某热稠油管道的水力特性分析

与一般热油管道相比,热稠油管道的流动特性主要有两个特点,一是在给定加热温度和管段压降条件下,该管段流量的试算过程可能陷入其特性曲线的不稳定区,该区域内管段的摩阻损失随流量增加而降低;二是稠油在管道中的流动可能位于层流和紊流的过渡区,通常用临界雷诺数2 000作为层流和紊流的分界点,而分别按层流和紊流公式确定的该点的摩阻系数有较大差别,因此对于某些加热温度和管段压降而言,可能不存在合适的流量与之对应。基于对某热稠油管道在不同加热温度、不同总传热系数和不同流量下的水力计算,得出了其一个站间管段的一组管路特性曲线,即摩阻损失和流量之间的关系曲线,以此可以确定其不稳定区的流量区间。认为从保障流动安全的角度出发,管道应该避免在流量不稳定区间工作。

The Hydraulic Characteristics of a Heated Heavy Crude Pipeline

The paper addresses the hydraulic characteristics of a heated heavy crude pipeline.It is worth notice that the pipeline does not behave like the usual hot oil pipelines in two ways.Firstly,under given heating temperature and pressure drop,the convergence of the trial-and-error process to solve the flow-rate of the pipeline segment would be likely damaged by an unstable flow-rate interval,in which the friction loss of a pipeline segment decreases with the increase of flow-rate,just contrary to usual oil pipelines.Secondly,the flow of heated heavy crude through the pipeline is probably in the critical regime between laminar flow and turbulent flow.Because of different friction factors of the critical Reynolds number 2000 used as the interface of these two regimes determined respectively from laminar flow and turbulent flow,it is possible that an exact flow-rate can not be found corresponding to the combination of heating temperature and pressure drop of the segment.For the pipe segment,based on its hydraulic calculations at different upstream oil temperatures,different heat transfer conditions between it and its surroundings,and different flow-rates,the curves of fiction loss versus flow-rate are plotted,from which the unstable flow-rate intervals may be determined.From the angle of safe operation,the unstable flow-rate interval should be avoided.