Thermal/hydraulic characteristics of a rectangular channel with inline/staggered perforated baffles

Abstract

In this work, the effectiveness of using baffle turbulators on the thermal/hydraulic characteristics of a baffled rectangular channel has been investigated experimentally and numerically over the range of Reynolds numbers of (Re=12,000–32,000). The baffles turbulators (inline and staggered) were fitted on the inner upper and lower surfaces of the rectangular channel with an aspect ratio (3:1). Different perforation ratios of the baffles (β=0% (solid baffle) to 40%) are considered. Flow structure, local Nusselt number, average Nusselt number, and friction factor are reported and discussed. General correlations for Nusselt number and friction factor for both baffles arrangements are presented. The current investigation results reveal that all cases of the proposed baffle configurations provide a considerable heat transfer augmentation, which is about 410% compared to the condition of the smooth channel. For the entire range of perforation ratios and at the same operating condition, it is observed that the inline arrangement shows higher friction loss than the staggered arrangement. Furthermore, less perforation ratio in both baffles arrangements results in a better thermal performance. The staggered arrangement shows higher heat transfer augmentation than the inline arrangement at higher perforation ratios (β=20–40%), while in case of the lowest perforation ratios (β=0 and10%), the inline baffles outperform the staggered ones with an increase of the Nusselt number by about 280.9–301% and 164.6–179% over the smooth channel for the inline solid/perforated baffles, respectively. The calculated thermal enhancement factor (TEF) is more significant in the staggered arrangement than in the inline arrangement. The largest TEF is captured for the case of staggered arrangement with (β=0%) (solid baffles) at Re=12,000, while the minimum TEF is for the inline baffles with (β=30%) at Re=32,000.