| As a new greening mode,living wall has attracted people ’ s attention in recent years due to its beautiful appearance and energy saving advantages in the construction of green ecological cities.The transpiration of plants and the evaporation of substrate surface will constantly change the water content of the substrate,thus changing the thermal performance of the substrate.Therefore,studying the correlation between the volumetric water content of the living wall substrate and its thermal performance is helpful to scientifically evaluate the comprehensive influence of the living wall on the thermal performance of the building.In this study,the influence of the change of water content in the vertical section of the living wall substrate on the thermal properties is an important content.The two methods of field investigation and measured experiment are adopted.Firstly,the basic composition of outdoor plant living wall in Wuhan is summarized through field investigation.The field test of plant living wall shows that water content is not evenly distributed on the whole wall surface,and shows a decreasing trend from top to bottom.The difference of water content is more than 21%.Secondly,the mathematical model of water content in vertical section was established based on the more accurate quantitative study of water content change pattern in vertical section through the measured experiment of plant living wall.At the same time,the effect of volume water content change on thermal properties was tested,and the mathematical model of plant living wall and volume water content was finally established by combining the water content in vertical section with thermal properties.The experimental results show that :(1)After the completion of drip irrigation,the overall water content of the substrate has obvious diurnal fluctuation with time.The decline of water content in the daytime is greater than that in the evening,and the decline of water content in the daytime is the largest at 14 : 00-18 : 00.Sorting by water holding capacity,formula soil > coconut shell peat soil > soft soil > garden soil > sawdust.There is a regularity in the vertical height of the matrix.The water content decreases with the increase of the height,and the matrix height is inversely proportional to the water content.(2)There is water gradient in the vertical section of five substrates.The water gradient of each substrate is related to the type of substrate,and has no obvious relationship with season.The order of water gradient is : formula soil > soft soil > coconut shell peat soil > garden soil > sawdust.(3)The thermal conductivity and specific heat capacity of the matrix increase with the increase of water content,and the increase is faster in the early stage and slower in the later stage and tends to be stable.The change of thermal diffusivity and moisture content of matrix is related to the type of matrix.Formula soil,coconut shell peat soil and soft soil all increase first and then decrease with moisture content.The thermal diffusivity of garden soil increases first and then remains stable and then decreases with moisture content.The thermal diffusivity of sawdust increases first and then remains stable with moisture content.The thermal resistance of the matrix decreases rapidly at first and then remains stable with the increase of water content. |
