湿空气对开放块石层湿热特性影响的试验研究

Model experimental study on the influence of moist air on the hydrothermalproperties of open crushed rock layers

青藏高原暖湿化趋势日益加剧,空气中的水汽质量分数随季节变化差异较大致使空气物性参数、焓值等产生变化,可能会间接影响块石路基的换热过程。本文基于模型试验及空气热力学理论,对等压条件下干、湿空气中块石层内湿热特性进行了分析。结果表明:在等压条件下干、湿空气温差与水汽质量分数呈正相关关系,且水汽质量分数变化速率低于温差变化速率8%。基于地表能量平衡方法计算了考虑水汽影响的块石表层感热通量,发现两种空气条件下的感热通量差值与水汽质量分数也呈正相关关系,此时水汽质量分数变化速率高于感热通量差值变化速率9.8%。日出后干、湿空气与深层块石的对流换热差值主要受空气相对湿度控制,日落后由于干、湿空气温差较大则受空气温差影响。水汽质量分数较低时,干、湿空气焓值差变化速率高于水汽质量分数变化率约87%,焓值差变化率高于水汽质量分数变化率约21%,该现象随着水汽质量分数下降而愈加明显。研究结果对于评价和预测湿空气条件下块石结构路基的长期热稳定性具有重要工程意义。

Warming and humidification trend of the Qinghai-Xizang Plateau is becoming increasingly severe,and the water vapor mass fraction in the air seasonally varies,resulting in changes in air physical parameters,enthalpy values,etc.,which may indirectly affect the heat transfer process of the crushed rock structural em-bankment.This paper analyzes the hydrothermal characteristics inside the crushed rock layer in dry and wet air under the same pressure conditions based on model experiments and air thermodynamics theory.The results indi-cate that under isobaric conditions,the temperature difference between dry and moist air is positively correlated with water vapor mass fraction,and the changing rate in water vapor mass fraction is 8%lower than the varying rate of temperature difference.The surface sensible heat flux of crushed rock considering the thermal influence of vapor was calculated based on the surface energy balance method,and it was found that the difference in sensi-ble heat flux under the two air conditions is also positively correlated with water vapor mass fraction.At this time,the changing rate of water vapor mass fraction is 9.8%higher than the varying rate of sensible heat flux difference.After sunrise,the convective heat transfer difference between dry and moist air and the deep-layer rock mainly depends on the relative humidity of the air.After sunset,due to the large temperature difference be-tween dry and moist air,it is mainly influenced by the temperature difference.When the water vapor mass frac-tion is at a low level,the changing rate in enthalpy difference between dry and moist air is about 87%higher than the changing rate in water vapor mass fraction,and the changing rate in enthalpy difference is about 21%higher than the rate of change in water vapor mass fraction.This phenomenon becomes more pronounced as the water vapor mass fraction decreases.The research results are of great significance for evaluating and predicting the long-term thermal stability of crushed rock structural embankment considering humid air conditions in permafrost regions.