The objective of this work was to compare the hygrothermal responses and the moisture performance... more The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amon...
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR)... more The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council...
Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an... more Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance....
A moisture reference year (MRY) is generally used to assess the durability, or long-term performa... more A moisture reference year (MRY) is generally used to assess the durability, or long-term performance of building envelopes within a long climatological time period, e.g. a 31 year timeframe. The intent of this paper is to develop a set of moisture reference years that can be used to assess risk to the formation of mould growth in wood-frame buildings over the long-term. The set of moisture reference years have been developed based on 15 realizations of 31-year climate data. Replicated Latin Hypercube Sampling is applied to select 15 sub-realizations with 7 representative years having different levels of moisture index (MI) from each realization. Thereafter, hygrothermal simulations are performed for a brick veneer clad wood-frame wall assembly using the 15 sub-realizations; that sub-realization which produces the highest value of maximum mould growth index over 7-year period is selected as the MRY. The selection process is then implemented for all 15 realizations of the 31-years of ...
A mathematical model based on the water potential concept was used to simulate the effect of leng... more A mathematical model based on the water potential concept was used to simulate the effect of length and diameter on the drying rate of aspen logs. The moisture content-water potential relationship and the effective water conductivity were determined during independent experiments. The set of equations describing heat and mass transfer during the drying process were solved by the finite element method. As expected, diameters and lengths had a strong effect on log drying rate. Smaller diameter logs dried faster than larger ones. Shorter logs dried faster than longer ones. Over a critical diameter or length value, however, there was no further marked difference in drying rate for larger or longer logs. For a given length, drying was predominantly radial in smaller diameter logs, whereas in larger logs, longitudinal drying was predominant. For longer logs, drying occurred essentially in the radial direction.
A log drying model describing heat and mass transfer in logs during drying is presented. The mode... more A log drying model describing heat and mass transfer in logs during drying is presented. The model is based on the water potential concept. The moisture content-water potential relationship and effective water conductivity were determined through independent experiments. The resistance of bark to moisture flow was estimated by fitting the theoretical drying curve to the experimental one. The set of equations describing heat and mass transfer during the drying was then solved by the finite element method. The model accurately simulates the drying of aspen logs and shows that bark removal significantly affects log drying rate. Under the simulation conditions selected, the average drying rate of aspen logs with debarked areas of 25, 50, 75, and 100 percent was roughly 1.5, 2, 2.5, and 3 times greater, respectively, than for logs with 0 percent bark loss.
Previous studies have shown that the effects of climate change on building structures will increa... more Previous studies have shown that the effects of climate change on building structures will increase the mould growth risk of the wood-frame building envelope in many circumstances. This risk can be controlled by wind-driven rain deflection, improving water tightness of the exterior facade, and improving cladding ventilation. However, the effectiveness of these risk mitigation strategies are subject to various uncertainties, such as the uncertainties of wall component properties and micro-climatic conditions. The objective of this paper is to apply stochastic hygrothermal simulation to evaluate the mould growth risk of a brick veneer-clad wood-frame wall with a drainage cavity under historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone. An extensive literature review was conducted to quantify the range of stochastic variables including rain deposition factor, rain leakage moisture source, cladding ventilation rate and material properties ...
This paper evaluates the reliability of the currently used climate-based indices in selecting a m... more This paper evaluates the reliability of the currently used climate-based indices in selecting a moisture reference year (MRY) for the freeze-thaw (FT) damage risk assessment of internally insulated solid brick walls. The evaluation methodology compares the ranking of the years determined by the climate-based indices and response-based indices from simulations, regarded as actual performance. The hygrothermal response of an old brick masonry wall assembly, before and after retrofit, was investigated in two Canadian cities under historical and projected future climates. Results indicated that climate-based indices failed to represent the actual performance. However, among the response-based indices, the freeze-thaw damage risk index (FTDR) showed a better correlation with the climate-based indices. Additionally, results indicated a better correlation between the climatic index (CI), the moisture index (MI), and FTDR in Ottawa; however, in Vancouver, a better fit was found between MI a...
