Numerical Simulation Of Thermal Response Of LPG Tank At Petrochemical Base In Fire Hazard Environment

Liquefied petroleum gas(LPG)is increasing widely used in people's lives and social production activities because of its high calorific value,cleanliness,and easily stored and transportation.Although there are strict protective measures in the design and use,fire and explosion accidents caused by LPG leakage are still common in our life,especially in large port petrochemical bases.Once an accident occurs,it will cause extremely bad impact on society.Experts and scholars at home and abroad have conducted many experiments and simulations to study the thermal response behavior of LPG tanks in fire hazard environment,and found that in addition to thermal insulation facilities and safety valves,the thermal stratification phenomenon during the thermal response of storage tank can effectively prevent the LPG tank inactivation and the risk of boiling liquid expanding vapor explosion(BLEVE).Therefore,analyzing the thermal response behavior of LPG storage tanks in a fire hazard environment is of great theoretical value and guiding significance for preventing and controlling the occurrence of fire and explosion accidents,improving fire protection design,ensuring equipment safety and improving production efficiency.The main work of this paper is as follows:(1)Based on the thermal response behavior of LPG tank in fire hazard environment,a hypothesis was proposed and a numerical model was constructed.The thermal response and heat transfer mechanism of LPG tank in Lingang Petrochemical Base in fire hazard environment is analyzed theoretically.Firstly,determine the base conservation equation,and select the turbulent flow model,the rigid wall heat transfer model,the two-phase flow model and the heat transfer model with phase change according to the characteristics of the model,then choose a reasonable solving method.(2)According to the models property,the computing model of storage tank is constructed by the pre-processing software ICEM,and proper mesh are divided.Based on the boundary conditions and initial conditions of the simulation set up by the existing experiments,the simulation was conducted by using FLUENT software,and the simulation results were compared with the experimental data to ensure its effectiveness.(3)Analyzing the results of simulation calculation,the flow mode of the inside fluid in the storage tank,the mechanism of the formation and elimination of thermal stratification,the maintenance time of thermal stratification and the heat transfer rule of wall temperature were analyzed through the pressure response,wall temperature response and medium temperature inside the storage tank.(4)Based on the existing numerical simulation,changing the initial conditions,propane was used as the filling medium,the flame radiation temperature was set as the flame temperature of real fire hazard environment.The filling rate,tank wall thickness,external flame temperature and convective heat transfer coefficient of liquid phase were changed by the method of control variables,and relative simulation calculations were conducted under these conditions in order to study the influence of these factors on the thermal response process of LPG tank.The simulation results show that: the decrease of filling rate will accelerate the pressure growth of tank body,increase the high-temperature region of tank body surface,make the temperature stratification phenomenon of medium more obvious,which makes thermal stratification last for a longer time.The increase of tank wall thickness means the increase of thermal-conduction resistance of the wall,which also increases the blast pressure value for tank inactivation,and delay of rate of temperature increase of tank wall and reduce the pressure inside the tank and the rising rate of medium temperature.Therefore,improving the stability of tank can greatly reduce the risk of tank inactivation.The increase of external flame temperature will accelerate the pressure growth of the tank and make the change of medium temperature more obvious,which is not conducive to the maintenance of thermal stratification.If the stability of the tank body is worse,the tank is more likely to fail and break.The decrease of convective heat transfer coefficient accelerates pressure growth of tank body,and the growth rate of medium and tank body surface temperature also accelerates,which is not conducive to maintaining the stability of tank body and increases the risk of rupture.Choosing reasonable filling rate,scientific design of tank wall thickness and taking scientific measures to reduce the external flame temperature are of great significance to reduce the risk of tank inactivation.The innovation of this paper: propane was used as the filling medium in the storage tank,so the initial pressure inside the storage tank is changed accordingly,and a reasonable flame radiation temperature is set according to the actual fire situation,which is more similar to the real fire hazard environment;Combining the characteristics of strong wind throughout the year of the Lingang Petrochemical Base,the convection heat transfer coefficient at different wind speeds is used to represent the heat loss rate of the storage tank under different wind speeds,and the impact of the change of this factor on the thermal response behavior of the storage tank is analyzed,which is more similar to actual environment.In the next step,a more complex model can be established to study the coupling effect of wind speed on the thermal response of the tank.