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A phase-sensitive technique for measurements of liquid thermal conductivity / Zhefu Wang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051601-1/8] Titre : A phase-sensitive technique for measurements of liquid thermal conductivity Type de document : texte imprimé Auteurs : Zhefu Wang, Auteur ; Richard B. Peterson, Auteur Article en page(s) : pp. [051601-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  conduction  Measurement  techniques  Thermal  properties  Phase  detection  nanofluids Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental technique based on the thermal wave approach for measuring the thermal conductivity of liquids is developed in this paper. A stainless steel strip functions as both a heating element and a sealing cover for a chamber containing a test liquid. A periodic current passing through this metal strip generates a periodic Joule heating source. An infrared detector measures the temperature response at the front surface of the stainless steel strip. The phase and magnitude of the temperature response with respect to the heating signal were measured by a lock-in amplifier at various frequencies from 22 Hz to 502 Hz. A one-dimensional, two-layered transient heat conduction model was developed to predict the temperature response on the front surface of the stainless steel strip. The phase information from this temperature response shows high sensitivity to the change in thermal properties of the liquid layer and is employed to match experimental data to find the thermal properties of the test liquid. The measured thermal conductivities of water and ethylene glycol agree quite well with the data from literature and support the validity of this measurement technique. An aqueous fluid consisting of gold nanoparticles is tested and anomalous thermal conductivity enhancement is observed. A discrepancy in the thermal transport behavior between pure liquids and nanofluids is suggested from our experimental results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] A phase-sensitive technique for measurements of liquid thermal conductivity [texte imprimé] / Zhefu Wang, Auteur ; Richard B. Peterson, Auteur . - pp. [051601-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [051601-1/8] Mots-clés : Heat  conduction  Measurement  techniques  Thermal  properties  Phase  detection  nanofluids Index. décimale : 536 Chaleur. Thermodynamique Résumé : An experimental technique based on the thermal wave approach for measuring the thermal conductivity of liquids is developed in this paper. A stainless steel strip functions as both a heating element and a sealing cover for a chamber containing a test liquid. A periodic current passing through this metal strip generates a periodic Joule heating source. An infrared detector measures the temperature response at the front surface of the stainless steel strip. The phase and magnitude of the temperature response with respect to the heating signal were measured by a lock-in amplifier at various frequencies from 22 Hz to 502 Hz. A one-dimensional, two-layered transient heat conduction model was developed to predict the temperature response on the front surface of the stainless steel strip. The phase information from this temperature response shows high sensitivity to the change in thermal properties of the liquid layer and is employed to match experimental data to find the thermal properties of the test liquid. The measured thermal conductivities of water and ethylene glycol agree quite well with the data from literature and support the validity of this measurement technique. An aqueous fluid consisting of gold nanoparticles is tested and anomalous thermal conductivity enhancement is observed. A discrepancy in the thermal transport behavior between pure liquids and nanofluids is suggested from our experimental results. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Thermal wave applications in flow fields with steady velocity profile / Zhefu Wang in Journal of heat transfer, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054501-1/4] Titre : Thermal wave applications in flow fields with steady velocity profile Type de document : texte imprimé Auteurs : Zhefu Wang, Auteur ; Richard B. Peterson, Auteur Article en page(s) : pp. [054501-1/4] Note générale : Physique Langues : Anglais (eng) Mots-clés : Convection  Periodic  boundary  conditions  Complex  combination  Phase  shift Index. décimale : 536 Chaleur. Thermodynamique Résumé : This study explores the use of a thermal wave approach for flow field measurement applications, such as flow diagnostics near surfaces and in microfluidic systems. The basic mathematical characteristics of the governing equations of heat convection, with periodic heating boundary conditions in steady flow, are discussed and the validity of applying the complex combination method to this problem is illustrated. A scaling analysis of a two-dimensional thermal wave configuration with a linear velocity profile is performed to provide important insights into this type of heat transfer phenomena. A two-dimensional conjugate heat transfer model is developed and solved numerically with a finite difference method to demonstrate an example of imposing a thermal wave onto a flow field. The simulation results show that the temperature signal, especially the phase information, can be used for the measurement of flow properties near the surface, such as the wall shear stress. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Thermal wave applications in flow fields with steady velocity profile [texte imprimé] / Zhefu Wang, Auteur ; Richard B. Peterson, Auteur . - pp. [054501-1/4]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 5 (Mai 2010) . - pp. [054501-1/4] Mots-clés : Convection  Periodic  boundary  conditions  Complex  combination  Phase  shift Index. décimale : 536 Chaleur. Thermodynamique Résumé : This study explores the use of a thermal wave approach for flow field measurement applications, such as flow diagnostics near surfaces and in microfluidic systems. The basic mathematical characteristics of the governing equations of heat convection, with periodic heating boundary conditions in steady flow, are discussed and the validity of applying the complex combination method to this problem is illustrated. A scaling analysis of a two-dimensional thermal wave configuration with a linear velocity profile is performed to provide important insights into this type of heat transfer phenomena. A two-dimensional conjugate heat transfer model is developed and solved numerically with a finite difference method to demonstrate an example of imposing a thermal wave onto a flow field. The simulation results show that the temperature signal, especially the phase information, can be used for the measurement of flow properties near the surface, such as the wall shear stress. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]