Pub Date : 2023-06-02DOI: 10.1177/17442591231178778
D. Deckers, H. Janssen
With the development of more efficient hygrothermal computer models, simulation studies have become increasingly important in the design of building components. To obtain trustworthy results from these studies, accurate hygric properties are required. The existing methods for moisture storage properties, however, are not very well suited to accurately measure moisture retention curves within a compact timeframe. To improve on this front, this paper introduces the steady state centrifuge technique, a common experiment in soil physics, for use on porous building materials. The laboratory centrifuge, used for the validation of this technique, is self-made to limit its cost and account for specific design choices. In the first part of the paper, the design of the laboratory centrifuge is described and all problems encountered during the development are explained and resolved. The two main problems are excessive heat generation by the motor and unwanted evaporation from the sample’s surfaces. The excessive heat generation is solved by extraction of heat both at the source, by using a ventilator, and at the rotor, by adding carefully positioned air extraction holes. The unwanted evaporation is eliminated by incorporating sample holders to shield the sample from the surrounding air. In the second part of the paper, the steady state centrifuge experiment is used to measure the desorption moisture retention curves of a ceramic brick starting from both saturated and capillary moisture content. The results are validated by their similarity to the curves obtained by mercury intrusion porosimetry. Besides providing accurate results, the determination of the full moisture retention curve requires only 1–2 weeks, which is significantly quicker than other common protocols, such as the pressure plates, which take about 2 months. Additionally, the ability to measure the desorption moisture retention curve from capillary moisture content as well as the limited cost of the centrifuge design (€6000) provide major advantages.
{"title":"Development and validation of the steady state centrifuge experiment for the moisture retention curve of porous building materials","authors":"D. Deckers, H. Janssen","doi":"10.1177/17442591231178778","DOIUrl":"https://doi.org/10.1177/17442591231178778","url":null,"abstract":"With the development of more efficient hygrothermal computer models, simulation studies have become increasingly important in the design of building components. To obtain trustworthy results from these studies, accurate hygric properties are required. The existing methods for moisture storage properties, however, are not very well suited to accurately measure moisture retention curves within a compact timeframe. To improve on this front, this paper introduces the steady state centrifuge technique, a common experiment in soil physics, for use on porous building materials. The laboratory centrifuge, used for the validation of this technique, is self-made to limit its cost and account for specific design choices. In the first part of the paper, the design of the laboratory centrifuge is described and all problems encountered during the development are explained and resolved. The two main problems are excessive heat generation by the motor and unwanted evaporation from the sample’s surfaces. The excessive heat generation is solved by extraction of heat both at the source, by using a ventilator, and at the rotor, by adding carefully positioned air extraction holes. The unwanted evaporation is eliminated by incorporating sample holders to shield the sample from the surrounding air. In the second part of the paper, the steady state centrifuge experiment is used to measure the desorption moisture retention curves of a ceramic brick starting from both saturated and capillary moisture content. The results are validated by their similarity to the curves obtained by mercury intrusion porosimetry. Besides providing accurate results, the determination of the full moisture retention curve requires only 1–2 weeks, which is significantly quicker than other common protocols, such as the pressure plates, which take about 2 months. Additionally, the ability to measure the desorption moisture retention curve from capillary moisture content as well as the limited cost of the centrifuge design (€6000) provide major advantages.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"45 1","pages":"36 - 61"},"PeriodicalIF":2.0,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75746896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-28DOI: 10.1177/17442591231177426
B. Jamal, L. El moutaouakil, M. Boukendil, A. Abdelbaki, Z. Zrikem
The aim of this study is to determine the thermal conductance of concrete hollow bricks, which is crucial for assessing the energy efficiency of buildings. The study focuses on three types of concrete hollow bricks that are frequently used to build walls in Morocco. The three modes of heat transfer by convection, conduction and radiation are taken into account. The thermal behavior of the three types was simulated using a computational model created with the finite volume method. The effect of internal surfaces emissivity and solid wall thermal conductivity on overall heat transfer is investigated using practical values of the thermal excitations. Simulation results of the three types were compared and showed that the concrete hollow brick of Type (C) is the best performing configuration. Indeed, it reduces the thermal conductance (U-value) by 40% compared to hollow brick of Type (B), which will contribute to improve the thermal resistance of the building walls.
