Computational study of heat transfer in subsea deadlegs for evaluation of possible hydrate formation

Abstract

The background for this project is the request of achieving more knowledge of the temperature and velocity fields in different subsea deadleg geometries. This is important to avoid hydrate formation in subsea equipment. The literature review revealed only a few studies on this topic. Two studies on corrosion, both experimental and numerical, in subsea deadlegs where performed by Habib. Results show almost stagnant flow 3-4 Di into the deadleg. To study the heat transfer in such systems, two deadlegs was modeled in Fluent, a vertical and a horizontal oriented deadleg. The choice of geometry and some input data is based on the former work done by IFE and Habib and his crew. The simulations where run with two different velocities and outer heat transfer coefficient. The effect of buoyancy in the vertical deadleg is also investigated. The results shows that the vertical deadleg has a more abrupt temperature profile outwards in the deadleg than the horizontal. For tree of the eight cases, the temperature crosses the HET (hydrate equilibrium temperature) and is therefore in the temperature range where hydrates will start to form. To be able to suggest a design criterion for subsea deadlegs, this problem should be further investigated.