冷热原油顺序输送过程的热力分析

建立冷热原油顺序输送过程的数学模型,将该过程中的水力系统视为准稳态,考察非稳态的热力系统。采用有限差分法求解热力特征方程从而求得管内非稳态的油流温度,用有限元法与有限差分法求解导热方程从而求得管外非稳态温度场。模拟冷热原油顺序输送过程并对模拟结果进行分析。结果表明:对周期性的冷热油顺序输送,其热力表现也呈周期性;一个输送周期中,两种油品相互取代过程的热力表现相反;交替输送冷热原油时,热油头首次到达下站进站口时的温度是该输送方式的安全临界温度,须保证其高于热油的凝点。

Thermal analysis on batch pipelining of cold and hot crude oilwith different temperatures

A mathematical model describing batch pipelining of cold and hot crude oil was developed. The hydraulic system was simplified as quasi steady and the unsteady thermodynamic system was studied. The thermal characteristic equation was solved to obtain the non-steady-state oil flow temperature in the tube by finite difference method. The thermal conductivity equation was solved to obtain the pipe outside non-steady-state temperature field using finite element method and finite difference method. A typical operation case was simulated by the computer program and the simulation results were analyzed. The simulation results indicate that when periodic transportation is formed, the thermal behaviors are nearly periodic. For each period, generally inverse behaviors are shown between the process of cold batch displacing hot batch and the process of hot batch displacing cold batch. In batch pipelining of cold and hot crude oil, when head of the hot batch just reaches the next station, its temperature comes to its lowest point, which is the critical temperature for safe transportation. This temperature should be at least above the oil ''s pour point for safety operation.