Determination of the thermophysical properties and the second virial coefficient of low density He3, He4 and their equivalent mixture in 1-10000 K temperature range

Due to severe harm to ozone, some of the fluids are not convenient for using them inrefrigerator industry, magnetohydrodynamic power systems, some kind of semi-conductorsproduction, electrical power supplies, and also in fuel systems operated by repulsiveforces. Whereas some of them, which are not harmful to ozone due their molecularstructures, and therefore, are more eligible for usages in terms of environmental concern.So recently, researches on using the fluids of 3He, 4He and their equivalent mixture havebeen begun for the systems mentioned above instead of those destroying the ozone.However, 3He, 4He and their equivalent mixture are used at extremely low temperatures insome areas, and also at high temperatures (1-104 K) in some other areas.Nowadays, thermophysical properties of 3He, 4He and their equivalent mixture must bedetermined as accurately with the lowest uncertainties. In this respect, both the equation ofquantum mechanical Ω(n,s)(T) collision integral for the determination of the thermophysicalABSTRACT (continued)properties and the quantum mechanical B(T) second virial equation for the calculation ofthermodynamic functions should be known at first. Therefore, the goal of this study is todetermine and calculate the thermophysical properties and thermodynamic functions of3He, 4He and their equivalent mixture at 1-104 K, as accurately with the lowestuncertainties.In this study, two methods have been employed to obtain the collision integral, Ω(n,s)(T)which used for calculation of thermophysical properties of fluids. The first method isemployed the equation of the classical quantum mechanical collision integral Ω(n,s)(T) foronly low density 4He. As a result of this calculation, the theoretical results were obtainedby using the equation of collision integral Ω(n,s)(T) in 1-104 K range. On the other hand, anew collision integral have been proposed which in employed as a second method, tocalculate the collision integral Ω(n,s)(T) for 4He, 3He and the equivalent mixture in 1-104 Krange. The viscosity η(T), thermal conductivity λ(T) and mass diffusion coefficient D(T)of fluids were calculated using the proposed equation for Ω(n,s)(T). In order to determinethe uncertainties of the results obtained from the proposed equation of collision integral,the results were compared with those obtained by ab initio and with experimental valuesbelonging to low density 4He, 3He and their equivalent mixture as accepted standards in theliterature.In this study, second virial coefficient B(T) for each fluid has been proposed to calculatethe thermodynamic functions such as Gibbs energy (∆U), enthalpy (∆H), entropy (∆S),heat capacity at constant volume (∆Cv) and at constant pressure (∆Cp), Joule-Thomsoncoefficient (µ), and sound velocity in fluids(c). Hence, four different types of second virialequations B(T) as analytical functions of temperatures have been proposed for each fluidsand the equivalent mixture.As shown in the diagrams, the proposed thermophysical semi-empirical calculation termshave smaller coefficients in comparison to those found in many proposed semi-empiricalterms in the literature. Therefore, the more sensitive results were obtained. It is alsoimportant that these proposed terms are comparatively not only more sensitive but alsoeasily understandable.ABSTRACT (continued)Key Words: Second virial coefficients, equation of state, Thermophysic,Thermodynamic, sound velocity in fluids, Helium, viscosity, thermalconductivity, mass diffusion coefficient.Science Code: 4040301