Abstract:

Submerged combustion vaporizer (SCV) is frequently applied for peaking systems of LNG receiving terminals, which both liquid flow and heat transfer characteristics of water bath on shell side of a vaporizer are key factors to determine whether the SCV could achieve high heat transfer efficiency. Influences of initial water level, volumetric flow rate and inlet temperature of flue gas on heat transfer coefficient of the water bath were investigated by visualization experiments and numerical simulation. The water bath absorbed sensible heat of the flue gas and latent heat of the steam condensation so that the temperature of outlet flue gas almost equaled to the equilibrium temperature of the water bath. Under the inductive impact of a great deal of heat transfer-generated bubbles, cycling water flows, which were formed by weir overflow in the water bath, could effectively collide tubular wall, decrease thickness of boundary layer and enhance heat transfer. The initial water level in combination with volumetric flow rate of flue gas largely affected overflow in water bath so the water bath heat transfer coefficient increased dramatically upon the occurrence of overflow. The ratio of fuel and air flow rates mainly affected inlet temperature of flue gas and the turbulent kinetic energy of water bath. In the case of smaller turbulent kinetic energy, the water bath heat transfer coefficient deceased although the inlet temperature of flue gas increased. This study can provide some scientific guidance to the design of SCV.

Key words: submerged combustion vaporizer, shell side, flue gas, water bath, heat transfer, numerical simulation

摘要：

沉浸式汽化器广泛应用于LNG接收站调峰系统，其中壳程水浴流动传热特性是影响汽化器换热效率的关键因素。为此，利用可视化实验研究与数值模拟两种手段研究了初始水位高度、烟气进气量和进气温度对水浴传热系数的影响规律。研究结果表明：壳程水浴能够吸收烟气携带的显热和水蒸汽冷凝释放的潜热，排烟温度与水浴平衡温度基本相当；水浴在大量换热气泡诱导作用下，通过围堰溢流形成的循环水流能有效冲刷管壁，减薄流动边界层，起到强化传热作用；初始水位高度和进气量匹配关系影响水浴溢流情况，溢流后水浴传热系数明显增加；燃料量和空气量配比情况影响烟气温度和水浴湍流动能，水浴湍流动能较小时，即使烟气进气温度增加水浴传热系数反而减小。本研究可以为沉浸式汽化器的设计提供参考。

关键词: 沉浸式汽化器, 壳程, 烟气, 水浴, 传热, 数值模拟