Study on the thermal performance of double pass solar air heater with PCM-based thermal energy storage system

Abstract

The solar air heater (SAH) is an efficient, eco-friendly, and cost-effective way for solar drying, space heating, crop yielding, and HVAC applications. However, SAH has two drawbacks: low heat transfer coefficient and the intermittent nature of solar energy. Different roughness elements were employed to enhance the heat transfer coefficient, while different PCM arrangements were used to increase thermal efficiency and operational hours. Accordingly, the composite geometry of semicircular PCM tubes and perforated blocks are investigated at non-dimensional parameters such as tube amplitude ratios (a/H) from 0.2 to 0.5 and relative blockage height ratios (e/H) from 0.4 to 0.8. In this study, the three-dimensional transient numerical investigation is carried out along with experimental validation. The effect of a/H and e/H on the thermal efficiency, heat storage rate and pumping power are analyzed at a mass flow rate (ṁ) from 0.011 kg/s to 0.047 kg/s. For the range of parameters studied, the maximum thermal efficiency is determined to be 97 %, corresponding to mass flow rate of 0.047 kg/s, a/H value of 0.2 and e/H value of 0.4, while the maximum heat storage rate is determined to be 637 W at a/H value of 0.5, mass flow rate of 0.011 kg/s and e/H value of 0.4. The improvement in thermal performance is considered at the expense of pumping power. Moreover, the maximum pumping power is determined to be 38.9 W at e/H value of 0.8, mass flow rate of 0.047 kg/s and a/H value of 0.3.