制冷剂瞬态喷雾冷却表面传热特性

喷雾冷却在工业工程中应用广泛，其表面相变传热过程非常复杂，需要开展深入研究揭示其机理与规律。以R134a、R407C及R404A制冷剂为工质开展瞬态喷雾冷却表面相变传热特性实验研究，提出了表征冷却表面内部导热阻力与喷雾表面对流传热阻力之比的喷雾Biot数，以及表征瞬态喷雾冷却最大热通量及其出现时刻的量纲1 Reynolds数Re_l和Fourier数Fo_l。将Jakob数Ja与Re_l及液滴Weber数We关联，提出了最大热通量及其出现时刻的通用量纲1关联式。发现不同制冷剂的瞬态喷雾冷却过程具有相似性，得到了热通量随时间变化的量纲1关联式。利用上述关联式对喷雾表面瞬态温度进行模拟，结果与实验结果吻合较好，证明了关联式的准确性。

Surface heat transfer characteristics during transient cryogen spray cooling

Spray cooling is widely used in industry. Complicated surface heat transfer characteristics are needed to reveal the mechanism. In this work, the surface heat transfer experiments of cryogen spray cooling (CSC) with R134a, R407C and R404A were conducted. The spray Biot number was defined to represent the ratio between the internal thermal resistance of substrate and the resistance of surface convective heat transfer. Dimensionless Reynolds number Re_l and Fourier number Fo_l were proposed to represent the maximum heat flux and the corresponding time, respectively. By coupling Jakob number with Re_l number and droplet Weber number (We), dimensionless correlations of maximum heat flux and the corresponding time were constructed. The similarity of the transient spray cooling process with different cryogens was found and the dimensionless correlation of time-dependent heat flux was obtained. By using these correlations, the simulated transient surface temperature during cryogen spray cooling agreed well with the experiment data, which proved the accuracy of the correlations.