一维和二维电热除冰相变传热特性的参数影响分析

基于飞机电热除冰过程冰层融化的特征,开展了一维和二维电热除冰相变传热特性数值计算研究和参数影响分析,重点考虑了加热模式、冷却时间、加热功率和加热单元间隔等参数对冰层相变传热的影响。采用了基于焓-多孔介质方法的热焓模型,将计算区域看作是包括多层材料和冰、水及其混合区的多孔介质,采用了结构化网格拓扑结构对计算区域进行划分,采用了有限体积方法对控制方程组进行离散,采用线性插值的方法获得混合区的物性参数,耦合能量方程和液态水体积分数公式,迭代求解了计算域的温度分布,获得了不同材料间界面温度的变化,重点分析了冰-保护层界面的温度变化。基于二维电热除冰模型的冰-保护层界面温度不均匀特征,提出了耦合考虑冰-保护层界面热点和冷点温度的冰脱落温度判断准则。研究表明:高功率的周期性加热模式要优于低功率的连续性加热模式,采用合理的冷却时间和加热功率,可获得更低的能量消耗和更好的除冰效果。合理设置加热单元间隔可以提高周期性的除冰效率,但也会形成冷点和热点,造成冰-保护层界面温度分布的不均匀。冰-保护层界面的冷点类似于锚点,即使此刻热点的冰已经融化,整个冰层也无法脱落和剥离。因此,冰脱落的判断要耦合考虑界面热点和冷点的温度特征。 

Analysis of parameteric influence on phase change heat transfer characteristics of 1-D and 2-D electrothermal deicing

Comparative analysis and numerical study on phase change heat transfer characteristics of one-dimensional (1-D) and two-dimensional (2-D) electrothermal deicing were presented. The effects of heating mode, cooling time, heater power and heater gap on phase change heat transfer characteristics were emphasized. The enthalpy model was applied due to the enthalpy-porous medium method. The computational domain was treated as a porous medium including multi-layer material, ice and water and mushy zone. The structured mesh topology was used to distribute the computational domain. The finite volume method was adopted to discretize the governing equations. The temperature was obtained by iteration of the energy equation coupled with the liquid volume fraction formula. The properties of the mushy zone can be obtained by linear interpolation. The interface temperature between different materials was obtained. The variation of interface temperature between ice and shield was emphasized. Due to the non-uniformity characteristics of ice-shield interface temperature of 2-D electrothermal deicing model, the temperature criterion to judge ice shedding coupled with hot point and cold point temperature of ice-shield interface was considered. It shows that periodic heating mode for high heater power is superior to continuous heating mode for low heater power. If reasonable combination of cooling time and heater power is adopted, better deicing performance and less energy consumption can be obtained. The reasonable distribution of heater gap can largely improve the deicing efficiency, but leading to the formation of hot point and cold point along ice-shield interface. It will make the ice-shield interface temperature uneven. The cold point at ice-shield interface is similar to stubborn anchor point, which will make the ice layer adhere to the shield surface firmly even if the ice at hot point melts completely. Therefore, the temperature characteristics of hot point and cold point at ice-shield interface for electrothermal deicer should be considered to judge the ice shedding from the shield surface.