Enhanced performance assessment of an integrated evacuated tube and flat plate collector solar air heater with thermal storage material

Abstract

The solar air heater incorporating flat plate solar collectors is a straightforward system suitable for domestic use. Nonetheless, it faces challenges with lower thermal efficiency, especially when applied to moderate-temperature purposes. This study aimed to enhance the solar air heater performance by integrating an evacuated tube collector with a flat plate collector and incorporating paraffin C20-C33 as thermal storage material. Inside the flat plate solar collector, the phase change material (paraffin C20-C33) is placed under the absorber surface where the copper air pipes are immersed. Different parameters like outlet temperature, temperature rise, heat gain, thermal efficiency, and pressure drop have been analyzed and discussed for varying weather conditions and mass air flow rates. Also, the system performance is compared by using phase change material (paraffin C20-C33) and without it. The experimental results show that the innovative design achieves higher efficiency, temperature output, and operation hours compared to the standard SAHs. In the presented SAH, the maximum air outlet temperature reached 119 °C at a flow rate of 0.015 kg/s. The maximum ratios of temperature rise to solar radiation at mass air flow rates 0.015, 0.02, and 0.025 kg/s were about 28 %, 26 %, and 25.5 % without PCM and 31 %, 28.5 %, and 27.6 % with PCM, respectively. The average daily thermal efficiency reached the highest values of 47.46 %, 56.12 %, and 64.53 % at air mass flow rates of 0.015, 0.02, and 0.025 kg/s respectively with PCM. The increase in the ratio of accumulated useful energy to average solar radiation through the day was found at 16 %, 14 %, and 13 % with PCM at 0.015, 0.02, and 0.025 kg/s respectively compared to the one without PCM. This developed solar air heater shows promising potential for various applications such as drying and industrial process heating.