Observations made during experimentation on SAH with encapsulated PCM on its absorber plate
A double pass packed bed solar air heater attached with encapsules filled with paraffin wax on its absorber plate is experimentally tested. Encapsules in circular and square cross sections in staggered and inline grid arrangements are used. Mass flow rate of air is changed to 0.00879 to 0.01484 kg/s. The absorber plate with cylindrical capsules in staggered arrangement was attached to SAH on the first day of the experiment and the blower was operated to supply air at a mass flow rate of 0.01484 kg/s. The direct solar radiation was recorded by placing solar power meter (WACO TM-206) perpendicular to the upper glass of the experimental setup. Thermocouples placed at different locations of SAH were connected to a multi-point temperature indicator to manually record temperatures at respective locations. The blower was allowed to run continuously for 30 minutes for each reading to ensure steady-state conditions are attained. Observations were recorded at every 5 minutes within these 30 minutes of time interval. PCM inside the capsules are charged during daytime from 9.45 a.m. to 2.15 p.m. The temperature of the air at SAH inlet and exit, temperatures of packed bed, absorber plate, lower glass, upper glass and PCM in capsules were manually recorded. In between 2.20 p.m. to 4.20 p.m, blower was switched off and the experimental setup was completely placed under insulation covers to minimize the heat loss to the surroundings. After 4.20 p.m. insulation covers were removed and blower was switched on to supply the air. This time PCM discharges stored heat to the air flowing over the capsules. The experiment for discharging process was conducted between 4.20 p.m. to 5.40 p.m. The temperature of the air at SAH inlet and exit, temperatures of packed bed, absorber plate, lower glass, upper glass and PCM in capsules were once again manually recorded.