Conjugate thermal-hydrodynamic model for the study of heavy oil transport

• Published in: Journal of petroleum science & engineering Vol. 179; pp. 997 - 1011
• Main Authors: Sánchez, S., Ascanio, G., Sánchez-Minero, F., Méndez, F., Aguayo, J.P., Ramírez-Jiménez, E., Alonso-Ramírez, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2019
• Subjects: Conjugate phenomenon; Dynamic viscosity; Lubrication theory; Scale analysis; temperature-dependent properties; Lubrication theory; Dynamic viscosity; temperature-dependent properties; Scale analysis; Conjugate phenomenon
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2019.04.083

In the present work, the thermal impact induced by the environment on the hydrodynamics of heavy oil transport in pipelines is analyzed. Here, the thermal dependence of the dynamic viscosity of heavy oils, in addition to the mechanical heating caused by viscous dissipation are taken into account; therefore, the mathematical models that represent the flow and temperature fields of the heavy oil have to be solved in a coupled manner. Moreover, given that the pipeline is protected by a thermal insulation (soil), the domain of study defines a conjugate system between the heavy oil, the pipeline and the soil, which indicates that before knowing the temperature in the fluid region, temperatures in the other two zones must be calculated. To define properly how thermal energy is transferred and generated during the crude oil transport, the analysis is carried out in dimensionless form, solving the conjugate mathematical model by using numerical approaches and simplified asymptotic approximations. The main results reveal that the transport of heavy oils is seriously affected by a small reduction in temperature, increasing substantially the dynamic viscosity and the flow rate is reduced significantly in comparison with the case of a full thermal insulation condition. Then, we can infer that when the losses of thermal energy and its effects on the hydrodynamics are controlled, an efficient transport process is obtained. Employing the asymptotic analysis, results show that such a condition can be achieved by two ways: the first one by improving the thermal insulation, and the second one by optimizing the ratio of the internal radius to the length of the pipeline or increasing the volumetric flow rate, which indicates that the conjugate phenomenon is a modified version of the Graetz-Nusselt problem. •Results obtained through the conjugate thermal-hydrodynamic model show important difference in comparison with other models reported in the literature.•The definition of the Nusselt number and the analysis was extended to evaluate the conjugate heat transfer phenomenon.•A modified version of the Graetz-Nusselt problem based on a non-isothermal hydrodynamic flow was determined.•A simple evaluation of the Graetz-Nusselt relationship can reveal if the heavy oil transport process is carried out efficiently.•The relevance of the analysis is based on the fact that for several renewable and non-renewable energy systems, heat and mass transfer occur through viscous fluids highly sensitive to temperature. Conjugate thermal-hydrodynamic model (modified Graetz-Nusselt problem). [Display omitted]