Relevant bibliographies by topics / Thermochromic liquid crystals; Colour calibration

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  1. Journal articles
  2. Dissertations / Theses
  3. Conference papers

Academic literature on the topic 'Thermochromic liquid crystals; Colour calibration'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Thermochromic liquid crystals; Colour calibration"

1

Farina, Dino J., James M. Hacker, Robert J. Moffat, and John K. Eaton. "Illuminant invariant calibration of thermochromic liquid crystals." Experimental Thermal and Fluid Science 9, no. 1 (July 1994): 1–12. http://dx.doi.org/10.1016/0894-1777(94)90002-7.

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Roesgen, T., and R. Totaro. "A statistical calibration technique for thermochromic liquid crystals." Experiments in Fluids 33, no. 5 (November 2002): 732–34. http://dx.doi.org/10.1007/s00348-002-0525-5.

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Solnař, Stanislav, Jan Medek, Abubakar Shola Suleiman, and Patrik Vyhlídal. "On a static and dynamic calibration of thermochromic liquid crystals." Acta Polytechnica 61, no. 4 (August 31, 2021): 562–69. http://dx.doi.org/10.14311/ap.2021.61.0562.

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The paper deals with a static and dynamic calibration of selected wide-range thermochromic liquid crystals (TLC - SolarDust 24C), which are very easy to ingest and can provide accurate information on the temperature distribution on different surfaces. Static calibration problems, such as TLC illumination angle or illumination intensity, are solved and conclusions are drawn for the application of such a measurement. Dynamic experiments also indicate a certain time delay (around 50 ms) of the applied TLC measurement layer, which is very important to know for dynamic experimental methods, but the error and inaccuracy of the experiment is too high to draw conclusions.
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Elkins, Christopher J., John Fessler, and John K. Eaton. "A Novel Mini Calibrator for Thermochromic Liquid Crystals." Journal of Heat Transfer 123, no. 3 (November 21, 2000): 604–7. http://dx.doi.org/10.1115/1.1370505.

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A small calibrator has been constructed to facilitate wide-band liquid crystal temperature measurements on complex, curved surfaces. The calibrator’s size, 21.3 mm by 20.3 mm by 10.0 mm thick, makes it ideal for in-situ calibrations at multiple sites on curved surfaces. Its design utilizes the heating/cooling ability of a thermoelectric cooler, and its temperature is quickly and accurately controlled by computer. To test the calibrator’s accuracy, a liquid crystal sample was calibrated. Subsequent comparisons to thermistor measurements of a uniform temperature copper block painted with liquid crystals showed the calibration to be accurate to +/−0.1°C between the red start and the approximate blue start temperatures, and the maximum error was less than +/−0.3°C in the dark blue/violet region.
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Bharara, M., J. E. Cobb, A. M. Anderson, and D. J. Claremont. "Characterisation and calibration of three physical forms of thermochromic liquid crystals." Imaging Science Journal 55, no. 4 (December 2007): 232–41. http://dx.doi.org/10.1179/174313107x189230.

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Guo, S. M., C. C. Lai, T. V. Jones, M. L. G. Oldfield, G. D. Lock, and A. J. Rawlinson. "Influence of Surface Roughness on Heat Transfer and Effectiveness for a Fully Film Cooled Nozzle Guide Vane Measured by Wide Band Liquid Crystals and Direct Heat Flux Gages." Journal of Turbomachinery 122, no. 4 (February 1, 2000): 709–16. http://dx.doi.org/10.1115/1.1312798.

