Theoretical simulations of a natural convection solar air heater.

K. S. Ong, Kenny Tan, W. N. Tee and Simrit Chandok., WREC2009, 2009

The thermal performance of a natural convection solar air heater was simulated using a thermal network analysis theoretical model. The performance of the solar air heater depends upon ambient conditions as well as its geometrical features and angle of inclination to the horizontal. Earlier experimental data suggested that the heat transfer to the air stream was mainly by natural convection from the absorber plate. Also, the air temperature varied non-linearly along the collector, tending to decrease towards the exit end of it. Theoretical simulations compared with the earlier experimental results showed that while satisfactory agreement was obtained for the air temperature and induced velocity, absorber and glass temperatures were over predicted. A simulation conducted with the theory showed optimum tilt angle was 45o. There was no optimum length. For a 1 m wide collector, the air gap should be greater than about 0.2 m deep.