Pub Date : 2022-12-17DOI: 10.1177/17442591221140465
Y. Nguyen, V. T. Nguyen
Using solar chimneys in buildings can enhance the thermal insulation of the building envelope and provide sufficient ventilation and cooling. The performance of a solar chimney is strongly affected by its configurational factors. This work examines the effects of the opening heights on the flow field in the cavity of a wall solar chimney with a Computational Fluid Dynamics (CFD) model. Both cases of equal and unequal opening areas were considered. The results show that the induced flow rate increases with the opening height and gradually becomes constant as the opening height is about 2.0–3.0 and 5.0–6.0 times the air gap for heating the left wall (HLW) and the right wall (HRW) of the air cavity, respectively. Particularly, using equal inlet and outlet heights that are equal to the air gap reduces the flow rate of 27% for HLW and 85% for HRW compared to the maximum ones. The optimal design of a wall solar chimney to achieve maximum flow rate is proposed for two cases of heating, that is, (a) for HLW, equal opening heights which are twice the air gap, and (b) for RHW, the inlet height equal to the air gap, and the outlet height equal to five times the air gap.
{"title":"Characterizing the induced flow through the cavity of a wall solar chimney under the effects of the opening heights","authors":"Y. Nguyen, V. T. Nguyen","doi":"10.1177/17442591221140465","DOIUrl":"https://doi.org/10.1177/17442591221140465","url":null,"abstract":"Using solar chimneys in buildings can enhance the thermal insulation of the building envelope and provide sufficient ventilation and cooling. The performance of a solar chimney is strongly affected by its configurational factors. This work examines the effects of the opening heights on the flow field in the cavity of a wall solar chimney with a Computational Fluid Dynamics (CFD) model. Both cases of equal and unequal opening areas were considered. The results show that the induced flow rate increases with the opening height and gradually becomes constant as the opening height is about 2.0–3.0 and 5.0–6.0 times the air gap for heating the left wall (HLW) and the right wall (HRW) of the air cavity, respectively. Particularly, using equal inlet and outlet heights that are equal to the air gap reduces the flow rate of 27% for HLW and 85% for HRW compared to the maximum ones. The optimal design of a wall solar chimney to achieve maximum flow rate is proposed for two cases of heating, that is, (a) for HLW, equal opening heights which are twice the air gap, and (b) for RHW, the inlet height equal to the air gap, and the outlet height equal to five times the air gap.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"297 1","pages":"630 - 653"},"PeriodicalIF":2.0,"publicationDate":"2022-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73168307","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 : 2022-10-20DOI: 10.1177/17442591221127279
CE Torres-Aguilar, J. Arce, J. Xamán, E. Macias-Melo
Solar chimneys provide natural ventilation for buildings, reducing the energy consumption of mechanical systems. Therefore, analyzing energy losses through solar chimney components and inlet/outlet of air channel is critical to develop a suitable design for this passive ventilation system. In this study, the performance and energy losses analysis of a single-channel solar chimney (SC-SOCH) is described; a parametric study under laboratory conditions was conducted regarding the air gap (0.10, 0.15, and 0.20 m) and heat flux of absorber plate (100, 200, 300, 400, and 500 Wm−2). The energy losses were analyzed with temperature sensors, heat flow transducers, and a net radiation transfer model. The parametric study results showed that between 10% and 15% of the total energy supplied to the absorber plate was dissipated to the laboratory environment through the glass cover. Furthermore, combining the different thermal insulation layers on the backside of the absorber plate and sidewalls of the air channel permitted only energy losses below 8% of the total energy supplied. The highest energy losses occurred due to radiative exchange; the radiative losses through the inlet and outlet of the air channel were between 9.38% and 25.78% of the total energy supplied. However, the radiative energy loss rate decreased as airflow increased; the volumetric flow rate was from 34.11 to 94.92 m3h−1, which was enough to satisfy the requirements of total ventilation rate for spaces of 9, 18, and 36 m2 according to ASHRAE 62.2–2019. Therefore, solar chimney designs must be optimized to minimize energy losses and increase airflow for natural ventilation.
