ENHANCED DOUBLE-PASS SOLAR AIR HEATER WITH AND WITHOUT POROUS MEDIUM

An energy and exergy study has been done on a double-pass flat-plate solar air collector with and without porous medium embedded inside the lower channel of the collector. Energy conservation equations are used to derive the energy-governing equations for all components of the collector. A second law analysis (the second law of thermodynamics) was carried out to optimize the mass flow rate, which leads to optimization of the energy efficiency. Theoretical results for energy and exergy efficiencies are plotted for the cases of with and without embedded porous medium. Results of this research show that the porous medium embedded inside the lower channel leads to an increase in the thermal efficiency of the collector of more than 30% compared with the case without porous medium, hence showing the importance of employing porous medium in thermal solar collectors. On the other hand, the pressure drop in the air caused by friction with porous medium is not negligible and is also studied here, using the second law analysis.