Oscillation Effect of Impingement Surface on Two-Dimensional Impingement Heat Transfer

Abstract

This paper describes the oscillation effect of impingement surface on two-dimensional impingement heat transfer with confined wall. The local temperature distribution on an impingement surface was measured using a thermosensitive liquid crystal sheet and an image processor. Experiments were conducted by using air as a working fluid. Experimental conditions were as follows: Reynolds number Re=1000–10,000, dimensionless distance between nozzle and impingement surface h∕B=1.0–4.0, frequency f=0–100Hz, and amplitudes a=0.5mm and 1.0mm. The local Nusselt number was improved for the comparatively low Reynolds number and low frequency and was depressed for high frequency. In the case of heat transfer enhancement, vortices on the impingement surface were renewed frequently, and on the other hand, in the case of heat transfer depression, thermal boundary layer thickness increased in appearance by the vibration of the impingement surface.