Study Of The Dual Capillary Viscometer In High Temperature Gas Viscosity Measurement

Reference acoustic thermometer has the minimal uncertainty in measuringthermodynamic temperature from500K to700K. The disturbance of thermal and viscousboundary layer in acoustic resonance cavity is the largest source of uncertainty, and theaccurate measurement of viscosity and conductivity of gas in the ideal gas state is the base ofthe perturbation correction. In addition, with the ab initio calculation model established on thepotential energy of gas molecules, the theoretical calculation of the thermodynamicand transport properties of helium achieves a high accuracy and has a agreement with theexperimental measurements, but it has no experimental measurement of high precision valuein high temperature (above120℃) to verify.The double capillary viscometer has the minimal uncertainty in measurementof viscosity and thermal conductivity of gas, but, at present, there is no hightemperature (above120℃) dual capillary viscometer in the world. In order to establisha high temperature dual capillary viscosity measurement system, we designed a high andconstant temperature device for high temperature double capillary viscometer. With thePID setting in temperature control, the temperature of the high and constant temperaturedevice from25℃to400℃can stabilize between±3mk, and meet the requirements fortemperature stability.In this paper we established a high-temperature dual capillary viscosity measuringsystem, improved the gas pipeline system, researched the influence of gas outlet pressure topressure control, and kept the pressure fluctuation level better than±15Pa, which meetingthe requirement for the uncertainty of pressure measurement.In this paper we measured the viscosity and thermal conductivity of argon from25℃to120℃in ideal gas state, and with the relative deviation less than0.04%compared with theexisting measurement results, we verified the availability and high accuracy of thedevice. We analyzed the effect of preheating system from250℃to400℃, studied the influence of gas flow rate and P4of preheating effect.Finally, we measured the viscosity and thermal conductivity of argon from120℃to380℃in ideal gas state. The relative standard uncertainty of measurement results is0.03%and0.0299%, and is in good agreement with the calculation values calculated by Vogelfrom25℃to380℃. We verified the reliability of the device, and laid an important technicalfoundation for the establishment of high temperature dual capillary viscosity measuringsystem above400℃.