{"title":"Numerical analysis of combined heat transfers through concrete hollow bricks in a hot climate of Morocco","authors":"B. Jamal, L. El moutaouakil, M. Boukendil, A. Abdelbaki, Z. Zrikem","doi":"10.1177/17442591231177426","DOIUrl":"https://doi.org/10.1177/17442591231177426","url":null,"abstract":"The aim of this study is to determine the thermal conductance of concrete hollow bricks, which is crucial for assessing the energy efficiency of buildings. The study focuses on three types of concrete hollow bricks that are frequently used to build walls in Morocco. The three modes of heat transfer by convection, conduction and radiation are taken into account. The thermal behavior of the three types was simulated using a computational model created with the finite volume method. The effect of internal surfaces emissivity and solid wall thermal conductivity on overall heat transfer is investigated using practical values of the thermal excitations. Simulation results of the three types were compared and showed that the concrete hollow brick of Type (C) is the best performing configuration. Indeed, it reduces the thermal conductance (U-value) by 40% compared to hollow brick of Type (B), which will contribute to improve the thermal resistance of the building walls.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"45 1","pages":"230 - 246"},"PeriodicalIF":2.0,"publicationDate":"2023-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78108610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-15DOI: 10.1177/17442591231172516
Xiaoyu Wang, Xingzhi Shi, Xing Jin
Phase change materials (PCMs) could be used in envelopes to moderate indoor temperature while hygroscopic materials could be used in envelopes to moderate indoor humidity. However, it remains unsolved whether these two materials are mixed to generate a better effect than single materials. Therefore, a transient model for coupled heat and moisture transfer through hygroscopic PCMs (HPCMs) was presented. The numerical cases of periodic boundary conditions and realistic weather conditions were conducted to investigate the heat and moisture transfer characteristics of three gypsum-based HPCMs containing different mass ratios of microencapsulated PCMs. Quantitative analyses were conducted to capture the effects of hygrothermal properties on heat and moisture transfer characteristics of HPCMs. The numerical results show that the mixing of PCMs and hygroscopic materials could generate a better temperature-humidity controlling effect than pure hygroscopic material, and the condensation risks inside the envelopes could also be reduced. Both the studied cases indicate that the HPCMs could be applied in building envelopes to passively moderate the indoor temperature and humidity simultaneously, reducing the building energy consumption and condensation risks inside the envelopes. The effects of hygroscopic and moisture transfer properties on temperature-control performance of HPCMs are relatively small, while the thermal properties play an important role in the improvement of temperature-humidity controlling performance of HPCMs with the increase of PCM concentration.