{"title":"Experimental study and numerical analysis of radiative losses of single-channel solar chimney","authors":"CE Torres-Aguilar, J. Arce, J. Xamán, E. Macias-Melo","doi":"10.1177/17442591221127279","DOIUrl":"https://doi.org/10.1177/17442591221127279","url":null,"abstract":"Solar chimneys provide natural ventilation for buildings, reducing the energy consumption of mechanical systems. Therefore, analyzing energy losses through solar chimney components and inlet/outlet of air channel is critical to develop a suitable design for this passive ventilation system. In this study, the performance and energy losses analysis of a single-channel solar chimney (SC-SOCH) is described; a parametric study under laboratory conditions was conducted regarding the air gap (0.10, 0.15, and 0.20 m) and heat flux of absorber plate (100, 200, 300, 400, and 500 Wm−2). The energy losses were analyzed with temperature sensors, heat flow transducers, and a net radiation transfer model. The parametric study results showed that between 10% and 15% of the total energy supplied to the absorber plate was dissipated to the laboratory environment through the glass cover. Furthermore, combining the different thermal insulation layers on the backside of the absorber plate and sidewalls of the air channel permitted only energy losses below 8% of the total energy supplied. The highest energy losses occurred due to radiative exchange; the radiative losses through the inlet and outlet of the air channel were between 9.38% and 25.78% of the total energy supplied. However, the radiative energy loss rate decreased as airflow increased; the volumetric flow rate was from 34.11 to 94.92 m3h−1, which was enough to satisfy the requirements of total ventilation rate for spaces of 9, 18, and 36 m2 according to ASHRAE 62.2–2019. Therefore, solar chimney designs must be optimized to minimize energy losses and increase airflow for natural ventilation.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"2 1","pages":"340 - 371"},"PeriodicalIF":2.0,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90088191","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 : 2022-10-19DOI: 10.1177/17442591221127280
L. P. Thomas, B. M. Marino, N. Muñoz
We introduce a statistical methodology to evaluate the thermal performance of vertical opaque envelopes and provide the most adequate design of energy-efficient buildings located across extended regions. The analytical procedure was applied to the extensive Argentinian territory with a variety of climates and a limited number of networked meteorological stations. Although the study was conducted over a full year, results are presented for January and June, when the building energy demand for heating and cooling is most significant, taking into account the local climate, the thermal properties of the walls and the effects of the daily variation in the solar radiation. By using the Fourier series expansion of the sol-air temperature and multivariate analysis, we first correlated the weather data and the steady-state and time-dependent heat fluxes transmitted by conduction through five types of typical walls facing north and south in 10 climatically differentiated cities where full weather data were recorded. Then, the mean values of the sol-air temperature and the amplitude of its time variations were interpolated throughout the territory, thus yielding the spatial distributions of these parameters for a typical day in the months of interest. Finally, the calculation of the heat fluxes exchanged through building opaque envelopes was extended to the whole country.
{"title":"Multivariate analysis for assessing the thermal performance of vertical opaque envelopes in extended regions","authors":"L. P. Thomas, B. M. Marino, N. Muñoz","doi":"10.1177/17442591221127280","DOIUrl":"https://doi.org/10.1177/17442591221127280","url":null,"abstract":"We introduce a statistical methodology to evaluate the thermal performance of vertical opaque envelopes and provide the most adequate design of energy-efficient buildings located across extended regions. The analytical procedure was applied to the extensive Argentinian territory with a variety of climates and a limited number of networked meteorological stations. Although the study was conducted over a full year, results are presented for January and June, when the building energy demand for heating and cooling is most significant, taking into account the local climate, the thermal properties of the walls and the effects of the daily variation in the solar radiation. By using the Fourier series expansion of the sol-air temperature and multivariate analysis, we first correlated the weather data and the steady-state and time-dependent heat fluxes transmitted by conduction through five types of typical walls facing north and south in 10 climatically differentiated cities where full weather data were recorded. Then, the mean values of the sol-air temperature and the amplitude of its time variations were interpolated throughout the territory, thus yielding the spatial distributions of these parameters for a typical day in the months of interest. Finally, the calculation of the heat fluxes exchanged through building opaque envelopes was extended to the whole country.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"7 1","pages":"259 - 291"},"PeriodicalIF":2.0,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78953839","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 : 2022-09-30DOI: 10.1177/17442591221121918
Jiashuai Wei, Shui Yu, Xiaoting Zhou
