CFD Study on Flow and Heat Transfer Characteristics of Counter-flow Straight Channel Printed Circuit Plate Heat Exchanger
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摘要: 印刷电路板式换热器（PCHE）凭借高紧凑性、耐高温高压、高换热效率等优势，在高温气冷堆氦气闭式布雷顿循环中具有较好的应用前景。本文利用计算流体力学（CFD）数值模拟研究了逆流式直通道PCHE型氦气回热器的流动与换热性能。通过改变通道水平间距、垂直间距以及流道半径，分析了层流条件下，几何参数对直通道PCHE内氦气流动换热的影响。计算结果表明，垂直间距仅对换热性能有影响，水平间距无明显影响，流道半径对PCHE流动换热性能均有影响。减小通道垂直间距，PCHE的换热性能提高；保持入口质量流量不变时，缩小通道半径，对流换热系数提高，换热性能增强，但沿程压降增大。此外，使用垂直或水平方向多通道PCHE模型进行模拟，通过比较不同通道的沿程温度和压降分布，以确定垂直和水平位置对PCHE热工水力性能的影响。通过对比多通道模型与单个换热单元的计算结果，表明周期性边界条件的单个换热单元能够较为准确模拟完整PCHE模型的大多数流道。Abstract: Printed circuit heat exchangers (PCHEs) have a good application prospect in the Helium closed Brayton cycle of high temperature gas cooled reactor because of its high compactness, high temperature and high pressure resistance and high heat transfer efficiency. In this paper, the flow and heat transfer performance of counter-flow straight channel PCHE helium regenerator is studied by using computational fluid dynamics (CFD) numerical simulation. The effect of geometric parameters on helium flow and heat transfer in straight channel PCHE is analyzed by changing the channel horizontal spacing, vertical spacing and flow channel radius. The calculation results show that the vertical spacing only has an effect on the heat transfer performance, while the horizontal spacing has no obvious effect, and the flow channel radius has an effect on the flow and heat transfer performance of PCHE. The heat transfer performance of PCHE is improved by reducing the channel vertical spacing; When the inlet mass flow rate is kept constant, if the channel radius is reduced, the convective heat transfer coefficient and heat transfer performance are enhanced, but the pressure drop along the channel increases. In addition, the vertical or horizontal multi-channel PCHE model is used to compare the temperature and pressure drop distribution along different channels to determine the effect of vertical and horizontal positions on the thermal and hydraulic performance of PCHE. By comparing the calculation results of the multi-channel model with that of a single heat exchange unit, it is shown that a single heat exchange unit with periodic boundary conditions can more accurately simulate most of the flow channels of the complete PCHE model.
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图 2 总传热系数随入口质量流量增加的变化
Figure 2. Variation of Total Heat Transfer Coefficient with the Increase of Inlet Mass Flow Rate
图 3 总传热系数随垂直间距的变化
Figure 3. Variation of Total Heat Transfer Coefficient with Vertical Interval
图 4 冷、热通道进出口压降随垂直间距的变化
Figure 4. Variation of Inlet and Outlet Pressure Drop of Cold and Hot Channels with Vertical Spacing
图 5 总传热系数随水平间距的变化
Figure 5. Variation of Total Heat Transfer Coefficient with Horizontal Spacing
图 6 冷通道进出口压降随水平间距的变化
Figure 6. Variation of Inlet and Outlet Pressure Drop of Cold Channels with Horizontal Spacing
图 7 冷通道对流换热系数随流道半径的变化
Figure 7. Variation of Convective Heat Transfer Coefficient with Flow Channel Radius in Cold Channel
图 8 冷通道进出口压降随流道半径的变化
Figure 8. Variation of Inlet and Outlet Pressure Drop of Cold Channel with Flow Channel Radius
图 9 水平多通道物理模型及边界条件示意图
Figure 9. Schematic Diagram of Horizontal Multi-Channel Physical Model and Boundary Conditions
图 10 不同水平位置冷通道的沿程氦气平均温度分布
Figure 10. Average Temperature Distribution of Helium Along the Cold Channel at Different Horizontal Positions
图 11 单换热单元与水平第5层换热单元的比较
Figure 11. Comparison between Single Heat Exchange Unit and Horizontal 5th Layer Heat Exchange Unit
图 12 垂直多通道物理模型及边界条件示意图
Figure 12. Schematic Diagram of Vertical Multi-Channel Physical Model and Boundary Conditions
图 13 不同垂直位置冷通道的沿程氦气平均温度分布
Figure 13. Average Temperature Distribution of Helium Along the Cold Channel at Different Vertical Positions
图 14 单换热单元与垂直第5层换热单元的沿程温度分布
Figure 14. Temperature Distribution Along a Single Heat Exchange Unit and a Vertical 5th Layer Heat Exchange Unit
图 15 垂直多层通道模型与单换热单元的冷、热通道氦气出口温度
Figure 15. Outlet Temperature of Helium in Cold and Hot Channels of Single Heat Exchange Unit and Vertical Multilayer Channel Model
图 16 垂直多层通道模型与单换热单元的冷、热通道进出口压降
Figure 16. Pressure Drop at Inlet and Outlet at Cold and Hot Channels of Single Heat Exchange Unit and Vertical Multilayer Channel Model
表 1 单个换热单元模型与上下不对称模型的比较
Table 1. Comparison between Single Heat Exchange Unit Model and Upper and Lower Asymmetric Model
参数 参数值 单个换热单元 非对称型模型 对称型模型 $ {\bar{T}}_{\mathrm{c},\mathrm{o}\mathrm{u}\mathrm{t}}/\mathrm{K} $ 1040.740 1038.674 1028.183 $ {\bar{T}}_{\mathrm{h},\mathrm{o}\mathrm{u}\mathrm{t}}/\mathrm{K} $ 945.264 947.336 936.313 $ \mathrm{\Delta }{P}_{\mathrm{c}}/\mathrm{P}\mathrm{a} $ 11390.800 11362.760 11156.536 $ \mathrm{\Delta }{P}_{\mathrm{h}}/\mathrm{P}\mathrm{a} $ 11498.300 11529.580 11298.840 
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