Experimental study on solar air heater with encapsulated phase change material on its absorber plate

Effective usage of solar air heaters (SAH) is limited to specific time due to nonavailability and low intensity of solar radiation. In addition, SAH suffers from lower thermal efficiencies. Encapsulated phase change material (PCM) on absorber plate of SAH is one of the passive techniques to improve thermal efficiency of SAH as well as to extend its application to nonsunshine hours. In this article, capsules of circular and square cross sections filled with PCM were used on absorber plate of a double pass counter flow SAH and SAH efficiency was experimentally determined. Capsules were placed in inline and staggered grid arrangements perpendicular to the flow direction of the air and paraffin wax was used as the PCM. Experiments were conducted each day in two cycles (charging PCM from 10:00 am to 2:00 pm and discharging PCM from 4:30 pm to 5:30 pm), with fixed mass flow rate of air in between 0.00879 and 0.01484 kg/s. It is found from the results that, efficiency of SAH with square staggered encapsules is at an average of 15.8% higher than the remaining arrangements. During PCM discharge, air temperature at the SAH exit was at an average of 5.17 degrees C greater than ambient temperature for all arrangements.

Automated summary

The study improved the thermal efficiency of solar air heaters by using capsules filled with phase change material on the absorber plate, allowing for effective operation during non-sunshine hours.