Abstract
Impingement jets are used for cooling and heating of a surface or a body for engineering purpose because high heat transfer coefficient is obtained near the stagnation point of the impingement plate where the jet impinges. Heat transfer characteristics of one row and double rows of jets, which impinge on the heated impingement plate, were investigated. The diameter of the jet hole D was 1mm, and the jet-to-jet distances L were 4mm and 12mm. The surface temperature of the impingement plate was measured using an infrared camera, from which the heat transfer coefficients on the surface were obtained. The jet flow was visualized by means of a high speed camera. The experiments were performed with the low Re of about 200, and with the values of H/D from 3 to 10, where H is the distance between the emitter plate and the impingement plate. It is found that the heat transfer coefficient h becomes larger, when L is smaller, Re is larger and double rows of jets are used compared with the use of one row of jets. The maximum h was obtained around the stagnation point of the jet. It is also found that the Nusselt number is not dependent on H/D.
