Browsing by Author "Huh, Michael"

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Heat Transfer and Friction in a Square Channel with Ribs and Grooves
(2016-01)
Liu, Yao-Hsien
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Lo, Yuan-Hsiang
;
Li, Xin-Xian
;
Huh, Michael
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機械工程學系
Turbulence promoters have been widely applied to enhance heat transfer in internal flow channels, although they cause pressure loss. This study employed the transient liquid-crystal technique to measure the heat transfer distribution in a square channel with compound turbulence promoters with orthogonal (90deg), continuous angled (45deg), discrete angled (45deg), V-shaped, and inverted-V-shaped rib configurations. The rib height-to-hydraulic diameter ratio (e/Dh) and the rib pitch-to-height ratio (P/e) were 0.1 and 8, respectively. Variations in the Nusselt number were observed after adding grooves between the ribs. The Reynolds number tested in this study ranged from 15,000 to 35,000. Adding grooves between the ribs enhanced the heat transfer. The convective heat transfer coefficient increased by up to 40%, whereas the friction factor ratio increased by less than 30%. The discrete angled configuration of grooved ribs exhibited the maximal heat transfer enhancement and thermal performance, whereas the orthogonal configuration attained the minimal heat transfer enhancement and thermal performance. The frictional loss of the V-shaped and inverted-V-shaped configurations was higher than that of the continuous or discrete arrangements for both ribs-only and ribbed-grooved configurations.
High rotation number effect on heat transfer in a trailing edge channel with tapered ribs
(2012-02-01)
Liu, Yao-Hsien
;
Huh, Michael
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Han, Je-Chin
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機械工程學系
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Department of Mechanical Engineering
Detailed heat transfer measurements were conducted in a wedge-shaped channel with lateral flow ejection, which is commonly found in the trailing edge cooling cavities of the gas turbine blade. Tapered ribs were applied on the leading and trailing surfaces to enhance heat transfer. Rib spacing (P/e(max)) was 8 and the ratio of rib height to channel height (e/H) was 0.125. The inlet Reynolds number ranged from 10,000 to 40,000. At the highest rotational speed of 400 rpm, the inlet rotation number was 0.8. Effect of flow ejection on pressure drop, mass flow rate and heat transfer distribution were investigated. Results show that the configuration of this tapered rib enhances heat transfer on the ribbed surface but ejection still has pronounced effects on heat transfer distribution. The experimental data has been correlated with the high rotation number and high buoyancy parameter in ranges similar to industry applications. (C) 2011 Elsevier Inc. All rights reserved.
High Rotation Number Effect on Heat Transfer in a Triangular Channel With 45 deg, Inverted 45 deg, and 90 deg Ribs
(2010-07-01)
Liu, Yao-Hsien
;
Huh, Michael
;
Han, Je-Chin
;
Moon, Hee-Koo
;
機械工程學系
Heat transfer and pressure drop have been experimentally investigated in an equilateral triangular channel (D(h)=1.83 cm), which can be used to simulate the internal cooling passage near the leading edge of a gas turbine blade. Three different rib configurations (45 deg, inverted 45 deg, and 90 deg) were tested at four different Reynolds numbers (10,000-40,000), each with five different rotational speeds (0-400 rpm). The rib pitch-to-height (P/e) ratio is 8 and the height-to-hydraulic diameter (e/D(h)) ratio is 0.087 for every rib configuration. The rotation number and buoyancy parameter achieved in this study were 0-0.58 and 0-2.3, respectively. Both the rotation number and buoyancy parameter have been correlated with predict the rotational heat transfer in the ribbed equilateral triangular channel. For the stationary condition, staggered 45 deg angled ribs show the highest heat transfer enhancement. However, staggered 45 deg angled ribs and 90 deg ribs have the higher comparable heat transfer enhancement at rotating condition near the blade leading edge region. [DOI: 10.1115/1.4000986]