The effect of concrete cracks on the evaluation of the thermal performance of walls has not been effectively considered within the assessment of the thermal and hygroscopic performance of buildings. Based on the dual permeability model, a conjugate method is proposed to reconstruct the PDE equation of unsaturated porous materials with cracks. The reliability of the model is verified from three angles: the heat-moisture coupling benchmark of matrix material, the analytical solution of two-dimensional single fracture heat flow coupling problem and the moisture absorption problem of unsaturated cracks. The reliability of the model is verified from three perspectives: the benchmark of thermal and hygroscopic coupling of matrix materials, the analytical solution to the two-dimensional single-break thermal flow coupling problem, and the hygroscopic problem of unsaturated cracks. The effect of heat and moisture transfer in cracked concrete was quantified by detailed modeling of cracks in terms of the probability of over-penetration, crack roughness, crack density, length, and angle of a two-dimensional discrete crack network, showing that cracks contribute to moisture transfer. This is followed by a 10 day experimental simulation of the meteorological environment, comparing the quantities of moisture accumulation, thermal performance, internal surface temperature and humidity within the fractured and non-fractured wall structures, illustrating the potential adverse effects of cracks on thermal performance and moisture transfer in walls under characteristic conditions. Finally, the necessity of applying moisture-proof layer to the damaged wall is demonstrated by comparing the results before and after the application of the moisture-proof layer.
{"title":"Study on influence of geometric characteristics of cracks on HAM coupling transfer and thermal performance of multi-layer cellular concrete wall","authors":"Jiashuai Wei, Shui Yu, Xiaoting Zhou","doi":"10.1177/17442591221121918","DOIUrl":"https://doi.org/10.1177/17442591221121918","url":null,"abstract":"The effect of concrete cracks on the evaluation of the thermal performance of walls has not been effectively considered within the assessment of the thermal and hygroscopic performance of buildings. Based on the dual permeability model, a conjugate method is proposed to reconstruct the PDE equation of unsaturated porous materials with cracks. The reliability of the model is verified from three angles: the heat-moisture coupling benchmark of matrix material, the analytical solution of two-dimensional single fracture heat flow coupling problem and the moisture absorption problem of unsaturated cracks. The reliability of the model is verified from three perspectives: the benchmark of thermal and hygroscopic coupling of matrix materials, the analytical solution to the two-dimensional single-break thermal flow coupling problem, and the hygroscopic problem of unsaturated cracks. The effect of heat and moisture transfer in cracked concrete was quantified by detailed modeling of cracks in terms of the probability of over-penetration, crack roughness, crack density, length, and angle of a two-dimensional discrete crack network, showing that cracks contribute to moisture transfer. This is followed by a 10 day experimental simulation of the meteorological environment, comparing the quantities of moisture accumulation, thermal performance, internal surface temperature and humidity within the fractured and non-fractured wall structures, illustrating the potential adverse effects of cracks on thermal performance and moisture transfer in walls under characteristic conditions. Finally, the necessity of applying moisture-proof layer to the damaged wall is demonstrated by comparing the results before and after the application of the moisture-proof layer.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"40 1","pages":"292 - 339"},"PeriodicalIF":2.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84628116","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 : 2022-09-21DOI: 10.1177/17442591221121924
Mohamed Ouakarrouch, N. Laaroussi, M. Garoum, Said Bousshine, A. Bybi, Abderrahim Benallel, A. Tilioua
The main objective of this paper is to elaborate and characterize new ecological composites based on cardboard waste and abandoned natural fibers, in the Drâa-Tafilalet region (South-East, Morocco), for the manufacture of local thermo-acoustical insulation panels. For this study, 25 samples were prepared by mixing 60% of cardboard waste and 40% of vegetable fibers (Reed tree, esparto fiber, fig tree, and Olive tree). The morphological analysis of the different fibers was carried out by scanning electron microscopy (SEM), while, the physical, thermal, and acoustical properties of samples were measured experimentally using standard methods. The experimental results showed that all new composites have better thermal and acoustical performances comparable to those of synthetic insulation materials. The density, thermal conductivity, thermal diffusivity, and sound absorption coefficient of those composites were in the range of 278.6–343.8 kg/m3; 0.072–0.10 W/m·K; 1254.5–1807.5 J/kg·K; 0.4–0.8, respectively. Consequently, the by-products recovered in this study are good candidates for the development of local insulation materials with useful properties for thermal and acoustical insulation applications in buildings, low environmental impact, low cost, and competition with commercialized synthetic insulation materials.
