Heat energy-saving characteristics of electric heat tracing in subsea gas-liquid multiphase-flow mixed transportation pipelines
In view of the flow assurance faced by the subsea gas-liquid mixed transportation pipelines,such as wax deposition,gelation,and excessive friction,an electric heat tracing method that saved heat energy was proposed.Compared with the common platform heating method,the mathematical analytic formula of relative heat consumption ratio(RHCR)of electric heat tracing was derived by calculus methods based on the principle of total heat balance of the subsea pipeline system.The main factors affecting the heat energy-saving effect of electric heat tracing were clarified,and the difference in heat consumption between electric heat tracing and platform heating was proved.In addition,the influence of key factors such as total heat transfer coefficient on the heat energy-saving characteristics of electric heat tracing was investigated.The results show that under the same mass flow,insulation measure,and outlet temperature conditions,the heat consumption of electric heat tracing is always less than that of platform heating.The specific heat energy-saving effect is only related to 5 key factors,such as total heat transfer coefficient,transportation distance,pipeline diameter,mass velocity and liquid phase mass fraction.The RHCR of electric heat tracing has an approximately linear negative correlation with the total heat transfer coefficient and transportation distance,an exponential positive correlation with pipeline diameter and mass velocity,and a linear positive correlation with the mass fraction of the liquid phase.When electric heat tracing is used,the heat energy-saving effect will be more significant under extremely low flow rate conditions,as it does not require additional water to ensure the"minimum safe flow rate"of the pipeline.The results can provide a theoretical basis for understanding the heat energy-saving characteristics of electric heat tracing in subsea gas-liquid multiphase-flow mixed transportation pipelines.
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