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The influence of surface roughness on heat transfer coefficient and cooling effectiveness for a fully film cooled three-dimensional nozzle guide vane (NGV) has been measured in a transonic annular cascade using wide band liquid crystal and direct heat flux gages (DHFGs). The liquid crystal methods were used for rough surface measurements and the DHFGs were used for the smooth surfaces. The measurements have been made at engine representative Mach and Reynolds numbers and inlet free-stream turbulence intensity. The aerodynamic and thermodynamic characteristics of the coolant flow have been modeled to represent engine conditions by using a heavy “foreign gas” (30.2 percent SF6 and 69.8 percent Ar by weight). Two cooling geometries (cylindrical and fan-shaped holes) have been tested. The strategies of obtaining accurate heat transfer data using a variety of transient heat transfer measurement techniques under the extreme conditions of transonic flow and high heat transfer coefficient are presented. The surfaces of interest are coated with wide-band thermochromic liquid crystals, which cover the range of NGV surface temperature variation encountered in the test. The liquid crystal has a natural peak-to-peak roughness height of 25 μm creating a transitionally rough surface on the NGV. The time variation of color is processed to give distributions of both heat transfer coefficient and film cooling effectiveness over the NGV surface. The NGV was first instrumented with the DHFGs and smooth surface tests preformed. Subsequently the surface was coated with liquid crystals for the rough surface tests. The DHFGs were then employed as the means of calibrating the liquid crystal layer. The roughness of 25 μm, which is the typical order of roughness for the in-service turbine blades and vanes, increases the heat transfer coefficient by up to 50 percent over the smooth surface level. The film cooling effectiveness is influenced less by the roughness. [S0889-504X(00)00804-7]
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Sun, J. H., K. C. Leong, and C. Y. Liu. "Influence of hue origin on the hue-temperature calibration of thermochromic liquid crystals." Heat and Mass Transfer 33, no. 1-2 (September 19, 1997): 121–27. http://dx.doi.org/10.1007/s002310050168.

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Anderson, M. R., and J. W. Baughn. "Thermochromic Liquid Crystal Thermography: Illumination Spectral Effects. Part 2: Theory." Journal of Heat Transfer 127, no. 6 (January 12, 2005): 588–97. http://dx.doi.org/10.1115/1.1915388.

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A theoretical model of a Thermochromic Liquid Crystal (TLC) imaging system was developed to aid in understanding the results of experiments on spectral effects and to investigate the various factors affecting the hue-temperature calibration of TLC’s. The factors in the model include the spectral distribution of the illumination source and UV filter, surface reflection of both the TLC and background, and the sensing device (camera) spectral characteristics and gain settings. It was found that typical hue-temperature calibration curves could not be entirely explained by a TLC reflectivity model with either a monochromatic spike or a narrow bandwidth reflectivity, which is often assumed. Experimental results could be explained, however, by a model that reflects over a relatively large band of wavelengths. The spectral characteristics of the five illumination sources (those for which experiments were performed) were considered. Background reflection, which commonly accounts for 30%–50% of the reflected light, was found to significantly attenuate the hue-temperature calibration curves toward the background hue value. The effect of the illumination source on the hue-temperature calibration curves is demonstrated and several experimentally observed phenomena are explained by the results of the theoretical calculations, specifically the spectral reflective properties of the liquid crystals and the transmissivity of the R, G, and B filters in the image capture camera.
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Christie, Robert M., and I. David Bryant. "An evaluation of thermochromic prints based on microencapsulated liquid crystals using variable temperature colour measurement." Coloration Technology 121, no. 4 (July 2005): 187–92. http://dx.doi.org/10.1111/j.1478-4408.2005.tb00271.x.

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Stasiek, Jan. "Thermochromic liquid crystals and true colour image processing in heat transfer and fluid-flow research." Heat and Mass Transfer 33, no. 1-2 (September 19, 1997): 27–39. http://dx.doi.org/10.1007/s002310050158.

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Dissertations / Theses on the topic "Thermochromic liquid crystals; Colour calibration"

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Chan, Tat Leung. "Application of liquid crystal thermography in heat transfer characteristics of slot jet impingement." Thesis, Nottingham Trent University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267018.

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Conference papers on the topic "Thermochromic liquid crystals; Colour calibration"

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Chan, T. L., K. Jambunathan, T. P. Leung, and Shirley A. Ashforth-Frost. "A SURFACE TEMPERATURE CALIBRATION METHOD FOR THERMOCHROMIC LIQUID CRYSTALS USING TRUE-COLOUR IMAGE PROCESSING." In International Heat Transfer Conference 10. Connecticut: Begellhouse, 1994. http://dx.doi.org/10.1615/ihtc10.3000.

