Numerical investigation on flow and heat transfer of pulsating flow in various ribbed channels

In this paper, numerical simulation is carried out to study the flow and heat transfer of pulsating flow in 30 degrees, 45 degrees, 60 degrees and 90 degrees ribbed channels (AR = 2). Turbulence model validation has been conducted for steady flow only, indicating that SST k-omega model predicts heat transfer in ribbed channels fairly well. The secondary flows and Nu distributions in ribbed channels are investigated for both steady flow and pulsating flow. Numerical results indicate that pulsating flow affects longitudinal secondary flow and transverse secondary flow in quite different ways. The time-averaged Nu on ribbed surface of pulsating flow is significantly higher than that of steady flow in most cases, especially for 90 degrees rib case. There is an optimal frequency for each channel to achieve the best heat transfer. In addition, increasing pulsation amplitude and Re will noticeably promote heat transfer for all the cases. Though pulsating flow introduces large pressure loss, considerable improvement of thermal performance will be achieved at high Re. The 90 degrees ribbed channel shows distinguished characteristics with pulsating flow, which gains an increment of 39% in overall thermal performance parameter at Re = 40,000, f = 150 Hz and A = 0.2.