Influence of Injection Type and Feed Arrangement on Flow and Heat Transfer in an Injection Slot

2001 ◽  
Vol 124 (1) ◽  
pp. 132-141 ◽  
Author(s):  
Hyung Hee Cho ◽  
Jin Ki Ham
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Transfer Coefficients ◽  
Counter Flow ◽  
Flow Paths ◽  
Mass Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Vertical Injection ◽  
Injection Type

An experimental investigation is conducted to improve a slot film cooling system used for the cooling of a gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical, and combined to the slot lip. The investigation is focused on the coolant supply systems of normal, inline, and counter-flow paths to the mainstream flow direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot wall with various injection types and coolant feeding directions. A numerical simulation is also conducted to help understand the flow patterns inside the slot for different injection types. The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the injection hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The dimensionless temperature distributions at the slot exits differ little with blowing rates, injection types, and secondary flow conditions. In the results of heat/mass transfer measurements, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effects of jet impingement. The lateral distributions of heat/mass transfer coefficients with the inline and counter-flow paths are more uniform than the normal-flow path. The average heat/mass transfer coefficients with the injection holes are about two to five times higher than that of a smooth two-dimensional slot path.

Influence of Injection Type and Feed Arrangement on Flow and Heat Transfer in an Injection Slot

2000 ◽  
Author(s):  
Hyung Hee Cho ◽  
Jin Ki Ham
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Transfer Coefficients ◽  
Counter Flow ◽  
Flow Paths ◽  
Mass Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Vertical Injection ◽  
Injection Type

An experimental investigation is conducted to improve a slot film cooling system used for the cooling of a gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical and combined to the slot lip. The investigation is focused on the coolant supply systems of normal-, inline-, and counter-flow paths to the mainstream flow direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot wall with various injection types and coolant feeding directions. A numerical simulation is also conducted to help understand the flow patterns inside the slot for different injection types. The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the injection hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The dimensionless temperature distributions at the slot exits differ little with blowing rates, injection types and secondary flow conditions. In the results of heat/mass transfer measurements, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effects of jet impingement. The lateral distributions of heat/mass transfer coefficients with the inline- and counter-flow paths are more uniform than the normal-flow path. The average heat/mass transfer coefficients with the injection holes are about 2∼5 times higher than that of a smooth two-dimensional slot path.

Effect of Rib Angle on Local Heat/Mass Transfer Distribution in a Two-Pass Rib-Roughened Channel

1988 ◽  
Vol 110 (2) ◽  
pp. 233-241 ◽  
Author(s):  
P. R. Chandra ◽  
J. C. Han ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Sherwood Number ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Test Channel ◽  
Mass Transfer Coefficients ◽  
Square Duct ◽  
Naphthalene Sublimation Technique

The heat transfer characteristics of turbulent air flow in a two-pass channel were studied via the naphthalene sublimation technique. The test section, which consisted of two straight, square channels joined by a sharp 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) was 0.063 and the rib pitch-to-height ratio (P/e) was 10. The local heat/mass transfer coefficients on the roughened top wall, and on the smooth divider and side walls of the test channel, were determined for three Reynolds numbers of 15,000, 30,000, and 60,000, and for three angles of attack (α) of 90, 60, and 45 deg. The results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle-of-attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of α = 60 and 45 deg were higher than those in the case of α = 90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the traverse-rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Effects of Fin Shapes and Arrangements on Heat Transfer for Impingement/Effusion Cooling With Crossflow

2005 ◽  
Author(s):  
Sung Kook Hong ◽  
Dong-Ho Rhee ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Flow Characteristics ◽  
Local Heat ◽  
Wall Jet ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Blowing Ratio ◽  
Transfer Characteristics ◽  
Sublimation Method

The present paper has investigated the effects of fin on the flow and heat/mass transfer characteristics for the impingement/effusion cooling with crossflow. The fins of circular or rectangular shape are installed between two perforated plates and the crossflow passes between these two plates. The blowing ratio is changed from 0.5 to 1.5 for a fixed jet Reynolds number of 10,000. A naphthalene sublimation method is used to obtain the local heat/mass transfer coefficients on the effusion plate. A numerical calculation is also performed to investigate the flow characteristics. Flow and heat/mass transfer characteristics are changed significantly due to installation of fins. In the injection region, wall jet spreads more widely than the case without fins because fin prevents the wall jet from being swept away by the crossflow. In the effusion region, higher heat/mass transfer coefficient is obtained due to the flow disturbance and acceleration by the fin. As the blowing ratio increases, the effects of fin against the crossflow become more significant and then the higher average heat/mass transfer coefficients are obtained. Especially, the cases with rectangular fins have about 40%∼45% enhancement at the high blowing ratio of M = 1.5. However, the increase of blockage effect gives more pressure loss in the channel.

Local Heat/Mass Transfer Measurement on the Effusion Plate in Impingment/Effusion Cooling System

2000 ◽  
Author(s):  
Hyung Hee Cho ◽  
Dong Ho Rhee
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Perforated Plate ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Perforated Plates ◽  
Flow Acceleration

The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged in two different configurations: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). In general, higher heat/mass transfer is obtained with smaller gap distance between two perforated plates.

