Gas Stability Mechanism And Experimental Study Of PVTt Standard Device Container

The pVTt gas flow standard device,as the standard gas flow measurement standard device,is the most advanced gas flow calibrating device at present.This paper aims at the problem that the gas stability time in the standard container of the 34m3 water jacket pVTt gas flow standard device is gradually becoming longer in the standard container.The multi field coupling model of the gas stable state in the standard container is established,and the factors that cause the problem are found through the simulation analysis.Through this study,the existing problems of the standard gas flow standard container with water jacket pVTt method can be solved and the theoretical basis is provided to reduce the gas stability time in the standard device container.To improve the efficiency of verification.At the same time,it provides a new model and method for the improvement of pVTt gas flow standard device.The main research contents and achievements are as follows:1.The technical index,working process and measuring methods of temperature,pressure and time of the pVTt gas flow standard device are studied.The basic quality flow of the standard device is modified to analyze the main factors affecting the time of gas stability in the standard container and the foundation of the uncertainty of the analysis device.2.The multi physical field coupling problems in the operation of standard containers of water jacketed pVTt standard system were systematically analyzed.A mathematical model of multi field coupling in a water jacket pVTt standard container is established.The gas mass flow equation of the intake process in the standard container is given.The Reynolds number of the gas flow in the intake process is calculated.The gas in the intake process is in a turbulent state,and a turbulent mathematical model is given.The analysis has established the standard.Different types of heat transfer models are involved in various conditions in a quasi vessel,and the thermal fluid solid coupling is synthetically analyzed and the coupling control equation and supplementary model are given.3.The simulation and simulation analysis of the gas stability process in the water jacket pVTt standard container is carried out.The results are compared with the actual operation results.The simulation results are in good agreement with the actual gas stability state.It shows that the simulation model can reflect the steady state of the actual gas more accurately,and the model of the constant temperature of the water jacket type and the no The simulation and comparison analysis of the natural constant temperature model of the water jacket is carried out.It is found that under the constant temperature state of the water jacket,the gas in the one hour content device enters the stable state,the maximum temperature difference is less than 0.2K,the standard container under the natural constant temperature state of the anhydrous jacket enters the stable state at 1.5h,and the maximum temperature difference is less than 0.25 K,The time is far longer than the water jacket type constant temperature model.The simulation results show that the water jacket type constant temperature model has the advantages of shortening the gas stability time in the standard container,improving the calibration efficiency and effectively eliminating the temperature gradient.It has some advantages in the large pVTt standard device.4.The influence of the external environment on the gas stability time in the standard container is simulated and analyzed.The results show that the existence of the solid container will weaken the heat transfer effect between the gas in the standard container and the water in the water jacket,but the weakening is not obvious,and the effect on the stability of the gas body is negligible;the water jacket has been ignored.The temperature difference between the temperature of the water and the temperature of the external environment will affect the steady state of the gas in the standard container and prolong the time of the gas stability,in which the influence of the temperature of the external environment is higher than that of the water temperature.Experiments were carried out on a 34m3 water jacket standard container.The final data confirm the conclusion of simulation analysis.After eliminating the influence of the influence factors on the standard container,the uncertainty of the standard container is calculated and the expansion uncertainty is 0.046%(k=2),which meets the requirement of the water jacket pVTt gas flow standard device.