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Theoretical and experimental study of a flexible wiretype Joule–Thomson microrefrigerator for use in cryosurgery / Adhika Widyaparaga in Journal of heat transfer, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 2 (Fevrier 2012) . - 07 p. Titre : Theoretical and experimental study of a flexible wiretype Joule–Thomson microrefrigerator for use in cryosurgery Type de document : texte imprimé Auteurs : Adhika Widyaparaga, Auteur ; Masashi Kuwamoto, Auteur ; Naoya Sakoda, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Coolants  Cooling  Equations  of  state  Finite  difference  methods  Flow  simulation  Heat  exchangers  Heat  radiation  Joule-Thomson  effect  Natural  convection  Refrigerators  Stainless  steel  Temperature  distribution  Temperature  measurement  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : We have developed a model capable of predicting the performance characteristics of a wiretype Joule–Thomson microcooler intended for use within a cryosurgical probe. Our objective was to be able to predict cold tip temperature, temperature distribution, and cooling power using only inlet gas properties as input variables. To achieve this, the model incorporated gas equations of state to account for changing gas properties due to heat transfer within the heat exchanger and expansion within the capillary. In consideration of inefficiencies, heat in-leak from free convection and radiation was also considered and the use of a 2D axisymmetric finite difference code allowed simulation of axial conduction. To validate simulation results, we have constructed and conducted experiments with two types of microcoolers differing in inner tube material, poly-ether-ether-ketone (PEEK) and stainless steel. The parameters of the experiment were used in the calculations. CO2 was used as the coolant gas for inlet pressures from 0.5 MPa to 2.0 MPa. Heat load trials of up to 550 mW along with unloaded trials were conducted. The temperature measurements show that the model was successfully able to predict the cold tip temperature to a good degree of accuracy and well represent the temperature distribution. For the all PEEK microcooler in a vacuum using 2.0 MPa inlet pressure, the calculations predicted a temperature drop of 57 K and mass flow rate of 19.5 mg/s compared to measured values of 63 K and 19.4 mg/s, therefore, showing that conventional macroscale correlations can hold well for turbulent microscale flow and heat transfer as long as the validity of the assumptions is verified. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000002 [...] [article] Theoretical and experimental study of a flexible wiretype Joule–Thomson microrefrigerator for use in cryosurgery [texte imprimé] / Adhika Widyaparaga, Auteur ; Masashi Kuwamoto, Auteur ; Naoya Sakoda, Auteur . - 2012 . - 07 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 2 (Fevrier 2012) . - 07 p. Mots-clés : Coolants  Cooling  Equations  of  state  Finite  difference  methods  Flow  simulation  Heat  exchangers  Heat  radiation  Joule-Thomson  effect  Natural  convection  Refrigerators  Stainless  steel  Temperature  distribution  Temperature  measurement  Turbulence Index. décimale : 536 Chaleur. Thermodynamique Résumé : We have developed a model capable of predicting the performance characteristics of a wiretype Joule–Thomson microcooler intended for use within a cryosurgical probe. Our objective was to be able to predict cold tip temperature, temperature distribution, and cooling power using only inlet gas properties as input variables. To achieve this, the model incorporated gas equations of state to account for changing gas properties due to heat transfer within the heat exchanger and expansion within the capillary. In consideration of inefficiencies, heat in-leak from free convection and radiation was also considered and the use of a 2D axisymmetric finite difference code allowed simulation of axial conduction. To validate simulation results, we have constructed and conducted experiments with two types of microcoolers differing in inner tube material, poly-ether-ether-ketone (PEEK) and stainless steel. The parameters of the experiment were used in the calculations. CO2 was used as the coolant gas for inlet pressures from 0.5 MPa to 2.0 MPa. Heat load trials of up to 550 mW along with unloaded trials were conducted. The temperature measurements show that the model was successfully able to predict the cold tip temperature to a good degree of accuracy and well represent the temperature distribution. For the all PEEK microcooler in a vacuum using 2.0 MPa inlet pressure, the calculations predicted a temperature drop of 57 K and mass flow rate of 19.5 mg/s compared to measured values of 63 K and 19.4 mg/s, therefore, showing that conventional macroscale correlations can hold well for turbulent microscale flow and heat transfer as long as the validity of the assumptions is verified. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000002 [...]