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首页> 外文期刊>Multiphase science and technology >HEAT TRANSFER AND FLOW CHARACTERISTICS OF A NON-UNIFORMLY HEATED TUBE UNDER LOWPRESSURE AND LOW MASS FLUX CONDITION
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HEAT TRANSFER AND FLOW CHARACTERISTICS OF A NON-UNIFORMLY HEATED TUBE UNDER LOWPRESSURE AND LOW MASS FLUX CONDITION

机译：低压低通量条件下非均匀加热管的传热和流动特性

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摘要

In an actual boiling channel, the circumferential heat flux is not uniform. Thus, the understanding of the heat transfer characteristics of non-uniformly heated tube becomes an important design factor for conventional boilers, especially for the compact water-tube boiler with tube-nested combustor. The small compact boiler is operated at low-pressure and low-mass flux condition compared with the large scale boiler, so that the non-uniformity in heat flux may strongly affect the heat transfer characteristics. In this investigation, non-uniform heat flux distribution along the circumferential direction was generated by using Joule heating of SUS304 eccentric tubes. The heated length of test-section was 900mm, inner diameter was 20mm, and outer diameter was 24mm. The eccentricity of the tube was s=0, 0.5, 1.0 and 1.5mm. Corresponding maximum/minimum heat fluxes rations were 1.0, 1.7, 3.0 and 7.0, respectively. Experiments were conducted for upward and downward flows, with system pressures 0.3 and 0.4MPa, mass flux range 10-100kg/m~2s and inlet temperatures 30 and 80deg.C. The eccentricity resulted in an increase in the CHF of the upward flow, while the effect was hardly observed in the downward flow. The effect of eccentricity on the CHF was well interpreted by the liquid film redistribution. In this paper, the local heat transfer coefficient along the circumferential direction was also presented.
机译：在实际的沸腾通道中，周向热通量不均匀。因此，对不均匀加热管的传热特性的了解成为常规锅炉的重要设计因素，特别是对于带有管式嵌套燃烧器的紧凑型水管锅炉。与大型锅炉相比，小型紧凑型锅炉在低压和低质量流量的条件下运行，因此热通量的不均匀会严重影响传热特性。在这项研究中，通过使用SUS304偏心管的焦耳加热产生了沿周向的不均匀热通量分布。试验部的加热长度为900mm，内径为20mm，外径为24mm。管的偏心率是s ＝ 0、0.5、1.0和1.5mm。相应的最大/最小热通量比分别为1.0、1.7、3.0和7.0。进行了向上和向下流动的实验，系统压力为0.3和0.4MPa，质量通量范围为10-100kg / m〜2s，入口温度为30和80℃。偏心导致向上流动的CHF增加，而在向下流动中几乎没有观察到这种作用。液膜的重新分布很好地解释了偏心距对CHF的影响。本文还介绍了沿圆周方向的局部传热系数。

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