Performance of Finned Absorber Plate Solar Air Heater Having Multiple Triangular Air Flow Passages in Parallel Under Transition to Turbulent Flow Condition

This paper presents the results of thermal performance study of a solar air heater having absorber plate with inclined fins fitted in equilateral triangular flow passages in parallel using the governing equations under transition to turbulent flow and compares the same with the conventional solar air heater having low aspect ratio rectangular air flow duct at equal pumping power condition. The equal pumping power condition for the equilateral triangular passages of width w and rectangular duct height H has been found to be w = 2.65 H. The finned absorber plate solar air heater has been found to provide 7.3–25.8% better thermal efficiency than the conventional air heater because of the substantial increase in the effective heat transfer surface area due to the fins. The effects of variation of design, ambient, and operating parameters on the performance of the finned solar air heater show that the triangular passage width w must be increased with the increase in the collector length L to satisfy the condition of equal pumping power according to the relation w³/L^2.75 = constant. The results of the present study can be utilized for the development of enhanced-performance finned solar air heater with triangular passages.