{"title":"Sustainable thermo-acoustical insulation material from cardboard waste and natural fibers: Elaboration and performance evaluation","authors":"Mohamed Ouakarrouch, N. Laaroussi, M. Garoum, Said Bousshine, A. Bybi, Abderrahim Benallel, A. Tilioua","doi":"10.1177/17442591221121924","DOIUrl":"https://doi.org/10.1177/17442591221121924","url":null,"abstract":"The main objective of this paper is to elaborate and characterize new ecological composites based on cardboard waste and abandoned natural fibers, in the Drâa-Tafilalet region (South-East, Morocco), for the manufacture of local thermo-acoustical insulation panels. For this study, 25 samples were prepared by mixing 60% of cardboard waste and 40% of vegetable fibers (Reed tree, esparto fiber, fig tree, and Olive tree). The morphological analysis of the different fibers was carried out by scanning electron microscopy (SEM), while, the physical, thermal, and acoustical properties of samples were measured experimentally using standard methods. The experimental results showed that all new composites have better thermal and acoustical performances comparable to those of synthetic insulation materials. The density, thermal conductivity, thermal diffusivity, and sound absorption coefficient of those composites were in the range of 278.6–343.8 kg/m3; 0.072–0.10 W/m·K; 1254.5–1807.5 J/kg·K; 0.4–0.8, respectively. Consequently, the by-products recovered in this study are good candidates for the development of local insulation materials with useful properties for thermal and acoustical insulation applications in buildings, low environmental impact, low cost, and competition with commercialized synthetic insulation materials.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"12 1","pages":"372 - 392"},"PeriodicalIF":2.0,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78180680","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 : 2022-09-01DOI: 10.1177/17442591221121932
S. Van Linden, M. Lacasse, N. Van Den Bossche
Drainage reduces the amount of water able to infiltrate toward the interior of wall assemblies. However, a portion of the infiltrated water remains in the assembly after drainage has occurred. The degree to which this retained portion of water affects the durability of the wall assembly can be evaluated by means of hygrothermal simulations. However, the number of studies reporting information on the retention percentage that can be applied as input for hygrothermal simulations and on the drainage performance of wall assemblies is, in general, quite limited. Therefore, an experimental study was developed, to assess governing test methods to evaluate drainage characteristics and to quantify retention of water in wall test specimens having various cavity widths and incorporating different drainage materials. It was concluded that apart from the absolute amount of retained water, the lateral spreading of water in the cavity and the overall wetted area, should also be considered, thereby resulting in reporting the retained amount relative to the wetted area. The latter values provide more detailed information on the behavior of water in the cavity. Additionally, it was concluded that a clear cavity of 1 mm can drain water more efficiently than a cavity of 10 mm. As well, the surface texture of drainage materials affected the spreading and retention of water within the cavity and the use of a drainage mat in the cavity resulted in an increased relative retention but a reduced lateral spreading of the water.
