Study On The Influence Of Over-temperature On The Viscosity Of Liquid Phase Heat Transfer Fluids

Liquid phase heat transfer fluids will lead to its cracking and polymerization reaction in over-temperature,resulting in low-boilers and high-boilers,This phenomenon will cause the viscosity of heat transfer fluids to increase,worsen the heat transfer in the furnace tube,and cause coking of the tube wall on the furnace tube wall,even cause overheating of the pipe wall and bursts the pipe,which seriously affects the safety and reliable operation of the heat transfer fluids furnace.Therefore,the research on the effect of over-temperature on the viscosity of heat transfer fluids and its regularity has a high engineering practical value.Kinematic viscosity is one of the important physical parameters for judging the quality of heat transfer fluids and its detection technology is one of the key technologies that affect the safety of heat transfer fluids furnace.Based on the research of the influence of over-temperature on the viscosity of liquid phase heat transfer fluids,the relevant theoretical analysis and experimental study have been carried out in this study.Firstly,the development of liquid phase heat transfer fluids,main technical parameters and viscosity characteristics are briefly introduced.Heat transfer fluids is a new type of organic heat carriers accompanied by the increasing demand of industry in recent years.According to the boiling range,it can be classified into gas phase heat transfer fluids and liquid phase heat transfer fluids;Viscosity is one of the important parameters for liquid heat transfer fluids,and temperature is one of the important factors affecting the viscosity.Then,the concept of over-temperature is defined,that is,exceeds the maximum allowable operating temperature of the heat transfer fluids;the hazard brought by over-temperature is analyzed with actual cases,and the methods of slowing down the flow rate,avoiding mixing,and operating specifications to mitigate the change in the viscosity of over-temperature heat transfer fluids were discussed.Finally,a over-temperature liquid phase heat transfer fluids viscosity measurement platform was built with high-temperature viscometer and high-temperature density instrument as the main instruments.The upper limit of the measurement temperature was 350?,which breaks through the limit of the maximum allowable operating temperature for viscosity measurement in recent years;At the same time,five liquid phase heat transfer fluids with good thermal stability,strong oxidation resistance and different functionalities was used as experimental sample.The variation of viscosity with temperature was measured between these samples and their mixtures at high temperatures(250 °C to the maximum allowable operating temperature)and over-temperature(the maximum allowable operating temperature to 350 °C).The experimental results show that the change of viscosity with temperature will change significantly,and the viscosity of the high-temperature liquid phase heat transfer fluids decreases with the increase of temperature,showing a logarithmic declining trend;and the viscosity of the over-temperature liquid phase heat transfer fluids decreases first and then increases with the increase of temperature..Combined with the existing viscosity-temperature empirical formula,the experimental data of the single liquid phase heat transfer fluid over-temperature viscosity analyzed by the least-squares method to perform regression analysis.The results show that the calculated values obtained by the formula are closest to the measured results,and the average error is less than 4 % with high accuracy.It can be used to predict the viscosity of an over-temperature liquid phase heat transfer fluid.Mixing fluids have different mixing ratios,and their viscosity changes are also different.The variation trend of the viscosity of different types of mixed liquids is same as before mixing and the temperature nodes is related to the performance and proportion of the mixed liquid.In this paper,the kinematic viscosity as the object of study,using a combination of theoretical and experimental methods to study the effect of over-temperature on the viscosity of liquid phase heat transfer fluids.The results can be used to predict the viscosity of liquid phase heat transfer fluids and its mixture at over-temperature.It has certain practical significance.