Given the long lifespan of buildings it becomes inevitable to assess the impact of climate change... more Given the long lifespan of buildings it becomes inevitable to assess the impact of climate change when designing building envelopes or retrofitting solutions. Hygrothermal simulations would benefit from using a climate ensemble to account for the large uncertainties that come with modelled climate data. However, this has been rarely done so far, and no state-of-the-art methodology exists to implement ensemble data in hygrothermal simulations. This paper presents the application of a Canadian initial-condition ensemble CanRCM4 LE in hygrothermal (HAM) modelling. A brick-clad wood-stud wall assembly and historical solid masonry wall, before and after retrofitting, are analysed for Ottawa, CA. Variations in the HAM model are studied to evaluate whether the ensemble can be represented by one smaller "reduced" ensemble for different studies. And, the potential of climate-based indices to predict this "reduced" ensemble is studied. Further, the uncertainty of the ensemble is analysed, as well as the climate change signal of the damage functions. It is found that the application of a climate ensemble is highly valuable for HAM modelling, as it is able to account for the high uncertainty of climate change data. To maintain the level of information, it is recommended to perform HAM simulations using the entire ensemble. However, there is potential to select a "reduced" ensemble to represent spread of the climate change signal.
The objective of this study was to explore the potential of a machine learning algorithm, the Sup... more The objective of this study was to explore the potential of a machine learning algorithm, the Support Vector Machine Regression (SVR), to forecast long-term hygrothermal responses and the moisture performance of light wood frame and massive timber walls. Hygrothermal simulations were performed using a 31-year long series of climate data in three cities across Canada. Then, the first 5 years of the series were used in each case to train the model, which was then used to forecast the hygrothermal responses (temperature and relative humidity) and moisture performance indicator (mold growth index) for the remaining years of the series. The location of interest was the exterior layer of the OSB and cross-laminated timber in the case of the wood frame wall and massive timber wall, respectively. A sliding window approach was used to incorporate the dependence of the hygrothermal response on the past climatic conditions, which allowed SVR to capture time, implicitly. The variable selection ...
The objective of this work was to compare the hygrothermal responses and the moisture performance... more The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amon...
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR)... more The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council...
Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an... more Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance....
A moisture reference year (MRY) is generally used to assess the durability, or long-term performa... more A moisture reference year (MRY) is generally used to assess the durability, or long-term performance of building envelopes within a long climatological time period, e.g. a 31 year timeframe. The intent of this paper is to develop a set of moisture reference years that can be used to assess risk to the formation of mould growth in wood-frame buildings over the long-term. The set of moisture reference years have been developed based on 15 realizations of 31-year climate data. Replicated Latin Hypercube Sampling is applied to select 15 sub-realizations with 7 representative years having different levels of moisture index (MI) from each realization. Thereafter, hygrothermal simulations are performed for a brick veneer clad wood-frame wall assembly using the 15 sub-realizations; that sub-realization which produces the highest value of maximum mould growth index over 7-year period is selected as the MRY. The selection process is then implemented for all 15 realizations of the 31-years of ...
A mathematical model based on the water potential concept was used to simulate the effect of leng... more A mathematical model based on the water potential concept was used to simulate the effect of length and diameter on the drying rate of aspen logs. The moisture content-water potential relationship and the effective water conductivity were determined during independent experiments. The set of equations describing heat and mass transfer during the drying process were solved by the finite element method. As expected, diameters and lengths had a strong effect on log drying rate. Smaller diameter logs dried faster than larger ones. Shorter logs dried faster than longer ones. Over a critical diameter or length value, however, there was no further marked difference in drying rate for larger or longer logs. For a given length, drying was predominantly radial in smaller diameter logs, whereas in larger logs, longitudinal drying was predominant. For longer logs, drying occurred essentially in the radial direction.
A log drying model describing heat and mass transfer in logs during drying is presented. The mode... more A log drying model describing heat and mass transfer in logs during drying is presented. The model is based on the water potential concept. The moisture content-water potential relationship and effective water conductivity were determined through independent experiments. The resistance of bark to moisture flow was estimated by fitting the theoretical drying curve to the experimental one. The set of equations describing heat and mass transfer during the drying was then solved by the finite element method. The model accurately simulates the drying of aspen logs and shows that bark removal significantly affects log drying rate. Under the simulation conditions selected, the average drying rate of aspen logs with debarked areas of 25, 50, 75, and 100 percent was roughly 1.5, 2, 2.5, and 3 times greater, respectively, than for logs with 0 percent bark loss.
