Investigation Of Flow And Heat Transfer Characteristics Of Non-boiling Air-liquid Slug Flow In Cooling Process

Two-phase heat transfer occurs in chemical engineering,nuclear industry,petroleum production and many other engineering fields.In addition,the problem of two-phase heat transfer in the deep-water oil production is becoming more and more serious.It is very important and valuable to investigate the flow and heat transfer characteristics and to accurately predict the two-phase convective heat transfer coefficient in cooling process.In this paper the flow and heat transfer characteristics of different flow mediums at different cooling temperature are investigated.In this experiment,sensors such as thermocouples,thermoresistance,thermopiles,parallel conductance probes,capacitance probes and pressure sensors are used to measure the flow and heat transfer parameters.Besides,multiple-parameter correlations and a predicting model based on slug tracking model are proposed to accurately predict the two-phase slug flow convective heat transfer coefficients.The coefficient of two-phase slug flow is strongly influenced by liquid velocities.For air-water slug flow,heat transfer coefficients vary little with gas velocities while the convective heat transfer coefficients of air-oil slug flow vary much along gas velocities.It is found that the injection of air can effectively reduce the thermal boundary layer of air-oil slug flow.The influence of slug parameters such as slug velocity,length,frequency,liquid holdup and the length of liquid film on convective heat transfer are investigated.In addition,the effect of mediums,cooling temperature and velocities on temperature difference between the top and bottom of the pipe are investigated.The multiple-parameter correlations show good agreement with the experimental data.However,the leading coefficient and exponents depend much on the experimental data,which limits the application.The predicting model based on slug tracking model also shows good agreement with experimental data.It is shown that the predicting model could effectively reflect the influence of liquid velocities.It is found that the injection of gas for air-oil slug flow can effectively increase the heat transfer coefficient.The factor of gas for air-oil slug flow is brought in the predicting model.