TY - JOUR
T1 - Heat transfer enhancement by skewed wavy sidewall for two-pass ribbed channels with different aspect ratios
AU - Chang, Shyy Woei
AU - Gao, Jing Yan
N1 - Funding Information:
The research facilities are sponsored by the grant NSC 99-2221-E-022-015MY3 from National Science Council, Taiwan.
PY - 2014/6
Y1 - 2014/6
N2 - Thermal performances of the newly devised compound heat transfer enhancement (HTE) method by deploying the in-line 45 ribs and skewed waves along the two opposite pairs of channel endwalls and sidewalls, respectively, for three two-pass sharp-bend channels with aspect ratios (AR) of 0.5, 1 and 2 are studied. For each test channel at Reynolds number (Re) between 5000 and 20,000, the full-field Nusselt number (Nu) distributions over the ribbed endwall and the channel-averaged pressure drop coefficients (f) are measured to determine the thermal performance factors (TPF) as the efficiency indices for heat transmissions. A set of Nu, f and TPF data obtained from the three test channels is selected to illustrate the HTE properties and the associated f augmentations. With present orientations for the skewed sidewall waves and the 45 endwall ribs to trip the co-current axial swirls, the local and area-averaged endwall Nusselt numbers (NuA) are considerably raised by elevating the HTE benefits over the mid-rib regions. The NuA levels over the ribbed endwalls for present test channels with AR = 0.5, 1 and 2 are respectively raised to 4.74-3.83, 6.25-4.94 and 7.43-6.09 times of the Dittus-Boelter references. With the accompanying f augmentations to 24.54-12.44, 17.35-10.42 and 26.71-19.82 times of the Blassius levels, the TPF values for present test channels of AR = 0.5, 1 and 2 fall in the ranges of 1.74-1.62, 2.42-2.24 and 2.51-2.28 respectively. The averaged Nusselt number correlations over inlet/outlet legs, turning region and entire endwall, as well as the f correlations, for present test channels are generated to assist the design activities.
AB - Thermal performances of the newly devised compound heat transfer enhancement (HTE) method by deploying the in-line 45 ribs and skewed waves along the two opposite pairs of channel endwalls and sidewalls, respectively, for three two-pass sharp-bend channels with aspect ratios (AR) of 0.5, 1 and 2 are studied. For each test channel at Reynolds number (Re) between 5000 and 20,000, the full-field Nusselt number (Nu) distributions over the ribbed endwall and the channel-averaged pressure drop coefficients (f) are measured to determine the thermal performance factors (TPF) as the efficiency indices for heat transmissions. A set of Nu, f and TPF data obtained from the three test channels is selected to illustrate the HTE properties and the associated f augmentations. With present orientations for the skewed sidewall waves and the 45 endwall ribs to trip the co-current axial swirls, the local and area-averaged endwall Nusselt numbers (NuA) are considerably raised by elevating the HTE benefits over the mid-rib regions. The NuA levels over the ribbed endwalls for present test channels with AR = 0.5, 1 and 2 are respectively raised to 4.74-3.83, 6.25-4.94 and 7.43-6.09 times of the Dittus-Boelter references. With the accompanying f augmentations to 24.54-12.44, 17.35-10.42 and 26.71-19.82 times of the Blassius levels, the TPF values for present test channels of AR = 0.5, 1 and 2 fall in the ranges of 1.74-1.62, 2.42-2.24 and 2.51-2.28 respectively. The averaged Nusselt number correlations over inlet/outlet legs, turning region and entire endwall, as well as the f correlations, for present test channels are generated to assist the design activities.
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U2 - 10.1016/j.ijheatmasstransfer.2014.02.015
DO - 10.1016/j.ijheatmasstransfer.2014.02.015
M3 - Article
AN - SCOPUS:84897728549
SN - 0017-9310
VL - 73
SP - 217
EP - 230
JO - International Journal of Heat and Mass Transfer
JF - International Journal of Heat and Mass Transfer
ER -