Numerical study on thermal hydraulic performance improvement in solar air heater duct with semi ellipse shaped obstacles

This paper presents numerical study on heat transfer and friction characteristics in rectangular solar air heater duct with semi elliptical shape obstacles. 3-D simulations have been conducted using Renormalization-group k-epsilon turbulence model. Obstacles are placed on the absorber plate in V-down shape at different angle of attack (alpha), ranging from 30 degrees to 90 degrees. Two different arrangements of obstacles namely; inline and staggered arrangements have been investigated. Four different values of Reynolds number, ranging from 6000 to 18,000 have been considered to determine the values of Nusselt number and friction factor. Angle of attack (alpha) and obstacles arrangement significantly affect the Nusselt number and friction factor. In staggered arrangement, maximum enhancement in Nusselt number and friction factor have been observed 2.05 and 6.93, respectively, at an angle of attack (alpha) of 75 degrees and corresponding enhancement in case of inline arrangement are found as 1.73 and 6.12, respectively. The maximum enhancement in Nusselt number at 75 degrees angle of attack is due to combined effect of high turbulence and lateral movement of air flow. Thermohydraulic performance has also been determined which shows staggered arrangement are more superior than inline arrangement for all values of angle of attack (alpha) investigated in present study. (C) 2016 Elsevier Ltd. All rights reserved.