火灾中液化气储罐热响应CFD模拟的UDF程序设计

On the UDF program design for the CFD simulation of the thermal response to the liquefied gas storage tanks on fire

为了降低火灾环境下储罐内部介质热响应及储罐失效试验研究的成本和风险,更好地为储罐事故的预测预防提供模拟依据,利用Fluent 12.0软件对密闭容器内部介质的传热传质过程进行模拟,给出了内部介质在受热和冷却条件下相变的控制方程;通过考虑内部介质气化热随温度的变化及饱和温度与区域单元压力之间的关系,编写了内部介质在受热和冷却条件下质量和能量源项的用户自定义函数(UDF);通过对部分参数进行简化,分别给出了喷射火和池火条件下丙烷储罐热响应模拟的结果,并与试验结果进行了对比。结果表明:储罐热响应各主要参数(内部介质温度、壁面温度,储罐内部压力)的误差在喷射火条件下低于15%,在池火条件下低于12.4%。这表明模拟所需源项UDF正确,可以用于现实储罐热响应的模拟。

The present paper is aimed at simulating the thermal response to the medium within the sealed containers by using a software known as Fluent 12. 0 in hoping to reduce the cost and the risk of the experimental studies of the internal thermal response and the failure of a storage tank once it is on fire. To achieve our study goal,we have illustrated the phase transformation controlling equations for the media under the condition of the internal heating and cooling so as for them to be used to control the mass and energy volume change with the temperature rising or decreasing of one degree. And then,we have given the source term UDF program of mass and energy of internal medium under the heating and cooling condition while considering the relation of the two groups： Group one represents the change of heat of vaporization with the variation of temperature whereas Group two embodies the relation between the saturation temperature and the area unit pressure by using the Fluent software.Thus,after proper compilation,it would be possible for the users doing the simulation can choose the zones and do the phase transformations there. Each zone includes three source phases,namely,the gaseous phase source,the liquid source phase,and the energy source phase itself. And,when the simulations are done,it is possible for the users to compare the data and the experimental data about the thermal response of the propane tank under jet fire and pool fire,respectively,by simplifying the parameters concerned. All the above results show that the resulting errors of the main parameters of the thermal response of the storage tanks,including the temperature of the internal medium and the wall pressure,in addition to the internal pressure,would be under 15% but below 12. 4% under the pool fire condition. Therefore,the changing trend tends apparently to be able to indicate the good matching,which means that the source item of UDF program that is needed when the simulation is true. On the other hand,the matching can also be used in other thermal responses of storage tanks in reality. All the above examples demonstrate that more attention should be paid to choosing the parameters to be used in the similar simulations,especially to choose the thermal source,the heated area size,the uniformity of the heat volume acted on the tank wall,therefore,it is necessary to choose and appreciate theright and available mathematical models in doing the simulation.