紧凑式强预冷换热器叉排管束的大涡模拟

Large eddy simulation on the staggered tube bundle of the compact precooler

采用大涡模拟方法对紧凑式强预冷换热器叉排管束的对流换热问题进行了研究,并运用动力模态分解(DMD)方法对流场的拟序结构及换热统计特性进行了分析。结果表明:在计算工况内(Re≤6 000),前排管束的流动结构为有规律的剪切层运动和尾涡脱落。后排管束的流动结构为无规律的小尺度旋涡结构,同时其流场表现出无序性;前排管表面瞬时努塞尔数具有较为固定的波动频率,而后排管壁由于受到前排圆管脱落旋涡的无规律撞击,其管壁瞬时Nu无固定波动频率;在Re=2 600的工况下,管束内的熵产主要来源于换热而非耗散,主要流动结构对耗散熵产和换热熵产的贡献在管壁边界层和自由剪切层位置,其对前排管的熵产有较大贡献,而对后排管熵产的贡献较小。

The large-eddy simulation was carried out to research convective heat transfer in the staggered tube bundle of the compact precooler. Besides, the dynamic mode decomposition(DMD) method was used to analyze the coherent structure and statistical characteristic of heat transfer of cross-row tube bundles. Results showed that within the simulated operating range(Re≤6 000), the flow structure of the front tube bundle exhibited regular shear layer movement and wake vortex shedding. The flow structure of the rear tube bundle was an irregular small-scale vortex structure, and the disorderly flow field of the rear tube bundle was presented. The instantaneous Nusselt number on the surface of the front rows had a relatively fixed wave frequency, while the instantaneous Nu on the back rows had no fixed wave frequency because of the irregular impact of the falling vortex of the front rows. Under the condition of Re=2 600, the entropy production in the bundle mainly came from heat transfer rather than dissipation. The main flow structure contributed to the dissipative entropy production and heat transfer entropy production in the location of the boundary layer and free shear layer on the tube wall. It contributed greatly to the entropy production in the front row tubes, but less to the entropy production in the back row tubes.