Flow and Heat Transfer Characteristics of Circular Impinging Jet Accompanying Annular Suction Flow (Reduction of Suction Flow Rate by Excess Length of Suction Pipe)

Abstract

As one of the methods for reducing the suction flow rate in order to satisfy the operating condition as one blower, it was proposed to mount the excess length of the suction pipe from the injection pipe. The experiments were carried out to clarify the effects of various excess length of the suction pipe on the flow and heat transfer characteristics of a circular impinging jet accompanying an annular suction flow. As a result, it is found that the higher Nusselt number is obtained at the smaller suction flow rate adding the excess length of the suction pipe. Considering the power loss based on the pressure loss in the suction pipe, it is shown that the optimum excess length of the suction pipe is obtained as a half of the inner diameter of the injection pipe at given experimental conditions. In addition, the counter flow which seems to be an important factor increasing of the fluctuating velocity is observed inside of the suction pipe using Particle Image Velocimetry (PIV).