含蜡原油管道输送过程的熵产率分析

Entropy Generation Rate Analysis for Pipeline Transportation of Waxy Crude Oil

原油管道输送是同时存在扩散、传热和流动等多种不可逆现象的复杂过程。本文在已有普适性熵产率方程的基础上,推导了传热与黏滞两种不可逆现象耦合作用的"力"和"流",给出了含蜡原油管输过程的熵产率计算方法。对大庆油田某输油管道的应用分析表明,传热熵产率远大于黏滞熵产率;输油温度升高、管径减小,流量增大,均会使得传热熵产率变大;蜡沉积由于增加保温层有效厚度及减小流动原油密度,可大幅度降低传热熵产率。

Crude oil transportation is a complex process in which several kinds of irreversible phenomena such as diffusion, heat transfer and fluid flow coexist. This article draws from existing universal equation of entropy generation rate and derives the ＂force＂ and ＂flow＂ of two coupling irreversible phenomena, namely heat transfer and viscosity, and then the method to calculate entropy generation rate in the pipeline of waxy crude oil is also given in this article. The application analysis for certain oil transmission pipeline of Daqing Oilfield shows that entropy generation rate in heat transfer process is much higher than viscous entropy generation rate. Whereas, the rise of temperature, the decrease of pipe diameter and the increase of flux can all enlarge the entropy generation rate in heat transfer process. Wax deposition can significantly reduce entropy generation rate in heat transfer progress, for efficient thickness of insulation increases and the density of flowing oil decreases during deposition.