Stanovení tepelného odporu metodou nestacionární teplotního měření

Determination of Thermal Contact Conductance Based on Unsteady Temperature Measurement

conference paper

en

Thermal contact conductance (TCC) is a parameter which describes heat flow Thermal contact conductance (TCC) is a parameter which describes heat flow between solid bodies in contact with different temperatures and plays an important role in a numerical simulation of heat transfer in various areas of technology. The TCC has SI units in W/m2 .K. Many empirical and semi-empirical correlations to predict TCC were published. There are three core models: elastic model (Mikic) [1], plastic model (Cooper, Mikic, Yovanovich) [2] and elastoplastic model (Sridhar, Yovanovich) [3]. These models are widely used to simulate thermal contact between bodies, eg. Comsol Multiphysics uses these three methods. But Fieberg [4] shows that these methods are only valid with contact pressure up to 7 MPa and temperature up to 500 °C. Also with recently developed numerical simulations in steelmaking and continuous casting, theoretically derived TCCs are not accurate enough and there is a need for experimentally measured values of TCC. The Heat Transfer and Fluid Flow Laboratory of Brno Technical University conducted experiments to determine TCC between two specimens by a device which allows the experimental determination of the TCC as a function of different contact pressure, temperature, surface morphology etc. The temperature history of bodies during an experiment is measured by thermocouples which are then used to estimate time dependent values of TCC by an inverse heat conduction calculation.

Kontaktní tepelná vodivost (KTV) je parametr, který popisuje tepelný tok mezi dvěma pevnými tělesy v kontaktu s různými teplotami a hraje důležitou roli v numerické simulace přenosu tepla. KTV má SI jednotku v W/m2K. Mnoho empirické a semi-empirické korelace pro určení KTV byly zveřejněny. Existují tři základní modely: elastický model (Mikić) [1], plastový model (Cooper, Mikić, Yovanovich) [2] a elastoplastické model (Sridhar, Yovanovich) [3]. Tyto modely se široce používají k simulaci tepelného kontaktu mezi tělesy, např.: COMSOL Multiphysics používá tyto tři metody. Ale Fieberg [4] ukazuje, že tyto metody jsou platné pouze pro kontaktní tlak do 7 MPa a pro teplotu do 500 °C. V poslední době byly vyvinuty nové modely pro stanovení KTV. Bohužel tyto teoreticky odvozené KTV nejsou dostatečně přesné a je nutné použít experimentálně naměřené hodnoty KTV. Laboratoř přenosu tepla a proudění, VUT v Brně vyvinula zařízení pro experimentální stanovení KTV mezi dvěma vzorky. KTV je stanoveno jako funkce různých kontaktních tlaků, teploty, struktury povrchu atd. Termočlánky zabudované do vzorku jsou použity pro teplotní záznam experimentu. Tyto záznamy jsou pak použity jako vstupní hodnoty pro inverzní výpočet časově závislé hodnoty KTV. Dva vzorky jsou v kontaktu a jejich konce jsou zahřívány. Ochlazením se následně získá konstantní tepelný tok mezi nimi.

Thermal contact conductance (TCC) is a parameter which describes heat flow Thermal contact conductance (TCC) is a parameter which describes heat flow between solid bodies in contact with different temperatures and plays an important role in a numerical simulation of heat transfer in various areas of technology. The TCC has SI units in W/m2 .K. Many empirical and semi-empirical correlations to predict TCC were published. There are three core models: elastic model (Mikic) [1], plastic model (Cooper, Mikic, Yovanovich) [2] and elastoplastic model (Sridhar, Yovanovich) [3]. These models are widely used to simulate thermal contact between bodies, eg. Comsol Multiphysics uses these three methods. But Fieberg [4] shows that these methods are only valid with contact pressure up to 7 MPa and temperature up to 500 °C. Also with recently developed numerical simulations in steelmaking and continuous casting, theoretically derived TCCs are not accurate enough and there is a need for experimentally measured values of TCC. The Heat Transfer and Fluid Flow Laboratory of Brno Technical University conducted experiments to determine TCC between two specimens by a device which allows the experimental determination of the TCC as a function of different contact pressure, temperature, surface morphology etc. The temperature history of bodies during an experiment is measured by thermocouples which are then used to estimate time dependent values of TCC by an inverse heat conduction calculation.

tepelná vodivost, tepelný odpor, koeficient přestupu tepla

thermal contact conductance, thermal contact resistance, heat transfer coefficient

2015

04.05.2015

978-1-935117-46-9

1551-6997

AISTech 2015

3

3519–3525

7