Investigation On Efficient Precooling Methods Of High-pressure Liquid Oxygen Tank

With the development of cryogenic technology,the application of cryogenic liquid becomes more and more extensive.Cryogenic liquid has the characteristics of low boiling point,low latent heat and high production cost compared with conventional fluids.In order to transport and store single-phase cryogenic liquid safely,precooling process is indispensable.The control of precooling process still depends on operators in engineering field these days,it is in empirical or semi-empirical state,lacking clear theoretical guidance.And the precooling time and precooling medium consumption have to be optimized in order to save cost.Further research on the precooling process will help to solve these problems.It is very important to make a scientific and reasonable precooling scheme for high-pressure liquid oxygen tank,which is thicker than normal vessels.The existing research about precooling is mainly about thin and small diameter pipelines under normal pressure,and large LNG cargo tanks,few studies focus on high-pressure cryogenic tank.To cool down high pressure LO2 storage tank quickly,economically and safely,the following work is mainly carried out in this study:1)The precooling time and medium consumption are predicted based on the basic theory of thermodynamics.The mathematical model of precooling time and medium consumption are established using steady-state method and variable thermal conductivity method;the relationship between the temperature of tank and precooling time is deduced.And the interrelationship between inlet flow rate,precooling time and medium consumption are investigated.By combining different calculation methods,the optimum precooling flow rate can be selected.2)The CFD simulation method was used to simulate the cooling process of the tank.The temperature,pressure and gas-liquid distribution in the tank under different inlet flow rates were obtained by CFD simulation through phase-change model correction and time step verification,and the cooling trend of LO2 tank was obtained.3)The structure of tank was optimized in order to shorten precooling time and reduce thermal stress generated by temperature difference.The method of redesigning tank based on material property at low temperature and adding vertical nozzle were proposed.The present study is of significance for the optimum design of high-pressure liquid oxygen tank.