A Comparison of Full Surface Local Heat Transfer Coefficient and Flow Field Studies Beneath Sharp-Edged and Radiused Entry Impinging Jets

1996 ◽  
Author(s):  
D. R. H. Gillespie ◽  
S. M. Guo ◽  
Z. Wang ◽  
P. T. Ireland ◽  
S. T. Kohler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Static Pressure ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Impinging Jets ◽  
Velocity Variation

Full heat transfer coefficient and static pressure distributions have been measured on the target surface under impinging jets formed by sharp-edged and large entry radius holes. These geometries are representative of impingement holes in a gas turbine blade manufactured by laser cutting and by casting, respectively. Target surface heat transfer has been measured in a large scale perspex rig using both the transient liquid crystal technique and hot thin film gauges. A range of jet Reynolds numbers, representative of engine conditions, has been investigated. The velocity variation has been calculated from static pressure measurements on the impingement target surface. The heat transfer to the target surface is discussed in terms of the interpreted flow field.

The Effect of Impingement Jet Heat Transfer on Casing Contraction in a Turbine Case Cooling System

2014 ◽  
Author(s):  
Orpheas Tapanlis ◽  
Myeonggeun Choi ◽  
David R. H. Gillespie ◽  
Leo V. Lewis ◽  
Carlo Ciccomascolo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Cooling System ◽  
Impinging Jets ◽  
Tip Clearance ◽  
Scale Model ◽  
Number Range

This paper reports full local Nusselt number distributions under an array of impinging jets typical of those used for thermal tip clearance control through casing contraction. Characteristic features of this type of application are sparse arrays of short cooling holes flowing at low jet Reynolds numbers (700–11,000) and large stand-off distances from the surface into a semi-confined passage with multiple exits. These features are captured in a large scale model, approximately ten times engine scale. Heat transfer measurements are made using the transient thermochromic liquid crystal technique. The measurement domain was extended far downstream of the impingement array. This allowed the entire heat transfer coefficient distribution contributing to the contraction of the liner around the rotor blades to be captured. CFD studies were conducted to characterize the flow field obtained, which in turn is helpful in understanding the drivers of heat transfer. The results are compared to existing industry standard correlations, which are generally outside the geometric and Reynolds number range of interest. It was shown that, for the tested geometries, the heat transfer was sensibly unaffected by whether the flow was exhausted through one side of the exit passage or equally in both directions, and the bulk flow field could be predicted using a modified distributed injection model. The heat transfer coefficient distributions are linked to a thermal-mechanical finite element model to provide thermal boundary conditions on an idealized representation of the casing for casing contraction in the presence of cooling scheme. For one of the geometries tested, data from an engine casing thermocouple survey have been compared to predictions of casing temperature determined using the measured heat transfer coefficient distributions and these show reasonable agreement.

Heat Transfer Enhancement by Turbulent Impinging Jets

2000 ◽  
Author(s):  
M. Kumagai ◽  
R. S. Amano ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.

Detailed Flow and Heat Transfer Coefficient Measurements in a Model of an Internal Cooling Geometry Employing Orthogonal Intersecting Channels

2000 ◽  
Author(s):  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Geoff M. Dailey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Structural Integrity ◽  
Local Heat Transfer ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
Gas Temperature ◽  
Transfer Coefficients

Cast interconnecting passage Lattice cooling geometries offer the gas turbine designer higher structural integrity and improved convective efficiency when compared to traditional aerofoil rear cooling strategies. In this paper, local heat transfer coefficient distributions were measured in a model of an idealised engine lattice cooling geometry, with flow ejection through film-cooling holes. The measurements were made using the transient liquid crystal technique in a large-scale perspex model at low temperature. The technique allows very high data resolution. Heat transfer patterns on all surfaces of the device including the internal web are presented at engine representative Reynolds numbers. The results are discussed in terms of the interpreted flow field. Furthermore, a subsequent analysis which accounted for the changing driving gas temperature and mass flow rate through the model has allowed the heat transfer coefficients to be derived based on the mixed bulk temperature, and local passage Reynolds number.

Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array with Varying Jet Hole-Size and Spacing

2005 ◽  
Vol 128 (1) ◽  
pp. 158-165 ◽  
Author(s):  
U. Uysal ◽  
P.-W. Li ◽  
M. K. Chyu ◽  
F. J. Cunha
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Hole Size ◽  
Streamwise Direction ◽  
Actual Distribution ◽  
The Heat Transfer Coefficient ◽  
Jet Array

One significant issue concerning the impingement heat transfer with a jet array is related to the so-called “crossflow,” where a local jet performance is influenced by the convection of the confluence from the impingement of the jet∕jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossflow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and interjet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.

Local Heat Transfer Coefficient Distribution With Air Impingement Into a Cavity

1972 ◽  
Author(s):  
F. Burggraf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Local Heat Transfer Coefficient ◽  
Cavity Surface ◽  
Transfer Coefficients ◽  
Coefficient Distribution

Impingement heat transfer coefficients are presented for a row of holes impinging into an oval cavity with the spent air leaving through holes on one or both sides of the cavity. The distribution around the cavity surface is obtained and is correlated with a survey of the recent literature. In addition, local heat flux gages were used with an impingement jet air supply which could be changed in location along the axis of the test section. This permitted the determination of local heat transfer coefficient distribution over the surface both around the cavity and also in the region between the impinging jets. This two-dimensional distribution is shown to be influenced by the bleed geometry and the shape of the impinging jet holes.

Unsteady Analysis of Heat Transfer Coefficient Distribution in a Static Ribbed Channel for an Established Flow

2020 ◽  
Author(s):  
Aurélien Perrot ◽  
Laurent Gicquel ◽  
Florent Duchaine ◽  
Nicolas Odier ◽  
Jérôme Dombard ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Weak Link ◽  
Turbine Blades ◽  
Main Flow ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode

Abstract Turbulent ribbed channels are extensively used in turbomachinery to enhance convective heat transfer in internally-cooled components like turbine blades. One of the key aspect of such a problem is the distribution of the Heat Transfer Coefficient (HTC) in fully developed flows and many studies have addressed this problem by use of Computational Fluid Dynamics (CFD). In the present document, Large Eddy Simulation (LES) is performed for a configuration from a test-rig at the Von Karman Institute representing a square channel with periodic square ribs. The whole channel is computed in an attempt to better understand HTC maps in this specific configuration. Resulting mean and unsteady flow features are captured and predictions are used to further explain the obtained HTC distribution. More specifically turbulent structures are seen to bring cold gas from the main flow to the wall. A statistical analysis of these events using the joint velocity-temperature PDF and quadrant method allows to define 4 types of events happening at every location of the channel and which can then be linked to the HTC distribution. First the HTC is very high where the flow impacts the wall with cold temperature whereas it is lower where the hot gas is ejected to the main flow. In an attempt to link the HTC trace on the channel wall with structures in the flow field far-off the wall, the main modes are identified performing Power Spectral Density (PSD) analysis of the velocity along the channel. Dynamic Mode Decomposition (DMD) of the flow field data is then used to present the spatio-temporal characteristics of two of the identified most dominant modes: a vortex-street mode linked to the first rib and a rib-to-rib mode appearing because of the quasi-periodicity of the configuration. However DMD analysis of the HTC trace on the wall does not emphasize any dominant mode. This indicates a weak link between the main flow large scale features and the instantaneous and more local HTC distribution.

