Analytical and Experimental Studies on the Thermal Efficiency of the Double-Pass Solar Air Collector with Finned Absorber

Problem statement: The design of suitable air collectors is one of the most important factors controlling the economics of the solar drying. Air type collectors have two inherent disadvantages: Low thermal capacity of air and low absorber to air heat transfer coefficient. Different modifications are suggested and applied to improve the heat transfer coefficient between the absorber plate and air. These modifications include the use of extended heat transfer area, such as finned absorber. Approach: The efficiency of the solar collector has been examined by changing the solar radiation and the mass flow rate. An analytical and experimental study to investigate the effect of mass flow rate and solar radiation on thermal efficiency were conducted. The theoretical solution procedure of the energy equations uses a matrix inversion method and making some algebraic rearrangements. Results: The average error on calculating thermal efficiency was about 7%. The optimum efficiency, about 70% lies between the mass flow rates 0.07-0.08 kg sec^-1. The thermal efficiencies increase with flow rate and it increase about 30% at mass flow rate of 0.04-0.08 kg sec^-1. Conclusion: The efficiency is increased proportional to mass flow rate and solar radiation and .the efficiency of the collector is strongly dependent on the flow rate.