Influence of jet spacing on flow and heat transfer characteristics in intermittently controlled multiple impinging jets

Abstract

This paper presents the results of numerical simulation of multiple impinging jets. A single impinging jet (SIJ) produces a high heat transfer rate around an impinging position on an impinging wall, while the heat transfer performance decays increasing the distance from the impinging position. Thus, the heat transfer area is narrow and non-uniform heat transfer occurs in SIJ. In order to overcome these problems, multiple impinging jets (MIJ) are generally used. However, MIJ has shortcoming; the interaction between adjacent jets reduces the heat transfer performance on multiple impinging jets. Thus, in order to improve the heat transfer performance in MIJ, it is necessary to develop high-performance-control methods for MIJ. In the previous study, we introduced the intermittent control for MIJ so as to reduce the interaction between each jet. The intermittent control with a phase difference between two jets reproduces intermittently impingement. It turned out that the total heat transfer on the impinging plate is improved under the longer period and large phase difference within the control parameter range. However, it should be considered that the heat transfer performance of impinging jet is influenced by various parameters. In the present study, changing the distance between jets, we evaluate the flow characteristic and heat transfer performance of intermittently controlled MIJ. It turns out that the heat transfer performance of MIJ is improved under the shorter distance between jets and that the wall jet defuses strongly on the shorter distance.