Impact of boiling liquid on fluid-vapour-wall interaction in LNG transfer systems

The interaction between the wall and the boiling liquid at flow conditions is not well understood. Also the influence and effect on boiling phenomena, either positive of negative, on the overall flow is unknown. To gain a better understanding of the fluid-vapour-wall interaction of a liquid in near-to-boiling conditions, in-depth studying and numerical as well as physical modeling will be required.

The goal of the project is to develop a prediction model of the impact of boil-off gas in LNG transfer on the pressure loss of LNG transfer multi-composite hoses. Pressure loss prediction so far is based on water flow testing and a limited number of LNG transfer tests as performed by TNO.

Some of the results obtained show a large dependency of the pressure loss on the internal hose pressure, which can partially be explained as a result of the impact of internal pressure on the hose geometry (e.g., hose elongation and roughness). In addition, gas (bubble) formation in the hose as a result of heat-ingress or vortex shedding along the corrugations in the hose can result in an impact on friction factor and pressure loss in the hose.

A combined numerical/experimental investigation will be carried out on the effect of boiling in pipe flow with both smooth and corrugated walls. This project builds on existing expertise in observing gas bubbles in wall turbulence and in investigating multiphase flow in pipes. The effect of gas bubbles on the flow in smooth and corrugated pipes will be investigated both by measuring the pressure drop and distribution of gas bubbles in pipes under various operating conditions (gas volume fraction, bubble size, etc.), and by more detailed experiments on the underlying phenomena.

The final goal of the project is to obtain a validated prediction model for gas formation in LNG transfer and the impact on pressure loss in corrugated hoses and pipes, throughout the operating envelope.

This project is funded through Agentschap.NL (http://www.agentschap.nl/) and is a collaboration with TNO.