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

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Sung Kook Hong ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Coriolis Force ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Impinging Jet ◽  
Stagnation Region ◽  
Plate Spacing ◽  
Axis Of Rotation

In the present study, the effects of the rotating direction on heat/mass transfer in an impingement/effusion cooling system were investigated. The experiments were carried out with three different jet orientations relative to the axis of rotation and two plate spacing. For high H/d with an orthogonal jet orientation, low and nonuniform heat/mass transfer occurred between the effusion holes since the impinging jet was deflected by the Coriolis force. For a small H/d, the jet deflection effect was diminished, and rotation enhanced the heat/mass transfer in the stagnation region.

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.

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.

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.

Effect of Channel Orientation of Local Heat (Mass) Transfer Distributions in a Rotating Two-Pass Square Channel With Smooth Walls

1998 ◽  
Vol 120 (3) ◽  
pp. 624-632 ◽  
Author(s):  
C. W. Park ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Coriolis Force ◽  
Heat Mass Transfer ◽  
Control Volume ◽  
Local Heat ◽  
Local Mass ◽  
Square Channel ◽  
Sharp Turn ◽  
Local Mass Transfer ◽  
Channel Orientation

Naphthalene sublimation experiments have been conducted to study the effects of channel orientation, rotational Coriolis force, and a sharp turn, on the local heat (mass) transfer distributions in a two-pass square channel with a sharp turn and smooth walls, rotating about a perpendicular axis. The test channel was oriented so that the direction of rotation was perpendicular to or at a 45 deg angle to the leading and trailing walls. The Reynolds number was kept at 5,500 and the rotation number ranged up to 0.24. For the radial outward flow in the first straight pass of the diagonally oriented channel, rotation-induced Coriolis force caused large monotonic spanwise variations of the local mass transfer on both the leading and trailing walls, with the largest mass transfer along the outer edges of both walls. Rotation did not lower the spanwise average mass transfer on the leading wall and did not increase that on the trailing wall in the diagonally oriented channel as much as in the normally oriented channel. The combined effect of the channel orientation, rotation, and the sharp turn caused large variations of the local mass transfer distributions on the walls at the sharp turn and immediately downstream of the sharp turn. The velocity fields that were obtained with a finite difference control-volume-based computer program helped explain how rotation and channel orientation affected the local mass transfer distributions in the rotating two-pass channel.

Vadasz Number Influence on Vibration in a Rotating Porous Layer Placed Far Away From the Axis of Rotation

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
S. Govender
Keyword(s):  
Mass Transfer ◽  
Free Convection ◽  
Porous Layer ◽  
Heat Mass Transfer ◽  
Stability Criteria ◽  
Time Approximation ◽  
Axis Of Rotation ◽  
Vadasz Number ◽  
Transfer 21 ◽  
The Stability

We consider vibration effects on the classical Rayleigh–Be’nard problem and the classical Vadasz (1994, “Stability of Free Convection in a Narrow Porous Layer Subject to Rotation,” Int. Commun. Heat Mass Transfer, 21, pp. 881–890) problem, which includes rotation of a vertical porous layer about the z-axis. In particular, we focus on the influence of the Vadasz number on vibration for small to moderate and large Vadasz numbers. For small to moderate Vadasz numbers, we develop an analogy between the Vadasz problem (Vadasz, 1994, “Stability of Free Convection in a Narrow Porous Layer Subject to Rotation,” Int. Commun. Heat Mass Transfer, 21, pp. 881–890) placed far away from the axis of rotation and classical Rayleigh–Be’nard problem, both of which include the effects of vibration. It is shown here that the stability criteria are identical to the Rayleigh–Be’nard problem with vibration when g∗=ω∗2X0∗. The analysis for the large Vadasz number scaling indicates that a frozen time approximation is appropriate where the effect of vibration is modeled as small variations in the Rayleigh number definition.

scholarly journals Heat (mass) transfer between an impinging jet and a rotating disk

1998 ◽  
Vol 34 (2-3) ◽  
pp. 195-201 ◽  
Author(s):  
Y.-M. Chen ◽  
W.-T. Lee ◽  
S.-J. Wu
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Impinging Jet ◽  
Rotating Disk
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