A Technique for Processing Transient Heat Transfer, Liquid Crystal Experiments in the Presence of Lateral Conduction

2003 ◽  
Author(s):  
John C. P. W. Ling ◽  
Peter T. Ireland ◽  
Lynne Turner
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensions ◽  
Transient Heat Transfer ◽  
Adiabatic Wall ◽  
Full Intensity

New techniques for processing transient liquid crystal heat transfer experiment have been developed. The methods are able to measure detailed local heat transfer coefficient and adiabatic wall temperature in a three temperature system from a single transient test using the full intensity history recorded. Transient liquid crystal processing methods invariably assume that lateral conduction is negligible and so the heat conduction process can be considered one dimensional into the substrate. However, in regions with high temperature variation such as immediately downstream of a film-cooling hole, it is found that lateral conduction can become significant. For this reason, a procedure which allows for conduction in three dimensions was developed by the authors. The paper is the first report of a means of correcting data from the transient heat transfer liquid crystal experiments for the effects of significant lateral conduction. The technique was applied to a film cooling system as an example and a detailed uncertainty analysis performed.

A Technique for Processing Transient Heat Transfer, Liquid Crystal Experiments in the Presence of Lateral Conduction

2004 ◽  
Vol 126 (2) ◽  
pp. 247-258 ◽  
Author(s):  
John P. C. W. Ling ◽  
Peter T. Ireland ◽  
Lynne Turner
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensions ◽  
Transient Heat Transfer ◽  
Adiabatic Wall ◽  
Full Intensity

New techniques for processing transient liquid crystal heat transfer experiment have been developed. The methods are able to measure detailed local heat transfer coefficient and adiabatic wall temperature in a three temperature system from a single transient test using the full intensity history recorded. Transient liquid crystal processing methods invariably assume that lateral conduction is negligible and so the heat conduction process can be considered one-dimensional into the substrate. However, in regions with high temperature variation such as immediately downstream of a film-cooling hole, it is found that lateral conduction can become significant. For this reason, a procedure which allows for conduction in three dimensions was developed by the authors. The paper is the first report of a means of correcting data from the transient heat transfer liquid crystal experiments for the effects of significant lateral conduction. The technique was applied to a film cooling system as an example and a detailed uncertainty analysis performed.

An Advanced Method of Processing Liquid Crystal Video Signals From Transient Heat Transfer Experiments

1995 ◽  
Vol 117 (1) ◽  
pp. 184-189 ◽  
Author(s):  
Z. Wang ◽  
P. T. Ireland ◽  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Color Change ◽  
Transient Heat Transfer ◽  
Turbine Blade Cooling ◽  
Video Signals ◽  
Surface Heat Transfer Coefficient ◽  
Full Intensity ◽  
Cooling Passage

A new method of processing the liquid crystal color change data obtained from transient heat transfer experiments is presented. The approach uses the full-intensity history recorded during an experiment to obtain an accurate measurement of the surface heat transfer coefficient at selected pixels. Results are presented for a model of a turbine blade cooling passage with combined ribs and film cooling holes. The implementation of the technique and the advantages to be gained from its application are discussed.

An Advanced Method of Processing Liquid Crystal Video Signals From Transient Heat Transfer Experiments

1993 ◽  
Author(s):  
Zuolan Wang ◽  
Peter T. Ireland ◽  
Terry V. Jones
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Colour Change ◽  
Transient Heat Transfer ◽  
Turbine Blade Cooling ◽  
Video Signals ◽  
Surface Heat Transfer Coefficient ◽  
Full Intensity ◽  
Cooling Passage

A new method of processing the liquid crystal colour change data obtained from transient heat transfer experiments is presented. The approach uses the full intensity history recorded during an experiment to obtain an accurate measurement of the surface heat transfer coefficient at selected pixels. Results are presented for a model of a turbine blade cooling passage with combined ribs and film cooling holes. The implementation of the technique and the advantages to be gained from its application are discussed.