{"title":"Study on heat and moisture transfer characteristics of HPCMs","authors":"Xiaoyu Wang, Xingzhi Shi, Xing Jin","doi":"10.1177/17442591231172516","DOIUrl":"https://doi.org/10.1177/17442591231172516","url":null,"abstract":"Phase change materials (PCMs) could be used in envelopes to moderate indoor temperature while hygroscopic materials could be used in envelopes to moderate indoor humidity. However, it remains unsolved whether these two materials are mixed to generate a better effect than single materials. Therefore, a transient model for coupled heat and moisture transfer through hygroscopic PCMs (HPCMs) was presented. The numerical cases of periodic boundary conditions and realistic weather conditions were conducted to investigate the heat and moisture transfer characteristics of three gypsum-based HPCMs containing different mass ratios of microencapsulated PCMs. Quantitative analyses were conducted to capture the effects of hygrothermal properties on heat and moisture transfer characteristics of HPCMs. The numerical results show that the mixing of PCMs and hygroscopic materials could generate a better temperature-humidity controlling effect than pure hygroscopic material, and the condensation risks inside the envelopes could also be reduced. Both the studied cases indicate that the HPCMs could be applied in building envelopes to passively moderate the indoor temperature and humidity simultaneously, reducing the building energy consumption and condensation risks inside the envelopes. The effects of hygroscopic and moisture transfer properties on temperature-control performance of HPCMs are relatively small, while the thermal properties play an important role in the improvement of temperature-humidity controlling performance of HPCMs with the increase of PCM concentration.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"74 1 1","pages":"121 - 147"},"PeriodicalIF":2.0,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73023034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-01DOI: 10.1177/17442591231164037
H. Saber, D. Yarbrough
The thermal resistances (R-values) of airspaces depends on the emittance of all surfaces around an airspace, dimensions, heat-flow direction, and the temperatures of the bounding surfaces. Assessing the energy performance of building envelope components and fenestration systems requires accurate results for the R-values of any enclosed spaces. The evaluation of reflective insulation R-values has evolved to include use of computational fluid dynamics and surface-to-surface radiation to quantify convective and radiative contributions to the heat transfer across airspaces of all types. This paper compares an advanced and validated model for calculating enclosed airspace R-values with the widely-used ISO 6946 and airspace R-values in the ASHRAE Handbook-Fundamentals. The impact of construction and installation defects on the thermal performance of reflective insulation has not been previously evaluated. In this research, an advanced model was used to evaluate a construction defect and dimensional aspect ratios that one-dimensional methods do not address. Imperfect installation and defects that result in air movement into or through a reflective insulation assembly reduces the thermal resistance of the assembly. Additionally, the amount of thermal resistance reduction depends on the amount and temperature of invasive air or the size of internal defects that allows natural convection inside the reflective airspace. In this study, these performance issues are evaluated quantitatively using computer simulation techniques. The differences in results obtained using methods that are currently being used to evaluate the R-value and the advantages of the advanced method for evaluating the reflective insulation performance for different applications are discussed. For the case considered in this study, the results showed that the failure to achieve parallel surfaces results in less than a 5% decrease in thermal resistance. Also, the results showed that internal air gaps between airspaces result in negligible loss in R-value unless air gaps that allow circulation between airspaces are created.
{"title":"Numerical modeling for evaluation of the thermal resistance of reflective airspaces with and without defects","authors":"H. Saber, D. Yarbrough","doi":"10.1177/17442591231164037","DOIUrl":"https://doi.org/10.1177/17442591231164037","url":null,"abstract":"The thermal resistances (R-values) of airspaces depends on the emittance of all surfaces around an airspace, dimensions, heat-flow direction, and the temperatures of the bounding surfaces. Assessing the energy performance of building envelope components and fenestration systems requires accurate results for the R-values of any enclosed spaces. The evaluation of reflective insulation R-values has evolved to include use of computational fluid dynamics and surface-to-surface radiation to quantify convective and radiative contributions to the heat transfer across airspaces of all types. This paper compares an advanced and validated model for calculating enclosed airspace R-values with the widely-used ISO 6946 and airspace R-values in the ASHRAE Handbook-Fundamentals. The impact of construction and installation defects on the thermal performance of reflective insulation has not been previously evaluated. In this research, an advanced model was used to evaluate a construction defect and dimensional aspect ratios that one-dimensional methods do not address. Imperfect installation and defects that result in air movement into or through a reflective insulation assembly reduces the thermal resistance of the assembly. Additionally, the amount of thermal resistance reduction depends on the amount and temperature of invasive air or the size of internal defects that allows natural convection inside the reflective airspace. In this study, these performance issues are evaluated quantitatively using computer simulation techniques. The differences in results obtained using methods that are currently being used to evaluate the R-value and the advantages of the advanced method for evaluating the reflective insulation performance for different applications are discussed. For the case considered in this study, the results showed that the failure to achieve parallel surfaces results in less than a 5% decrease in thermal resistance. Also, the results showed that internal air gaps between airspaces result in negligible loss in R-value unless air gaps that allow circulation between airspaces are created.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"170 1","pages":"708 - 736"},"PeriodicalIF":2.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83893274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-21DOI: 10.1177/17442591231167609
