RETRACTED: Simulation of steady flow of natural gas in a subsea flexible riser with heat exchange (Retracted article. See vol. 52, pg. 629, 2018)

Flexible riser technology is widely used in today's offshore industry. Evaluating pressure, temperature and velocity profiles in a subsea riser or a flexible pipe is essential in the design of a gas transfer system. Conventional pipeline correlations fail to give an acceptable accuracy for sizing, design and flow assurance applications of flexibles. Hence, availability of a rather simple computational model, which can give results with acceptable accuracy is highly advantageous. The aim of this article is to present a simple numerical method which can be used efficiently to accomplish this goal. A one dimensional finite difference method is used where the riser length is discretized into small segments. Natural gas physical and transport properties are calculated in each segment and flow equations in addition to a state equation are solved simultaneously to find the velocity, pressure and temperature profiles in the flexible riser. The Lee-Kesler corresponding states EOS has been used as the state equation. MathcadTM has been applied for solving equations. The ability of the model to predict thermodynamic properties of natural gas has been compared with experimental data. Furthermore, friction and heat transfer models for a smooth and rough bore riser have been analyzed. For a rough bore riser with carcass corrugations, selecting a reasonable value for the equivalent sand grain roughness has been found to be crucial. The authors have also found the Joule-Thomson effect to be decisive in temperature change for a high pressure rough bore flexible gas riser subject to high pressure drop. (C) 2017 Elsevier B.V. All rights reserved.