Calculations Of Transport Properties Of Fluids By Kinetic Theory And Development Of Density/Viscosity Measurement System Using MEMS Sensor

The highly accurate transport property data are of interest in many scientific and engineering applications,which include the precise determination of the fundamental physical constants,the development of a high-quality viscosity database,and the construction of a new primary pressure/temperature standard.The measurement uncertainties in thermophysical properties have approached the minimal values that can be possibly achieved by the current experimental techniques.Advances in computer simulations can provide new methods to obtain the thermophysical properties of fluids.Traditionally,the instruments under laboratory conditions can make precise measurements on thermophysical properties over a wide range of temperature and pressure.MEMS sensors have several advantages over the traditional instruments in size,weight,and response speed.The developments of experimental systems based on MEMS sensors will assist industry in the future.Therefore,in this work,we investigated the thermophysical properties of fluid by both the theoretical and experimental approaches.The transport properties of dilute gases were calculated by the kinetic theory of gases.The viscosity of dense fluids were calculated by the Vesovic-Wakeham theory.In addition,a density/viscosity measurement system was developed using MEMS sensor.The main conclusions of this work are,1.The transport properties of monatomic gases and diatomic gases were calculated at low density by the kinetic theory of gases from ab initio potentials.The monatomic gases were helium and its isotopes?helium-4,helium-3,helium-4/helium-3?,argon,and four different binary mixtures of noble gases?He/Ne,He/Ar,Ne/Ar,Ar/Kr?.The diatomic gases were hydrogen,deuterium,hydrogen/deuterium mixtures.The transport properties considered here were viscosity,thermal conductivity,diffusion coefficient,and thermal diffusion factor.The temperature ranges were from 100 to 10,000 K.The transport property data in the literature were compared with the calculated values of this work.The extensive analysis showed that the calculated transport properties could be used as recommended values.2.The new interaction potentials of polyatomic gases were determined by the semi-empirical inversion theory.The systems considered here were R142b?CH₃CClF₂?,DME?CH₃OCH₃?,CO₂/O₂ mixtures,and CO₂/N₂ mixtures.The viscosity,thermal conductivity,diffusion coefficient,and thermal diffusion factor of polyatomic gases were calculated by the kinetic theory of gases from the new interaction potentials.The temperature ranges were from 273.15 to 3273.15 K.The available data in the literature were in agreement with the values calculated in this work for the different transport properties.The comparisons showed that the calculated transport properties were useful supplements to experimental measurements.3.The viscosity of HFCs refrigerant mixtures were calculated by the Vesovic-Wakeham theory for the temperature ranges from 298.15 to 423.15 K and at pressures up to 8.85 MPa.The HFCs refrigerant mixtures studied in this work were R32/R125,R32/R134 a,R32/R143 a,R32/R152 a,R125/R134 a,R125/R143 a,R125/R152 a,R134a/R143 a,R134a/R152 a and,R143a/R152 a.In addition,the viscosity of CO₂/HCs mixtures were calculated by the Vesovic-Wakeham theory for the temperature ranges between 273.15 and 973.15 K and at pressures up to 200 MPa.The CO₂/HCs mixtures studied in this work were CO₂/CH₄,CO₂/C₂H₆,CO₂/C₃H₈,CO₂/n-C₄H₁0,and CO₂/iso-C₄H₁0.The comparisons with the experimental data showed that the viscosity values calculated in this work could be used with confidence in scientific and engineering applications.4.An experimental system was built for the simultaneous measurement of the density and viscosity of fluids based on a MEMS sensor.The experimental system was calibrated with toluene.To check the quality of this system,the density and viscosity of n-heptane were studied.The measurements were carried out at five temperatures in the range from 283.15 to 303.15 K and at atmospheric pressure.The experimental data in this work were compared with that of literature values for density and viscosity.The mean absolute deviation and the maximum deviation for density were 0.93 % and 1.26 %,respectively.The mean absolute deviation and the maximum deviation for viscosity were 7.08 % and 16.67 %,respectively.The development of the experimental system will assist in situ measurement of thermophysical properties in the future.