Interior thermal insulation has been widely used to improve energy efficiency and indoor comfort of historic buildings.However,traditional vapour-tight insulation materials strongly influence the hygrothermal behaviou...Interior thermal insulation has been widely used to improve energy efficiency and indoor comfort of historic buildings.However,traditional vapour-tight insulation materials strongly influence the hygrothermal behaviour of facades,which may lead to moisture-related problems.Capillary-active insulation aims to enhance moisture permeance,ensuring the hygrothermal response of the masonry wall is more aligned with that of an uninsulated wall.While some capillary-active systems have proven their efficiency,global climate change and extreme weather conditions introduce additional uncertainties.This study investigates this specific issue.The hygrothermal responses of three massive masonry walls—one with vapour-tight insulation,one with capillary-active insulation,and one uninsulated—are monitored and simulated under real climate conditions in Leuven,Belgium.The simulations,conducted in DELPHIN 6 with monitored climate datasets as boundary conditions,are validated using measured temperature and relative humidity.The validated model is subsequently used with one current and two future climate datasets to compare the impacts of vapour-tight and capillary-active insulation on the hygrothermal behaviours of the masonry walls under climate change.The former exhibited more serious moisture-related risks,offering only marginally better energy performance,while the latter showed a similar hygrothermal behaviour to the uninsulated wall.Exterior climates significantly influence hygrothermal responses:both insulation systems inevitably increase mould growth and frost damage risks,though moisture failures are reduced in warmer outdoor environments.This paper highlights the nuanced balance between energy efficiency and moisture safety for researchers and practitioners.展开更多
This study investigates the ablation of internal insulation induced by the deposition of an alumina film with different lateral film speeds.A sub-scale test solid rocket motor(SRM)was designed in an impinging jet conf...This study investigates the ablation of internal insulation induced by the deposition of an alumina film with different lateral film speeds.A sub-scale test solid rocket motor(SRM)was designed in an impinging jet configuration to form an alumina film on the sample and to encourage the lateral movement of the film by a high-speed wall jet.Fifteen static fire tests of the test SRM were conducted with six different jet velocities(V_(jet)=100 m/s,150 m/s,200 m/s,268 m/s,330 m/s,and 450 m/s)that indirectly affected the velocity of the wall jet and the deposition rate of alumina droplets.The ablation velocity was deduced from the difference in the sample thickness after a test using a coordinate measuring machine.The droplet deposition mass flux and wall jet velocity were obtained via two-phase flow simulation with the same jet velocity and effective pressure.As a result,the characteristics of alumina-induced ablation and the changes in ablation with jet velocities were obtained.The area within0.8×jet diameter was focused upon,where the ratio of ablation velocity to incoming alumina mass was constant for each jet velocity,and showed a similarity in jet structure.When the ablation velocity was increased from 2.05 to 9.98 mm/s with increasing jet velocity,the ratio of the ablation velocity and alumina mass flux decreased from 1.07×10^(-4)to 0.49×10^(-4)m^(3)/kg as Al_(2)O_(3)-C reactions became less efficient with a reduced residence time of the film.Because the decrease in residence time by the wall jet is more pronounced for slow reactions involved in Al_(2)O_(3)-C reactions,fast reactions in Al_(2)O_(3)-C reactions are less affected and result in a convergence of the volumetric rate of ablation per unit mass of alumina.展开更多
Internal thermal insulation composite system(ITICS)can be an important measure for the energy-saving retrofitting of buildings.However,ITICS may cause harmful effects on the hygrothermal performance of building envelo...Internal thermal insulation composite system(ITICS)can be an important measure for the energy-saving retrofitting of buildings.However,ITICS may cause harmful effects on the hygrothermal performance of building envelopes.This work investigated the influence of the materials’hygric properties on the hygrothermal perfor-mance of a typical ITICS in different climate conditions in China.Two base wall materials,the traditional concrete and a new type aerated concrete,were tested and compared for their hygric properties firstly.The influence of the hygroscopicity of exterior plasters,the permeability of insulation materials and the climate conditions were then analyzed with WUFI simulations.The hygrothermal performance was evaluated with consideration of the total water content(TWC)of the walls and the moisture flux strength,the relative humidity(RH)and the mould growth risk at the interface between the base wall and the insulation layer(B-I interface).The numerical analysis implies that the TWC of internal insulated walls depends mainly on the hygroscopicity of exterior plaster and the wind-driven rain intensity.The upper limits for the water absorption coefficient of exterior plasters used in Bei-jing,Shanghai and Fuzhou are 1e-9,1e-10,1e-10 m^(2)/s respectively.When such limits are guaranteed,a vapour tight system created by using insulation materials with a large vapour resistance factor or adding a vapour barrier can improve the hygrothermal performance of ITICS,especially for concrete walls in cold climate.展开更多
基金supported by China Scholarship Council(NO.202006090005).
