Heat Transfer in Rotating, Trailing Edge, Converging Channels With Full- and Partial-Height Strip-Fins

Abstract

Abstract A wide variety of pin-fins have been used to enhance heat transfer in internal cooling channels. However, due to their large blockage in the flow direction, they result in an undesirable high pressure drop. This experimental study aims to reduce pressure drop while increasing the heat transfer surface area by utilizing strip-fins in converging internal cooling channels. The channel is designed with a trapezoidal cross section, converges in both transverse and longitudinal directions, and is also skewed β=120deg with respect to the direction of rotation to model a trailing edge cooling channel. Only the leading and trailing surfaces of the channel are instrumented, and each surface is divided into 18 isolated copper plates to measure the regionally averaged heat transfer coefficient. Utilizing pressure taps at the inlet and outlet of the channel, the pressure drop is obtained. Three staggered arrays of strip-fins are investigated: one full-height configuration and two partial fin height arrangements (Sz = 2 mm and 1 mm). In all cases, the strip-fins are 2 mm wide (W) and 10 mm long (Lf) in the flow direction. The fins are spaced such that Sy/Lf = 1 in the streamwise direction. However, due to the convergence, the spanwise spacing, Sx/W, was varied from 8 to 6.2 along the channel. The rotation number of the channel varied up to 0.21 by ranging the inlet Reynolds number from 10,000 to 40,000 and rotation speed from 0 to 300 rpm. It is found that the full-height strip-fin channel results in a more nonuniform spanwise heat transfer distribution than the partial-height strip-fin channel. Both trailing and leading surface heat transfer coefficients are enhanced under rotation conditions. The 2 mm height partial strip-fin channel provided the best thermal performance, and it is comparable to the performance of the converging channels with partial-length circular pins. The strip-fin channel can be a design option when the pressure drop penalty is a major concern.