ENHANCEMENT OF IMPINGING JET HEAT-TRANSFER BY MAKING USE OF MECHANO-FLUID INTERACTIVE FLOW OSCILLATION

Heat transfer and fluid flow measurements were conducted for a two-dim ensional impinging jet in which a cylinder suspended with springs at b oth its ends was inserted. The jet Reynolds number was set at about 10 ,000 and the target plate was mounted at two different distances from the jet exit of 3 and 5 times the jet slot width. Insertion of a rigid ly suspended cylinder deteriorates the heat transfer around the stagna tion region while it effectively enhances heat transfer outside the st agnation region. This is further improved by suspending the cylinder w ith springs. The maximum Nusselt number attained around the stagnation point was augmented by about 20% compared to the one for normal impin ging jet without the insertion of a cylinder. A cross-stream oscillato ry motion of the cylinder was produced perpendicular to its axis due t o the interaction between the vortex shedding from the cylinder and th e cylinder-spring mechanical oscillation system. Intensive periodical velocity and pressure fluctuations were induced in the wake of the cyl inder. The fluctuating flow pattern appearing near the geometrical cen ter of the target plate was estimated to be a swing-type one. (C) 1998 Elsevier Science Inc. All rights reserved.