Comparative Research on Double-Duct and Double-Pass Solar Air Collectors

Abstract

The 2-pass air collector is commonly used due to its high performance and simple construction. In this paper, two types of air collector with the same physical configuration are compared, namely double-duct solar air heater (DDSAH) and double-pass (DPSAH). The air flow and flow division in the DDSAH are varied to compare thermal efficiency, effective efficiency, and temperature distribution along the collector length. The examined air mass flowrate from 0.04 to 0.08 kg/s corresponds to the Reynolds number in DPSAH from 7675 to 15349. The flow ratio in the air channel of DDSAH varies from 0.25 to 0.75. The one-dimensional analytical model and the approximation method are used for the mathematical model of the air collectors. The results show that the thermal efficiency of DPSAH is about 0.6% higher than that of DDSAH. The effective efficiency of DDSAH is 3% higher than that of DPSAH at maximum air flow. When the air flow is higher than 0.05 kg/s then DDSAH should be used to achieve high thermo-hydraulic performance.