A major roadblock in achieving substantial building energy reduction is the low performance of old buildings that account for a significant portion of the building energy consumption.Finding low-cost energy retrofit s...A major roadblock in achieving substantial building energy reduction is the low performance of old buildings that account for a significant portion of the building energy consumption.Finding low-cost energy retrofit solutions that do not disrupt occupants’daily life during the retrofitting is the key to successful building energy retrofit initiatives.In this paper,a novel and low-cost exterior wall retrofitting solution is introduced,and its performance in reducing space cooling load was quantitatively evaluated to demonstrate its feasibility and effectiveness.The primary goal of this paper is to provide a quantitative assessment of the cooling-energy savings potential by using the proposed new wall system.The intended retrofitting targets are the large amount of existing cavity-wall buildings located in hot climate regions.The quantification of the before-after heat-flux reduction was conducted through a 3-dimensional steady-state low turbulence computational fluid dynamics(CFD)model,which is validated by benchmarking its prediction against the published experimental case results.The outcomes of the investigation suggest that this simple low-cost solution has great potentials in reducing buildings’summer cooling load in hot climate regions.The applicability of this solution is not limited to retrofitting existing buildings.New energy-efficient building designs can also adopt this solution in their envelope systems.展开更多
Natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method （LBM）. The physics of flow and energy transfer in open end cavities are addressed when the hot wal...Natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method （LBM）. The physics of flow and energy transfer in open end cavities are addressed when the hot wall is inclined. The combination of the two topics （open cavity and inclined walls） is the main novelty of the present study. The effects of the angle of the hot inclined wall on the flow field and heat transfer are thoroughly investigated. The Prandtl number is fixed to 0.71 （air）. The Rayleigh number and the angle of the hot inclined wall are varied in the range of 10^4 to 10^6 and 60° to 85°, respectively. The results are presented for two different aspect ratios, i.e., A = 1 and 2. The results obtained with the LBM are also compared with those of the finite volume method （FVM）. The predicted results of the LBM conform to those of the FVM. The results show that by increasing the angle of the hot inclined wall and the aspect ratio of the cavity, the average Nusselt number decreases. The trend of the local Nusselt number on the inclined wall is also discussed.展开更多
The purpose of this research is to assess thermal performance and energy saving of a residential building in the hot semi-arid climate of Marrakech(Morocco).The studied house is built as usual in Marrakech without any...The purpose of this research is to assess thermal performance and energy saving of a residential building in the hot semi-arid climate of Marrakech(Morocco).The studied house is built as usual in Marrakech without any thermal insula-tion except for its external walls,facing East and West,which are double walls with a 5 cm air gap in between(“cavity wall”technique).The cavity wall effec-tive thermal conductivity was carefully calculated taking into account both radia-tion and convection heat transfers.Experimental results,obtained from winter and summer monitoring of the house,show well dampening of air temperature,thanks to its thermal inertia.However,this temperature remained outside the standard thermal comfort zone leading to large cooling/heating load.Simula-tion results indicate that the cavity wall contributes to an overall reduction of 13%and 5%of the house heating and cooling loads respectively.Moreover,the addition of XPS roof thermal insulation significantly enhances the heating and cooling energy savings to 26%and 40%respectively.展开更多
文摘A major roadblock in achieving substantial building energy reduction is the low performance of old buildings that account for a significant portion of the building energy consumption.Finding low-cost energy retrofit solutions that do not disrupt occupants’daily life during the retrofitting is the key to successful building energy retrofit initiatives.In this paper,a novel and low-cost exterior wall retrofitting solution is introduced,and its performance in reducing space cooling load was quantitatively evaluated to demonstrate its feasibility and effectiveness.The primary goal of this paper is to provide a quantitative assessment of the cooling-energy savings potential by using the proposed new wall system.The intended retrofitting targets are the large amount of existing cavity-wall buildings located in hot climate regions.The quantification of the before-after heat-flux reduction was conducted through a 3-dimensional steady-state low turbulence computational fluid dynamics(CFD)model,which is validated by benchmarking its prediction against the published experimental case results.The outcomes of the investigation suggest that this simple low-cost solution has great potentials in reducing buildings’summer cooling load in hot climate regions.The applicability of this solution is not limited to retrofitting existing buildings.New energy-efficient building designs can also adopt this solution in their envelope systems.
文摘Natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method （LBM）. The physics of flow and energy transfer in open end cavities are addressed when the hot wall is inclined. The combination of the two topics （open cavity and inclined walls） is the main novelty of the present study. The effects of the angle of the hot inclined wall on the flow field and heat transfer are thoroughly investigated. The Prandtl number is fixed to 0.71 （air）. The Rayleigh number and the angle of the hot inclined wall are varied in the range of 10^4 to 10^6 and 60° to 85°, respectively. The results are presented for two different aspect ratios, i.e., A = 1 and 2. The results obtained with the LBM are also compared with those of the finite volume method （FVM）. The predicted results of the LBM conform to those of the FVM. The results show that by increasing the angle of the hot inclined wall and the aspect ratio of the cavity, the average Nusselt number decreases. The trend of the local Nusselt number on the inclined wall is also discussed.
基金supported by the PARS grant from the Hassan Ⅱ Academy of Sciences and Techniques,Morocco。
文摘The purpose of this research is to assess thermal performance and energy saving of a residential building in the hot semi-arid climate of Marrakech(Morocco).The studied house is built as usual in Marrakech without any thermal insula-tion except for its external walls,facing East and West,which are double walls with a 5 cm air gap in between(“cavity wall”technique).The cavity wall effec-tive thermal conductivity was carefully calculated taking into account both radia-tion and convection heat transfers.Experimental results,obtained from winter and summer monitoring of the house,show well dampening of air temperature,thanks to its thermal inertia.However,this temperature remained outside the standard thermal comfort zone leading to large cooling/heating load.Simula-tion results indicate that the cavity wall contributes to an overall reduction of 13%and 5%of the house heating and cooling loads respectively.Moreover,the addition of XPS roof thermal insulation significantly enhances the heating and cooling energy savings to 26%and 40%respectively.
