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.

Single-Phase Heat Transfer in Mems-Based Pin Fin Heat Sink

2005 ◽  
Author(s):  
Ali Kosar ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Pin Fins ◽  
Micro Pin Fins

An experimental study has been performed on single-phase heat transfer of de-ionized water over a bank of shrouded micro pin fins 243-μm long with hydraulic diameter of 99.5-μm. Heat transfer coefficients and Nusselt numbers have been obtained over effective heat fluxes ranging from 3.8 to 167 W/cm2 and Reynolds numbers from 14 to 112. The results were used to derive the Nusselt numbers and total thermal resistances. It has been found that endwalls effects are significant at low Reynolds numbers and diminish at higher Reynolds numbers.

scholarly journals An Experimental Investigation of Heat Transfer Coefficients in a Spanwise Rotating Channel With Two Opposite Rib-Roughened Walls

1989 ◽  
Author(s):  
M. E. Taslim ◽  
A. Rahman ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Reynolds Numbers ◽  
Blockage Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Rotating Channel

Liquid crystals are used in this experimental investigation to measure the heat transfer coefficient in a spanwise rotating channel with two opposite rib-roughened walls. The ribs (also called turbulence promoters or turbulators) are configured in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90° for all cases. Results are presented for three values of turbulator blockage ratio, e/Dh (0.1333, 0.25, 0.333) and for a range of Reynolds numbers from 15,000 to 50,000 while the test section is rotated at different speeds to give Rotational Reynolds numbers between 450 and 1800. The Rossby number range is 10 to 100 (Rotation number of 0.1 to 0.01). The effect of turbulator blockage ratios on heat transfer enhancement is also investigated. Comparisons are made between the results of geometrically identical stationary and rotating passages of otherwise similar operating conditions. The results indicate that a significant enhancement in heat transfer is achieved in both the stationary and rotating cases, when the surfaces are roughened with turbulators. For the rotating case, a maximum increase over that of the stationary case of about 45% in the heat transfer coefficient is seen for a blockage ratio of 0.133 on the trailing surface in the direction of rotation and the minimum is a decrease of about 6% for a blockage ratio of 0.333 on the leading surface, for the range of rotation numbers tested. The technique of using liquid crystals to determine heat transfer coefficients in this investigation proved to be an effective and accurate method especially for nonstationary test sections.

scholarly journals Heat Transfer Coefficients for Staggered Arrays of Short Pin Fins

1981 ◽  
Author(s):  
G. J. VanFossen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Total Heat Transfer ◽  
Optimum Length ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
Casting Technology ◽  
Nusselt Numbers ◽  
Pin Fins

Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

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 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.

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.

Experimental Investigation on Flow Resistance and Heat Transfer Coefficient of Internal Lamilloy

2016 ◽  
Author(s):  
Wei Zhang ◽  
Huiren Zhu ◽  
Guangchao Li ◽  
Chunyu Shang ◽  
Cunliang Liu
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Flow Resistance ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Jet ◽  
Pin Fins ◽  
Loss Coefficients

Flow resistance and heat transfer coefficients of the lamilloy with two kinds of film hole pitch were experimentally studied at the impinging Reynolds numbers ranging from 1×104 to 6×104. The detailed distributions of pressure coefficients on the target plate, impingement plate and pin-fins, local loss coefficients of jet, channel flow, effusion and the flow resistance coefficients of lamilloy were obtained by using a lot of pressure taps. The dense grids of the surfaces were generated and the pressure values of all the grid points were obtained by Kriging interpolation method based on the experimental data. Distributions of heat transfer coefficients on the target and the impingement surfaces ( The surface of the impingement plate in the impingement hole outlet surface) were tested by the transient liquid crystal technique. The coolant temperatures of both impingement hole inlet and the film hole outlet were measured by K type thermocouples. The results show that the pressure coefficients on the jet stagnation region increase firstly and then decrease along the radius direction from stagnation point. The pressure distributions on the two rows of pin-fins near the two film hole rows are significantly affected by the Reynolds numbers. The pressure coefficient values are nearly the same in the pin fin height direction which means the flow pattern near the pin fins of this two rows likes the crossflow past a circular cylinder at Re=3×104 and has the characteristics of reverse flow and flow around circular cylinder at Re=4×104. The loss coefficients of effusion are the biggest, those of channel flow are the second and those of impingement jet are the smallest. The loss coefficients of effusion of film hole increase at least 4 times and those of the impingement jet and the channel flow change slightly when the spacing of film hole decreases one half. The averaged heat transfer coefficient of target surface is higher than that of the impingement surface. This difference becomes obvious with the increase of Reynolds number. The differences of Nusselt number on the impingement surface and the target surface are 16% and 10% respectively under the two models at the Reynolds number of 6×104, indicating that the hole pitch has a weak influence on the averaged heat transfer coefficients. The second peak of heat transfer coefficients was found.

An Experimental Investigation of Heat Transfer Coefficients in a Spanwise Rotating Channel With Two Opposite Rib-Roughened Walls

1991 ◽  
Vol 113 (1) ◽  
pp. 75-82 ◽  
Author(s):  
M. E. Taslim ◽  
A. Rahman ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Reynolds Numbers ◽  
Blockage Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Rotating Channel

Liquid crystals are used in this experimental investigation to measure the heat transfer coefficient in a spanwise rotating channel with two opposite rib-roughened walls. The ribs (also called turbulence promoters or turbulators) are configured in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90 deg for all cases. Results are presented for the three values of turbulator blockage ratio e/Dh (0.1333, 0.25, 0.333) and for a range of Reynolds numbers from 15,000 to 50,000 while the test section is rotated at different speeds to give rotational Reynolds numbers between 450 and 1800. The Rossby number range is 10 to 100 (rotation number of 0.1 to 0.01). The effect of turbulator blockage ratios on heat transfer enhancement is also investigated. Comparisons are made between the results of geometrically identical stationary and rotating passage of otherwise similar operating conditions. The results indicate that a significant enhancement in heat transfer is achieved in both the stationary and rotating cases, when the surfaces are roughened with turbulators. For the rotating case, a maximum increase over that of the stationary case of about 45 percent in the heat transfer coefficient is seen for a blockage ratio of 0.133 on the trailing surface in the direction of rotation and the minimum is a decrease of about 6 percent for a blockage ratio of 0.333 on the leading surface, for the range of rotation numbers tested. The technique of using liquid crystals to determine heat transfer coefficients in this investigation proved to be an effective and accurate method especially for nonstationary test sections.

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