Recently, microchannel heat exchangers (MCHX) have been widely used in heat pump systems due to their high surface-to-volume ratio and high efficiency of heat transfer. However, when the MCHX operates in frosting conditions, its performance is adversely affected. To study the frost formation and distribution characteristics of MCHX, a comprehensive parametric study was performed for the MCHX with a larger fin pitch. The effects of fin geometries and environmental parameters on the frosting characteristics of MCHX were studied. Fin height () can effectively inhibit frost formation, which is due to the increase of surface temperature with the increase of . When increased from 6.0 mm to 11.8 mm, the frost time increased by 30.5 %. However, the increase in also brings the penalty of reduced heat transfer rate. The effect of fin depth () on frost formation performance is small because the frost is mainly deposited in the front part, resulting in the rear fin cannot work efficiently. Fin pitch () is the most significant structural parameter affecting frosting performance. When increases from 1.6 mm to 4 mm, the frosting time increases by 4 times and frost mass increased by 2.2 times. This is because with the increase of , the frost blocking in the front part can be effectively delayed, and the distribution uniformity of the frost layer is improved. Lower surface temperature and higher humidity ratio significantly promote frost formation and reduce the uniformity of frost distribution. When the inlet temperature is reduced from −5 °C to −8 °C, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 55.7 %. When the relative humidity increases from 76 % to 92 %, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 42.5 %. The air velocity has a minor impact on the growth rate of frost in the front part. However, as the air velocity increases, the uniformity of frost distribution is significantly improved. When the air velocity increased from 1.1 m s to 2.2 m s, the mass of accumulated frost increased by 29.5 %. Furthermore, frost thickness and air-side heat transfer coefficient correlations were developed by testing 12 samples. The developed heat transfer coefficient correlation can accurately capture the changing trend of the -factor. This study provides a fundamental understanding of the frosting characteristics of MCHX and can effectively guide the louvered fin optimization.

中文翻译：

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微通道换热器的结霜特性：参数研究和相关性开发


近年来，微通道换热器（MCHX）由于其高表面积体积比和高传热效率而被广泛应用于热泵系统。然而，当 MCHX 在结霜条件下运行时，其性能会受到不利影响。为了研究MCHX的结霜和分布特征，对较大翅片间距的MCHX进行了综合参数研究。研究了翅片几何形状和环境参数对 MCHX 结霜特性的影响。翅片高度()能有效抑制霜的形成，这是由于表面温度随着 的增加而增加。当从 6.0 毫米增加到 11.8 毫米时，结霜时间增加了 30.5%。然而，增加也带来了传热率降低的代价。翅片深度()对结霜性能的影响较小，因为霜主要沉积在前部，导致后翅片无法有效工作。翅片节距()是影响结霜性能最显着的结构参数。当从1.6毫米增加到4毫米时，结霜时间增加4倍，霜质量增加2.2倍。这是因为，随着 的增大，可以有效延缓前部霜的堵塞，提高霜层分布的均匀性。较低的地表温度和较高的湿度比显着促进霜的形成并降低霜分布的均匀性。当入口温度从-5℃降低到-8℃时，结霜时间缩短2.15倍，霜量减少55.7%。当相对湿度从76%增加到92%时，结霜时间缩短2.15倍，霜质量减少42.5%。 风速对前部霜的生长速度影响较小。但随着风速的增加，霜分布的均匀性显着提高。当风速从1.1米/秒增加到2.2米/秒时，积霜质量增加了29.5%。此外，通过测试 12 个样品，得出了霜厚度和空气侧传热系数的相关性。开发的传热系数相关式可以准确捕捉因子的变化趋势。这项研究提供了对MCHX结霜特性的基本了解，可以有效指导百叶窗式翅片的优化。