Abstract
An experimental work on the performance of new design of solar air heater (SAH) called tubular solar heater (TSAH) is investigated experimentally. In this design, the flat absorber plate of the flat solar air heater (FSAH) is replaced by adjacent tubes at the same direction of the airflow through the SAH. Two SAHs (FSAH and TSAH) having the same dimensions and materials except their absorbers are constructed to compare their performance at different airflow rates through the SAHs. Results reveal that the TSAH has higher efficiency, output power, and outlet air temperature and lower top heat loss compared to FSAH. Moreover, it is found that the efficiency of the presented TSAH is greater than the efficiency of the studied previous SAHs designs. TSAH achieves a maximum rise of 13.2 degrees C for the outlet air temperature from the SAH compared to FSAH at inlet air mass flow rate 0.025 kg/s to the SAHs. The average daily TSAH efficiency is about 83.6%, 76.3% and 59.8% at air mass flow rate 0.075, 0.05 and 0.025 kg/s, respectively with an increase of 132.6%, 58.6%, and 43.5%, respectively compared to FSAH. The daily top heat loss of TSAH decreases by about 10% compared to FSAH. (C) 2019 Elsevier Ltd. All rights reserved.