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Douglass, C. J., J. S. Kapat, E. Divo, A. J. Kassab, J. Tapley, and M. Durham. "Steady Thermochromic Liquid Crystal Technique for Study of Conjugate Heat Transfer Problems." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38587.

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This paper presents a steady measurement technique based on thermochromic liquid crystals (TLC) that can be used for study of conjugate heat transfer. In contrast to the more commonly used transient thermochromic liquid crystal technique, this technique requires steady-state experiments, and eliminates some of the limitations of the transient version at the cost of measurements or knowledge of thermal conditions all surfaces and increased computations for data reduction. This technique requires that thermal boundary conditions be known or measured on all internal or external surfaces of the test block. All surfaces that are exposed to external air flow are coated with a broad-bandwidth TLC. The thermal boundary conditions are then sent to a steady conduction solver that involves the boundary element method (BEM) and an inverse problem approach (BEM/IP). This combined BEM/IP approach minimizes the effects of random experimental error in measured data and calculates surface heat flux, from which the intended convective heat flux coefficients can then be calculated. The technique is applied to a prismatic stainless steel block exposed to warm air flows on three sides — an arrangement that has been used often to simulate flow through a blade tip gap. It is found that an in-situ pixel-by-pixel calibration of TLC hue vs temperature is needed in order to obtain reasonable accuracy. A calibration-curve-fit uncertainty of better than 0.4°C (at 95% confidence level) was obtained in this process. In the actual experiments, conjugate heat transfer was set up by passing cold water through three cooling channels that span the test block. Once the experiments are completed and the TLC colors are converted to surface temperature distributions, the BEM/IP approach is used to obtain surface heat flux distributions, and then distribution of heat transfer coefficients.
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Fung, Tracy Helen, Shih-Hui Chao, Joseph E. Peach, and Deirdre R. Meldrum. "Liquid Crystal Thermography of an On-Chip Polymerase Chain Reaction Micro-Thermocycler." In ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2006. http://dx.doi.org/10.1115/icnmm2006-96175.

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Microscale liquid crystal thermography is a technique to measure temperature distribution of microfabricated devices in real-time. This method utilizes a microscope to image the color map of a layer of temperature-sensitive encapsulated thermochromic liquid crystals (TLC) coated on a microfabricated device. This paper describes the TLC coating process on microscale devices, the characteristics of colorimetric hysteresis, and the calibration of temperature measurements. The calibrated measurements have been applied for characterization of an on-chip polymerase chain reaction (PCR) microscale thermocycler where precise and dynamic temperature control is essential for efficient DNA amplification. Tests on the micro-thermocycler were done around the ranges centered at 30 °C and 95 °C. The results illustrate the effects on the temperature distribution due to micro-thermocycler geometry, and provide important insight for micro-thermocycler design.
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Guo, S. M., C. C. Lai, T. V. Jones, M. L. G. Oldfield, G. D. Lock, and A. J. Rawlinson. "Influence of Surface Roughness on Heat Transfer and Effectiveness for a Fully Film Cooled Nozzle Guide Vane Measured by Wide Band Liquid Crystals and Direct Heat Flux Gauges." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0204.

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The influence of surface roughness on heat transfer coefficient and cooling effectiveness for a fully film cooled 3D nozzle guide vane (NGV) has been measured in a transonic annular cascade using wide band liquid crystal and direct heat flux gauges (DHFGs). The liquid crystal methods were used for rough surface measurements and the DHFGs were used for the smooth surfaces. The measurements have been made at engine representative Mach and Reynolds numbers and inlet freestream turbulence intensity. The aerodynamic and thermodynamic characteristics of the coolant flow have been modelled to represent engine conditions by using a heavy “foreign gas” (30.2% SF6 and 69.8% Ar by weight). Two cooling geometries (cylindrical and fan-shaped holes) have been tested. The strategies of obtaining accurate heat transfer data using a variety of transient heat transfer measurement techniques under the extreme conditions of transonic flow and high heat transfer coefficient are presented. The surfaces of interest are coated with wide-band thermochromic liquid crystals which cover the range of NGV surface temperature variation encountered in the test. The liquid crystal has a natural peak-to-peak roughness height of 25 μm creating a transitionally rough surface on the NGV. The time variation of colour is processed to give distributions of both heat transfer coefficient and film cooling effectiveness over the NGV surface. The NGV was first instrumented with the DHFGs and smooth surface tests preformed. Subsequently the surface was coated with liquid crystals for the rough surface tests. The DHFGs were then employed as the means of calibrating the liquid crystal layer. The roughness of 25 μm, which is the typical order of roughness for the in service turbine blades and vanes, increases the heat transfer coefficient by up to 50% over the smooth surface level. The film cooling effectiveness is influenced less by the roughness.
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Salameh, Tareq, and Bengt Sunden. "Effects of Ribs on Internal Blade-Tip Cooling." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45118.