Benyamin Salehpour, M. Ghobadi, H. Ge, T. Moore
Reducing energy consumption and Greenhouse Gas (GHG) emissions is an essential part of the clean growth and climate change framework recently developed by the Canadian government, which emphasizes the importance of energy-efficient building constructions. In this paper, the effects of thermal mass and placement of the thermally massive layer within wall assemblies on the transient thermal performance of walls and energy performance of a case study office building were studied. Three climate conditions representative of the heating-dominated, temperate, and cooling-dominated climates were considered. As for the assessment of energy demands, two cases for the indoor air temperature were taken into account: (i) indoor temperature was maintained at 20°C throughout the year, and (ii) during summertime, there was a set-point of 24°C and a setback of 35°C during the rest of the day while during wintertime, the set-point and setback values were 22°C and 18°C, respectively. The cases were compared according to the resulting decrement factor, the time required to reach quasi-steady state conditions, amplitudes of changes of heat fluxes and indoor surface temperatures, and the energy demands. The results showed that, for the cases studied, the wall, for which the thermally massive layer is not directly exposed to the indoor and outdoor climate conditions, resulted in the lowest decrement factor, the minimum amplitude of changes of heat fluxes and indoor surface temperatures, and maximum time required to reach quasi steady-state conditions. As for the energy performance, on the other hand, the wall, for which the thermally massive layer is exposed to the interior and exterior climate conditions, performed best amongst the cases investigated.
{"title":"Effects of thermal mass on transient thermal performance of concrete-based walls and energy consumption of an office building","authors":"Benyamin Salehpour, M. Ghobadi, H. Ge, T. Moore","doi":"10.1177/17442591231167609","DOIUrl":"https://doi.org/10.1177/17442591231167609","url":null,"abstract":"Reducing energy consumption and Greenhouse Gas (GHG) emissions is an essential part of the clean growth and climate change framework recently developed by the Canadian government, which emphasizes the importance of energy-efficient building constructions. In this paper, the effects of thermal mass and placement of the thermally massive layer within wall assemblies on the transient thermal performance of walls and energy performance of a case study office building were studied. Three climate conditions representative of the heating-dominated, temperate, and cooling-dominated climates were considered. As for the assessment of energy demands, two cases for the indoor air temperature were taken into account: (i) indoor temperature was maintained at 20°C throughout the year, and (ii) during summertime, there was a set-point of 24°C and a setback of 35°C during the rest of the day while during wintertime, the set-point and setback values were 22°C and 18°C, respectively. The cases were compared according to the resulting decrement factor, the time required to reach quasi-steady state conditions, amplitudes of changes of heat fluxes and indoor surface temperatures, and the energy demands. The results showed that, for the cases studied, the wall, for which the thermally massive layer is not directly exposed to the indoor and outdoor climate conditions, resulted in the lowest decrement factor, the minimum amplitude of changes of heat fluxes and indoor surface temperatures, and maximum time required to reach quasi steady-state conditions. As for the energy performance, on the other hand, the wall, for which the thermally massive layer is exposed to the interior and exterior climate conditions, performed best amongst the cases investigated.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"484 1","pages":"92 - 120"},"PeriodicalIF":2.0,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87687891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-19DOI: 10.1177/17442591231163459
D. Chung, Jin Wen, L. J. Lo
The analysis of heat, air, and moisture (H.A.M.) transport for building envelopes are known to be highly dependent on climate loads and air infiltration rates. Moisture content within the assembly is often a key H.A.M. analysis outcome to assess risk and transport behavior. ASHRAE Standard 160-2016 states that building envelope H.A.M. analysis should be done using moisture design reference data or using a minimum of 10 consecutive years of weather. While there has been progress and methods for selecting or designing moisture reference years there has been a lack of study in the impact of multi-year (particularly 10-year) weather scenarios on simulation results in comparison to reference year simulations. This paper presents research using stochastic 1, 2, and 10-year weather data and air infiltration rates to study the range of simulated moisture content outcomes for four wall assemblies in Philadelphia and compares these to the outcomes when using reference years. Results from the study show that air infiltration, starting month, and multi-year duration have significant impacts on simulated moisture content, mold, and corrosion analysis results. Regression analysis using annual averages of climate input parameters did not yield useable models for selecting weather years, however an estimated mold index value using outdoor climate data may be useful in selecting weather years with varying starting months for mold growth assessment.
