Measuring the temperature of fluid in a micro-channel using thermochromic liquid crystals

Basson, Meir; Pottebaum, Tait

doi:10.1007/s00348-012-1326-0

Cited by 20 publications

(16 citation statements)

References 24 publications

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“…Furthermore, this is the first method capable of tracking the temperature of individual flow tracers with these levels of uncertainty. The only other reports of temperature measurements in individual tracers were written by Park et al (2001) and Basson and Pottebaum (2012) where they reported uncertainty values more than twice as high as those obtained in this study, though the confidence interval is unknown for Park et al (2001) results. Park et al (2001) used a sophisticated neural network calibration approach in highly seeded flow where particle tracking is rather challenging while Basson and Pottebaum (2012) experimented with an innovative circularly polarized illumination system, to reduce background noise.…”

Section: Resultsmentioning

confidence: 49%

“…This reduction in uncertainty, however, comes at the expense of a lower spatial resolution due to the averaging over interrogation windows. Basson and Pottebaum (2012), recently reported temperature measurements in a microchannel using individual encapsulated TLC particles. They demonstrate interesting advantages provided by an innovative circularly polarized illumination system on micro-encapsulated TLCs also manufactured by Hallcrest (NSL33R35C5 W), yielding average uncertainties of 1.2 K over a temperature range of 36.3 and 43.7°C (16 %).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 99%

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

Segura

Cierpka

Rossi

et al. 2012

Microfluid Nanofluid

View full text Add to dashboard Cite

show abstract

“…For this purpose, many different measurement techniques with each having its own specific advantages and disadvantages have proven to be successful, enabling the choice of an appropriate measurement technique based on the application. Among those techniques for simultaneous measurements of the velocity and temperature field, the use of TLCs is distinguished by offering the possibility to measure temperatures in macroscopic (Fujisawa et al 2004;Moller et al 2019) and microscopic (Basson and Pottebaum 2012;Segura et al 2013) applications over a relatively small temperature range very precisely. Therefore, TLCs are predestinated for applications, which require only a small temperature measuring range.…”

Section: Introductionmentioning

confidence: 99%

On the application of neural networks for temperature field measurements using thermochromic liquid crystals

2020

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This study presents an investigation regarding the applicability of neural networks for temperature measurements using thermochromic liquid crystals (TLCs) and discusses advantages as well as disadvantages of common calibration approaches. For the characterization of the measurement technique, the dependency of the color of the TLCs on the temperature as well as on the observation angle and, therefore, on the position within the field of view of a color camera is analyzed in detail. In order to consider the influence of the position within the field of view on the color, neural networks are applied for the calibration of the temperature measurements. In particular, the focus of this study is on analysis of the error of temperature measurement for different network configurations as well as training methods, yielding a mean absolute deviation and a mean standard deviation in the range of 0.1 K for instantaneous measurements. On the basis of a comparison of this standard deviation to that of two further calibration approaches, it is shown that neural networks are suited for temperature measurements via the color of TLCs. Finally, the applicability of this measurement technique is illustrated at an exemplary temperature measurement in a horizontal plane of a Rayleigh-Bénard cell with large aspect ratio, which clearly shows the emergence of convective flow patterns by means of the temperature field.

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“…Thermochromic colorants present different colours with changes in ambient temperature, showing various functions such as sensing, indicating and monitoring. This property has received increasing interest in recent years and is widely applied in smart coating materials , textiles , conductive elastomers , energy‐saving materials and temperature‐indicating materials . The applications of thermochromic colorants can endow substrates with functions such as temperature sensing and colour‐change warnings.…”

Section: Introductionmentioning

confidence: 99%

A sultone‐based reversible dark red‐yellow conversion thermochromic colorant with adjustable switching temperature

Wan

Zeng

et al. 2018

Coloration Technology

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A reversible, adjustable thermochromic colorant with bichromatic conversion from dark red (cool state) to yellow (heat state) was prepared using bromocresol purple (BCP) as colour former. The thermochromic behaviour of this colorant was investigated during the heating‐cooling cycle, including the colour depth, colour difference and switching temperature. The mechanism of thermochromic colorant switching between dark red and yellow originated from the transformation of the conjugated structures of BCP, which was confirmed by infrared spectrometry. The switching temperature can be flexibility adjusted between 13–46 °C by mixing solvents according to Schröder's equation, which was demonstrated by differential scanning calorimetry measurement. The thermochromic colorant presented good reversible thermochromic performance with stable changes in colour parameters for 50 heating‐cooling cycles. This sultone‐based reversible dark red‐yellow conversion thermochromic colorant is suitable for application as thermal‐indicating material under various conditions.

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Measuring the temperature of fluid in a micro-channel using thermochromic liquid crystals

Cited by 20 publications

References 24 publications

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

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

On the application of neural networks for temperature field measurements using thermochromic liquid crystals

A sultone‐based reversible dark red‐yellow conversion thermochromic colorant with adjustable switching temperature

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