Abstract
Impingement jets are often used for cooling and heating of a surface or a body in the fields of purpose because high heat transfer coefficient is obtained near the stagnation point of the impingement plate where the jet impinges. Heat transfer characteristics using one row and double rows of jets, which impinge on the heated impingement plate, were investigated. Single jet experiments were also carried out. The jet holes with the diameters D of 1 and 2mm were used. L/D were 4, 8 and 12, where L is the distance between the adjacent jets. H/D was from 1 to 10, where H is the distance between the emitter plate and the impingement plate. The experiments were performed with the Re of 250-1600. The surface temperature of the impingement plate was measured using an infrared camera, from which heat transfer coefficients on the surface were obtained. The jet flow was visualized by using a Laser Light Sheet (LLS) methods. The stagnation and the secondary stagnation points were observed on the impingement plate. It was found that heat transfer coefficients are larger in the order of double rows of jets, one row of jets and a single jet. It was also found that the averaged and stagnation Nusselt numbers becomes larger, when L/D is smaller, Re and D are larger.