{"title":"Examining the impact of stochastic multi-year weather and air infiltration on hygrothermal moisture risks","authors":"D. Chung, Jin Wen, L. J. Lo","doi":"10.1177/17442591231163459","DOIUrl":"https://doi.org/10.1177/17442591231163459","url":null,"abstract":"The analysis of heat, air, and moisture (H.A.M.) transport for building envelopes are known to be highly dependent on climate loads and air infiltration rates. Moisture content within the assembly is often a key H.A.M. analysis outcome to assess risk and transport behavior. ASHRAE Standard 160-2016 states that building envelope H.A.M. analysis should be done using moisture design reference data or using a minimum of 10 consecutive years of weather. While there has been progress and methods for selecting or designing moisture reference years there has been a lack of study in the impact of multi-year (particularly 10-year) weather scenarios on simulation results in comparison to reference year simulations. This paper presents research using stochastic 1, 2, and 10-year weather data and air infiltration rates to study the range of simulated moisture content outcomes for four wall assemblies in Philadelphia and compares these to the outcomes when using reference years. Results from the study show that air infiltration, starting month, and multi-year duration have significant impacts on simulated moisture content, mold, and corrosion analysis results. Regression analysis using annual averages of climate input parameters did not yield useable models for selecting weather years, however an estimated mold index value using outdoor climate data may be useful in selecting weather years with varying starting months for mold growth assessment.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"284 1","pages":"4 - 35"},"PeriodicalIF":2.0,"publicationDate":"2023-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73181937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-12DOI: 10.1177/17442591231167638
Menghao Qin, C. Rode
the determination of thermal resistances (R-values) for reflective insulation by considering multi-dimensional radiative exchange between all surfaces. Results are presented for varied aspect ratios (width/depth) to characterize the geometry and effective emittance (E) variation from 0 to 0.82. Additionally, the use of CFD to evaluate convective heat transport allows the evaluation of installation defects that impact the R -value. R -values calculated for single and double air spaces show the greatest variation with aspect ratio for E 0.05. Modeling of assemblies with non-parallel surfaces has also been evaluated. Double airspaces with gaps that permit air flow between regions show that installation with unin-tended gaps at one end of a cavity results in small reductions in R-value while gaps at both ends of a cavity have R -value reductions approaching 50% for E in the reflective range. These examples provide a glimpse of a new dimension in the evaluation of reflective assemblies to be used in buildings.
{"title":"Editorial: Special issue IBPC2021","authors":"Menghao Qin, C. Rode","doi":"10.1177/17442591231167638","DOIUrl":"https://doi.org/10.1177/17442591231167638","url":null,"abstract":"the determination of thermal resistances (R-values) for reflective insulation by considering multi-dimensional radiative exchange between all surfaces. Results are presented for varied aspect ratios (width/depth) to characterize the geometry and effective emittance (E) variation from 0 to 0.82. Additionally, the use of CFD to evaluate convective heat transport allows the evaluation of installation defects that impact the R -value. R -values calculated for single and double air spaces show the greatest variation with aspect ratio for E 0.05. Modeling of assemblies with non-parallel surfaces has also been evaluated. Double airspaces with gaps that permit air flow between regions show that installation with unin-tended gaps at one end of a cavity results in small reductions in R-value while gaps at both ends of a cavity have R -value reductions approaching 50% for E in the reflective range. These examples provide a glimpse of a new dimension in the evaluation of reflective assemblies to be used in buildings.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"151 1","pages":"657 - 658"},"PeriodicalIF":2.0,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73041168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-05DOI: 10.1177/17442591231165992
Kazuma Fukui, C. Iba, D. Ogura
Porous building materials, such as board materials, wood, stones, fired clay materials, and bio-based materials, often have anisotropic properties. This study investigates adequate numerical models for the coupled hygrothermal and mechanical behaviors of strongly anisotropic building materials during freezing and thawing. First, strain measurements are reported for two types of fired clay materials to confirm the anisotropy of deformation during freezing and thawing. In calculations, the anisotropy of the Biot coefficient of a material is considered based on anisotropic poroelasticity. The comparison between the measurements and calculations revealed that the anisotropic deformation during the measurement cannot be reproduced without considering the anisotropies of the Biot coefficient as well as those of the mechanical properties. In addition, analysis of the causes of the deformation reveals that the expansion in the direction normal to the material thickness due to the water pressure development during the freezing is suppressed by the small Biot coefficient. These results indicate that the anisotropy of the Biot coefficient significantly influence the deformation due to frost actions; consequently, the anisotropic Biot coefficient should be adequately considered in numerical simulations.
