scholarly journals Heat Transfer Measurements for Rotating Turbine Discs

1989 ◽  
Author(s):  
G. Qureshi ◽  
M. H. Nguyen ◽  
N. R. Saad ◽  
R. N. Tadros
Keyword(s):  
Heat Transfer ◽  
Coolant Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Rotating Discs ◽  
Turbine Disc ◽  
State Technique

To optimise the turbine disc weight and coolant flow requirements, the aspect of improving thermal analysis was investigated. As a consequence, an experimental investigation was undertaken to measure the rates of convective heat transfer. The constant temperature steady state technique was used to determine the local and average heat transfer coefficients on the sides of rotating discs. The effects of coolant flow rates, CW (3000 ≤ CW ≤ 18600) with two types of cavity in-flow conditions and of the rotational speeds, Reθ (from 4×105 to 1.86×106) on the disc heat transfer were studied and correlations developed. For a rotating disc in confined cavities with superimposed coolant flows, Nusselt numbers were found to be higher than those for the free rotating disc without confinement.

Heat Transfer From Rotating Discs With Finite Thickness Subjected to Outer Air Streams

2010 ◽  
Author(s):  
Stefan aus der Wiesche
Keyword(s):  
Heat Transfer ◽  
Large Range ◽  
Finite Thickness ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Rotating Discs ◽  
Air Stream ◽  
Air Streams

The heat transfer from rotating discs in an outer air stream is of major importance for many technical applications. Experimentally determined heat transfer coefficients are presented for a large range of rotational and crossflow Reynolds numbers including also the effects of finite disc thickness and incidence to the uniform air stream. The extreme conditions of a rotating disc in still air and a stationary disc in an air crossflow are considered, too.

Heat Transfer in a Surfactant Drag-Reducing Solution—A Comparison With Predictions for Laminar Flow

2005 ◽  
Vol 128 (6) ◽  
pp. 557-563 ◽  
Author(s):  
Paul L. Sears ◽  
Libing Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Drag Reducing Additive ◽  
Good Agreement

Heat transfer coefficients were measured for a solution of surfactant drag-reducing additive in the entrance region of a uniformly heated horizontal cylindrical pipe with Reynolds numbers from 25,000 to 140,000 and temperatures from 30to70°C. In the absence of circumferential buoyancy effects, the measured Nusselt numbers were found to be in good agreement with theoretical results for laminar flow. Buoyancy effects, manifested as substantially higher Nusselt numbers, were seen in experiments carried out at high heat flux.

Heat Removal and Thermal Stabilization of High-temperature Surfaces by a Dispersed Coolant Flow

Vestnik MEI ◽  
2021 ◽  
pp. 19-26
Author(s):  
Valentin S. Shteling ◽  
◽  
Vladimir V. Ilyin ◽  
Aleksandr T. Komov ◽  
Petr P. Shcherbakov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Flow Rate ◽  
Heat Flux Density ◽  
Coolant Flow ◽  
Transfer Coefficients ◽  
Stationary Heat ◽  
Heat Transfer Coefficients ◽  
Stationary Heat Transfer

The effectiveness of stabilizing the surface temperature by a dispersed coolant flow is experimentally studied on a bench simulating energy intensive elements of thermonuclear installations A test section in which the maximum heat flux density can be obtained when being subjected to high-frequency heating was developed, manufactured, and assembled. The test section was heated using a VCh-60AV HF generator with a frequency of not lower than 30 kHz. A hydraulic nozzle with a conical insert was used as the dispersing device. Techniques for carrying out an experiment on studying a stationary heat transfer regime and for calculating thermophysical quantities were developed. The experimental data were obtained in the stationary heat transfer regime with the following range of coolant operating parameters: water pressure equal to 0.38 MPa, water mass flow rate equal to 5.35 ml/s, and induction heating power equal to 6--19 kW. Based on the data obtained, the removed heat flux density and the heat transfer coefficients were calculated for each stationary heat transfer regime. The dependences of the heat transfer coefficient on the removed heat flux density and of the removed heat flux density on the temperature difference have been obtained. High values of heat transfer coefficients and heat flux density at a relatively low coolant flow rate were achieved in the experiments.

Conjugate Heat Transfer in Air-to-Refrigerant Airfoil Heat Exchangers

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Yutaka Ito ◽  
Naoya Inokura ◽  
Takao Nagasaki
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Exchange System ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Heat Exchange System ◽  
Inverse Heat Transfer ◽  
Transfer Method

A light and compact heat exchange system was realized using two air-to-refrigerant airfoil heat exchangers and a recirculated heat transport refrigerant. Its heat transfer performance was experimentally investigated. Carbon dioxide or water was used as a refrigerant up to a pressure of 30 MPa. Heat transfer coefficients on the outer air-contact and inner refrigerant-contact surfaces were calculated using an inverse heat transfer method. Correlations were developed for the Nusselt numbers of carbon dioxide and water on the inner refrigerant-contact surface. Furthermore, we proposed a method to evaluate a correction factor corresponding to the thermal resistance of the airfoil heat exchanger.