Turbulent Shear Flow and Heat Transfer Over the Repeated Two-Dimensional Square Ribs on Ground Plane

1993 ◽  
Vol 115 (4) ◽  
pp. 631-637 ◽  
Author(s):  
Shiki Okamoto ◽  
Shozo Seo ◽  
Kouichirou Nakaso ◽  
Itsurou Kawai
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Static Pressure ◽  
Ground Plane ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Turbulent Shear ◽  
Two Dimensional

This paper describes the flow structure over the repeated two-dimensional square ribs of side length D, placed at a pitch S on a ground plane. The value of S/D which most augments the turbulence of the free stream and, hence the heat transfer is calculated. The region of interest in this investigation is far downstream where the velocity and temperature distributions follow similarity rules. The time-mean velocity, static pressure, and the velocity vectors were measured by Pivot-and static pressure tubes and a three hole cylindrical yawmeter. The turbulence intensities and integral scale were obtained using a hot wire anemometer. The mean temperature distribution was measured by thermocouples and the local heat transfer coefficient was then calculated. It is found that at S/D=9 the turbulence intensity is maximized. As a result of this effect and the fact that for S/D=9 the flow reattaches within a groove, the heat transfer is also maximized. The measurements show how the location of reattachment depends on S/D and that high local heat transfer coefficient coincides with the reattachment point. The average heat transfer coefficient and the pressure drop correlation is quantified.

Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array With Varying Jet Hole-Size and Spacing

2005 ◽  
Author(s):  
U. Uysal ◽  
P.-W. Li ◽  
M. K. Chyu ◽  
F. J. Cunha
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Hole Size ◽  
Streamwise Direction ◽  
Actual Distribution ◽  
The Heat Transfer Coefficient ◽  
Jet Array

One significant issue concerning the impingement heat transfer with a jet array is related to the so-called “crossflow”, where a local jet performance is influenced by the convection of the confluence from the impingement of the jet/jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossflow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and inter-jet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.

Local Heat Transfer and Flow Distributions for Impinging Jet Arrays of Dense and Sparse Extent

2002 ◽  
Author(s):  
J. C. Bailey ◽  
R. S. Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Impinging Jet ◽  
Axial Direction ◽  
Lateral Direction ◽  
Wide Range ◽  
Limiting Case

Full-surface heat transfer coefficient distribution measurements have been made using a liquid crystal thermography technique for several cases of normally impinging jet arrays onto a flat, smooth surface within a region bounded on three sides. While the impingement target plate remains of a fixed size, the impingement jet array has been changed to cover a wide range of conditions, extending beyond the currently available literature data. Axial and lateral jet spacing values of x/D and y/D of 3, 6, and 9 have been used, all with square orientation and in-line jets. The jet plate-to-target surface distance z/D has been varied from 1.25 to 5.5. Jet Reynolds numbers ranged from 14,000 to 65,000. In the sparse array limiting case, the number of jet rows is four in the axial direction and three in the lateral direction. For the dense array limiting case, the number of jet rows is 26 in the axial direction and 20 in the lateral direction. Using both heat transfer and pressure distribution measurements, results are compared to the existing correlation of Florschuetz et al. [1], showing excellent agreement in regions of common parameters. In regions not previously reported in the literature, the present study extends the streamwsie row-averaged heat transfer coefficient correlation of [1] with a modified correlation for design use.

Heat Transfer in Free Swirling Flow in a Pipe

1975 ◽  
Vol 97 (3) ◽  
pp. 411-416 ◽  
Author(s):  
N. Hay ◽  
P. D. West
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Swirling Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Swirl Number ◽  
Pipe Axis ◽  
Air Inlet

The local heat transfer coefficient, for air flowing through a pipe with a swirling motion, was measured at various stations downstream of the swirling air inlet. The swirling motion of the air was produced by a single tangential slot, initially at 90 deg to the pipe axis, through which the air was introduced. The dimensions of the slot and the angle of tangency were varied and the resultant flow field inside the pipe was measured and expressed in the form of local “swirl numbers”. The augmentation of heat transfer was found to be a function of the swirl number and a correlation for this function is presented. At some locations, the augmentation can be as much as eight times the value for fully developed nonswirling turbulent flow.

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