Enhancement of Heat Transfer in Solar Air Heater Duct having Different Pitch of Triangular Protrusions as Roughness Elements on Absorber Plate

Objective: This paper elucidates the experimentation based on improving the heat transfer rate in the solar air heating apparatus of triangular protrusions designed in a zigzag pattern on the aluminum plate surface. Method: Triangular protrusions of varying pitch of 10, 15, 20, 25 and 30 mm facilitates artificial roughness on the outer surface of the aluminum plate. These protrusions possess an angle of 45; the relative thickness of each protrusion is 0.11mm respectively. The operating parameters are developed by the various researches for roughed ducts of the solar based air heater. Air flow parameter value has to be maintained between ‘0.017-0.0182 Kg/Sec. The air flow corresponds to Reynolds number (Re) between 10300 to 12000, and the Nusselt number ranges from 50 and 110, and friction factor of air lines at 4.5-6.8x10-3’. Findings: It was observed that when the thickness of triangular protrusions over the aluminum collector is 25 mm, it has the highest rate of heat transfer of 104, for which the rate of airflow is 0.0182 kg/Sec and thermo hydraulic performance is 1.71. Applications: The setup can be used to trap solar energy for various thermal applications, it can be used in heat exchangers for effective heat transfer, it can also be effectively used for space heating and curing of materials and for drying of agricultural products etc.