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This work concerns an experimental study of pressure drop and heat transfer for turbulent flow inside a U-duct with relevance for tip cooling of gas turbine blades. The U-duct models the internal blade cooling flow passages. Both friction factors and convective heat transfer coefficients were measured along the bend (turn) part of the U-duct for three different rib configuration cases, namely (a) single rib at three different rib positions, i.e., inlet, middle and outlet, (b) two ribs with three different configurations, i.e., at the inlet and middle, at the middle and outlet as well as at the inlet and outlet, and (c) three ribs. The rib height-to-hydraulic diameter ratio, e/Dh, was 0.1 and the pitch ratios were 10 and 20. The Reynolds number was varied from 8,000 to 20,000. The test rig has been built in such a way that various experimental setups can be handled as the bend (turn) part of the U-duct can easily be removed and the rib configurations can be changed. The surface temperature was measured by using a high-resolution measurement technique based on narrow band thermochromic liquid crystals (TLC R35C5W) and a CCD camera placed facing the bend (turn) part of the U-duct. The calibration of the TLC is based on the hue-based color decomposition system using an in-house designed calibration box. Both the friction factor and heat transfer coefficient were affected by the position and configuration of the ribs along the bend wall. The highest friction factor was found for two ribs placed at the middle and outlet positions of the bend wall, respectively. The highest heat transfer coefficient was found for two ribs placed at the inlet and middle positions of the bend wall, respectively. The uncertainties in the experiments were estimated to be 3% and 6% for the Nusselt number and friction factor, respectively.
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Salameh, Tareq, and Bengt Sunden. "Comparison of Continuous and Truncated Ribs on Internal Blade Tip Cooling." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68028.

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In the present work, an experimental study related to turbulent flow inside the bend part of a U-duct geometry was performed concerning pressure drop and heat transfer. Such duct geometries can be found inside gas turbine blades, where the cooling air extracts heat from hot internal walls while it is flowing inside the cooling passage. Both friction factors and convective heat transfer coefficients were established inside the bend part of the U-duct for two different rib cases, namely continuous and truncated ribs with varying Reynolds number from 8,000 to 20,000. For the continuous rib case, the length of the ribs was equal to the height of the duct while in the truncated rib case two different rib lengths, i.e., 46 mm and 40 mm, respectively, were considered. The rib height-to-hydraulic diameter ratio, e/Dh, was 0.1 and the pitch ratio was 10. The test rig has been built in such a way that various experimental setups can be handled as the outer wall of the bend (turn) part of the U-duct can easily be removed and the ribs can be changed. Both the U-duct and the ribs were made from acrylic material to allow optical access for measuring the surface temperature by using a high-resolution measurement technique based on the narrow band thermochromic liquid crystals (TLC R35C5W) and a CCD camera placed facing the bend (turn) part of the U-duct. The calibration of the TLC is based on the hue-based color decomposition system using an in-house designed calibration box. The ribs were placed transversely to the direction of the main flow at the outer wall of the bend (turn) part where the wall was heated by an electrical heater. The pressure drop was almost identical for the continuous and truncated rib cases, while the heat transfer coefficient is 10% higher for the continuous rib case at Re = 20000. The uncertainties in the evaluated properties were 3% and 6% for the Nusselt number and friction factor, respectively.
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Salameh, Tareq, and Bengt Sunden. "An Experimental Study of Heat Transfer and Pressure Drop on the Bend Surface of a U-Duct." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22139.