Effects of Embedded Vortices on Film-Cooled Turbulent Boundary Layers

1989 ◽  
Vol 111 (1) ◽  
pp. 71-77 ◽  
Author(s):  
P. M. Ligrani ◽  
A. Ortiz ◽  
S. L. Joseph ◽  
D. L. Evans
Keyword(s):  
Heat Transfer ◽  
Boundary Layers ◽  
Film Cooling ◽  
Free Stream ◽  
Flow Behavior ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Boundary Layers ◽  
Stream Velocity ◽  
Longitudinal Vortices

Heat transfer effects of longitudinal vortices embedded within film-cooled turbulent boundary layers on a flat plate were examined for free-stream velocities of 10 m/s and 15 m/s. A single row of film-cooling holes was employed with blowing ratios ranging from 0.47 to 0.98. Moderate-strength vortices were used with circulating-to-free stream velocity ratios of −0.95 to −1.10 cm. Spatially resolved heat transfer measurements from a constant heat flux surface show that film coolant is greatly disturbed and that local Stanton numbers are altered significantly by embedded longitudinal vortices. Near the downwash side of the vortex, heat transfer is augmented, vortex effects dominate flow behavior, and the protection from film cooling is minimized. Near the upwash side of the vortex, coolant is pushed to the side of the vortex, locally increasing the protection provided by film cooling. In addition, local heat transfer distributions change significantly as the spanwise location of the vortex is changed relative to film-cooling hole locations.

Transpiration Cooling Using Porous Triple-Laminated Plates

2003 ◽  
Author(s):  
H. L. Wu ◽  
X. F. Peng
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Efficiency ◽  
Velocity Ratio ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Laminated Plates ◽  
Transpiration Cooling ◽  
Transfer Behavior ◽  
Crossflow Velocity

Transpiration cooling using porous triple-laminated plates was numerically investigated to understand the associated flow mechanism and heat transfer characteristics with/without crossflow. The flow structure and heat transfer behavior are very similar in the two laminate gaps, and crossflow has little influence on them. The cooling performance shows very good uniformity and high efficiency. Violent impingement and turbulent flow inside the plate contribute greatly to local heat transfer intensification. The cooling efficiency might be further improved with enhancement of film cooling effect, by enlarging the discharge holes to decrease the local jet-to-crossflow velocity ratio, or by using inclined discharge holes to increase the film attaching ability.

scholarly journals Heat Transfer Enhancement of Impingement Cooling by Adopting Circular-Ribs or Vortex Generators in the Wall Jet Region of A Round Impingement Jet

2020 ◽  
Vol 5 (3) ◽  
pp. 17 ◽  
Author(s):  
Ken-Ichiro Takeishi ◽  
Robert Krewinkel ◽  
Yutaka Oda ◽  
Yuichi Ichikawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Wall Jet ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Impingement Jet

In the near future, when designing and using Double Wall Airfoils, which will be manufactured by 3D printers, the positional relationship between the impingement cooling nozzle and the heat transfer enhancement ribs on the target plate naturally becomes more accurate. Taking these circumstances into account, an experimental study was conducted to enhance the heat transfer of the wall jet region of a round impingement jet cooling system. This was done by installing circular ribs or vortex generators (VGs) in the impingement cooling wall jet region. The local heat transfer coefficient was measured using the naphthalene sublimation method, which utilizes the analogy between heat and mass transfer. As a result, it was clarified that, within the ranges of geometries and Reynolds numbers at which the experiments were conducted, it is possible to improve the averaged Nusselt number Nu up to 21% for circular ribs and up to 51% for VGs.

Effect of Film Extraction on Impingement Heat Transfer Characteristics of Jet Arrays on Spherical-Dimpled Surfaces

2015 ◽  
Author(s):  
Xing Yang ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Coupling Effect ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Separation Distance ◽  
Plate Spacing

Detailed heat transfer distributions are numerically investigated on a multiple jet impingement target surface with staggered arrays of spherical dimples where coolant can be extracted through film holes for external film cooling. The three dimensional Reynolds-averaged Navier-Stokes analysis with SST k-ω turbulence model is conducted at jet Reynolds number from 15,000 to 35,000. The separation distance between the jet plate and the target surface varies from 3 to 5 jet diameters and two jet-induced crossflow schemes are included to be referred as large and small crossflow at one and two opposite exit openings correspondingly. Flow and heat transfer results for the dimpled target plate with three suction ratios of 2.5%, 5.0% and 12.0% are compared with those on dimpled surfaces without film holes. The results indicate the presence of film holes could alter the local heat transfer distributions, especially near the channel outlets where the crossflow level is the highest. The heat transfer enhancements by applying film holes to the dimpled surfaces is improved to different degrees at various suction ratios, and the enhancements depend on the coupling effect of impingement and channel flow, which is relevant to jet Reynolds number, jet-to-plate spacing and crossflow scheme.

