Abstract:

The air source heat pump (ASHP) system has excellent energy saving and emission reduction effects. However, under environmental conditions of low temperature and high humidity in winter, frost will occur on the surface of the evaporator easily, which affects the heat transfer performance and reliability of the system. The experimental study of frost growth characteristics on the surface of the finned-tube heat exchangers was carried out in this paper. The frost surface temperature was measured by the infrared thermal imager, and calibrated by using the direct measurement with micrometer and thermocouple device. The effects of the ambient temperature, relative humidity and face velocity on the frost thickness, frost mass and the frost-wet air interface conditions are analyzed. The difference between the frost surface temperature and the ambient temperature is regarded as the heat transfer driving force of frosting, and the difference between the water vapor partial pressure in wet air and the saturated water vapor partial pressure at the interface, i.e., the interface water vapor pressure difference, is regarded as the mass transfer driving force of frosting. The frosting mechanism of the finned-tube heat exchangers is analyzed, which lay a foundation for the optimum design and anti-frosting and defrosting of ASHP system.

摘要：

空气源热泵系统节能减排效果显著，但在低温高湿的冬季制热工况下，室外蒸发器表面会发生结霜现象，霜层会直接影响换热性能，进而影响系统运行的可靠性及能效。对翅片管换热器霜层生长特性进行了实验研究，实验中采用红外热成像仪对霜层表面温度进行测量，并用千分尺热电偶直接测量装置进行校核。分析了环境温度、相对湿度及迎面风速对结霜厚度、结霜量、霜层-湿空气界面条件的影响，并将霜层表面温度与环境温度之差作为结霜的传热驱动力，将湿空气中水蒸气分压力与霜表面温度下饱和水蒸气分压力之差作为结霜的传质驱动力，对结霜机理进行了分析，为换热器的防结霜和除霜提供了依据，为优化空气源热泵系统的设计奠定了基础。