IMPINGEMENT COOLING OF A CONFINED CIRCULAR AIR-JET

A measurement of the local Nusselt number of a confined circular air j et vertically impinging on a Aat plate is performed. The jet dow, afte r impingement, is constrained to exit in two opposite directions. Part of the impinging surface is maintained at a constant heat flux condit ion and the rest is adiabatic. The constant surface heat flux conditio n is modeled by conducting electricity through a thin stainless foil w ith a thickness of 0.01 mm. The heating foil was given constant heat f lux values of 500, 1000, 1500 and 2000 W m(-2). Four diameters of the impinging jet 3, 4, 6 and 9 mm are considered individually. The jet Re ynolds number is in the range of 30,000-67,000. The Hid is 2.0. The re circulation and mixing effect on the heal transfer is investigated by varying the jet diameter, surface heat dux, Reynolds number and surfac e heating width. The correlations of the local Nusselt number and the jet to-adiabatic wall temperature difference are obtained. Copyright ( C) 1996 Elsevier Science Ltd.