Investigation Of Flow And Heat Transfer Characteristics Of Non-boiling Oil-gas Slug Flow In Cooling Process In Horizontal Pipe

Oil-gas slug flow is a common flow pattern for subsea multiphase transportation pipeline.The temperature difference between cold seawater and hot product may lead to several safety problems.It is very important and valuable to investigate the flow and heat transfer characteristics for accurately predicting the two-phase temperature distribution in cooling process.In this paper the investigation of flow and heat transfer characteristics for oil-gas slug flow was carried out in two-phase horizontal pipe simulating the subsea low temperature environment.In this experiment,sensors such as capacitance probes are used to measure the flow parameters and sensors such as thermocouples,thermoresistance are used to measure the heat transfer parameters.The influe nce of flow characters to heat transfer characters was carried out and a predicting model based on local characteristic of convective heat transfer coefficient and gas strengthening factor is proposed to accurately predict the two-phase slug flow convective heat transfer coefficients.The capacitance sensor with?=150°,b=0.1mm,d_s=20mm is best.The oil-gas flow pattern transitional boundary moves to the direction of low superficial velocity with greater fluid viscosity.The slug flow pressure drop,slug frequency and void fraction are growing with greater fluid viscosity.The convective heat transfer coefficient of oil-gas slug flow is strongly influenced by liquid velocities and slightly increases with gas velocities.The oil-gas coefficient is far less than the water-gas coefficient.The coefficient of oil-gas slug flow increases with the increase of the average slug velocity.It is found that the injection of air can more effectively reduce the thermal boundary layer of air-oil slug flow than air-water.The analysis of local heat transfer coefficient around pipe shows that the coefficient at the bottom and its speed is much higher than the coefficient at the top.The reinforcement of the gas phase mainly reflects in the pipe bottom liquid film zone.Three empirical empirical correlations applicable to oil-gas slug flow are evaluated.The result shows that these correlations have some limitations because of dependency on experiment conditions.The predicting model based on local characteristic of convective heat transfer coefficient and gas strengthening factor shows great agreement with experiment data.