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This work concerns an experimental study of pressure drop and heat transfer for turbulent flow inside a U-duct. Such duct geometries can be found in many engineering applications where cooling air extracts heat from hot internal walls of the duct, e.g., passage cooling inside gas turbine blades. Both friction factors and convective heat transfer coefficients were measured inside a U-duct for three different cases, namely (a) the smooth straight part, (b) the smooth bend (turn) part, and (c) a rough (ribbed) bend (turn) part. The details of the duct geometry were as follows: the cross section area of the straight part was 50×50 mm2, the inside length of the bend part 240 mm, the cross section area of the rib was 5×5 mm2 and the rib height-to-hydraulic diameter ratio, e/Dh, was 0.1. The Reynolds number was varied from 8,000 to 20,000. The test rig has been built in such a way that various experimental setups can be handled as the bend (turn) part of the U-duct can easily be removed and the rib configuration can be changed. Both the U-duct and the rib were made from plexiglass material to allow optical access for measuring the surface temperature by using a high-resolution measurement technique based on narrow band thermochromic liquid crystals (TLC R35C5W) and a CCD camera placed facing the bend (turn) part of the U-duct. The calibration of the TLC is based on the hue-based color decomposition system using an in-house designed calibration box. The rib was placed transversely to the direction of the main flow at the outer wall of the bend (turn) part where the wall was heated by an electrical heater. The friction factor ratio and the heat transfer enhancement ratio for case (c) at a Reynolds number of 20,000 were 48.75 and 2.66, respectively. It is found that the presence of the rib increases the heat transfer coefficient on the outer wall of the bend part (tip of side U-duct). The uncertainties were 3% and 6% for the Nusselt number and friction factor, respectively.
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Ferguson, James R. "Simultaneous Thermochromic Liquid Crystal Calibration and Calculation of Heat Transfer Coefficients." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28124.

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The use of thermochromic liquid crystals (TLCs) to indicate surface temperature in transient experiments designed to measure heat transfer coefficients requires careful calibration of the crystals. The calibration can be affected by lighting and viewing angles, light source spectral characteristics, surface preparation, and application procedure of the TLCs. A method is proposed whereby the calibration of the TLCs and calculation of heat transfer coefficients are conducted simultaneously using inverse techniques for the case of a suddenly heated semi-infinite wall. The calibration inherently accounts for the problems typically associated with the use of liquid crystals and results from simulated experiments indicate accuracy to within five percent is possible.
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Brauckmann, Dennis, and Jens von Wolfersdorf. "Infrared Thermography With In-Situ Calibration Using Thermochromic Liquid Crystals Applied to Film Cooling." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53855.

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This paper presents an application of infrared thermography measurements on a film cooled flat surface using a single cylindrical film cooling hole. Infrared thermography (IR) is used to obtain the full field surface distribution of the temperature and therefore the film cooling effectiveness. For accurate results in-situ calibration of the infrared radiation intensity during the experiment needs to be performed, which is usually done using surface mounted thermocouples. For the near hole region thermochromic liquid crystals (TLC) are applied to obtain additional information for the calibration. A mixture of two narrow band TLCs is used, leading to discrete temperature lines on the surface. Using small variations in the test temperature settings, the TLC-lines can be located on the test surface into the regions of interest and the influence on the obtained infrared calibration results can be investigated. Experimental results for the film cooling effectiveness are presented for several blowing rates.
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Me´nard, Vale´rie, Adel Stitou, Ste´phane Le Masson, David No¨rtersha¨user, and Pierre Millan. "Velocity and Temperature Fields Measurement of Natural Convection Flow Using Thermochromic Liquid Crystals." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72153.

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Based on a particular property of some liquid crystal to reflect a specific wavelength for a specific temperature, Particle Image Velocimetry and Thermometry (PIVT) is a method allowing to measure simultaneously velocity and temperature fields. In a first part, this study discusses PIVT calibration methods and especially the effect of liquid crystal particle deposition on hue and intensity response. An experimental set-up is designed and the results confirm the high variations of intensity response with time and the need to use a simple relationship between hue and temperature. In a second place, these results are used to apply PIVT to an unsteady natural convection flow in a cavity containing an internal heat source.
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