冷风侵入对候车厅地板辐射采暖的影响研究

Application of Radiant Floor Heating in Large Space Buildings with Significant Air Infiltration through Door Openings

地板辐射采暖以其舒适性高,节能环保的特点而在中小型高铁站中广泛采用,成为候车厅冬季主要的采暖方式。地面温度对维持室内热环境至关重要,而地板采暖的辐射换热比例直接决定房间的表面温度,继而决定室内的舒适度情况。对寒冷地区5个中小型高铁站进行调研,总结了候车厅的主要类型及其地面温度的分布规律,证实了冷风侵入的不利影响。之后利用实测验证的CFD模型,对不同冷风侵入速度下辐射地板的辐射换热比例进行了量化分析。最终基于CFD模拟的结果,分析了冷风侵入下地板表面对流换热系数的变化,并与ASHRAE手册推荐的自然对流换热系数计算公式及文献中引用较多的机械通风条件下混合对流换热系数计算公式得到的结果进行对比,说明了冷风影响下,地板表面复合换热特性的变化。最终结果表明,当入口处风速从0.05 m/s增大至0.9 m/s时,辐射地板的辐射换热比例将从67%下降到39%,低于辐射采暖地板规定的最小辐射换热比例;而受冷风侵入和地板表面温度、室内温度的共同作用,辐射地板表面的对流换热系数将随入口处风速的增大而增大,当风速从0.05 m/s增大至0.5m/s时,对流换热系数从3.1 W/(m^2·K)增大至3.5 W/(m^2·K),当风速大于0.5 m/s后,对流换热系数有所减小并趋于常值(3.4 W/(m^2·K))。这一结果说明,现行计算方法中将地板表面边界条件中的对流换热系数及当量辐射换热系数取为定值的做法并不可取,有必要对冷风侵入条件下辐射地板表面传热特性的变化慎重考虑。为设计阶段量化冷风影响,合理确定供暖系统设计参数提供了参考和依据。

Radiant floor heating system(RFHS)has proved to be suitable for environmental control in large space buildings with glass facades.However,the uneven thermal distribution and extremely cold area of the heating floor,caused by cold air infiltration through door openings,is commonly found in our filed measurements cold regions of China.The impact of air infiltration on heat-transfer process at the radiant surface is investigated.CFD simulation is employed and validated against field measurements.The results verifies the significant negative effect of increased air infiltration on RFHS.As a result,regression models are derived for rough estimation of the radiant heat flux under a certain infiltration air speed,which can also be used as a preliminary reference for current design method.