| The application of cryogenic technology is very extensive,from people's daily life to industrial and agricultural production process,from medical technology to scientific research,are inseparable from cryogenic technology.Low temperature measurement is an important guarantee for cryogenic research,In the process of cryogenic measurement,a variety of leakage heat such as solid conduction heat,radiation heat transfer and residual gas thermal conductivity is always present,the existence of these heat load will lead to temperature difference which between the temperature sensor and the measured medium,the temperature parameter is not accurate so that it can not be used to correctly determine the actual state of cryogenic fluid and system performance,etc.So analyzing the temperature measurement efficiency factors and acquiring accurate temperature parameters have great significance.The heat transfer model of the platinum resistance temperature sensor in the cryogenic fluid pipeline transportation system was studied,the effects of different factors on temperature measurement were analyzed.The research contents of this paper are as follows:(1)The mathematic model of the heat transfer process when wall-mounted platinum resistance temperature sensor and the armored coaxial platinum resistance temperature sensor is used in the foam insulated pipe and the vacuum insulated pipe is established,and the thermal resistance network is analyzed.The temperature error between the measured temperature and the true temperature of the fluid under different thermal resistance is analyzed quantitatively.The results show that the temperature measured by the adherent and plug-in platinum resistance sensors is different from the fluid temperature,and different thermal resistance items will lead to different temperature trends and temperature difference,the temperature error changes in the order of 10-1K to 101K range.(2)The mathematical model of unsteady heat transfer is established for two kinds of temperature measurement models in this paper.The influence of different thermal environment and temperature sensor structure on unsteady temperature measurement is analyzed quantitatively.The results show that:Leakage and the structure of the sensor cause the response time of the sensor to extend for several tens to several hundred seconds.(3)The horizontal cryogenic fluid transportation pipeline is taken as the research object,the experimental and theoretical comparison were carried out,and the pipeline is the pre-cooling condition of the liquid nitrogen liquid.The temperature change curve which measured by PT100 and the simulation calculation are comparative analyzed,The results show that when the mass flux is 410.5Kg/h,The temperature of the T1 curve's demarcation point is about-112 ?.Before this point,the fluid flows is in a single-phase gaseous or gas-liquid two-phase state,and then become the single-phase liquid;the temperature of T2 curve's demarcation point is about-139 ? the end of the pipeline at the top and bottom of the temperature are-160.49 ?,-194.64 ?,the end of the pipeline reach the gas-liquid stratified flow state.When the liquid nitrogen is filled with 615.8Kg/h flow,the temperature of the T1 curve's demarcation point is about-129 ?,and the steady temperature at the top and bottom ends are-190.05 ? and-195.45 ?.Respectively,the fluid is present essentially in the liquid phase.(4)The factors that affect the accuracy of static and dynamic temperature measurement during cryogenic fluid transport are analyzed,there is a reference significance that the measures which to eliminate or reduce the measurement error are put forward for different influencing factors. |
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