文摘Interior thermal insulation has been widely used to improve energy efficiency and indoor comfort of historic buildings.However,traditional vapour-tight insulation materials strongly influence the hygrothermal behaviour of facades,which may lead to moisture-related problems.Capillary-active insulation aims to enhance moisture permeance,ensuring the hygrothermal response of the masonry wall is more aligned with that of an uninsulated wall.While some capillary-active systems have proven their efficiency,global climate change and extreme weather conditions introduce additional uncertainties.This study investigates this specific issue.The hygrothermal responses of three massive masonry walls—one with vapour-tight insulation,one with capillary-active insulation,and one uninsulated—are monitored and simulated under real climate conditions in Leuven,Belgium.The simulations,conducted in DELPHIN 6 with monitored climate datasets as boundary conditions,are validated using measured temperature and relative humidity.The validated model is subsequently used with one current and two future climate datasets to compare the impacts of vapour-tight and capillary-active insulation on the hygrothermal behaviours of the masonry walls under climate change.The former exhibited more serious moisture-related risks,offering only marginally better energy performance,while the latter showed a similar hygrothermal behaviour to the uninsulated wall.Exterior climates significantly influence hygrothermal responses:both insulation systems inevitably increase mould growth and frost damage risks,though moisture failures are reduced in warmer outdoor environments.This paper highlights the nuanced balance between energy efficiency and moisture safety for researchers and practitioners.
文摘This study investigates the ablation of internal insulation induced by the deposition of an alumina film with different lateral film speeds.A sub-scale test solid rocket motor(SRM)was designed in an impinging jet configuration to form an alumina film on the sample and to encourage the lateral movement of the film by a high-speed wall jet.Fifteen static fire tests of the test SRM were conducted with six different jet velocities(V_(jet)=100 m/s,150 m/s,200 m/s,268 m/s,330 m/s,and 450 m/s)that indirectly affected the velocity of the wall jet and the deposition rate of alumina droplets.The ablation velocity was deduced from the difference in the sample thickness after a test using a coordinate measuring machine.The droplet deposition mass flux and wall jet velocity were obtained via two-phase flow simulation with the same jet velocity and effective pressure.As a result,the characteristics of alumina-induced ablation and the changes in ablation with jet velocities were obtained.The area within0.8×jet diameter was focused upon,where the ratio of ablation velocity to incoming alumina mass was constant for each jet velocity,and showed a similarity in jet structure.When the ablation velocity was increased from 2.05 to 9.98 mm/s with increasing jet velocity,the ratio of the ablation velocity and alumina mass flux decreased from 1.07×10^(-4)to 0.49×10^(-4)m^(3)/kg as Al_(2)O_(3)-C reactions became less efficient with a reduced residence time of the film.Because the decrease in residence time by the wall jet is more pronounced for slow reactions involved in Al_(2)O_(3)-C reactions,fast reactions in Al_(2)O_(3)-C reactions are less affected and result in a convergence of the volumetric rate of ablation per unit mass of alumina.
基金This research was funded by National Key R&D Program of China(2017YFC0702800),which is gratefully acknowledged.
文摘Internal thermal insulation composite system(ITICS)can be an important measure for the energy-saving retrofitting of buildings.However,ITICS may cause harmful effects on the hygrothermal performance of building envelopes.This work investigated the influence of the materials’hygric properties on the hygrothermal perfor-mance of a typical ITICS in different climate conditions in China.Two base wall materials,the traditional concrete and a new type aerated concrete,were tested and compared for their hygric properties firstly.The influence of the hygroscopicity of exterior plasters,the permeability of insulation materials and the climate conditions were then analyzed with WUFI simulations.The hygrothermal performance was evaluated with consideration of the total water content(TWC)of the walls and the moisture flux strength,the relative humidity(RH)and the mould growth risk at the interface between the base wall and the insulation layer(B-I interface).The numerical analysis implies that the TWC of internal insulated walls depends mainly on the hygroscopicity of exterior plaster and the wind-driven rain intensity.The upper limits for the water absorption coefficient of exterior plasters used in Bei-jing,Shanghai and Fuzhou are 1e-9,1e-10,1e-10 m^(2)/s respectively.When such limits are guaranteed,a vapour tight system created by using insulation materials with a large vapour resistance factor or adding a vapour barrier can improve the hygrothermal performance of ITICS,especially for concrete walls in cold climate.
