Description And Analysis Of Thermodynamics Exergy Flow In Oil Pipeline Transportation System

This paper was financially supported by National Natural Science Foundation of China (No.51106020, No.51174042, No.51051002), PetroChina Innovation Foundation (2012D-5006-0610) and Youth Scholar Backbone Supporting Plan Project of Heilongjiang General Colleges and Universities (1252G005).With the development of the technology in crude oil pipeline, pipeline transportation has become the most important mode because of its outstanding advantages such as large throughput, high safety, and so on. However, the crude oil produced in our country is high waxy crude, needing the heating transportation, which makes the continuous operation pipeline to be high energy consumption unit. Thus, the improvement of energy efficiency, energy conservation and emission reduction have become one of the most important issues in crude oil pipeline.Firstly, from the point of thermodynamics first and second law, the origin of the exergy concept, exergy value calculation and the characteristics of exergy analysis are reviewed and concluded. Then, according to the purposes and characteristics of pipeline transportation technology, the exergy equilibrium model of transportation for hot oil is built and the exergy flow is then classified. The expressions of valid and invalid pressure exergy consumption, valid and invalid heat exergy consumption are respectively derived and the variation rules of valid pressure exergy consumption and diameter, throughput and insulation thickness are discussed with the related theories of heat transfer and fluid mechanics. And based on existing energy efficiency evaluation index system in crude oil pipeline transportation process, the exergy consumption evaluation index for pipeline transportation, which mainly focuses on exergy consumption for unit oil turnover, is proposed as well. The exergy consumption analysis for an oil pipeline of Daqing Oilfield shows that theory temperature range in economic operation is50.4～51.71℃, of which the total valid exergy consumption for unit oil turnover is minimum. At last, on the foundation of exergoeconomic theories and methods, exergoeconomic theoretical model is established based on exergy consumption index. The relationship curves between exergy consumption index and parameters including diameter, throughput and insulation thickness are obtained respectively.