Numerical Study on Heat Transfer Characteristics of Different Rectangular Impinging Jets

Abstract

A numerical study has been made to examine the thermal fields of rectangular impinging jets with different duty cycle(DC), which is defined as the ratio of pulse cycle on-time to off cycle time in one period, inlet Reynolds number and frequency. The Nusselt numbers show best enhancement with DC=1:3, Re=22000 and f=40Hz. The possible reason for this is that the instantaneous velocity change in this case from off to on and on to off, especially when the velocity changes from on to off, is more severe than other cases.

Micro scale jet impingement cooling and its efficacy on turbine vanes : a numerical study

“…This shift could be explained as the shift of toroidal vortices for decreasing H/D ratios. A contrasting result was reported by Liping et al [42] The Nusselt values along the wall region shows only a slight variation except for H/D=1 and lower, which may be accounted for reduced radial velocity and less mixing of turbulence. Thus the influence of H/D ratios tends to either increase or decrease the stagnation Nusselt values with very slight variation along the wall jet region.…”