Effect of Channel Orientation in a Rotating Smooth Wedge-Shaped Cooling Channel With Lateral Ejection

2013 ◽  
Author(s):  
Lu Qiu ◽  
Hongwu Deng ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Bulk Temperature ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Critical Rotation ◽  
Fundamental Research ◽  
Channel Orientation ◽  
Better Than

The effect of channel orientation on heat transfer in a rotating wedge-shaped cooling channel is experimentally investigated in current work. In order to perform a fundamental research, all turbulators are removed away. The classical copper plate technique is employed to measure the regional averaged heater transfer coefficients. The inlet Reynolds number and rotational speed range from 5100 to 21000 and zero to 1000rpm respectively, which results in the inlet Rotation number varies from zero to 0.68. In order to study the effect of channel orientation, five different angles are selected in current study. Furthermore, details such as local bulk temperature calculation and local mass flow rate determination are discussed in current paper. Interestingly, a two-dimensional bulk temperature distribution is observed. Due to the experimental results, the most evident rotation effect on heat transfer happens in 90° configuration. Compared to the non-rotating condition, there is about 35% overall heat transfer enhancement under highest rotation number. However, the greatest leading-to-trailing heat transfer difference happens in 135° or 112.5° configuration which depends on Rotation number. The highest difference is up to 40%. Besides, at the realistic 135° channel orientation, a critical Rotation number is observed after which the decreasing trend of heat transfer is traversed. The inlet Rotation is better than local one to describe this critical point. With the inlet parameter, the critical Rotation number is about 0.3 at all the locations in this channel.

Effect of Channel Orientation on Heat Transfer in Rotating Smooth Square U-Duct at High Rotation Number

2014 ◽  
Author(s):  
Yang Li ◽  
Hongwu Deng ◽  
Guoqiang Xu ◽  
Lu Qiu ◽  
Shuqing Tian
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Flow Channel ◽  
Transfer Coefficients ◽  
Number Range ◽  
Average Heat ◽  
Critical Rotation ◽  
First Pass ◽  
Channel Orientation

The effect of channel orientation on heat transfer in a rotating, two-pass, square channel is experimentally investigated in current work. The classical copper plate technique is employed to measure the regional averaged heat transfer coefficients. The inlet Reynolds number and Rotation number range from 25000 to 35000 and 0 to 0.82, respectively. Five different channel angles (−45°, −22.5°, 0°, 22.5°, 45°) are selected to study the effect of channel orientation on heat transfer. In the radially outward flow channel, the surface average heat transfer in β = 0° channel are higher than those in angled-channel (±22.5°, ±45°) on the trailing surface at all Rotation number ranges (0–0.82). While on the leading surface, surface average heat transfer are lower before a critical Rotation number, and turn higher after the critical point. Channel orientations show less influence on heat transfer in the radially inward flow channel. Compared with their corresponding perpendicular channel orientation values (β = 0° channel), heat transfer in angled-channels decrease on the pressure side and increase on the suction side at a relatively lower Rotation number (Ro<0.4) for both inward and outward channels. While at higher Rotation number (Ro>0.4), heat transfer in angled-channel decrease on both the leading and trailing walls in the first pass, and increase on both the leading and trailing walls in the second pass. By considering the effect of channel orientations, the relation between critical Rotation number on the leading surface in the first pass and dimensionless location (X/D) obeys a simple rule: (Roc·X/D)·cosβ = 1.31. The trailing-to-leading heat transfer differences induced by rotation increase with the increasing of Rotation number in angled-channel, and they are larger than β = 0° channel after the critical Rotation number in both passages.