{"title":"Coupled hygrothermal and mechanical simulations of highly anisotropic building material during freezing and thawing","authors":"Kazuma Fukui, C. Iba, D. Ogura","doi":"10.1177/17442591231165992","DOIUrl":"https://doi.org/10.1177/17442591231165992","url":null,"abstract":"Porous building materials, such as board materials, wood, stones, fired clay materials, and bio-based materials, often have anisotropic properties. This study investigates adequate numerical models for the coupled hygrothermal and mechanical behaviors of strongly anisotropic building materials during freezing and thawing. First, strain measurements are reported for two types of fired clay materials to confirm the anisotropy of deformation during freezing and thawing. In calculations, the anisotropy of the Biot coefficient of a material is considered based on anisotropic poroelasticity. The comparison between the measurements and calculations revealed that the anisotropic deformation during the measurement cannot be reproduced without considering the anisotropies of the Biot coefficient as well as those of the mechanical properties. In addition, analysis of the causes of the deformation reveals that the expansion in the direction normal to the material thickness due to the water pressure development during the freezing is suppressed by the small Biot coefficient. These results indicate that the anisotropy of the Biot coefficient significantly influence the deformation due to frost actions; consequently, the anisotropic Biot coefficient should be adequately considered in numerical simulations.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"6 1","pages":"659 - 685"},"PeriodicalIF":2.0,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81701975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1177/17442591231165987
Lin Wang, H. Ge, Jieying Wang
Cross-laminated timber (CLT) is one of the most important mass timber materials that are commonly used in mid-rise or even high-rise timber buildings. However, exposure to moisture during construction may increase the moisture damage risks, and impact the durability performance of CLT buildings. To investigate potential solutions for avoiding wetting of CLT components during construction, CLT specimens having different moisture protection measures were tested in the damp and mild wintertime climate in Vancouver. This follow-up work focuses on two-dimensional (2-D) hygrothermal modeling of the wetting and drying behavior of bare CLT (without any protection) and the validation with measurements from the field exposure test, emphasizing the influence of material properties. The hygrothermal models are firstly calibrated for two CLT specimens positioned horizontally, with and without a butt joint, by using material properties from different laboratory tests, and assuming different rain penetration paths. The calibrated models are then applied to simulate CLT specimens positioned vertically, which have end grain directly exposed to rain or damp concrete in the test. The work reveals that the moisture storage function above RH 95%, which includes the saturation water content reported in different literature, has a significant influence on the hygrothermal simulation results; meanwhile, assigning different water absorption coefficients for the transverse and longitudinal directions of wood significantly improves the accuracy of the hygrothermal model created for simulating rainwater penetration into the CLT panel. This paper provides a recommendation on how to properly model the CLT panels exposed to rainwater, which often occurs during construction.
