Simultaneously combined liquid crystal surface heat transfer and PIV flow-field measurements

2001 ◽  
Vol 30 (1) ◽  
pp. 1-10 ◽  
Author(s):  
T. J. Praisner ◽  
D. R. Sabatino ◽  
C. R. Smith
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Flow Field ◽  
Crystal Surface ◽  
Field Measurements ◽  
Surface Heat ◽  
Surface Heat Transfer

Aerothermal Investigation of a Single Row Divergent Narrow Impingement Channel by Particle Image Velocimetry and Liquid Crystal Thermography

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Alexandros Terzis ◽  
Christoforos Skourides ◽  
Peter Ott ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Particle Image Velocimetry ◽  
Liquid Crystal ◽  
Flow Field ◽  
Particle Image ◽  
Field Measurements ◽  
Single Row ◽  
Transient Techniques ◽  
Liquid Crystal Thermography ◽  
Image Velocimetry

Integrally cast turbine airfoils with wall-integrated cooling cavities are greatly applicable in modern turbines providing enhanced heat exchange capabilities compared to conventional cooling passages. In such arrangements, narrow impingement channels can be formed where the generated crossflow is an important design parameter for the achievement of the desired cooling efficiency. In this study, a regulation of the generated crossflow for a narrow impingement channel consisting of a single row of five inline jets is obtained by varying the width of the channel in the streamwise direction. A divergent impingement channel is therefore investigated and compared to a uniform channel of the same open area ratio. Flow field and wall heat transfer experiments are carried out at engine representative Reynolds numbers using particle image velocimetry (PIV) and liquid crystal thermography (LCT). The PIV measurements are taken at planes normal to the target wall along the centerline for each individual jet, providing quantitative flow visualization of jet and crossflow interactions. The heat transfer distributions on the target plate of the channels are evaluated with transient techniques and a multilayer of liquid crystals (LCs). Effects of channel divergence are investigated combining both the heat transfer and flow field measurements. The applicability of existing heat transfer correlations for uniform jet arrays to divergent geometries is also discussed.

Thermal and Flow Field Characteristics in a Rectangular Duct With Broken V-Shaped Ribs

2003 ◽  
Author(s):  
Lieke Wang ◽  
Xiufang Gao ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Field Measurements ◽  
High Heat ◽  
Rectangular Duct ◽  
Local Maxima ◽  
High Heat Transfer

In the present study, the thermal and hydraulic characteristics of a rectangular duct with aspect ratio of 1/8 roughened by broken V-shaped ribs pointing upstream are investigated experimentally using Liquid Crystal Thermography (LCT) and Particle Image Velocimetry (PIV). The heat transfer distributions on the roughened wall were evaluated using liquid crystal images. It was found that the heat transfer coefficient had a spanwise variation on the ribbed wall, with high heat transfer coefficient at the upstream end of the rib and low value at the other end, similar to the continuous V-shaped ribs. However, the heat transfer distribution in the case of broken V-shaped ribs was observed more uniform, with local maxima due to the gap flow. In addition, the saw-tooth fashion of heat transfer distribution was also observed along the streamwise direction. The isothermal flow field measurements were obtained by PIV to catch the flow structures introduced by the ribs. The spanwise profile of the main flow velocity was found altered, and a complicated secondary flow was detected over the cross section. This flow phenomenon was caused by the ribs and the gaps between ribs.

Surface Heat Transfer Measurements of a Scaled Rib-Roughened Serpentine Cooling Passage by Use of a Transient Liquid Crystal Technique

1998 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Kouhei Ishizawa ◽  
Shigemichi Yamawaki
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Surface Heat ◽  
Bulk Temperature ◽  
Test Model ◽  
Thermochromic Liquid Crystal ◽  
Scaled Model ◽  
Surface Heat Transfer ◽  
Cooling Passage ◽  
Straight Duct

This study is aimed at providing heat transfer characteristics of the three-pass turbulated serpentine cooling channel inside a 10:1 scaled model of an actual turbine blade. A transient method using Thermochromic Liquid Crystal (TLC) is employed to measure the surface heat transfer distribution inside the model. Great attention is paid to the streamwise decrease in the mainstream temperature due to the heat absorption into the test model. To overcome this problem, the present study employed the linear interpolating method used by Ekkad and Han (1997) to estimate the local air bulk temperature. The soundness of the measuring method is verified through the heat transfer measurements of straight-duct models with and without turbulence promoting ribs. It follows from the heat transfer measurement of the serpentine model, in conjunction with the flow visualization, that the geometries of the cross-section of the cooling passage influence the flow pattern, resulting in substantial change in heat transfer distribution in the serpentine model in comparison with that of the straight-duct model.

A Transient Liquid Crystal Method Using Hue Angle and a 3-D Inverse Transient Conduction Scheme

2000 ◽  
Author(s):  
Mingjie Lin ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Surface Heat ◽  
Heat Transfer Surface ◽  
Transfer Coefficients ◽  
Data Set ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Hue Angle ◽  
Transient Conduction

Various transient liquid crystal methods have been widely and routinely employed to measure surface heat transfer coefficients. Typically, the heat transfer surface was modeled as a one-dimensional, transient heat conduction over a semi-infinite surface to retrieve information of the surface heat transfer coefficients. To satisfy the theoretical initial and boundary conditions, inconvenient and/or complex designs are required. Frequently, the conditions are not exactly satisfied. To resolve these issues, an approach of measuring heat transfer coefficients coupling the transient liquid crystal method with a 3-D inverse transient conduction scheme was developed and was applied to a nonuniform heat transfer surface produced by arrays of impinging jets. The present method utilized the hue-angle method to process the color images captured from the liquid crystal color play. Instantaneous temperature readings from embedded thermocouples were utilized for in-situ calibration of hue angle for each data set. The convective heat transfer coefficient results were obtained by performing a 3-D inverse transient conduction calculation over the entire jet impingement target surface and the substrate. The results of average heat transfer coefficients agreed well with previous experimental results of point measurements by thermocouples.

Sign in / Sign up

Export Citation Format

Share Document