The objective of this work was to compare the hygrothermal responses and the moisture performance... more The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amon...
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR)... more The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council...
Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an... more Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance....
A moisture reference year (MRY) is generally used to assess the durability, or long-term performa... more A moisture reference year (MRY) is generally used to assess the durability, or long-term performance of building envelopes within a long climatological time period, e.g. a 31 year timeframe. The intent of this paper is to develop a set of moisture reference years that can be used to assess risk to the formation of mould growth in wood-frame buildings over the long-term. The set of moisture reference years have been developed based on 15 realizations of 31-year climate data. Replicated Latin Hypercube Sampling is applied to select 15 sub-realizations with 7 representative years having different levels of moisture index (MI) from each realization. Thereafter, hygrothermal simulations are performed for a brick veneer clad wood-frame wall assembly using the 15 sub-realizations; that sub-realization which produces the highest value of maximum mould growth index over 7-year period is selected as the MRY. The selection process is then implemented for all 15 realizations of the 31-years of ...
A mathematical model based on the water potential concept was used to simulate the effect of leng... more A mathematical model based on the water potential concept was used to simulate the effect of length and diameter on the drying rate of aspen logs. The moisture content-water potential relationship and the effective water conductivity were determined during independent experiments. The set of equations describing heat and mass transfer during the drying process were solved by the finite element method. As expected, diameters and lengths had a strong effect on log drying rate. Smaller diameter logs dried faster than larger ones. Shorter logs dried faster than longer ones. Over a critical diameter or length value, however, there was no further marked difference in drying rate for larger or longer logs. For a given length, drying was predominantly radial in smaller diameter logs, whereas in larger logs, longitudinal drying was predominant. For longer logs, drying occurred essentially in the radial direction.
A log drying model describing heat and mass transfer in logs during drying is presented. The mode... more A log drying model describing heat and mass transfer in logs during drying is presented. The model is based on the water potential concept. The moisture content-water potential relationship and effective water conductivity were determined through independent experiments. The resistance of bark to moisture flow was estimated by fitting the theoretical drying curve to the experimental one. The set of equations describing heat and mass transfer during the drying was then solved by the finite element method. The model accurately simulates the drying of aspen logs and shows that bark removal significantly affects log drying rate. Under the simulation conditions selected, the average drying rate of aspen logs with debarked areas of 25, 50, 75, and 100 percent was roughly 1.5, 2, 2.5, and 3 times greater, respectively, than for logs with 0 percent bark loss.
Previous studies have shown that the effects of climate change on building structures will increa... more Previous studies have shown that the effects of climate change on building structures will increase the mould growth risk of the wood-frame building envelope in many circumstances. This risk can be controlled by wind-driven rain deflection, improving water tightness of the exterior facade, and improving cladding ventilation. However, the effectiveness of these risk mitigation strategies are subject to various uncertainties, such as the uncertainties of wall component properties and micro-climatic conditions. The objective of this paper is to apply stochastic hygrothermal simulation to evaluate the mould growth risk of a brick veneer-clad wood-frame wall with a drainage cavity under historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone. An extensive literature review was conducted to quantify the range of stochastic variables including rain deposition factor, rain leakage moisture source, cladding ventilation rate and material properties ...
This paper evaluates the reliability of the currently used climate-based indices in selecting a m... more This paper evaluates the reliability of the currently used climate-based indices in selecting a moisture reference year (MRY) for the freeze-thaw (FT) damage risk assessment of internally insulated solid brick walls. The evaluation methodology compares the ranking of the years determined by the climate-based indices and response-based indices from simulations, regarded as actual performance. The hygrothermal response of an old brick masonry wall assembly, before and after retrofit, was investigated in two Canadian cities under historical and projected future climates. Results indicated that climate-based indices failed to represent the actual performance. However, among the response-based indices, the freeze-thaw damage risk index (FTDR) showed a better correlation with the climate-based indices. Additionally, results indicated a better correlation between the climatic index (CI), the moisture index (MI), and FTDR in Ottawa; however, in Vancouver, a better fit was found between MI a...
