An Experimental and Numerical Study of Heat Transfer and Pressure Losses of V- and W-Shaped Ribs at High Reynolds Numbers

Abstract

An experimental and numerical investigation was conducted to assess the thermal performance of V- and W-shaped ribs in a rectangular channel. The ribs were located on one channel sidewall in order to simulate a typical combustor liner cooling. The cross section of the channel had an aspect ratio of 2:1. Local heat transfer coefficients were measured using the transient thermochromic liquid crystal technique. Pressure taps along the channel sidewall were used to obtain the periodic pressure losses. The rib height-to-hydraulic diameter ratio (e/Dh) was set to 0.02, and the rib pitch-to-height ratios (P/e) were 5 and 10. The Reynolds numbers investigated varied from 80,000 to 500,000. All rib configurations were additionally investigated numerically and the obtained computational results were compared with experimental data. For all computations the commercial software FLUENT™ was used with a two-layer k-ε turbulence model. It could be demonstrated that applying W-shaped ribs instead of V-shaped ribs has the advantage of an increased heat transfer enhancement, but is accompanied by a rise in pressure loss. Reducing the rib pitch-to-height ratio from 10 to 5 decreases the heat transfer enhancement, but results in a significantly reduced pressure loss. Finally, the best thermal performance was found for W-shaped ribs with a pitch-to-height ratio of 10, having a slightly increased pressure loss but with considerable rise in heat transfer enhancement compared to V-shaped ribs.