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首页> 外文期刊>Journal of Heat Transfer >Wall Heat Flux Partitioning During Subcooled Flow Boiling: Part 1—Model Development
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Wall Heat Flux Partitioning During Subcooled Flow Boiling: Part 1—Model Development

机译：过冷沸腾过程中壁热通量的分配：第1部分—模型开发

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摘要

In this work a mechanistic model has been developed for the wall heat flux partitioning during subcooled flow boiling. The premise of the proposed model is that the entire energy from the wall is first transferred to the superheated liquid layer adjacent to the wall. A fraction of this energy is then utilized for vapor generation, while the rest of the energy is utilized for sensible heating of the bulk liquid. The contribution of each of the mechanisms for transfer of heat to the liquid—forced convection and transient conduction, as well as the energy transport associated with vapor generation has been quantified in terms of nucleation site densities, bubble departure and lift-off diameters, bubble release frequency, flow parameters like velocity, inlet subcooling, wall superheat, and fluid and surface properties including system pressure. To support the model development, subcooled flow boiling experiments were conducted at pressures of 1.03-3.2 bar for a wide range of mass fluxes (124-926 kg/m~2s), heat fluxes (2.5-90W/cm~2) and for contact angles varying from 30° to 90°. The model developed shows that the transient conduction component can become the dominant mode of heat transfer at very high superheats and, hence, velocity does not have much effect at high superheats. This is particularly true when boiling approaches fully developed nucleate boiling. Also, the model developed allows prediction of the wall superheat as a function of the applied heat flux or axial distance along the flow direction.
机译：在这项工作中，为过冷流沸腾过程中壁热通量分配建立了一个机械模型。提出的模型的前提是，来自壁的全部能量首先被转移到与壁相邻的过热液体层。然后，该能量的一小部分被用于产生蒸气，而其余的能量被用于显着加热散装液体。通过成核点密度，气泡偏离和提离直径，气泡，可以量化将热量传递到液体的对流和瞬态传导以及与蒸汽产生相关的能量传输的每种机制的贡献。释放频率，流量参数（例如速度），入口过冷，壁过热，流体和表面特性（包括系统压力）。为了支持模型开发，在1.03-3.2 bar的压力下进行了过冷流沸腾实验，其质量流量范围（124-926 kg / m〜2s），热通量（2.5-90W / cm〜2）和接触角从30°到90°不等。所建立的模型表明，瞬态传导成分在非常高的过热度下可能成为热传递的主要方式，因此，在过热度很高的情况下速度没有太大影响。当沸腾接近完全发展的核沸腾时，尤其如此。此外，开发的模型还可以根据所施加的热通量或沿流动方向的轴向距离来预测壁过热。

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