长距离地上输油管道保温层厚度设计

Design of insulation thickness for long-distance-ground oil pipeline

科学设计管道保温层厚度,既能保障原油正常输送,也能做到成本有效控制。建立了长距离地上管道保温层设计的传热有限元模型,考虑了管道及保温层内外膜阻、外部空气对流换热及管道与保温层传热的综合作用。以管道出口温度为目标迭代求解管道保温层的最小厚度,讨论了保温层导热系数、管径和管道流量3个因素对保温层厚度的影响。结果表明,原油内摩擦产生的热量能够小幅提高原油输送温度;保温层导热系数的增加主要影响管道的热传导性能;管径的增加则加强了对流散热而降低了流体内摩擦做功产热,对隔热层设计影响较大;而输送流量增加则减少原油与管壁的传热时间,流速增加也增加了流体内摩擦做功产热,可以有效降低保温层厚度需求。在工程实践中,应综合考量保温层导热系数、管径和管道流量的设计,平衡三者与热传导和热对流之间的关系。

The scientifically designed insulation layer thickness of the pipeline can not only guarantee the normal transportation of crude oil,but also effectively control the cost.In this paper,a finite element model of heat transfer for long-distance-groundpipeline insulation layer was established,and the comprehensive effects of the internal and external film resistance of pipeline and insulation layer,the external air convection heat transfer and the conduction between pipeline and insulation layer were considered.The minimum thickness of pipeline insulation layer was solved iteratively with the outlettemperature of pipeline as the target.The influences of the thermal conductivity of insulation layer,the inner diameter of pipeline and the flow rate of pipeline on the thickness of insulation layer were discussed.The results show that the heat generated by the internal friction of crude oil can slightly increase the temperature of crude oil transportation;the increase of thermal conductivity of insulation layer mainly affects the thermal conductivity of the pipeline.With theincrease of pipe diameter,the convective heat dissipation is enhanced,and the heat production by internal friction of the fluid is reduced,which has a great influence on the design of heat insulation layer.Meanwhile,the increase of the flow rate shortens the heat transfer time between the crude oil and the pipe wall,and the increase of flow velocity also increases the heat generation caused by the internal friction of the fluid,which can effectively reduce the requirement of insulation thickness.