6 - Bundled Pipelines: Coupled Annular Velocity and Temperature

Abstract

This chapter describes the coupled annular velocity and temperature in bundled pipelines. Fluid flows axially out of the page within the large circle below, with the small circle defining a region of space held at a much higher temperature. The dark rectangular region surrounding both circles represents the much colder ocean, which for all practical purposes, is infinite in extent. All three momentum equations must be considered together with the complete mass continuity equation and since viscosity is temperature dependent, there is further coupling with the energy equation. It is observed that if one assumes that the pipeline is flowing under a fixed pressure gradient, that is, acting through reservoir pressure alone, it is clear that under isothermal conditions, the volume flow rate for the annulus in general increases with increasing eccentricity. Centralization of the heating pipe suggests fewer throughputs in the sense that there is less eccentricity. It is found that that the economic optimization problem is very nonlinear, and must include the coupled velocity and thermal simulator as an essential element. The modeling focuses on computational methods for eccentric annular domains.