Effect of jet orientation in the presence of crossflow in a rectangular channel

Abstract

Crossflow is a common phenomenon in multi-jet impingement cooling. It has a complex impact on heat transfer. Although a higher mass flow rate increase heat transfer, it may drastically reduce the heat transfer by decreasing the jets' cooling effectiveness. Few studies employed turbulators in the flow field to mitigate the crossflow effect on jets and to enhance heat transfer. However, this substantially increased the requirement for pumping power. It is essential to enhance heat transfer without compromising the pumping power. Therefore, the present study is conducted to reduce the crossflow influence on jet impingement heat transfer without significant increment in pumping power. In this work, single and multi-jet impingement of square jets with three orientation angles of 0°, 22.5°, and 45° are considered. The jet Reynolds number of 10000 and velocity ratios of 0.1 and 0.2 are used. It is observed that the jet penetration in the crossflow is higher at jet orientation of a θ = 45° than other configurations at both velocity ratios due to the greater resistance offered to the crossflow entrainment. The average Nusselt number of θ = 45° jet configuration is increased by 30.7% for an increase in 21% and 1.3% respectively in pressure drop caused by jet and crossflow compared to the θ = 0° oriented jet for the single jet case. The maximum thermal performance factor achieved for θ = 45° for the single jet case is 1.29 whereas for multi-jet case are 1.2 at velocity ratio of 0.2.