抄録
Present paper describes on the heat transfer and flow characteristics of a laminar annular impinging jet for various positions of inner-tube. In the first case, inner-tube is protruded to the flow passage. In the second case, inner-tube is retracted and relatively, outer-tube with confined insulated wall is protruded. Numerical values were obtained for the dimensionless distance between nozzle and impingement surface, H =0.5,1.0, the diameter ratio, d/D=0.2~0.6, the protrusion or retraction dimensionless length, L/H=0.0~0.8 at the Reynolds number, Re=1,000,the Prandtl number, Pr =0.72 and Grashof number, Gr = 1,000, In the first case, the flow is divided into the stagnant regionand the recirculated region in the minor flow and the major flow region. The local heat transfer for minor flow is depressed with increase of L/H. In the second case, the heat transfer increases locally with increase of L/H. Consequently, local heat transfer is controlled by combining protrusion and retraction.