Heat-Flux Measurements for a Realistic Cooling Hole Pattern With Multiple Flow Conditions

2013 ◽  
Author(s):  
Jeremy B. Nickol ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Local Heat Transfer ◽  
Axial Direction ◽  
Local Heat ◽  
Data Sets ◽  
Adiabatic Wall ◽  
Adiabatic Cooling ◽  
Cooling Hole ◽  
Flux Measurements

Predicting cooling flow migration and its impact on surface heat flux for a turbine operating at design-corrected conditions is a challenging task. While recent data sets have provided a baseline for comparison, they have also raised many questions about comparison methods and the proper implementation of boundary conditions. Simplified experiments are helpful for bridging the gap between the experimental and computational worlds to develop the best procedures for generating predictions and correctly comparing them to experiments. To this end, a flat-plate configuration has been developed that replicates the cooling hole pattern of the pressure side of a high-pressure turbine blade. The heat transfer for this configuration is investigated for a range of flow properties of current interest to the industry using a medium-duration blowdown facility. Heat-flux measurements are obtained using double-sided Kapton heat-flux gauges arrayed in two rows in the axial direction along the centerline of the hole pattern. Gauges are located upstream of the holes, in between rows of holes, and extending far downstream of the last row of holes. New parameters are proposed for analyzing the data including a corrected Stanton number and the length-corrected heat flux reduction parameter. These parameters are used for exploring the influence of Reynolds number and blowing ratio on local heat transfer. In addition, the temperatures of the main flow and the test section walls were varied to determine the effect of cooling on the local adiabatic wall temperature and to enable comparisons using the adiabatic cooling effectiveness.

Three-Dimensional Transient Heat Conduction Equation Solution for Accurate Quantification of Heat Transfer Coefficient in Transient Liquid Crystal Experiments

2019 ◽  
Author(s):  
Shoaib Ahmed ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Conduction Model

Abstract Liquid crystal thermography and infrared thermography techniques are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models. One such practice, which is very popular and easy to use, is the transient liquid crystal thermography using one-dimensional semi-infinite conduction model. In these experiments, a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used where a step-change in coolant air temperature is induced and surface temperature response is recorded. An error minimization routine is then employed to guess heat transfer coefficients of each pixel, where wall temperature evolution is known through an analytical expression. The assumption that heat flow in the solid is essentially in one-dimension, often leads to errors in HTC determination and this error depends on true HTC, wall temperature evolution and HTC gradient. A representative case of array jet impingement under maximum crossflow condition has been considered here. This heat transfer enhancement concept is widely used in gas turbine leading edge and electronics cooling. Jet impingement is a popular cooling technique which results in high convective heat rates and has steep gradients in heat transfer coefficient distribution. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. The HTC results obtained using 1D semi-infinite conduction model and 3D conduction model were compared and it was found that the heat transfer coefficient obtained using the 3D model was consistently higher than the conventional 1D model by 3–16%. Significant deviations, as high as 8–20% in local heat transfer at the stagnation points of the jets were observed between h1D and h3D.

scholarly journals Systematic Investigation on Conjugate Heat Transfer Rates of Film Cooling Configurations

2005 ◽  
Vol 2005 (3) ◽  
pp. 211-220 ◽  
Author(s):  
Dieter Bohn ◽  
Jing Ren ◽  
Karsten Kusterer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Systematic Investigation ◽  
Transfer Condition ◽  
Film Cooling Effectiveness ◽  
Conjugate Calculation

For the determination of the film-cooling heat transfer, the design of a turbine blade relies on the conventional determination of the adiabatic film-cooling effectiveness and heat transfer conditions for test configurations. Thus, additional influences by the interaction of fluid flow and heat transfer and influences by additional convective heat transfer cannot be taken into account with sufficient accuracy. Within this paper, calculations of a film-cooled duct wall and a film-cooled real blade with application of the adiabatic and a conjugate heat transfer condition have been performed for different configurations. It can be shown that the application of the conjugate calculation method comprises the influence of heat transfer within the cooling film. The local heat transfer rate varies significantly depending on the local position.

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