摘要
流体工质的热、质扩散系数是表征其传热和传质的重要迁移性质,往往需要采用不同设备测量获得。为探索可同时测量热、质扩散系数的动态光散射方法,研究了采样时间、入射角、黏度、折射率偏差及路易斯数Le等因素对测量可靠性及精度的影响。利用二元混合流体正己烷/正癸烷、正己烷/正十六烷体系进行验证,结果表明:当采样时间为弛豫时间的1.5~3倍且入射角度为8°~12°时,具有较低黏度、较高折射率偏差(>4%)的体系且Le值为10~80时,可以同时可靠地获取流体热、质扩散系数,且测量不确定度低于5%;与已有方法对比,热、质扩散系数的偏差分别为4.00%和3.56%,证明了该测量方法和系统的可靠性。
The thermal and mutual diffusion coefficients of fluid working fluids are important transfer properties that characterize their heat and mass transfer in the field of refrigeration,petroleum,chemical and others.Reliable thermal and mutual diffusion coefficient data are normally necessary for design and optimization of the equipment and process.The thermal and mutual diffusion coefficients can be determined with different equipment.The dynamic light scattering method owns the advantages of measuring properties under equilibrium condition and in the non-contact and absolute way.However,it is still not an easy way to obtain the two properties simultaneously and reliably by the dynamic light scattering method.Therefore,the present study tries to understand the influence of sampling time,incident angle,viscosity,refractive index deviation and Lewis number Le in dynamic light scattering method on the reliability and accuracy of the method.In consideration of the difference of viscosity and refractive index,three binary systems of n-Hexane/n-Decane,n-Hexane/n-Hexadecane and n-Hexane/n-Decane at the defined molar fractions(0.50/0.50,0.06/0.94 and 0.85/0.15,respectively)are selected as reference fluids.The first and third systems have similar viscosity,but different refractive index difference of the components;the second and third systems have similar refractive index difference,but different viscosity.The measurement is performed in the saturated condition at different sampling times,incident angles and in a wide temperature range.Correlations are established based on the experimental data for both properties.The results show that the thermal diffusion coefficient and Le number decrease as the temperature increases,while the mutual diffusion coefficient increases as the temperature increases.The relaxation times of temperature fluctuations and concentration fluctuations of the binary system of n-Hexane and n-Decane with equal molar fractions satisfy a proportional relationship with the inverse of the square of the wave number,and the temperature and concentration fluctuations corresponding to the heat and mutual diffusion coefficients are verified to be consistent with the hydrodynamic model at the same time.The maximum fitting deviations between the measured thermal diffusivity and the calculated value of the fitting equation are 1.50%,1.10%and 1.00%respectively,and the average absolute deviations are 4.00%,0.34%and 1.95%respectively;the maximum deviations of mutual diffusion coefficient are 2.00%,5.62%and 1.00%respectively,and the average absolute deviations are 1.06%,2.58%and 0.31%respectively.As the sampling time is 1.5 to 3 times of the relaxation time,the incident angle is between 8°and 12°,the system has lower viscosity and higher refractive index deviation(>4%)and the Le value is 10~80,so it is possible to obtain both the thermal and mutual diffusion coefficients of the binary mixtures with an uncertainty of less than 5%.The dynamic light scattering experimental system developed in this study can be used to obtain the thermal and mutual diffusion coefficients of various complex binary systems simultaneously under the above defined conditions,providing a method for the study of diffusion in complex binary systems.
作者
高鹏
赵贯甲
尹建国
马素霞
GAO Peng;ZHAO Guanjia;YIN Jianguo;MA Suxia(Key Laboratory of Clean and Efficient Combustion and Utilization in the Circulating Fluidized Bed,College of Electrical and Power Engineering,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2023年第4期158-169,共12页
Acta Photonica Sinica
基金
国家自然科学基金(No.51976132)
山西省揭榜招标项目(No.202001101014)。
关键词
动态光散射法
热扩散系数
质扩散系数
正己烷
正癸烷
正十六烷
Dynamic light scattering
Mutual diffusivity
Thermal diffusivity
n-Hexane
n-Decane
n-Hexadecane
作者简介
第一作者:高鹏,gaop688@163.com;通讯作者:赵贯甲,xjtuthermo@foxmail.com。
