EXPERIMENTAL INVESTIGATION OF THE HEAT TRANSFER CHARACTERISTICS OF CONFINED IMPINGING SLOT JETS

Abstract

This article presents an experimental investigation of the heat transfer characteristics between the confined impinging slot jets and a flat surface. During the experiments, single slot, multiple slots with cross-flow effects, and multiple slots with symmetrical exhaust ports between neighboring jets are tested. The exhaust ports are manufactured to eliminate the cross-flow effects from the upstream slot, which degrade the heat transfer of the downstream impinging jets.Liquid crystal thermography is employed to map the temperature distributions on the test plate. Local heat transfer coefficients are obtained, and then the average heat transfer coefficients are evaluated. The effects of the nozzle-to-plate spacing H/B, Reynolds number, and the presence of the exhaust ports on the local Nusselt number distributions are examined. The local distributions of the heat transfer coefficients of the single slot jet and the central slot of the three slot arrays are compared with each other. The spent fluid removal diminishes the influence of the cross flow, and the heat transfer rates are enhanced compared with the multiple impinging slot jets with cross-flow effects. The average heat transfer coefficients of two slot systems with different slot widths are compared with each other at the same nozzle-to-plate spacing, and the narrower one gives higher heat transfer rates at the same jet exit velocity.