Friction and Heat Transfer in a Rotating Rib-Roughened Square U-Duct Under High Rotation Numbers

2014 ◽  
Author(s):  
Xuewang Wu ◽  
Zhi Tao ◽  
Lu Qiu ◽  
Shuqing Tian ◽  
Yang Li
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Experimental Investigations ◽  
Absolute Pressure ◽  
Transfer Coefficients ◽  
Number Range ◽  
Pressure Drops ◽  
Critical Rotation ◽  
Smooth Case

Experimental investigations have been conducted on a rotating two-pass square channel, in which staggered ribs (attack angle of 45 degree) are roughened on both leading and trailing surfaces. The hydraulic diameter of the channel is 24 mm, and the pitch-to-height ratio and diameter-to-height ratios of the ribs are both 10:1. Reynolds number and rotational speed range from 20000 to 40000 and zero to 1000 rpm respectively. Since the absolute pressure in this channel is increased above 5 atm, the maximum rotation number reaches to 1.025. Regional averaged heat transfer coefficients are measured by classical copper plate technique. Pressure drops are measured by newly designed rotating pressure measurements module. Data are compared to that obtained in rotating smooth U-duct. It shows that the ribbed U-duct achieves enhanced regional heat transfer performances than the smooth case under stationary and rotating conditions at almost all locations except the turn region which has no ribs placed in. In the first passage of the ribbed case, the trends of stream-wise heat transfer distribution on both leading and trailing surfaces are altered compared to the counterparts in smooth case at rotation number range of 0–1.025. Besides, different from the smooth case in which the critical rotation number on heat transfer in the first leading passage decreases as X/D increases, the trend of critical rotation number in the ribbed case is not clear. Moreover, various phenomena reveal that the inserting ribs can offset the effect of rotation on heat transfer. The trends of friction factor and thermal performance as a function of rotation number in ribbed case are totally different to smooth case and they both achieve optimized value at Ro = 0.6.

Effect of Channel Orientation in a Rotating Wedge-Shaped Cooling Channel With Pin Fins and Ribs

2012 ◽  
Author(s):  
Lu Qiu ◽  
Hongwu Deng ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Reynolds Numbers ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Narrow Region ◽  
Pin Fins ◽  
Channel Orientation ◽  
Rotating Channel

Experiments are preformed to investigate the effect of channel orientation in a rotating wedge-shaped cooling channel with lateral flow extraction. The test section bears the following characteristics. Staggered ribs are arranged in the inner wide region of the channel, while the pin-fins are located in the outer narrow region. The regionally averaged heat transfer coefficients are obtained to study the characteristics of heat transfer variations in this channel under rotating and non-rotating conditions. The experiments are conducted under four inlet Reynolds numbers (6100, 15000, 25100, 33000), five rotational speeds (0, 300, 500, 800, 1000rpm) and three channel orientations (90°, 135°, 180° angle from the channel symmetry plan to the rotating plan). The inlet rotation number ranges from zero to 0.62. Finally, the experimental data demonstrates that the streamwise heat transfer variations under rotating condition are strongly affected by channel orientation in this configuration. Furthermore, compared with the data under two channel orientation 90° and 180° (the direction of rotation is perpendicular and parallel to the channel symmetry plan), the heat transfer characteristics under 135° configuration, which is regarded as the typical trailing edge orientation, approaches to the 180° one in this rotating channel. An evident critical rotation number, after which the nature of heat transfer changes abruptly, exists under 180° and 135° configuration but not under 90° one.

Local Heat Transfer in Rotating Smooth and Ribbed Two-Pass Square Channels With Three Channel Orientations

1996 ◽  
Vol 118 (3) ◽  
pp. 578-584 ◽  
Author(s):  
S. Dutta ◽  
J.-C. Han
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Channel Changes ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Channel Orientation

This paper presents experimental heat transfer results in a two-pass square channel with smooth and ribbed surfaces. The ribs are placed in a staggered half-V fashion with the rotation orthogonal to the channel axis. The channel orientation varies with respect to the rotation plane. A change in the channel orientation about the rotating frame causes a change in the secondary flow structure and associated flow and turbulence distribution. Consequently, the heat transfer coefficient from the individual surfaces of the two-pass square channel changes. The effects of rotation number on local Nusselt number ratio distributions are presented. Heat transfer coefficients with ribbed surfaces show different characteristics in rotation number dependency from those with smooth surfaces. Results show that staggered half-V ribs mostly have higher heat transfer coefficients than those with 90 and 60 deg continuous ribs.

