ensure sound performance. Water is used as a working fluid inside the receiver tube, and experiments were done with three different mass flow rates of 0.0072,0.0112 and 0.0158 kg/s. Two heat-collecting elements, such as a stainless-steel receiver tube and a glass-coated copper receiver tube, were tested with a parabolic trough. The performance was analyzed based on the difference in the inlet and outlet temperature of the working fluid at the ends of the receiver tubes of the parabolic trough. The instantaneous efficiency of the parabolic trough with two different materials of receiver tube at three different flow rates were evaluated.  The results showed that the glass coated copper tube surpassed in performance compared with stainless steel receiver tubes. The instantaneous efficiency of the glass coated copper tube is found to be 71.17% at a flow rate of 0.0158 kg/s which was significantly high when compared with that of the stainless-steel receiver tube. The glass coated copper tube prevents the convective heat transfer loss and thereby increases the efficiency. The experiment shows that the performance of the parabolic trough solar collector strongly depends upon solar light tracking and the focal line containing the receiver tube.