A comparative study of the thermal performances of cross-corrugated and V-groove solar air collectors

Abstract

In this paper, the thermal performance of cross-corrugated and v-groove solar air collectors has been compared under a wide range of configuration and operating conditions. For cross-corrugated collectors, the air flow channel is formed by the wavelike absorbing plate and the wavelike bottom plate, which are transversely positioned, whereas for v-groove collectors it is formed by the v-groove absorbing plate and the flat bottom plate. The use of the transversely positioned wavelike bottom plate in cross-corrugated collectors is to achieve better thermal performance by enhancing the heat transfer rate inside the air flow channel via augmented turbulence. It is found that cross-corrugated collectors are superior to v-groove ones for all the configurations and operating conditions considered, confirming that the use of the transversely positioned wavelike bottom plate, in cross-corrugated collectors improves the thermal performance. The results also show that a slender configuration along the air flow direction, a small gap between the absorbing plate and the bottom plate, a selected coating on the absorbing plate and the glass cover that has a very high absorptivity of solar radiation but quite a small emissivity of thermal radiation, an air mass flow rate per unit area of collector above 0.1 kg/m2·s, and maintaining the inlet fluid temperature close to that of the ambient fluid, will lead to improved thermal performance for both collectors. However, it is found that the mean gap between the cover and the absorbing plates, thexemissivity of thermal radiation of the bottom plate, the solar insolation, and the inclination of the collectors have negligible effects on the efficiencies of both collectors.