{"title":"Drainage of infiltrated rainwater in wall assemblies: Test method, experimental quantification, and recommendations","authors":"S. Van Linden, M. Lacasse, N. Van Den Bossche","doi":"10.1177/17442591221121932","DOIUrl":"https://doi.org/10.1177/17442591221121932","url":null,"abstract":"Drainage reduces the amount of water able to infiltrate toward the interior of wall assemblies. However, a portion of the infiltrated water remains in the assembly after drainage has occurred. The degree to which this retained portion of water affects the durability of the wall assembly can be evaluated by means of hygrothermal simulations. However, the number of studies reporting information on the retention percentage that can be applied as input for hygrothermal simulations and on the drainage performance of wall assemblies is, in general, quite limited. Therefore, an experimental study was developed, to assess governing test methods to evaluate drainage characteristics and to quantify retention of water in wall test specimens having various cavity widths and incorporating different drainage materials. It was concluded that apart from the absolute amount of retained water, the lateral spreading of water in the cavity and the overall wetted area, should also be considered, thereby resulting in reporting the retained amount relative to the wetted area. The latter values provide more detailed information on the behavior of water in the cavity. Additionally, it was concluded that a clear cavity of 1 mm can drain water more efficiently than a cavity of 10 mm. As well, the surface texture of drainage materials affected the spreading and retention of water within the cavity and the use of a drainage mat in the cavity resulted in an increased relative retention but a reduced lateral spreading of the water.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"43 1","pages":"1022 - 1056"},"PeriodicalIF":2.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77662761","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 : 2022-08-10DOI: 10.1177/17442591221109956
Klaus Viljanen, J. Puttonen, Xiaoshu Lü
The study comprises three laboratory tests in which typical Finnish highly insulated (HI) walls were exposed to concentrated leakages of indoor air under steady outdoor temperatures of 1–5°C. Airflows with a relative humidity of 50% and at rates of 1–3 L/min were directed close to the wooden frames inside the walls. The thermal resistance ratios between the exterior sheathing(s) and the whole wall (Γ) were 20%–22% and 1%–10% for the HI and baseline (BL) walls. The HI walls that presented Γ values of at least 20% were observed to be resistant to air exfiltration, and their durability was not affected by the addition of a gypsum sheathing outside the wooden frame or a more permeable vapor retarder. This is related to the negative linear correlation that exists between the moisture accumulation rate in wood-based material and the dew point depression (DPD) value. The developed approach, called the DPD method, shows that a significant degree of moisture accumulation does not occur even for DPD values of as low as −2°C if the exterior sheathing is vapor permeable. The airflow does not penetrate into the rigid mineral wool sheathing, which helps to avoid interstitial condensation. Regardless of thermal transmittance, the HI and BL walls with maximum Γ values of 1% were exposed to a high relative humidity and even interstitial condensation because the DPD values were often below −2°C. For these walls, the mold index analysis and visual observations confirmed the local risk for mold growth on the opposite side of the leakage point. In practice, long-term mold growth may be limited if the seasonal periods during which the outdoor temperature is 1–5°C last for a maximum of about 1 month every year.
{"title":"Hygrothermal performance of highly insulated external walls subjected to indoor air exfiltration","authors":"Klaus Viljanen, J. Puttonen, Xiaoshu Lü","doi":"10.1177/17442591221109956","DOIUrl":"https://doi.org/10.1177/17442591221109956","url":null,"abstract":"The study comprises three laboratory tests in which typical Finnish highly insulated (HI) walls were exposed to concentrated leakages of indoor air under steady outdoor temperatures of 1–5°C. Airflows with a relative humidity of 50% and at rates of 1–3 L/min were directed close to the wooden frames inside the walls. The thermal resistance ratios between the exterior sheathing(s) and the whole wall (Γ) were 20%–22% and 1%–10% for the HI and baseline (BL) walls. The HI walls that presented Γ values of at least 20% were observed to be resistant to air exfiltration, and their durability was not affected by the addition of a gypsum sheathing outside the wooden frame or a more permeable vapor retarder. This is related to the negative linear correlation that exists between the moisture accumulation rate in wood-based material and the dew point depression (DPD) value. The developed approach, called the DPD method, shows that a significant degree of moisture accumulation does not occur even for DPD values of as low as −2°C if the exterior sheathing is vapor permeable. The airflow does not penetrate into the rigid mineral wool sheathing, which helps to avoid interstitial condensation. Regardless of thermal transmittance, the HI and BL walls with maximum Γ values of 1% were exposed to a high relative humidity and even interstitial condensation because the DPD values were often below −2°C. For these walls, the mold index analysis and visual observations confirmed the local risk for mold growth on the opposite side of the leakage point. In practice, long-term mold growth may be limited if the seasonal periods during which the outdoor temperature is 1–5°C last for a maximum of about 1 month every year.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"9 1","pages":"967 - 1021"},"PeriodicalIF":2.0,"publicationDate":"2022-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84221839","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 : 2022-05-15DOI: 10.1177/17442591221093057
G. Ramírez-Zúñiga, Guillermo Barrios, Guadalupe Huelsz Lesbros, Vanessa Sattele
There is a worldwide effort aimed at reducing energy consumption in buildings. Part of this effort includes bioclimatic design in the curricula for architects and engineers. The selection of constructive systems for the building envelope according to the climate is of significant importance for bioclimatic design. This has to be done by calculating the heat transfer through the constructive system using the time-dependent model. However, because the time-dependent model is easier to use it is also more commonly employed. To contribute to the teaching of the importance of using the time-dependent model, a didactic device and a practice were proposed. This paper presents the physical problem and the heat transfer models; the didactic device’s design process, its components and operating method; as well as the methodology for the practice. The didactic device and practice were created by the interaction of experts and students who gave their opinions and suggestions during different workshops.
