A New Hue Capturing Technique for the Quantitative Interpretation of Liquid Crystal Images Used in Convective Heat Transfer Studies

1991 ◽  
Author(s):  
Cengiz Camci ◽  
Kuisoon Kim ◽  
S. A. Hippensteele
Keyword(s):  
Heat Transfer ◽  
Image Processing ◽  
Liquid Crystal ◽  
Single Crystal ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Present Method ◽  
Heat Transfer Surface ◽  
Blue Color ◽  
Quantitative Interpretation

This study focuses on a new image processing based color capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies. The present method is highly applicable to the surfaces exposed to convective heating in gas turbine engines. The study shows that, in single crystal mode, many of the colors appearing on the heat transfer surface strongly correlate with the local temperature. A very accurate quantitative approach using an experimentally determined linear hue versus temperature relation is possible. The new hue capturing process is discussed in detail, in terms of the strength of the light source illuminating the heat transfer surface, effect of the orientation of the illuminating source with respect to the surface, crystal layer uniformity and the repeatability of the process. The method uses a 24 bit color image processing system operating in hue-saturation-intensity domain which is an alternative to conventional systems using red-green-blue color definition. The present method is more advantageous than the multiple filter method because of its ability to generate many isotherms simultaneously from a single crystal image at a high resolution, in a very time efficient manner. The current approach is valuable in terms of its direct application to both steady state and transient heat transfer techniques currently used for the hot section heat transfer research in air breathing propulsion systems.

A New Hue Capturing Technique for the Quantitative Interpretation of Liquid Crystal Images Used in Convective Heat Transfer Studies

1992 ◽  
Vol 114 (4) ◽  
pp. 765-775 ◽  
Author(s):  
C. Camci ◽  
K. Kim ◽  
S. A. Hippensteele
Keyword(s):  
Heat Transfer ◽  
Image Processing ◽  
Liquid Crystal ◽  
Single Crystal ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Present Method ◽  
Heat Transfer Surface ◽  
Blue Color ◽  
Quantitative Interpretation

This study focuses on a new image processing based color capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies. The present method is highly applicable to the surfaces exposed to convective heating in gas turbine engines. The study shows that, in single-crystal mode, many of the colors appearing on the heat transfer surface correlate strongly with the local temperature. A very accurate quantitative approach using an experimentally determined linear hue versus temperature relation is possible. The new hue-capturing process is discussed in detail, in terms of the strength of the light source illuminating the heat transfer surface, effect of the orientation of the illuminating source with respect to the surface, crystal layer uniformity, and the repeatability of the process. The method uses a 24-bit color image processing system operating in hue-saturation-intensity domain, which is an alternative to conventional systems using red-green-blue color definition. The present method is more advantageous than the multiple filter method because of its ability to generate many isotherms simultaneously from a single-crystal image at a high resolution, in a very time-efficient manner. The current approach is valuable in terms of its direct application to both steady-state and transient heat transfer techniques currently used for the hot section heat transfer research in air-breathing propulsion systems.

scholarly journals Inorganic fouling of heat transfer surface from potable water during convective heat transfer

2020 ◽  
pp. 116271
Author(s):  
Amthal Al-Gailani ◽  
Olujide Sanni ◽  
Thibaut V.J. Charpentier ◽  
Richard Crisp ◽  
Jantinus H. Bruins ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Potable Water ◽  
Heat Transfer Surface ◽  
Inorganic Fouling

Convective Heat Transfer Studies in Mini-Channels Using Digital Interferometry

2009 ◽  
Author(s):  
V. Sajith ◽  
Divya Haridas ◽  
C. B. Sobhan ◽  
G. R. C. Reddy
Keyword(s):  
Heat Transfer ◽  
Image Processing ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Digital Image Processing ◽  
Convective Heat ◽  
Digital Image ◽  
Test Section ◽  
Average Heat ◽  
Mini Channels

Convective heat transfer in micro and mini channels has been recommended as an effective heat removal method for various electronic packages and systems. Experimental and theoretical investigations on the thermal performance of micro and mini channels have gained immense attention and hence, heat transfer studies in mini channels are of great importance. Some of the experimental results found in the literature on heat transfer in small-dimension channels are of contradicting nature even though some generally agreeing results are also found. One of the probable reasons for such deviations is the intrusive nature of the measurement techniques used. The traditional method of temperature measurement in channels uses the thermocouple probe, and for obtaining temperature distribution across the channel either a number of probes or a moving probe technique is required, both of which disturb the flow field and cause measurement errors. Hence a non intrusive measurement technique, such as an optical method is preferable for temperature measurement in small channels. In the present work, convective heat transfer studies have been performed on water flowing through a mini channel of hydraulic diameter 4 mm, using the non-intrusive technique of laser interferometry, coupled with digital image processing. The channel is fabricated using high quality optical glass and aluminum blocks. Mach Zehnder Interferometry is used for obtaining the temperature distribution in the channel. The experimental arrangement consists of two identical channels, one placed in the test section and the other in the reference section of the interferometric set up. As the test section is heated, a density variation is produced in the medium, which causes a refractive index variation, deforming interference fringes. This enables the calculation of the temperature distribution inside the channel. The interferograms are grabbed using a CCD camera and an AVT Fire package software. Digital image processing technique, using MATLAB software is used for locating the fringe-centers, and calculating the temperature distribution. The temperature profiles are obtained at different sections of the channel for various values of the average Reynolds number and various heating levels. The local and average heat flux values are obtained from the constructed temperature distributions. Variations of the local and average heat transfer coefficients and Nusselt number are determined and discussed. Results of parametric studies are compared and contrasted with relevant entry length solutions from the literature.