Heat Transfer in a “Cover-Plate” Pre-Swirl Rotating-Disc System

1998 ◽  
Author(s):  
Robert Pilbrow ◽  
Hasan Karabay ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Turbine Disc ◽  
Cooling Air

In most gas turbines, blade-cooling air is supplied from stationary pre-swirl nozzles that swirl the air in the direction of rotation of the turbine disc. In the “cover-plate” system, the pre-swirl nozzles are located radially inward of the blade-cooling holes in the disc, and the swirling air flows radially outwards in the cavity between the disc and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder-Sharma and the Morse low-Reynolds-number k-ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disc” are compared with measured values obtained from a rotating-disc rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 × 106 to 1.5 × 106, and for 0.9 < βp < 3.1, where βp is the pre-swirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disc). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

Conjugate Heat Transfer in a Rotor-Stator System With Through-Flow

2002 ◽  
Author(s):  
Reby Roy ◽  
B. V. S. S. S. Prasad ◽  
S. Srinivasa Murthy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer Thickness ◽  
Conjugate Heat Transfer ◽  
Rotating Disk ◽  
Thermal Boundary Layer Thickness ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Through Flow

The conjugate heat transfer in a stationary cylindrical cavity with a rotating disk and fluid through-flow is analysed at various rotational speeds ranging from 10000 to 50000 rpm by using a finite volume commercial code. The numerical model and code are validated for a problem, which involves rotation and fluid through-flow. A reduction of the thermal boundary layer thickness and increase in the heat transfer coefficients are observed with increase in the rotational speed. Marked differences are noticed between the Nusselt numbers obtained from the conjugate and constant temperature analyses.

Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part I—Effect on Heat Transfer Coefficients

1994 ◽  
Vol 116 (4) ◽  
pp. 721-729 ◽  
Author(s):  
S. Ou ◽  
J.-C. Han ◽  
A. B. Mehendale ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Transition Region ◽  
Density Ratio ◽  
Wake Flow ◽  
Transfer Coefficients ◽  
Pressure Surface ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio ◽  
Nusselt Numbers ◽  
Unsteady Wake

The effect of unsteady wake flow and air (D.R. = 1.0) or CO2 (D.R. = 1.52) film injection on blade heat transfer coefficients was experimentally determined. A spoked wheel-type wake generator produced the unsteady wake. Experiments were performed on a five-airfoil linear cascade in a low-speed wind tunnel at the chord Reynolds number of 3 × 105 for the no-wake case and at the wake Strouhal numbers of 0.1 and 0.3. Results from a blade with three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces show that the Nusselt numbers are much higher than those for the blade without film holes. On a large portion of the blade, the Nusselt numbers “without wake but with film injection” are much higher than for “with wake but no film holes.” An increase in wake Strouhal number causes an increase in pressure surface Nusselt numbers; but the increases are reduced at higher blowing ratios. As blowing ratio increases, the Nusselt numbers for both density ratio injectants (air and CO2) increase over the entire blade except for the transition region where the effect is reversed. Higher density injectant (CO2) produces lower Nusselt numbers on the pressure surface, but the numbers for air and CO2 injections are very close on the suction surface except for the transition region where the numbers for CO2 injection are higher. From this study, one may conclude that the additional increases in Nusselt numbers due to unsteady wake, blowing ratio, and density ratio are only secondary when compared to the dramatic increases in Nusselt numbers only due to film injection over the no film holes case.

Effect of Rotation and Coolant Throughflow on the Heat Transfer and Temperature Field in an Enclosure

1976 ◽  
Vol 98 (3) ◽  
pp. 387-394 ◽  
Author(s):  
E. M. Sparrow ◽  
Leonardo Goldstein
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Flow Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Transfer Coefficients ◽  
Disk System ◽  
Heat Transfer Coefficients

Measurements were performed to determine the local heat transfer coefficients along the heated shroud of a shrouded parallel disk system. The temperature field within the enclosure formed by the shroud and the disks was also measured. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air was introduced into the enclosure through an aperture at the center of the stationary disk and exited through a slot at the rim of the rotating disk. The coolant entrance-exit arrangement differed from that of previous studies, with the additional difference that the incoming coolant stream was free of rotation. The coolant flow rate, the disk rotational speed, and the aspect ratio of the enclosure were varied during the experiments. The heat transfer coefficients were found to be increasingly insensitive to the absence or presence of rotation as the coolant flow rate increased. There was a general increase of the transfer coefficients with increasing coolant flow rate, especially for low rotational speeds. The temperature field in the enclosure differed markedly depending on the relative importance of rotation and of coolant throughflow. When the latter dominates, the temperature in the core is relatively uniform, but in the presence of strong rotation there are significant nonuniformities. A comparison was made between the present Nusselt number results and those of prior experiments characterized by different coolant entrance—exit arrangements. The positioning of the coolant exit slot relative to the direction of the boundary layer flow on the shroud emerged as an important factor in the comparison.

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.

The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane

2000 ◽  
Author(s):  
Hans Reiss ◽  
Albin Bölcs
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection. The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.

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