Heat Transfer in Trailing Edge, Wedge-Shaped Cooling Channels Under High Rotation Numbers

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Lesley M. Wright ◽  
Yao-Hsien Liu ◽  
Je-Chin Han ◽  
Sanjay Chopra
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cooling Channels ◽  
Heat Transfer Coefficients ◽  
Buoyancy Parameter ◽  
Cooling Passage

Heat transfer coefficients are experimentally measured in a rotating cooling channel used to model an internal cooling passage near the trailing edge of a gas turbine blade. The regionally averaged heat transfer coefficients are measured in a wedge-shaped cooling channel (Dh=2.22cm, Ac=7.62cm2). The Reynolds number of the coolant varies from 10,000 to 40,000. By varying the rotational speed of the channel, the rotation number and buoyancy parameter range from 0 to 1.0 and 0 to 3.5, respectively. Significant variation of the heat transfer coefficients in both the spanwise and streamwise directions is apparent. Spanwise variation is the result of the wedge-shaped design, and streamwise variation is the result of the sharp entrance into the channel and the 180deg turn at the outlet of the channel. With the channel rotating at 135° with respect to the direction of rotation, the heat transfer coefficients are enhanced on every surface of the channel. Both the nondimensional rotation number and buoyancy parameter have proven to be excellent parameters to quantify the effect of rotation over the extended ranges achieved in this study.

Heat Transfer in Trailing Edge, Wedge Shaped Cooling Channels With Slot Ejection Under High Rotation Numbers

2008 ◽  
Author(s):  
Yao-Hsien Liu ◽  
Michael Huh ◽  
Lesley M. Wright ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
Buoyancy Parameter ◽  
Narrow Side ◽  
Cooling Passage

Heat transfer coefficients are experimentally measured in a rotating cooling channel with slot ejection. This test section is used to model an internal cooling passage near the trailing edge of a gas turbine blade where the spent coolant exhausts through the slot to the mainstream flow. The regionally averaged heat transfer coefficients are measured in a wedge-shaped cooling channel (Dh = 2.22cm, Ac = 7.62cm2). Due to the discharging of coolant through the slots, the local mass flow rate decreases along the streamwise direction. The effect of slot ejection enhances the heat transfer near the narrow side of the channel, while heat transfer on the wide side decreases. The inlet Reynolds number of the coolant varies from 10000 to 40000 and the rotational speeds varies from 0 to 500 rpm. The inlet rotation number is from 0 – 1.0. The local rotation number and buoyancy parameter vary by the rotational speeds and the local Reynolds number in each region. The effect of rotation in this wedge-shaped channel with slot ejection is presented in this paper. This study shows that the rotation number and buoyancy parameter are good parameters to quantify the effect of rotation with slot ejection over the extended ranges achieved in this study.

Heat Transfer in a Rotating Rib-Roughened Wedge-Shaped U-Duct

2017 ◽  
Author(s):  
Liang Ding ◽  
Shuqing Tian ◽  
Hongwu Deng
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Enhancement Effect ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Pressure Drops ◽  
Maximum Heat Transfer ◽  
Rotation Numbers ◽  
First Pass

Heat transfer in a rotating two-pass trapezium-shaped channel, with staggered 90-deg ribs on both leading and trailing surfaces is experimentally investigated. The hydraulic diameter of the first and second pass is 24.5 mm and 16.9 mm, respectively. The inlet Reynolds number and rotational speed range from 10000 to 50000 and zero to 1000 rpm, respectively, which results in the inlet rotation number varying from zero to 1.0. The heated copper plate technique is employed to measure the regional averaged heater transfer coefficients. Pressure drops are measured by newly designed rotating pressure measurements module. Both ribbed cases and smooth cases are compared to present rib enhancement effect. For non-rotating result, the results show that the trailing surface presents much higher heat transfer than other cases due to the special wedge-shaped geometry. The ribbed wedge-shaped achieves enhanced regional heat transfer performances than the smooth case at all locations. Compared with the non-rotating results in the first pass, heat transfer on both trailing and leading surfaces is enhanced except for the position near the turn region, but weakened on outer surface in stream-wise direction. And at high rotation numbers, the highest maximum heat transfer on railing surface happens at a location of approximately X/D = 10. In the first pass, rotation always enhances heat transfer on the trailing surface as rotation number increases and the rotation-to-stationary Nusselt number ratio reaches to 2.0 at the rotation number of 0.5. The leading and outer surfaces both have a critical rotation number located at Roc = 0.05.

