Heat Transfer in a Two-Pass Rectangular Channel (AR=1:4) Under High Rotation Numbers

Abstract

This paper experimentally investigated the rotational effects on heat transfer in a two-pass rectangular channel (AR=1:4), which is applicable to the channel near the leading edge of the gas turbine blade. The test channel has radially outward flow in the first passage through a redirected sharp-bend entrance and radially inward flow in the second passage after a 180deg sharp turn. In the first passage, rotation effects on heat transfer are reduced by the redirected sharp-bend entrance. In the second passage, under rotating conditions, both leading and trailing surfaces experienced heat transfer enhancements above the stationary case. Rotation greatly increased heat transfer enhancement in the tip region up to a maximum Nu ratio (Nu∕Nus) of 2.4. The objective of the current study is to perform an extended parametric study of the low rotation number (0–0.3) and low buoyancy parameter (0–0.2) achieved previously. By varying the Reynolds numbers (10,000–40,000), the rotational speeds (0–400rpm), and the density ratios (inlet density ratio=0.10–0.16), the increased range of the rotation number and buoyancy parameter reached in this study are 0–0.67 and 0–2.0, respectively. The higher rotation number and buoyancy parameter have been correlated very well to predict the rotational heat transfer in the two-pass, 1:4 aspect ratio flow channel.

Effect of rib height on heat transfer in a two pass rectangular channel (AR=1:4) with a sharp entrance at high rotation numbers

“…This was not the case for the smooth channel as reported by Liu et al [17] in which a clear difference was observed.…”

“…These effects were previously stated to be mainstream flow separation, recirculation, reattachment, turbulent mixing, and angled secondary flow. To investigate the effects of the ribs on heat transfer in the stationary channel, the current study is compared to the smooth results of Liu et al [17] in Fig. 7.…”

“…10. Comparison of regional tip Nu ratios (Nu/Nus) as a function of rotation number (Ro) for the current study (P/e = 10, e/Dh = 0.156), Huh et al [8] (P/e = 10, e/Dh = 0.078), and Liu et al [17] (smooth). served by noticing that an increase in Nu/Nu s ratios begins to occur at smaller and smaller buoyancy parameter values as you move along in the streamwise direction.…”

“…They also showed that the influence of the entrance geometry on the heat transfer is more apparent in the smooth channels than in the ribbed channels. More recently, Liu et al [17] investigated heat transfer at high rotation numbers of 0-0.65 in a narrow aspect ratio channel of 1:4. The entrance condition for that study was a sharp bend.…”

Shape optimization of staggered ribs in a rotating equilateral triangular cooling channel

“…A computational study on the heat transfer in the rectangular internal cooling channel with angle ribs (60°and 90°) on the opposite surfaces was performed by Murata and Mochizuki [3]. Liu et al [4] experimentally investigated the rotation effects on the heat transfer in a two-pass rectangular channel. They concluded that increasing the Rotation number increases the Nusselt number on the trailing surface, and decreases the Nusselt number on the leading surface in the first passage.…”