Design and performance analysis of solar air heater with phase change materials

A novel solar air heater (SAH) with provision of integrating phase change material (PCM) was designed and developed in the Department of Energy, Tezpur University located in (26.7003 degrees N and 92.8308 degrees E). A code was developed in MATLAB platform to estimate design parameters of the PCMSAH viz., (i) air mass flow rate (0.018 kg/s), (ii) length of the absorber plate (1.57 m) and thickness of PCM cavity (1 cm) based on energy analysis. Required quantities of selected PCMs viz., acetamide (14.56 kg), stearic acid (12.12 kg) and paraffin wax (11.30 kg) were also assessed based on the PCM melting depth. Close agreement between the simulated and experimental outlet temperature was obtained and the mean relative error between experimental and theoretical outlet temperature for three different PCMs are 4.50 % (paraffin wax), 2.32 % (stearic acid) and 2.63 % (acetamide). Performances of the SAH with various PCMs (including acetamide, stearic acid, and paraffin wax) were compared to those of an identical SAH without PCM during both charging and discharging periods of operation. According to the outlet temperature profile of SAH with PCM compared to SAH without PCM, use of PCM becomes advantageous in terms of higher and smoother outlet temperature during the low sunshine period. The absorbed, useful, loss and stored heat for all the three PCMs were estimated, and paraffin wax was found to be highest as 36.56 kW, 14.13 kW, 0.83 kW and 21.59 kW. In terms of efficiency the paraffin wax (52.83 %) based SAH ranked first followed by stearic acid (52.31 %) and acetamide (47.25 %). During performance comparison between SAH with PCM and without PCM, efficiency of SAH with acetamide is found to be 15.09 % higher to the SAH without acetamide, similarly for SAH with paraffin wax is 8.18 % and acetamide is 6.67 % higher to the SAH without PCM respectively. The uncertainty analysis was carried out for thermal efficiency of the SAH is determined to be +/- 2.02 %. The novel PCM integrated SAH will be useful in space heating and solar drying of the local perishable agricultural products. It is also possible to carry out detail technique for selection of PCM for solar drying application along with the exergy, economy, and environmental analysis of the PCMSAH.