In order to support mega-events in the near future such as the FIFA 2022 World Cup, the Qatari co... more In order to support mega-events in the near future such as the FIFA 2022 World Cup, the Qatari construction sector is dealing with exceptional opportunities and challenges in the Building Information Modeling (BIM) domain. Big projects based on the use of this advanced new process are currently under development in new economic cluster areas in the country. For this reason, BIM is being implemented using any available method on many large projects despite the absence of any mandated BIM standards and/or government policies. Most companies in Qatar are collating portions of international BIM standards to produce guidelines aimed at resolving problems and overcoming projects constraints. All this raises a need for higher BIM competencies. An assessment in terms of BIM competencies to understand where Qatars construction industry practitioners are and where they are trying to go has become a necessity. Accordingly, this article seeks to provide a local insight of the BIM competencies a...
Workers in hot environment experience high heat stresses that affect their productivity and worki... more Workers in hot environment experience high heat stresses that affect their productivity and working intervals. A cooling vest containing phase change material packets (PCMs) is used as a passive body cooling method to remove body heat for a relatively long duration. The aim of this work is to improve the design of the PCM-vest by making its weight lighter if possible or choosing a suitable melting temperature of the PCMs without jeopardizing the duration of its applicability. The study uses a validated transient mathematical model of heat and mass transfer through clothing layers containing PCM packets (fabric-PCM model) and integrated with a segmental bio-heat model to perform a parametric study on the effect of the melting temperature of PCM packets and their mass on trunk skin temperature and heat loss. The bio-heat model divides the torso into upper and lower segments to allow the incorporation of non-uniformity in skin temperature of torso as an interacting boundary for the PCM-vest. A parametric study is performed to investigate the effect of the mass of the PCM packets and PCM melting temperature on the upper and lower torso segments. The cooling duration of the cooling vest and cooling rate are determined and a number of recommendations are developed on desired PCM mass as well as melting temperature for maintaining lowest trunk skin temperature for the longest period in given environmental conditions and activity level. It is found that a lower melting temperature is favored when fast cooling is needed. Moreover, the mass of the PCM affects directly the total duration of melting but not the cooling rate. 2016 Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.. All rights reserved.The authors would like to acknowledge the financial support of the Qatar National Research Funds (a member of the Qatar Foundation), Grant #NPRP 7 - 486 - 2 - 185, State of Qatar.Scopu
Abstract The addition of fixed external shading devices to glazed surfaces reduces the space load... more Abstract The addition of fixed external shading devices to glazed surfaces reduces the space loads and sensations of visual discomfort caused by excessive day-lighting. The slat-to-slat separation distance of the brise-soleil blinds is crucial in controlling the beam and diffuse solar radiation penetration into the space. In this study, a model of an office space with fully-glazed facade and shaded with brise-soleil was developed to quantify its corresponding daylight glare index and space load. Results were successfully validated experimentally. Then, a parametric study was carried out on the slat separation-to-width of the validated model to find the ratio that ensures no occupant discomfort caused by glare and results in maximum possible energy savings for both south and east oriented fully-glazed facade offices in Qatar. The selection of slat separation-to-width ratio should ensure total blockage of beam solar radiation. Consequently, the sun altitude determines the ratio that yields no discomfort glare; due to the country's latitude, this ratio has to be less than unity in south orientations and slightly larger than the sine of the slat inclination angle in east orientations. The proper selection of separation-to-width ratio leads to significant energy savings which, if integrated with lighting control for internal electric lights, may reach 39.5% and 36.6% in south and east-oriented Clear glazed facade offices, respectively. For a country with high greenhouse gas emissions, this simple energy-conservation measure also provides a cheap technique that is able to reduce CO2 emissions by up to 52.7 kg/m2/year.
Abstract This study investigates the application of the evaporatively-cooled window system in hot... more Abstract This study investigates the application of the evaporatively-cooled window system in hot and humid climates and assesses its seasonal performance and benefits in terms of energy savings. The validated system is a hybrid combination of solar chimney, window and evaporative cooler that induces a natural buoyant flow originated by direct solar radiation application. As proper solar radiation data is critical in applying solar-driven technologies, an on-site weather station was established in Qatar for the measurement of several meteorological parameters for the entire year of 2016. The measurements represent actual validated data recordings in the city of Doha, mimicking harshly hot and humid weather conditions. The simple application of the evaporatively-cooled window on a typical office space subjected to such driving weather conditions was found to save 8.8% of the space total annual energy demand. During the summer, the performance of the system was enhanced by saving 11.3% of the space total daily heat gain. However, the benefits of the system diminished and were sometimes unfavorable during the winter due to its limited cooling performance caused by high humidity.
Abstract Energy efficiency in buildings is crucial for the design of sustainable cities, especial... more Abstract Energy efficiency in buildings is crucial for the design of sustainable cities, especially in hot climates where demands are high. This study investigates the impact of the shading optical properties on the space energy demands when brise soleil is installed in offices with one fully-glazed facade in four different orientations. The criteria for the selection of best shading property are an office with minimal possible total energy demand and maximum outdoor view without any occupant sensation of visual discomfort caused by glare at any time of the year. In addition, this study examines the feasibility of integrating light dimming control to these offices. A simulation model of an office space with external shading on a fully-glazed facade in one pre-selected orientation was developed and validated. Parametric studies on the shading reflectance and transmittance properties were conducted and their effects on spaces energy demands were observed for Qatar's climate, mimicking a developing country with harshly hot weather conditions. In south-oriented offices, savings caused by the addition of brise soleil reach 36.3%; unreflective or barely transmissive slats are recommended and light dimming control is unjustified. Moreover, unreflective opaque shading without light dimming control is found to be optimal in east and west-oriented offices as it saves 37.2% of the space overall energy demand. In contrary, installing highly-transmissive shadings with light dimming control is justified in north-oriented offices as it keeps full outdoor visual sight and still saves energy of up to 11.6%.