{"title":"Didactic device for teaching the importance of the time-dependent model for heat transfer calculations in constructive systems of buildings","authors":"G. Ramírez-Zúñiga, Guillermo Barrios, Guadalupe Huelsz Lesbros, Vanessa Sattele","doi":"10.1177/17442591221093057","DOIUrl":"https://doi.org/10.1177/17442591221093057","url":null,"abstract":"There is a worldwide effort aimed at reducing energy consumption in buildings. Part of this effort includes bioclimatic design in the curricula for architects and engineers. The selection of constructive systems for the building envelope according to the climate is of significant importance for bioclimatic design. This has to be done by calculating the heat transfer through the constructive system using the time-dependent model. However, because the time-dependent model is easier to use it is also more commonly employed. To contribute to the teaching of the importance of using the time-dependent model, a didactic device and a practice were proposed. This paper presents the physical problem and the heat transfer models; the didactic device’s design process, its components and operating method; as well as the methodology for the practice. The didactic device and practice were created by the interaction of experts and students who gave their opinions and suggestions during different workshops.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"14 1","pages":"1091 - 1102"},"PeriodicalIF":2.0,"publicationDate":"2022-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78248475","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 : 2022-04-20DOI: 10.1177/17442591221085734
Bruno Vanderschelden, Klaas Calle, N. Van Den Bossche
Historic masonry has a rich and colorful history making it a treasured part in our society. To preserve and protect this heritage, adequate moisture control, retrofit, and restauration strategies are required. However, due to the large range of material properties inherent to historic brickwork, a single uniform renovation strategy appears impossible. To describe similarity in brickwork, the existing clustering approach developed by Zhao was evaluated. The idea is that different types of bricks with similar properties can be represented by a single representative brick for that cluster, for example, when conducting hygrothermal simulations. It could help improve existing retrofit practice by reducing characterization processes and minimizing time-consuming laboratory measuring tests. However, in this paper the approach presented by Zhao is questioned since the clustering is solely based on an equal impact of the material properties and the response behavior and associated degradation risks are neglected. The aim of this paper was twofold. Firstly, similarity in brickwork obtained by clustering according to Zhao was evaluated by means of hygrothermal simulations to see whether bricks in the same cluster show similar degradation risks. Zhao’s clustering provides homogenous clusters regarding physical material properties, but significant variation was found in degradation risks for different bricks within the same cluster. Secondly, a methodology is presented to translate similarities in degradation profiles toward similarities in material properties. Sensitivity analyses were used to study the response behavior based on three degradations risks: mold growth, wood rot, and frost damage. Finally, an overall clustering scheme was generated for brickwork, based on classification trees for different degradation phenomena.