Heat Transfer Characteristics of an Obliquely Impinging Circular Jet

1980 ◽  
Vol 102 (2) ◽  
pp. 202-209 ◽  
Author(s):  
E. M. Sparrow ◽  
B. J. Lovell
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Local Heat ◽  
Maximum Point ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Local Coefficients ◽  
Naphthalene Sublimation

Measurements of local heat (mass) transfer coefficients were made on a surface on which a circular jet impinges at an oblique angle. The angle of inclination of the jet relative to the surface was varied from 90 deg (normal impingement) to 30 deg. The Reynolds number and the distance between the jet orifice and the impingement plate were also varied parametrically. To facilitate the experiments, the naphthalene sublimation technique was employed, and the resulting mass transfer coefficients were converted to heat transfer coefficients by the well-established analogy between the two processes. It was found that the point of maximum mass transfer is displaced from the geometrical impingement point, with the extent of the displacement increasing with greater jet inclination. The local coefficients on the uphill side of the maximum point drop off more rapidly than do those on the downhill side, thus creating an imbalance in the cooling/heating capabilities on the two sides. Neither the maximum transfer coefficient nor the surface-averaged transfer coefficient are highly sensitive to the inclination of the jet; during the course of the experiments, the largest inclination-induced decreases in these quantities were in the 15 to 20 percent range.

Local Heat/Mass Transfer and Friction Loss Measurement in a Rotating Matrix Cooling Channel

2009 ◽  
Author(s):  
In Taek Oh ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Jun Su Park ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Sherwood Number ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Matrix Channel ◽  
Rotation Numbers ◽  
The Matrix

The present investigation provides detailed local heat/mass transfer distribution and pressure drop characteristics in a matrix cooling channel under rotating conditions. The matrix channel has cooling sub-passages with crossing angle of 45 degrees. Detailed heat/mass transfer coefficients are measured using the naphthalene sublimation method. The pressure drops are also measured. The experiments were conducted under various Reynolds numbers (10,000 to 44,000) and rotation numbers (0.0 to 0.8). For the stationary case, the heat transfer characteristics are dominated by turning, impinging and swirling flow which are induced by the matrix channel geometry. Averaged heat/mass transfer coefficients on the leading and trailing surfaces in the stationary channel are approximately 2.1 times higher than those in a smooth channel. For the rotating cases, the effect of rotation on heat/mass transfer characteristics shows different tendency compared to typical rotating channels with radially outward flow. As the rotation number increases, the Sherwood number ratios increase on the leading surface, but changed slightly on the trailing surface. The thermal performance factors increases with increasing rotation numbers due to increased Sherwood number ratios and decreased friction factor ratios.

Effect of Rotation on Heat/Mass Transfer for an Impingement/Effusion Cooling System

2007 ◽  
Author(s):  
Sung Kook Hong ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Local Heat ◽  
Hole Diameter ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Plate Spacing ◽  
Jet Cooling ◽  
Flow Mixing

The purpose of this study is to investigate the effect of rotation on the heat/mass transfer in an impingement/effusion cooling system. To simulate the rotating impingement/effusion system, a test duct with injection and effusion holes is installed on the rotating system. The jet Reynolds number based on the hole diameter is fixed to 3,000 and the Rotation number is set to 0.032. The experiments are carried out for various parameters such as the plate spacing to hole diameter ratio (H/d), orientation of the jet relative to the rotating axis and the tests for the array jet cooling are performed together. The naphthalene sublimation method is used to obtain the heat/mass transfer coefficients on the effusion plate. The local heat/mass transfer distributions are altered by the rotation. For the impingement/effusion cooling with orthogonal orientation, the low and non-uniform heat/mass transfer occurs between the effusion holes because the impinging jet is deflected by the Coriolis force. At a small H/d, the rotation enhances the heat/mass transfer in the stagnation region due to an increase in flow mixing. The impingement/effusion cooling with H/d = 2 shows the most efficient cooling performance and it is confirmed that the crossflow and H/d affect the averaged Sh value significantly under rotating conditions.

Heat Transfer on Rotating Channel With Various Heights of Pin-Fin

2008 ◽  
Author(s):  
Jun Su Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Pin Fins ◽  
Naphthalene Sublimation ◽  
Pin Fin Array

Pin-fins have been used to enhance the heat transfer near the trailing edge of a turbine airfoil. Previous pin-fin heat transfer studies focused mainly on the array geometry of pin height-to-diameter equal to unity in a stationary frame. This study experimentally examines the effects of pin height-to-diameter ratio (Hp/Dp) from 2 to 4 and rotation number (Ro) from 0 to 0.2. The tested model used a staggered pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation technique with a heat-mass transfer analogy. The data measured suggest that an increase in Hp/Dp increases the level of array heat/mass transfer. Array averaged Sherwood numbers for Hp/Dp = 3 and Hp/Dp = 4 are approximately 10% and 35% higher than that of Hp/Dp = 2. The effect of rotation induces notable difference in heat/mass transfer between the leading surface and the trailing surface. The heat transfer coefficients change a little although the rotating number increases in the tested range because the pin-fins break the rotation-induced vortices.

scholarly journals Measurements of Mass Transfer Coefficient and Effectiveness in the Recovery Region of a Film-Cooled Surface

1986 ◽  
Author(s):  
W. P. Webster ◽  
S. Yavuzkurt
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Large Area ◽  
Mass Transfer Equation ◽  
Mass Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Naphthalene Sublimation Technique

Mass transfer coefficients and the film cooling effectiveness are measured downstream of a single row of holes inclined 30 degrees with the surface and inline with the main turbulent boundary layer flow. The mass transfer coefficients (based on the difference between the free stream and the surface concentrations) are measured using a naphthalene sublimation technique. The effectiveness is determined through the injection of a trace gas into the secondary (cooling jets) flow and measuring its concentration at the impermeable wall. Experiments are carried out in a subsonic, zero pressure gradient turbulent boundary layer, under isothermal conditions with three blowing ratios (Uj/U∞): 0.4, 0.8, and 1.2. The data is collected in a region 7 to 80 jet diameters downstream of the injection location. From the data on mass transfer coefficients and effectiveness obtained under the same flow conditions a general mass transfer equation is derived. This paper presents extensive data and discussions; and is believed to be one of the few studies in which both of these variables are measured on the same surface and in a large area in the recovery region.

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