Influence of Channel Orientation on Heat Transfer in a Two-Pass Smooth and Ribbed Rectangular Channel (AR=2:1) Under Large Rotation Numbers

Abstract

Experiments were conducted in a rotating two-pass cooling channel with an aspect ratio of 2:1 (Dh = 16.9 mm). Results for two surface conditions are presented: smooth and one ribbed configuration. For the ribbed channel, the leading and trailing walls are roughened with ribs (P/e = 10, e/Dh = 0.094) and are placed at an angle (α = 45°) to the mainstream flow. For each surface condition, two angles of rotation (β = 90°, 135°) were studied. For each angle of rotation, five Reynolds numbers (Re = 10K–40K) were considered. At each Reynolds number, five rotational speeds (Ω = 0–400 rpm) were considered. The maximum rotation number and buoyancy parameter reached were 0.45 and 0.85, respectively. Results showed that rotation effects are minimal in ribbed channels, at both angles of rotation, due to the strong interaction of rib and Coriolis induced vortices. In the smooth case, the channel orientation proved to be important and a beneficial heat transfer increase on the leading surface in the first pass (radially outward flow) was observed at high rotation numbers. The correlations developed in this study for predicting heat transfer enhancement due to rotation using the buoyancy parameter showed markedly good agreement with experimental data (+/-10%). Finally, heat transfer under rotating conditions on the tip cap showed to be quite dependent on channel orientation. The maximum tip cap Nu/Nus ratio observed was 2.8.

Heat transfer study in a rotating ribbed two-pass channel with engine-similar cross section at high rotation number

“…The same results were obtained in the investigation of Dutta and Han [18]. Then, Huh et al [19] performed a study on a rectangular channel with smooth and ribbed wall. They draw the conclusion that in the smooth case, the channel orientation was important and beneficial to the enhancement of heat transfer on the leading surface in the first pass.…”

“…Thus for a rotation number Ro = 0 (stationary) the Nu/Nu s ratio is 1. This normalized method has widely used by the domestic and international researches [14,19,26,27,35,36]. In the current study, experiments are carried out at nine different rotation numbers and ten different rotate speeds.…”

Heat transfer investigation in rotating smooth square U-duct with different wall-temperature ratios and channel orientations

“…Heat transfer results from Huh et al [25] are selected to validate the current study, as is shown in Fig. 4.…”

“…Results showed that the 0-deg channel orientation creates a greater heat transfer difference between the leading and trailing walls than the 45-deg channel for both aspect ratio under rotating conditions. In 2009 and 2012, Huh et al [24,25] (Ro 6 0.45) investigated heat transfer in rotating two-pass rectangular channel with channel orientation angles of 0 and 45-deg. Their observed that channel orientation could enhance heat transfer on leading surface in the first passage at high rotation numbers.…”

Heat transfer in a rotating smooth wedge-shaped channel with lateral fluid extraction

“…They inferred that the core flow was shifted from the centerline to the trailing edge, while the channel orientation varied from 90 to 120 . Huh et al [18] investigated smooth and rib-roughened rectangular channels (AR ¼ 2). Leading-to-trailing heat-transfer differences were weakened when b changed from 90 to 135 in the smooth channel.…”