Heat transfer augmentation of axisymmetric impinging jet using a perforated plate set in front of a target plate. (1st report. The effects of diameter and pitch of holes in a perforated plate).

Abstract

This report deals with the heat transfer augmentation of an axisymmetric impinging jet using a perforated plate which is installed in front of a target plate. The effects of the diameter (d) and pitch (p) of the holes in the perforated plate, and the spacing between the perforated and target plates on impinging jet heat transfer have been experimentally studied. The obtained results demonstrate that the effects of the present perforated plates on heat transfer augmentation are maximum inside the potential core region. When a perforated plate with a pitch-to-diameter ratio of 2 (p/d=2) is installed at a distance from the impinging plate less than twice the hole diameter (2d), the heat transfer coefficient at the stagnation point on the target plate becomes maximum and goes up to about 2.3 times as large as that in the case without a perforated plate. Under the appropriate conditions of the perforated plate, the mean heat transfer coefficient averaged within some distance from the stagnation point is larger than that without the perforated plate, even when the averaging distance is longer than 1.5 times the nozzle-diameter.