{"title":"Model validation and 2-D hygrothermal simulations of wetting and drying behavior of cross-laminated timber","authors":"Lin Wang, H. Ge, Jieying Wang","doi":"10.1177/17442591231165987","DOIUrl":"https://doi.org/10.1177/17442591231165987","url":null,"abstract":"Cross-laminated timber (CLT) is one of the most important mass timber materials that are commonly used in mid-rise or even high-rise timber buildings. However, exposure to moisture during construction may increase the moisture damage risks, and impact the durability performance of CLT buildings. To investigate potential solutions for avoiding wetting of CLT components during construction, CLT specimens having different moisture protection measures were tested in the damp and mild wintertime climate in Vancouver. This follow-up work focuses on two-dimensional (2-D) hygrothermal modeling of the wetting and drying behavior of bare CLT (without any protection) and the validation with measurements from the field exposure test, emphasizing the influence of material properties. The hygrothermal models are firstly calibrated for two CLT specimens positioned horizontally, with and without a butt joint, by using material properties from different laboratory tests, and assuming different rain penetration paths. The calibrated models are then applied to simulate CLT specimens positioned vertically, which have end grain directly exposed to rain or damp concrete in the test. The work reveals that the moisture storage function above RH 95%, which includes the saturation water content reported in different literature, has a significant influence on the hygrothermal simulation results; meanwhile, assigning different water absorption coefficients for the transverse and longitudinal directions of wood significantly improves the accuracy of the hygrothermal model created for simulating rainwater penetration into the CLT panel. This paper provides a recommendation on how to properly model the CLT panels exposed to rainwater, which often occurs during construction.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"101 1","pages":"737 - 761"},"PeriodicalIF":2.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84109136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-27DOI: 10.1177/17442591231154010
Kazuma Fukui, C. Iba, D. Ogura
To better understand the mechanisms of the deformation of fired clay materials due to frost actions, we investigated the effects of rapid freezing due to supercooling on the deformation through both experimental and numerical approaches. We conducted a freeze–thaw experiment to measure the strain evolution of the material during freezing and thawing. Subsequently, we developed a coupled hygrothermal and mechanical model of the freezing and thawing processes including supercooling, and conducted numerical simulations corresponding to the freeze–thaw experiment. The model was based on the theory of poromechanics. The results of the freeze-thaw experiment revealed that the supercooling effects were small in fired clay materials compared to cement-based materials examined in literature, and the material expanded significantly associated with subsequent freezing after the rapid freezing due to the supercooling stopped. Based on the results of the experiments and numerical simulations, the equilibrium freezing temperature and water movement toward the material surfaces enhanced by relatively large moisture permeability restrict pressure development in the material even though the freezing of the supercooled water in the material was considerably rapid. The results of the numerical simulations also showed that the effect of the supercooling can be much more significant if a material had a low moisture permeability.
{"title":"Deformation of fired clay material during rapid freezing due to supercooling","authors":"Kazuma Fukui, C. Iba, D. Ogura","doi":"10.1177/17442591231154010","DOIUrl":"https://doi.org/10.1177/17442591231154010","url":null,"abstract":"To better understand the mechanisms of the deformation of fired clay materials due to frost actions, we investigated the effects of rapid freezing due to supercooling on the deformation through both experimental and numerical approaches. We conducted a freeze–thaw experiment to measure the strain evolution of the material during freezing and thawing. Subsequently, we developed a coupled hygrothermal and mechanical model of the freezing and thawing processes including supercooling, and conducted numerical simulations corresponding to the freeze–thaw experiment. The model was based on the theory of poromechanics. The results of the freeze-thaw experiment revealed that the supercooling effects were small in fired clay materials compared to cement-based materials examined in literature, and the material expanded significantly associated with subsequent freezing after the rapid freezing due to the supercooling stopped. Based on the results of the experiments and numerical simulations, the equilibrium freezing temperature and water movement toward the material surfaces enhanced by relatively large moisture permeability restrict pressure development in the material even though the freezing of the supercooled water in the material was considerably rapid. The results of the numerical simulations also showed that the effect of the supercooling can be much more significant if a material had a low moisture permeability.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"51 1","pages":"762 - 788"},"PeriodicalIF":2.0,"publicationDate":"2023-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86171061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：