EXPERIMENTAL INVESTIGATION OF THE EFFECT EXERTED BY NANOPARTICLES ON THE HEAT TRANSFER COEFFICIENT OF HERSCHEL-BULKLEY FLUIDS

2014 ◽  
Vol 45 (6) ◽  
pp. 485-505
Author(s):  
Roozbeh Mollabbasi ◽  
Seyyed Hosein Noie ◽  
Saeed Zeinali Heris
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
The Heat Transfer Coefficient

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.

Experimental Investigation of Double Rows Film Cooling on Vane Pressure Side

2012 ◽  
Author(s):  
T. Elnady ◽  
I. Hassan ◽  
L. Kadem ◽  
T. Lucas
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Radius Of Curvature ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
The Heat Transfer Coefficient

An experimental investigation has been performed to study the effect of hole shape and position on the cooling performance of a gas turbine stator. Two rows of laid-back fan-shaped holes are placed on the pressure side of a scaled vane in a two-dimensional cascade and compared with two identical rows of standard cylindrical exit. Both hole shapes have the same base diameter and were investigated at three different blowing ratios (1, 1.35, and 1.7) with the same coolant flow rate used in each case. The experiments are conducted for the first row of holes only, then for the second row only, and finally for both two rows together at a 0.9 density ratio. The mainstream inlet Reynolds number based on the true chord is 1.4E5 and the exit Mach number is 0.23. The local distributions of the heat transfer coefficient and film cooling effectiveness are obtained using a transient TLC technique. The second row of holes, with by a higher local radius of curvature, shows a 40% decrease in the cooling effectiveness as well as a 10% increase in the heat transfer coefficient near downstream of the hole compared with that obtained by the first hole. The double injection provides a slight increase in the cooling effectiveness and a lower heat transfer coefficient due to the favorable interaction between both injections.

scholarly journals Effect of Acceleration on the Heat Transfer Coefficient on a Film Cooled Surface

1990 ◽  
Author(s):  
H. D. Ammari ◽  
N. Hay ◽  
D. Lampard
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Mass Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Density Ratio ◽  
Base Line ◽  
Density Ratios ◽  
The Heat Transfer Coefficient

Results are presented of an experimental investigation into the influence of mainstream acceleration on the heat transfer coefficient downstream of injection through a row of 35° holes in a flat plate. A mass transfer analogue technique was used, with two uniform acceleration parameters, K (=ν(du∞/dx)/u∞2), of 1.9 × 10−6 and 5.0 × 10−6 in addition to the zero acceleration base-line case. Two injectants, air and carbon dioxide, were employed to give coolant to mainstream density ratios of 1.0 and 1.52 respectively. The blowing rate varied from 0.5 to 2.0. The heat transfer coefficient beneath the film reduced progressively as the acceleration increased, with maximum reductions from the zero acceleration datum case of about 27%. In the presence of acceleration, the heat transfer coefficient at a given blowing rate was dependent on the density ratio, an increase in the density ratio leading to a decrease in the heat transfer coefficient. An empirical correlation of the data over most of the range of densities and blowing rates of the experiments has been developed.

Experimental Investigation of Louver Cooling Scheme on Gas Turbine Vane Pressure Side

2010 ◽  
Author(s):  
T. Elnady ◽  
W. Saleh ◽  
I. Hassan ◽  
L. Kadem ◽  
T. Lucas
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Pressure Side ◽  
Local Pressure ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
The Heat Transfer Coefficient

An experimental investigation has been performed to measure the cooling performance of the louver scheme using a two-dimensional cascade simulating the scaled vane of a high-pressure gas turbine. Two rows of an axially oriented louver scheme are distributed in a stagger arrangement over the pressure side. The effect of hole location on the cooling performance is investigated for each row individually, then the row interaction is investigated for both rows. The temperature distribution on the vane is mapped using a transient Thermochromic Liquid Crystal (TLC) technique to obtain the local distributions of the heat transfer coefficient and film cooling effectiveness. The performance of the louver scheme for each case is compared with that of two similar rows with a standard cylindrical exit at 0.9 density ratio. The exit Reynolds number based on the true chord is 1.5E5 and exit Mach number is 0.23. The local distributions of the effectiveness and the heat transfer coefficient are presented at four different blowing ratios ranging from 1 to 2. The louver scheme shows a superior cooling effectiveness than that of the cylindrical holes at all blowing ratios in terms of protection and lateral coverage. The row location highly affects the cooling performance for both the louver and cylindrical scheme due to the local pressure change and the variation of the surface curvature.

Experimental Investigation of Flow Boiling Inside Three Three-Dimensional Surface Enhanced Heat Transfer Tubes

2017 ◽  
Author(s):  
Weiyu Tang ◽  
Zhengjiang Zhang ◽  
Jincai Du ◽  
Wei Li ◽  
Jincheng Han ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Velocity ◽  
Enhanced Heat Transfer ◽  
Low Mass ◽  
Respective Surface ◽  
Enhanced Surface ◽  
The Heat Transfer Coefficient

An Experimental investigation was conducted to compare the evaporation characteristics of R410A inside three newly developed horizontal enhanced heat transfer (EHT) tubes with the same OD12.70mm and ID11.50mm, and the result of them are compared with that of a plain tube. The inner enhanced surface of 1EHT tube consists of dimples/protrusions and petal arrays, while that of 2EHT-1 tube and 2EHT-2 tube is composed by longitudinal grooves and dimples of different depths. The mass velocities are in the range of 70kg/m2s-200kg/m2 s with a nominal saturation temperature fixed at 279K and the vapor quality in the test section varies from 0.2∼0.9. As the mass flux increases, both the heat transfer coefficient and pressure penalty increase accordingly. The heat transfer coefficient of EHT tubes can achieve 1.14–1.53 times higher than that of the smooth tube while the pressure gradients is 1.43–1.83 times larger than that of smooth tubes. Besides, the enhancement ratios of all the enhanced surface tubes are larger than their respective surface area ratio, and the enhancement ratio comparisons of heat transfer coefficient are made to obtain the enhancing mechanism. The results show that the EHT tubes appear higher performance at low mass fluxes. In all, the EHT1 tube has the best heat transfer performance at low mass velocity, which can be attributed to its special enhanced inner surface, resulting in the increase of nucleation sites, flow separation and turbulent fluctuations. The other two 2EHT tubes can enhance the evaporation greatly with small respective surface ratios as well as relatively little pressure drop penalty, and them shows outstanding performance especially at high mass velocity.

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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