A comparison of trichromic systems for use in the calibration of polymer-dispersed thermochromic liquid crystals

Hay, Jennifer L.; Hollingsworth, D. Keith

doi:10.1016/0894-1777(95)00013-5

Cited by 106 publications

(40 citation statements)

References 7 publications

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“…A top-hat smoothing filter subsequently produced smooth colour images of the liquid crystal surface. After filtering the images, temperatures are determined from the hue values of the colours (Hay & Hollingsworth 1996) by using a lookup table.…”

Section: 3mentioning

confidence: 99%

Wall imprint of turbulent structures and heat transfer in multiple impinging jet arrays

Geers¹,

Hanjalić

Tummers

2005

J. Fluid Mech.

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Thermal imprint and heat transfer on the target surface in multiple impinging jet arrays have been investigated in conjunction with flow pattern and large-scale eddy structure. Surface temperature was measured with liquid crystal thermography (LCT) in a range of jet configurations with hexagonal and in-line orifice arrangements for different combinations of distances between the orifices s/D m = 2-6 and between the orifice plate and the impingement surface H/D m = 3-10 (where D m is the orifice diameter). The hexagonal arrangement was considered with two different orifice shapes: sharp-edged and contoured. For selected configurations, the distribution of Nusselt number and its peculiarities were analysed in relation with the underlying eddy structure educed by proper orthogonal decomposition (POD) of the snapshots of fluid velocity measured with particle image velocimetry (PIV). Owing to the breakdown of the jets, heat transfer deteriorates with increasing orifice-to-plate distance. The jet interaction and breakdown become more severe as the jets are placed closer to each other. The large-scale eddies originating from the jet-edge shear layers grow as they are convected towards the impingement plate. Eddies of sizes between 0.2 and 0.3 orifice diameters are shown to break up the jets and cause mixing of fresh and spent fluid, lowering the beneficial temperature gradient. In some configurations, an asymmetric flow pattern is generated with embedded weak eddies on only one side of the diagonal symmetry line, which is reflected in an asymmetrical heat transfer distribution on the impingement plate. For H/D m > 4, the Nusselt number shows peak values in and around the jet impingement centres, but relatively uniform distribution of turbulence kinetic energy with local negative energy production close to the impingement surface.

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Section: 3mentioning

confidence: 99%

Wall imprint of turbulent structures and heat transfer in multiple impinging jet arrays

Geers¹,

Hanjalić

Tummers

2005

J. Fluid Mech.

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“…This transformation provides non-dimensonal HSI values, where H is a simplified approximation of Hay and Hollingsworth (1996) formulation, normalized with 2p, and I is normalized with the maximum pixel count for an individual sensor of the digital camera (255 for each 8-bit sensor). Furthermore, the minimum and maximum hue and saturation values, respectively, detected in temperatures under the red start temperature of the TLC material (25°C) were used as a threshold level under which the negative radian value of H would be used in order to obtain a better fit to a continuous third degree polynomial function.…”

Section: Image Processingmentioning

confidence: 99%

“…For the purposes of this study, a simplified version of Hay and Hollingsworth (1996)'s formulation will be used, employed by the 'rgb2hsv' function of the MATLAB software package where, Fig. 4 a RGB image.…”

Section: Image Processingmentioning

confidence: 99%

Non-encapsulated thermo-liquid crystals for digital particle tracking thermography/velocimetry in microfluidics

Segura

Cierpka

Rossi

et al. 2012

Microfluid Nanofluid

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The ever accelerating state of technology has powered an increasing interest in heat transfer solutions and process engineering innovations in the microfluidics domain. In order to carry out such developments, reliable heat transfer diagnostic techniques are necessary. Thermo-liquid crystal (TLC) thermography, in combination with particle image velocimetry, has been a widely accepted and commonly used technique for the simultaneous measurement and characterization of temperature and velocity fields in macroscopic fluid flows for several decades. However, low seeding density, volume illumination, and low TLC particle image quality at high magnifications present unsurpassed challenges to its application to three-dimensional flows with microscopic dimensions. In this work, a measurement technique to evaluate the color response of individual non-encapsulated TLC particles is presented. A Shirasu porous glass membrane emulsification approach was used to produce the nonencapsulated TLC particles with a narrow size distribution and a multi-variable calibration procedure, making use of all three RGB and HSI color components, as well as the proper orthogonally decomposed RGB components, was used to achieve unprecedented low uncertainty levels in the temperature estimation of individual particles, opening the door to simultaneous temperature and velocity tracking using 3D velocimetry techniques.

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“…The technique for temperature measurement on various surfaces and in fluids has been in use since the 1960s. The liquid crystal technique for the determination of temperature distribution on surfaces in heat transfer investigations is discussed, among others, in [4][5][6][7][8][9][10][11][12][13][14].…”

Section: Applications Of Liquid Crystalsmentioning

confidence: 99%

Determination of the Temperature Field Using Liquid Crystal Thermography and Analysis of Two-Phase Flow Structures in Research on Boiling Heat Transfer in a Minichannel

Piasecka¹

2013

Metrology and Measurement Systems

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The paper presents the application of liquid crystal thermography for temperature determination and visualisation of two phase flow images on the studied surface. Properties and applications of thermochromic liquid crystals are discussed. Liquid crystals were applied for two-dimensional detection of the temperature of the heating foil forming one of the surfaces of the minichannel along which the cooling liquid flowed. The heat flux supplied to the heating surface was altered in the investigation and it was accompanied by a change in the color distribution on the surface. The accuracy of temperature measurements on the surface with liquid crystal thermography is estimated. The method of visualisation of two-phase flow structures is described. The analysis of monochrome images of flow structures was employed to calculate the void fraction for some cross-sections. The flow structure photos were processed using Corel graphics software and binarized. The analysis of phase volumes employed Techsystem Globe software. The measurement error of void fraction is estimated.

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A comparison of trichromic systems for use in the calibration of polymer-dispersed thermochromic liquid crystals

Cited by 106 publications

References 7 publications

Wall imprint of turbulent structures and heat transfer in multiple impinging jet arrays

Wall imprint of turbulent structures and heat transfer in multiple impinging jet arrays

Non-encapsulated thermo-liquid crystals for digital particle tracking thermography/velocimetry in microfluidics

Determination of the Temperature Field Using Liquid Crystal Thermography and Analysis of Two-Phase Flow Structures in Research on Boiling Heat Transfer in a Minichannel

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