Study On Hydrogen Loss And Thermodynamic Performance Of Mobile Liquid Hydrogen Filling Vehicle During Charging

With the rapid development of hydrogen energy industry,the storage and utilization of liquid hydrogen has become a research hotspot.Liquid hydrogen has the characteristics of ultra-low temperature,easy boiling and evaporation.Before the low-temperature pressure vessel used for storage and transportation of liquid hydrogen is put into use,it needs to be pre-cooled to avoid a large amount of liquid hydrogen evaporation in a short time,so as to reduce the cold shock to the system and the container.At present,the experimental studies on liquid hydrogen vessels are relatively few,and the filling time,loss and other dynamic characteristics are mostly engineering experience values.Therefore,in order to explore the relevant laws of liquid hydrogen container filling process,the paper takes mobile liquid hydrogen filling vehicle as the research object and analyzes its dynamic characteristics and thermal stress during filling process.The specific work is as follows:Firstly,based on the basic theory of thermodynamics,the fluid flow pattern and the change of boiling heat transfer mode in the container and low-temperature pipeline system of the filling truck were discussed,and a relevant mathematical model was established to study the relationship between the container wall temperature and the precooling flow rate,precooling time and loss.Secondly,the AMESim software is used to build the mobile liquid hydrogen refueling vehicle system.Based on the model verification,the dynamic research is carried out on the loss,precooling time,charging rate,container temperature and pressure changes in the container filling process,centering on the three influencing factors of precooling flow rate,charging mode and medium undercooling.The rate of dryness change was introduced to evaluate the charging process rate.The results show that the increase of precooling flow can shorten the charging time,but the loss increases,the temperature drop rate increases,and the pressure fluctuation is obvious.In gas-liquid precooling mode,the temperature and pressure of the container change gently,but the filling time and loss increase.When the subcooling degree of the medium increases,the filling time is shortened and the loss is reduced,but the influence on other factors is not obvious.The average consumption of liquid hydrogen per kilogram of stainless steel is 7.41×10^-2 kg when the liquid hydrogen container is precooled from normal atmospheric temperature 20?C to liquid hydrogen temperature range-252.78?C.The precooling loss of liquid hydrogen container with different volume and weight can be estimated according to this data.Finally,the unidirection transient thermo-solid coupling model of mobile liquid hydrogen filling vehicle is built by ANSYS software,and the thermal stress of the container is studied based on the calculation results of wall temperature and internal pressure in AMESim software.The results show that the precooling flow rate and the medium undercooling degree are directly proportional relationship with the thermal stress and stress growth rate of the container,and the gas-liquid precooling mode can reduce the thermal stress and make the stress change to be gentle.The maximum equivalent stress value appears at the connection between the head and the cylinder.Through the simulation research on the filling process of liquid hydrogen filling vehicle,the dynamic characteristics and thermal stress change law of container under various influencing factors are obtained,and the filling method with both safety and economy is explored,which provides reasonable guidance for the application of low-temperature medium in engineering practice.