(94c) Evaluation of Sloshing in Coil Wound Heat Exchangers Used in Floating LNG Applications

Coil wound heat exchangers are used in most of the land-based, large-scale natural gas liquefaction facilities. They have a well-proven track record for performance and robustness. As the implementation of liquefaction processes extended to off-shore floating LNG facilities, it was important to investigate the effect of vessel motion on heat exchanger performance. One important aspect to consider was the potential for sloshing at locations in the exchanger where liquid is collected and distributed.

The flow characteristics are different from the classical study of sloshing where the fluid is enclosed inside a vessel (e.g. storage tank) with no flow in or out. The liquid in coil wound heat exchanger distributors continuously flow in and out of the system. To understand this key difference, a CFD model was developed to simulate the liquid motion inside a partially filled cylinder with and without continuous flow in and out. For a partially filled vertical cylinder without any continuous flow in and out, the CFD model was able to capture the well-known sloshing behavior documented in the literature. For the cylinder with a continuous steady in and out flow, the CFD simulation results demonstrate that the continuous flow suppresses sloshing. An analysis based on potential flow theory is described and confirms the CFD results, further demonstrating that flow in and out of the distributor changes the natural frequency of the system and thereby suppresses sloshing.