Experimental Study On Thermal Response Process Of Liquefied Gas Tanks

During the production and using process of liquefied gas, when the tank is attacked by an external fire, the pressure and media in the tank will increase, and the wall material strength will decrease. If the tank is ruptured, the media may leak out to the environment, which may cause serious accident. One of the most serious forms of accident is the boiling liquid expanding vapor explosion (BLEVE). Scholars have already done abundant experimental studies and numerical studies on the subject. In this paper, discussion by experiment has done to study the thermal response progress of liquefied gas tank. The main work and conclusions as follows:(1) A small scale device is built which include of thermal stratification experimental facility and explosive boiling discharge experimental facility. The electrical heater band is used to simulate fire. This heating method is safe and easy to control. The explosive boiling experiment increases a rapid pressure relief device based on the thermal stratification experiment, which could simulate the moment of tank rupture well. Temperature measurement and acquisition system use armored thermal resistance, thermocouple and Agilent34970A capture card. Pressure acquisition use piezoresistive precision pressure sensors and high-frequency pressure sensor respectively.(2) Water and R22is used to do the thermal stratification experiment in the liquefied gas tank. The results indicate that:When the tank is heated only on the liquid wall, the internal temperature is homogeneous. No thermal stratification will produce. When the tank is heated on both vapor wall and liquid wall, thermal stratification appears. The greater range of the vapor wall is heated, the thermal stratification in the liquid will be more obvious. The lower liquid filling rate would lead to bigger stratification, and the pressure rises faster. When the heating power improves, the liquid thermal stratification also increases. The thermal stratification mode of heat transfer of the small scale vertical tank is analysed through the experimental study. The heating strength of the liquid surface part is the necessary conditions of thermal stratification.(3) Water is used in the explosive boiling discharge experiment. When the media is discharged abruptly, the pressure rapidly dropped, then violently repressurize. The maximum pressure rebound is close to the pressure before the discharge, but it will not higher than the initial pressure. The results show that liquid filling rate, initial pressure, rupture area all lead to a certain degree of depressurization and repressurization. At filling rate of60%-90%, the repressurization is larger. The greater initial pressure increases the discharge rate. Larger opening area leads to stronger liquid superheating. When there was temperature stratification in the liquid, the intensity of explosive boiling and repressurization rate were much lower than the uniform temperature of the liquid in the same pressure.