Effect of Baffles Position on Thermo-Hydraulic Efficiency of a Solar Air Heater

Abstract

Providing artificial irregularity in the form of baffles on the bottom plate of a solar air heater improves the thermal performance of the heater, whereas it reduces the hydraulic efficiency due to friction losses. To optimize the thermo-hydraulic performance of a rectangular duct solar air heater, a thermo-hydraulic performance factor (THPF), dependent on shape, position and size of baffles, is considered in this study. The performance of the heater in various configurations related to the position of the baffles was evaluated considering Renormalization group k-£ model to simulate the fully turbulent flow for a forced convection condition. At a constant value of heat flux of 1000 W/m2 on the absorber plate and a fixed value of Reynolds number as 2350, pitch between the baffles was varied from 15mm to 75mm. Further, the distance of 1st row of baffles from the inlet was varied from 200mm to 500mm and the optimum configuration was figured out. For pitch value of 60mm between the baffles and the distance of 1st row of baffles as 200mm from the inlet, the highest value of THPF was obtained as 0.9339. The fluid behavior in presence of baffles was analyzed together with its influence on the thermo-hydraulics parameters.