Heat transfer and pressure drop measurements in a square cross-section converging channel with V and W rib turbulators

Data are presented for straight ribs normal to the flow, V ribs with included apex angle of 45° and with apex pointing in the upstream and downstream directions, W ribs with all included angles of 45° and with central apex pointing in the upstream and downstream directions. The inlet Reynolds number (Rein) was varied from 5000 to 35,000. The rib height (e) was maintained constant throughout the length of the channel. The rib height to mean duct hydraulic diameter ratio (e/Dh,m) was kept constant at 0.08. Data for three pitch to height ratios (P/e) equal to 6, 10 and 17.5 are reported for straight and V ribs. The optimum P/e ratio based on constant pumping power thermal performance criterion was observed to be equal to 10 and this was the only configuration studied for W ribs. The difference in thermal performance between the V and W ribs was within uncertainty limits. However, the local variation in heat transfer coefficient in the cross stream direction on the ribbed wall was noticed to be very high for the V ribs compared to that for the W ribs making the W ribs a better choice as enhancement device.