Abstract:

Submerged combustion vaporizer (SCV) is widely used in LNG receiving terminals. In order to study the flow and heat-transfer characteristics of supercritical LNG in SCV coil tubes, a three-dimensional computation model is established to analyze the influence on fluid temperature and local heat transfer coefficient, base on pressure, heat flux, inlet velocity and variation of physical properties. The results indicate that the local heat transfer coefficient first increases and then decreases along the flow direction, and the maximum occurs at the pseudo-critical temperature. Due to the secondary flow, the coefficient of local heat transfer increases abruptly. In the range of operational pressure, the maximum of local heat transfer coefficient decreases with increasing tube-side pressure. As the heat flux increases, the maximum of local heat transfer coefficient increases and appears earlier, and drops faster after the maximum. Higher heat flux deteriorates the heat transfer. The maximum of local heat transfer coefficient increases and appears later as the inlet velocity increases. The numerical simulation study provides scientific guidance to the design of SCV.

Key words: surpercritical fluid, LNG, SCV, numerical simulation, heat transfer, coil tubes

摘要：

LNG沉浸式汽化器在液化天然气接收站应用广泛,管内超临界LNG的传热特性对SCV运行有重要影响,为此,建立了单根蛇形换热管内LNG流动传热过程的数值计算模型。分析了管程压力、热通量、入口速度及物性变化对管内流体温度与局部传热系数的影响规律。计算结果表明,局部传热系数沿流动方向呈先增大后减小的趋势,并在准临界点附近达到峰值;由于二次流现象,传热系数在弯管处发生突变。在操作压力范围内,压力越大,局部传热系数峰值越小;热通量越大,局部传热系数峰值越早出现,峰值过后系数下降越快,出现传热恶化现象;而入口速度越大,局部传热系数越大,其峰值出现位置越靠后。该数值模拟结果可为LNG沉浸式汽化器的设计提供参考。

关键词: 超临界流体, 液化天然气, SCV, 数值模拟, 传热, 蛇形换热管