Unified Model of Heat Transfer in Gas-Liquid Pipe Flow

A unified model of multiphase heat transfer is developed for different flow patterns of gas-liquid pipe flow at all inclinations from –90 to +90 from horizontal. The required local flow parameters are predicted by use of the unified hydrodynamic model for gas-liquid pipe flow recently developed by Zhang et al. 2 The model prediction of the pipe inside convective heat transfer coefficients are compared with experimental measurements for a crude oil/natural gas system in horizontal and upward vertical flows, and good agreement is observed. Introduction As oil and gas production moves to deep and ultra-deep waters, flow assurance issues such as wax deposition, hydrate formation, and heavy oil flow become very crucial in transportation of gas, oil and water to processing facilities. These flow assurance problems are strongly related to both the hydraulic and thermal behaviors of the multiphase flow. Therefore, multiphase hydrodynamics and heat transfer need to be modeled properly to optimize the design and operation of the flow system. Compared to experimental and modeling studies of multiphase hydrodynamics, very limited research results can be found in the open literature for multiphase heat transfer. Davis et al. presented a method for predicting local Nusselt numbers for stratified gas-liquid flow under turbulent liquid/turbulent gas conditions. A mathematical model based on the analogy between momentum transfer and heat transfer was developed and tested, using heat transfer and flow characteristics data taken for air/water flow in a 63.5-mm inside diameter (ID) tube. Shoham et al. measured heat transfer characteristics for slug flow in a horizontal pipe. The time variation of temperature, heat transfer coefficients, and heat flux were reported for the different zones of slug flow. Substantial difference in heat transfer coefficient was found to exist between the bottom and top of the slug. Most previous modeling studies were aimed at developing heat transfer correlations for different flow patterns. Kim et al. evaluated 20 heat transfer correlations against experimental data collected from the open literature, and made recommendations for different flow patterns and inclination angles. However, these recommended correlations did not give satisfactory predictions when compared with experimental results by Matzain. Manabe developed a comprehensive mechanistic model for heat transfer in gas-liquid pipe flow. The overall performance was better than previous correlations in comparison with experimental data. However, some inconsistencies in the hydrodynamic model and the heat transfer formulations for stratified (annular) and slug flows need to be improved. A unified hydrodynamic model has been developed for gas-liquid pipe flow at the Tulsa University Fluid Flow Projects (TUFFP). The major advantage of this model compared with previous mechanistic models is that the predictions for both flow pattern transition and flow behavior are incorporated into a single unified model based on slug dynamics. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. The objective of this study is to develop a unified heat transfer model for gas-liquid pipe flow that is consistent with the unified hydrodynamic model.