Heat Transfer in Trailing Edge, Wedge-Shaped Cooling Channels Under High Rotation Numbers

2007 ◽  
Author(s):  
Lesley M. Wright ◽  
Yao-Hsien Liu ◽  
Je-Chin Han ◽  
Sanjay Chopra
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cooling Channels ◽  
Heat Transfer Coefficients ◽  
Buoyancy Parameter ◽  
Cooling Passage

Heat transfer coefficients are experimentally measured in a rotating cooling channel used to model an internal cooling passage near the trailing edge of a gas turbine blade. The regionally averaged heat transfer coefficients are measured in a wedge-shaped cooling channel (Dh = 2.22cm, Ac = 7.62cm2). The Reynolds number of the coolant varies from 10,000 to 40,000. By varying the rotational speed of the channel, the rotation number and buoyancy parameter range from 0–1.0 and 0–3.5, respectively. Significant variation of the heat transfer coefficients in both the spanwise and streamwise directions is apparent. Spanwise variation is the results of the wedge-shaped design, and streamwise variation is the result of the sharp entrance into the channel and the 180° at the outlet of the channel. With the channel rotating at 135° with respect to the direction of rotation, the heat transfer coefficients are enhanced on every surface of the channel. Both the non-dimensional rotation number and buoyancy parameter have proven to be excellent parameters to quantify the effect of rotation over the extended ranges achieved in this study.

High Rotation Number Effect on Heat Transfer in a Leading Edge Cooling Channel of Gas Turbine Blades With Three Channel Orientations

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Szu-Chi Huang ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Turbine Blades ◽  
Leading Edge ◽  
Cooling Channel ◽  
Number Range ◽  
Gas Turbine Blades ◽  
Rotation Numbers ◽  
Mainstream Flow ◽  
Channel Orientation

Heat transfer in a leading edge, triangular-shaped cooling channel with three channel orientations under high rotation numbers is investigated in this study. Continuous ribs and V-shaped ribs (P/e = 9, e/Dh = 0.085), both placed at an angle (α = 45 deg) to the mainstream flow, are applied on the leading and trailing surfaces. The Reynolds number range is 15,000–25,000 and the rotation number range is 0–0.65. Effects of high rotation number on heat transfer with three angles of rotation (90 deg, 67.5 deg, and 45 deg) are tested. Results show that heat transfer is influenced by the combined effects of rib and channel orientation. When the rotation number is smaller than 0.4, rotation causes a decrease in the average Nusselt number ratios on the leading surface at a channel orientation of 90 deg. Heat transfer is enhanced gradually on the leading surface when the channel orientation varies from 90 deg to 45 deg for both ribbed cases. The highest heat transfer enhancement due to rotation is found at the highest rotation number of 0.65.

Heat Transfer Measurements in an Internal Cooling System Using a Transient Technique With Infrared Thermography

2012 ◽  
Author(s):  
Christian Egger ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Data Analysis ◽  
Infrared Thermography ◽  
Outer Surface ◽  
Cooling System ◽  
Internal Cooling ◽  
Test Model ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper a transient method for measuring heat transfer coefficients in internal cooling systems using infrared thermography is applied. The experiments are performed with a two-pass internal cooling channel connected by a 180° bend. The leading edge and the trailing edge consist of trapezoidal and nearly rectangular cross sections, respectively, to achieve an engine-similar configuration. Within the channels rib arrangements are considered for heat transfer enhancement. The test model is made of metallic material. During the experiment the cooling channels are heated by the internal flow. The surface temperature response of the cooling channel walls is measured on the outer surface by infrared thermography. Additionally, fluid temperatures as well as fluid and solid properties are determined for the data analysis. The method for determining the distribution of internal heat transfer coefficients is based on a lumped capacitance approach which considers lateral conduction in the cooling system walls as well as natural convection and radiation heat transfer on the outer surface. Because of time-dependent effects a sensitivity analysis is performed to identify optimal time periods for data analysis. Results are compared with available literature data.

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