Experimental Research On The Thermal Insulation Performance Of CLB Wall

Bamboo is a kind of green and ecological building material with light weight,high strength and unique advantage of carbon sequestration.Compared with other traditional building structures,bamboo structure is a natural and sustainable building.Therefore,this paper proposes a new type of bamboo structure based on cross-laminated bamboo boards.Cross-Laminated Bamboo（CLB）is formed by the interlacing of parallel and transverse bamboo plates.In this paper,the thermal insulation performance of CLB wall is explored by the combination of experimental research,theoretical analysis and computer simulation.The main research contents are as follows:（1）The thermal conductivity of the recombinant bamboo and expanded polystyrene（EPS）insulation materials were measured by the guarded hot plate apparatus.λ_bamboo=0.263W/（m·K）,λ_EPS=0.040 W/（m·K）.The thermal conductivity results provide data support for the experimental research and finite element simulation analysis in the following chapters.Compared with commonly building materials,the thermal conductivity of bamboo is smaller and its thermal insulation performance is excellent.（2）The influence of different thickness,laminates and compositions on the steady-state thermal insulation performance of CLB walls were investigated and measured using the hot box-heat flow meter method.The results show that the heat transfer coefficient of CLB wall decreases with the increase of the wall thickness.The effect of external thermal insulation on the heat transfer performance of the CLB composite wall is significant.Adding 30mm EPS board can reduce the heat transfer coefficient of the CLB wall by 48.2%⁵3.9%.The theoretical value of the heat transfer coefficient agrees well with the experimental value of CLB wall.The CLB specimens can be widely used in various thermal zones in China,which can provide references for the energy-saving design of bamboo structures.（3）The error between finite element simulation results and experimental values is less than 5%,and the variation trend of the heat flux density and temperature is consistent with the experimental results.Therefore,ABAQUS can accurately simulate the heat transfer process of the CLB wall.Considering the changes of solar radiation and air temperature,this paper gives the calculation formula of outdoor comprehensive temperature,which can be used as a reference for the unsteady analysis of building structures.The results of finite element method show that compared with steel-concrete wall,the temperature variation of CLB wall is smaller,the indoor thermal environment is more stable,and the thermal insulation performance is superior.The most reasonable position of the insulation layer is on the outside of the wall.The external insulation of the wall can significantly reduce the heat flow into or out of the wall,effectively reduce the impact of external temperature fluctuation on the load-bearing layer of the wall,which is more conducive to the durability of the building wall.（4）The influence of different walls on the annual cooling and heating loads of buildings are investigated and measured by the building energy simulation software,DeST-h.According to the results,under the same thickness of the building walls,the CLB structure can economize energy consumption by 18.7%compared with steel-concrete structure and13.5%compared with brick-concrete structure.The annual cooling and heating load of the building decreases with the increase of the thickness of CLB wall and EPS insulation layer.But the downward trend is more and more gentle,that is to say,the contribution of EPS insulation layer to the reduction of building energy consumption is getting smaller and smaller.