{"title":"On the potential of clustering approaches for hygrothermal material properties based on three degradation risks in solid masonry constructions","authors":"Bruno Vanderschelden, Klaas Calle, N. Van Den Bossche","doi":"10.1177/17442591221085734","DOIUrl":"https://doi.org/10.1177/17442591221085734","url":null,"abstract":"Historic masonry has a rich and colorful history making it a treasured part in our society. To preserve and protect this heritage, adequate moisture control, retrofit, and restauration strategies are required. However, due to the large range of material properties inherent to historic brickwork, a single uniform renovation strategy appears impossible. To describe similarity in brickwork, the existing clustering approach developed by Zhao was evaluated. The idea is that different types of bricks with similar properties can be represented by a single representative brick for that cluster, for example, when conducting hygrothermal simulations. It could help improve existing retrofit practice by reducing characterization processes and minimizing time-consuming laboratory measuring tests. However, in this paper the approach presented by Zhao is questioned since the clustering is solely based on an equal impact of the material properties and the response behavior and associated degradation risks are neglected. The aim of this paper was twofold. Firstly, similarity in brickwork obtained by clustering according to Zhao was evaluated by means of hygrothermal simulations to see whether bricks in the same cluster show similar degradation risks. Zhao’s clustering provides homogenous clusters regarding physical material properties, but significant variation was found in degradation risks for different bricks within the same cluster. Secondly, a methodology is presented to translate similarities in degradation profiles toward similarities in material properties. Sensitivity analyses were used to study the response behavior based on three degradations risks: mold growth, wood rot, and frost damage. Finally, an overall clustering scheme was generated for brickwork, based on classification trees for different degradation phenomena.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"25 1","pages":"882 - 922"},"PeriodicalIF":2.0,"publicationDate":"2022-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77567116","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 : 2022-04-12DOI: 10.1177/17442591221084351
Francesco Squadroni, Giuseppe De Michele, E. Mazzucchelli, I. Demanega, S. Mangialardo, S. Avesani
This paper presents a study of the thermo-hygrometric behaviour of a Double Skin Façade (DSF) unit. The study aims (i) at comparing currently used calculation procedures according to European and American standards (UNI EN ISO 10077, UNI EN ISO 12631:2018, ISO 15099:2003, ANSI/NFRC 100 for the thermal performance and ISO 13788:2012 (2012) for the condensation risk), and (ii) at assessing the 2D hygrothermal performance of a double skin module through a Finite Element Method (FEM)-based model. According to the current standards, a detailed characterization of thermal and fluid dynamic phenomena in closed and ventilated cavities is neglected and a simplified approach is proposed, which tends to overestimate the overall U-value of the curtain wall (UCW) due to an incremental thermal resistance that depends on the thickness of the air gap layer and the level of ventilation. The potential risk of this simplification is that the DSF estimated design performance, whilst complying with regulatory requirements, present inconsistencies respect to the real behaviour, impacting energy, comfort, material degradation, etc. Accurate assessments could be done already during design through detailed FEM multi-physic analyses. Nevertheless, those require a specific knowledge, are cost and time-consuming. As a first step, this study focuses on comparing the normed calculation approach for the design, against a detailed FEM-based multi-physics methodology. Specifically, this couples CFD, hygrothermal and Ray Tracing physics in a tool for the calculation of thermal transmittance, g-value and relative humidity of a DSF with a customizable geometry. As a second step, given a real DSF unit that showed unforeseen phenomena of surface condensation inside the cavity during several hours in spring and autumn, the multi-physic tool has been used to evaluate the condensation risk with the current and modified DSF design, under static and time-dependent boundary conditions. Graphical abstract
本文介绍了一种双皮肤farade (DSF)装置的热湿特性的研究。该研究旨在(i)根据欧洲和美国标准(UNI EN ISO 10077、UNI EN ISO 12631:2018、ISO 15099:2003、ANSI/NFRC 100的热性能和ISO 13788:2012(2012)的冷凝风险)比较目前使用的计算程序，以及(ii)通过基于有限元法(FEM)的模型评估双蒙皮模块的二维湿热性能。根据目前的标准，忽略了封闭通风腔体中热和流体动力学现象的详细表征，并提出了一种简化的方法，该方法往往高估了幕墙(UCW)的总体u值，因为热阻增量取决于气隙层的厚度和通风水平。这种简化的潜在风险是，DSF估计的设计性能虽然符合法规要求，但与实际行为存在不一致，影响能源、舒适性、材料降解等。通过详细的有限元多物理场分析，在设计过程中就可以得到准确的评价。然而，这些需要特定的知识，成本高，耗时长。作为第一步，本研究的重点是比较设计的规范计算方法，与详细的基于有限元的多物理场方法。具体来说，它将CFD、湿热和光线追踪物理结合在一个工具中，用于计算具有可定制几何形状的DSF的热透射率、g值和相对湿度。第二步，给出了一个真实的DSF单元，该单元在春季和秋季的几个小时内显示了腔内不可预见的表面冷凝现象，在静态和时间相关的边界条件下，使用多物理场工具评估了当前和改进的DSF设计的冷凝风险。图形抽象
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