Performance Enhancement of Solar Air Heaters Using Triangular Channels

This paper provides a comparative numerical analysis of two solar air heater (SAH) designs: an improved design with internal triangular air flow channels (SAH 2) and a standard flat-plate duct design (SAH 1). The thermal performance of the two systems under varying levels of solar radiation, typical of a typical day, was investigated using computational fluid dynamics (CFD) from COMSOL Multiphysics. Transient behaviour of heat transfer and airflow was modelled using a time-dependent solver over a period of 08:00-18:00, when solar irradiance varied on an hour-by-hour basis between 180W/m2 to 1000W/m2. It was obtained that the overall thermal performance of SAH 2 under all measured parameters has greatly increased when using triangular channels. The outlet temperature and useful heat gain in SAH 2 have been seen to be higher than in SAH 1 and thus peak colony temperatures in excess of 330K and improvement of the thermal efficiency of up to 20.5 can be observed as well. There were increased convective heat transfer coefficients and inter mixing of air flow because of the changes in geometry leading to increased efficiency in the use of solar energy. Although an increase of the pressure drop occurs at moderate levels, these benefits on performance can justify the application of SAH 2 as a potential passive solar heating solution. This paper demonstrates that triangular channel enhancement to the geometry is a valid way of enhancing the effectiveness of solar thermal systems.