油页岩地下原位转化螺旋折流板式井下加热器表面传热特性及数值传热模拟研究

Research on Heat Transfer Characteristics and Numerical Simulation of Oil Shale In-situ Pyrolysis Heater with Spiral Baffle

摘要:

油页岩地下原位转化技术的关键是要把油页岩加热至高温裂解状态，采用井中直接加热的方式可实现对油页岩地层的直接加热，能量利用率最高，热损失最小，已经成为油页岩原位转化的主要加热方式。本文研究了一种新型的井下螺旋折流板式加热器，其传热通道呈螺旋形连续分布，能有效地增加气体和加热管的接触时间，可显著提高加热管表面的传热系数。本文重点研究螺旋折流板式井中加热器的表面传热特性，通过数值模拟及理论推导，综合分析了螺旋折流板的螺距和气体的质量流量对加热管表面传热系数的影响规律，得出了折流板螺距越小或气体质量流量越大加热管表面传热系数越高的结论，并求出了加热管表面传热系数随螺距和气体质量流量变化的拟合方程，为螺旋折流板加热器的后续设计提供了理论支撑。

关键词:油页岩;原位开采;螺旋折流板;数值模拟;传热系数;折流板螺距;气体质量流量

Abstract:

The ultimate aim of the oil shale in-situ pyrolysis technology is to heat the oil shale to the state of pyrolysis. Direct heating, which can be realized by heating in the well to achieve the highest energy utilization rate with the smallest heat loss, has become the main heating way of the in-situ pyrolysis. In this paper, a new type of downhole heater with spiral baffle is developed, and due to the spiral continuos distribution, the contact time of gas and heating rod can be effectively prolonged to remarkably increase the heat transfer coefficient of heat rod surface. This paper also focuses on surface heat transfer characteristics of the in-situ pyrolysis heater with spiral baffle. Through the numerical simulation and theorecical deduction, the effects of the spiral baffle’s pitch and the gas mass flow on the heat transfer coefficient of the heating rod surface is analyzed, it is concluded that the smaller the pitch of the baffle or the larger the gas mass flow the higher the heat transfer coefficient of the heating rod; in the meanwhile, the fitting equations for heat transfer coefficient of heating rod surface changing with the pitch and gas mass flow are obtained to provide the theoretical support for the following-up design of the heater with spiral baffle.

Key words:oil shale; in-situ pyrolysis; spiral baffle; numerical simulation; heat transfer coefficient; spiral baffle’s pitch; gas mass flow