LNG泄漏在地面上蒸发速率的计算

针对LNG泄漏在地面上潜在危险的分析，需要对其在地面上扩散和蒸发速率的变化进行准确预测。基于液体扩散的动力学模型和热传递模型，采用微分方法建立了LNG在连续性泄漏情况下液池漫延半径、蒸发速率随时间变化的预测模型，克服了现有预测模型单纯依赖一维傅里叶导热方程的局限性。根据所建立的预测模型，LNG液池蒸发速率先随时间线性增加到最大值，随后随时间的延长而降低，即与时间的平方根成反比。以5m^3圆柱形LNG储罐为例，计算得到LNG泄漏的速率为19．92kg／s，泄漏完全所需时间为69S，液池半径达到最大的时间为33S，液池半径最大值为7m，0～33S时间内LNG蒸发速率先线性达到最大值19．92kg／s，34-69s时间内液池蒸发速率与时间平方根成反比，液池厚度由2．3mm逐渐增加到6mm。

Calculation of evaporation rate of leaked LNG on the ground

In order to analyze potential hazard of LNG leaked to the ground, it is necessary to predict its diffusion and evaporation rate accurately. Based on dynamic model of liquid diffusion and heat transfer model, this paper uses a differential method to establish a prediction model of diffusion radius and evaporation rate. The model, changing with time and set under the condition of continuous LNG leakage, overcomes the limitation of 1D Fourier equation. According to the established forecast model, the evaporation rate of LNG liquid pool increases linearly with time before reaching maximum value, and then decreases with time, that is, inversely proportional to the square root of time. Taking the cylindrical 5 m^3 LNG storage tank as an example, the calculation shows the leakage rate of LNG is 19.92 kg/s, it takes 69 sec to leak completely, 33 sec to reach the maximum radius of the liquid pool which is 7 m. Evaporation rate increases linearly to the maximum of 19.92 kg/s from 0 sec to 33 sec, is inversely proportional to the square root of time during 34 sec to 69 sec. During this period, thickness of the liquid pool increases gradually from 2.3 mm to 6 mm.