Evaluation of a Hue Capturing Based Transient Liquid Crystal Method for High-Resolution Mapping of Convective Heat Transfer on Curved Surfaces

1993 ◽  
Vol 115 (2) ◽  
pp. 311-318 ◽  
Author(s):  
C. Camci ◽  
K. Kim ◽  
S. A. Hippensteele ◽  
P. E. Poinsatte
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Steady State ◽  
Liquid Crystals ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Bottom Surface ◽  
Curved Surfaces ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Accurate determination of convective heat transfer coefficients on complex curved surfaces is essential in the aerothermal design and analysis of propulsion system components. The heat transfer surfaces are geometrically very complex in most of the propulsion applications. This study focuses on the evaluation of a hue capturing technique for the heat transfer interpretation of liquid crystal images from a complex curved heat transfer surface. Impulsively starting heat transfer experiments in a square to rectangular transition duct are reported. The present technique is different from existing steady-state hue capturing studies. A real-time hue conversion process on a complex curved surface is adopted for a transient heat transfer technique with high spatial resolution. The study also focuses on the use of encapsulated liquid crystals with narrow color band in contrast to previous steady-state hue based techniques using wide band liquid crystals. Using a narrow band crystal improves the accuracy of the heat transfer technique. Estimated uncertainty for the heat transfer coefficient from the technique is about 5.9 percent. A complete heat transfer map of the bottom surface was possible using only seven liquid crystal image frames out of the 97 available frames during the transient experiment. Significant variations of heat transfer coefficients are quantitatively visualized on the curved surfaces of the transition duct.

The Application of a Hue-Based Liquid Crystal Technique to Determine Convective Heat Transfer Downstream of Non-Axisymmetric Circular-to-Square Expansions

1999 ◽  
Author(s):  
Anthony W. Guile ◽  
Roy Garwood ◽  
John Ward
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
High Spatial Resolution ◽  
Test Method ◽  
Image Capture ◽  
Inherent Problem ◽  
Transfer Problems

Abstract A liquid crystal technique has been applied to the problem of convective heat transfer downstream of a circular to square abrupt expansion. This configuration is similar to that found with a burner firing into a furnace or boiler. There is little data available in the literature for these expansions as most previous investigations have concentrated on a simple circular to circular geometry. Liquid crystals were selected for the tests because of their ability to provide a full surface temperature map with a high spatial resolution. With the progress of image capture and processing technology a transient test method was preferred as it makes the construction of models very simple by eliminating the need to heat the surface with the inherent problem of uniformity and the difficulty in viewing the surface. The application of liquid crystals produced results which were found to be accurate and repeatable, when compared with results obtained from other investigations in the area. It gave quantitative data, allowing spanwise and axial distributions of heat transfer to be calculated in these geometries. The hue capturing technique thus provides quantitative, accurate and repeatable temperature measurements, and when applied to heat transfer problems is a powerful experimental tool.

The Design of Transient Wall Heating Experiments for the Determination of Convective Heat Transfer Using Liquid Crystal Thermography

2000 ◽  
Author(s):  
David Graham ◽  
Jeff Rhine
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Liquid Crystal Thermography ◽  
Heat Transfer Coefficients ◽  
Wall Heating ◽  
Convective Heat Transfer Coefficients

The use of liquid crystals as surface temperature sensors in transient wall heating experiments, to measure steady-state convective heat transfer coefficients, is becoming increasingly popular. This paper describes a simple graphical method to assist in the design of these experiments. The analysis assumes that the test specimen, perspex in the given example, behaves as a semi-infinite solid. Given an expected range of convective heat transfer coefficients, the experimenter can determine the optimum combination of liquid crystal colour change temperature, bounding wall thickness and experiment duration. It is also possible to determine the sensitivity of experimental uncertainty to the operating conditions and the physical properties of the bounding wall. Emphasis is given to the use of liquid crystal thermography but the methodology could be applied when other temperature measurement devices are employed.

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