Research On Heat Transfer Performance Of Large-scale LNG Ambient Air Vaporizer

The demand for natural gas in the domestic market is increasing year by year,and importing a large amount of LNG is one of the main ways to solve the contradiction between market supply and demand.Since it is necessary to convert liquefied natural gas into gaseous natural gas through a vaporizer before pipeline transportation,the LNG vaporizer is one of the core equipment for liquefied natural gas transportation.At present,most of the vaporizer used in LNG receiving terminals are seawater open-frame vaporizer or submerged combustion vaporizer,but these two vaporizers have the disadvantages of polluting the marine environment and expensive application costs.Therefore,it has positive practical significance for the research of the new LNG ambient air vaporizer used in the large-scale LNG receiving terminal.In this paper,the SST K-? turbulence model is mainly used to study the heat transfer performance of supercritical LNG in an ambient air vaporizer by numerical simulation.First,use REFPROP software to calculate and analyze the physical properties of liquefied natural gas,Then build the model through the modeling software,use the ICEM software for grid division and verify the grid independence,to ensure the accuracy of the subsequent research results,and compare with the existing research results to verify the accuracy of the simulation method used in this article.The temperature field distribution and velocity field distribution of liquefied natural gas in the ambient air vaporizer after coupled heat and mass transfer process are obtained by simulation.By changing the temperature of the air outside the tube,the air flow rate,the LNG composition in the tube,the LNG inlet flow rate and other parameters,the temperature of the vaporizer outlet fluid under different conditions and the average heat transfer coefficient outside the vaporizer tube are analyzed.The following conclusions are drawn:The fluid temperature at the outlet of the vaporizerand the heat transfer coefficient outside the vaporizer tube increase as the air temperature increases.The air temperature is increased from 263 K to 313 K,the vaporizer outlet fluid temperature is increased from 242 k to 294 k,the outlet fluid temperature is increased by21.5%,and the heat transfer coefficient is increased by 32.3%.As the air velocity outside the tube increases,the temperature of the fluid outlet in the tube and the heat transfer coefficient on the air side outside the tube will increase.When the air velocity is increased from 1m / s to 2m / s,the outlet fluid temperature is increased by 4.7%,and the heat transfer coefficient is increased by 7.1%;The trend of LNG physical properties of different components with temperature changes is basically the same,but from the inlet to the outlet,the difference in the average temperature of the fluid in the pipe is continuously increasing;The effect of LNG composition changes on the heat transfer performance of the vaporizer cannot be ignored;the temperature of the LNG outlet in the tube decreases with the increase of the LNG inlet flow rate,but the heat transfer coefficient on the air side outside the tube increases,and the overall heat transfer effect is strengthened.In this study,the CFD numerical simulation method is used to analyze the fluid-solid coupling heat transfer process of the new LNG ambient air vaporizer tube,which provide data reference for intelligent operation of vaporizer and improvement of gasification efficiency.At the same time,it provides theoretical basis for the design optimization of the LNG ambient air vaporizer in the future.