Given the long lifespan of buildings it becomes inevitable to assess the impact of climate change... more Given the long lifespan of buildings it becomes inevitable to assess the impact of climate change when designing building envelopes or retrofitting solutions. Hygrothermal simulations would benefit from using a climate ensemble to account for the large uncertainties that come with modelled climate data. However, this has been rarely done so far, and no state-of-the-art methodology exists to implement ensemble data in hygrothermal simulations. This paper presents the application of a Canadian initial-condition ensemble CanRCM4 LE in hygrothermal (HAM) modelling. A brick-clad wood-stud wall assembly and historical solid masonry wall, before and after retrofitting, are analysed for Ottawa, CA. Variations in the HAM model are studied to evaluate whether the ensemble can be represented by one smaller "reduced" ensemble for different studies. And, the potential of climate-based indices to predict this "reduced" ensemble is studied. Further, the uncertainty of the ensemble is analysed, as well as the climate change signal of the damage functions. It is found that the application of a climate ensemble is highly valuable for HAM modelling, as it is able to account for the high uncertainty of climate change data. To maintain the level of information, it is recommended to perform HAM simulations using the entire ensemble. However, there is potential to select a "reduced" ensemble to represent spread of the climate change signal.
The objective of this study was to explore the potential of a machine learning algorithm, the Sup... more The objective of this study was to explore the potential of a machine learning algorithm, the Support Vector Machine Regression (SVR), to forecast long-term hygrothermal responses and the moisture performance of light wood frame and massive timber walls. Hygrothermal simulations were performed using a 31-year long series of climate data in three cities across Canada. Then, the first 5 years of the series were used in each case to train the model, which was then used to forecast the hygrothermal responses (temperature and relative humidity) and moisture performance indicator (mold growth index) for the remaining years of the series. The location of interest was the exterior layer of the OSB and cross-laminated timber in the case of the wood frame wall and massive timber wall, respectively. A sliding window approach was used to incorporate the dependence of the hygrothermal response on the past climatic conditions, which allowed SVR to capture time, implicitly. The variable selection ...
The objective of this work was to compare the hygrothermal responses and the moisture performance... more The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amon...
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR)... more The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council...
Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an... more Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance....
A moisture reference year (MRY) is generally used to assess the durability, or long-term performa... more A moisture reference year (MRY) is generally used to assess the durability, or long-term performance of building envelopes within a long climatological time period, e.g. a 31 year timeframe. The intent of this paper is to develop a set of moisture reference years that can be used to assess risk to the formation of mould growth in wood-frame buildings over the long-term. The set of moisture reference years have been developed based on 15 realizations of 31-year climate data. Replicated Latin Hypercube Sampling is applied to select 15 sub-realizations with 7 representative years having different levels of moisture index (MI) from each realization. Thereafter, hygrothermal simulations are performed for a brick veneer clad wood-frame wall assembly using the 15 sub-realizations; that sub-realization which produces the highest value of maximum mould growth index over 7-year period is selected as the MRY. The selection process is then implemented for all 15 realizations of the 31-years of ...
A mathematical model based on the water potential concept was used to simulate the effect of leng... more A mathematical model based on the water potential concept was used to simulate the effect of length and diameter on the drying rate of aspen logs. The moisture content-water potential relationship and the effective water conductivity were determined during independent experiments. The set of equations describing heat and mass transfer during the drying process were solved by the finite element method. As expected, diameters and lengths had a strong effect on log drying rate. Smaller diameter logs dried faster than larger ones. Shorter logs dried faster than longer ones. Over a critical diameter or length value, however, there was no further marked difference in drying rate for larger or longer logs. For a given length, drying was predominantly radial in smaller diameter logs, whereas in larger logs, longitudinal drying was predominant. For longer logs, drying occurred essentially in the radial direction.
A log drying model describing heat and mass transfer in logs during drying is presented. The mode... more A log drying model describing heat and mass transfer in logs during drying is presented. The model is based on the water potential concept. The moisture content-water potential relationship and effective water conductivity were determined through independent experiments. The resistance of bark to moisture flow was estimated by fitting the theoretical drying curve to the experimental one. The set of equations describing heat and mass transfer during the drying was then solved by the finite element method. The model accurately simulates the drying of aspen logs and shows that bark removal significantly affects log drying rate. Under the simulation conditions selected, the average drying rate of aspen logs with debarked areas of 25, 50, 75, and 100 percent was roughly 1.5, 2, 2.5, and 3 times greater, respectively, than for logs with 0 percent bark loss.
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Papers by Maurice Defo