HEAT-TRANSFER IN A RECTANGULAR CHANNEL WITH PERFORATED TURBULENCE PROMOTERS USING HOLOGRAPHIC-INTERFEROMETRY MEASUREMENT

An experimental study is conducted to examine the effect of perforated ribs on turbulent heat transfer and friction in a rectangular channel. Perforated ribs with an open-area ratio of 50% are staggered on two opposite walls of the channel. Four rib pitch-to-height ratios (Pi/H = 5, 10: 15 and 20) and two rib height-to-channel hydraulic diameter ratios (H/De = 0.081 and 0.162) are examined. The Reynolds number ranges from 10 000 to 50 000. To facilitate comparison, results of conventional solid-type ribs are also compiled. Laser holographic interferometry is employed to measure the heat transfer coefficients of the ribbed wall. The results indicate that the perforated ribs have the advantages of eliminating the hot-spots and providing a superior heat transfer performance. Roughness friction and heat transfer correlations are also developed in terms of flow and rib parameters.