Cooling vests incorporating phase change material (PCM) packets are used to improve comfort of wo... more Cooling vests incorporating phase change material (PCM) packets are used to improve comfort of workers in hot environments. This work aims to investigate by modeling and experimentation the effect of dividing the working duration into two bouts, where different PCM melting temperatures are used in each bout. An integrated bio-heat and fabric-PCM model predictions of physiological and subjective votes are validated via active human subject testing at hot conditions. A parametric study is performed to select, at two conditions (40°C and 45°C), the optimal PCM melting temperatures of the two bouts that would result with similar thermal comfort and sensation to the optimal single-bout case. The optimal case achieves most reductions in energy use for PCM regeneration, PCM carried weight and material cost. The results of the parametric study showed that heat storage is reduced in the second bout due to wearing the second vest with lower PCM melting temperature, thus thermal comfort and se...
The diffusion of BIM practices and the increasing connotation of BIM contributed to the emergence... more The diffusion of BIM practices and the increasing connotation of BIM contributed to the emergence of several BIM-based specialist roles within the Architectural, Construction, Engineering and Facility Management (AEC-FM) sector. Both the competencies of each specialist role and the potential areas of competency overlap across these roles are not clearly identified in both academic and industry literature. Addressing this gap is important for: creating vocational and tertiary learning opportunities; supporting performance improvement of individuals and potential certification schemes; and defining roles within contract and on projects, and drafting recruitment profiles. The paper aims to identify the competencies for four key BIM specialist roles – selected based on their citation frequency – and analyze their competency overlap. Three knowledge sieves are used to identify the BIM roles and their competencies: academic literature; national BIM guides and specifications from the UK, U...
Abstract This study aims at evaluating experimentally phase change material (PCM) cooling vest pe... more Abstract This study aims at evaluating experimentally phase change material (PCM) cooling vest performance when incorporating two types of PCM with different melting temperatures with varied PCM placement on the lower, upper, front and back of the torso. Experiments on a thermal manikin were conducted to assess cooling rate observed with the various PCM arrangements while experiments on six male subjects were conducted to assess associated physiological and comfort votes after exercising for 45 min. The main findings of manikin testing were that an improved cooling effect can be achieved by covering the upper torso with PCM packets at 28 °C melting temperature while covering the lower torso with the 18 °C packets. Human subject testing established that similar improvements in thermal comfort and sensation levels could be attained when covering the back or lower torso segments with 18 °C instead of covering all the torso. In addition, a maximum reduction in local skin temperatures of 5.45 ± 1 °C was achieved accompanied with a reduction of 64 W in body heat storage. Covering the chest and upper back segments with the 18 °C packets suppressed sweat production and improved wetness sensation. Finally, 16% lower vest weight might be possible with prolonged working periods of two hours at 35 °C.
Abstract Shading devices installed on windows are designed to reduce solar radiation transmission... more Abstract Shading devices installed on windows are designed to reduce solar radiation transmission into the space by absorbing and reflecting radiation rays. This study investigates the effect of shading and day-lighting controls when applied on fully-glazed facades on the annual energy savings in hot climates. For this reason, a dynamic simulation model of a space containing brise soleil and venetian blinds added to the facade exterior surface was developed on EnergyPlus and validated experimentally for office spaces located in Doha, Qatar. Comparison between the experimental and simulation models showed maximum discrepancies of 11.8% and 13.5% in surface temperature and peak space thermal load, respectively. Upon validation, the simulation model was used to evaluate the annual energy savings associated with the use of shading devices on both south and north-oriented facades in Qatar. For the south-oriented facade, brise soleil and fixed blinds with 90° with the vertical were found to save 18.6% and 20.6% of the space energy demands respectively, while mitigating glare risks. As for the north facade, the addition of brise soleil and blinds saves 7.7% and 9.1% of the space total energy demands respectively and removes all risks associated with glare. The adoption of a shading control for the blind angle and day-lighting control for the electric lights was found to save 26.1% of the space total energy without compromising the comfortable glare limit. This control strategy allows the occupants to benefit from the fully-glazed facade while still upholding the indoor space requirements in terms of outdoor visual comfort and day-lighting entrance.
Abstract The objective of this work is to optimize the arrangement of Phase Change Material (PCM)... more Abstract The objective of this work is to optimize the arrangement of Phase Change Material (PCM) packets in a cooling vest by targeting torso segments that can trigger comfort when cooled. An integrated fabric-PCM and bio-heat simulation model is used in the optimization to predict human segmental core and skin temperatures to determine overall human thermal comfort during moderate activity in hot environment over a specified working period. The variables of the optimization were the number of PCM packets on the upper and lower front and back torso segments. The constraints to be met were: a core temperature not to exceed 38 °C, a comfort level not to be less than −1.4 on a comfort scale varying from very uncomfortable at −4 to very comfortable at +4 and a PCM melted mass fraction between 0.85 and 1.0. Three environmental conditions were considered at 28 °C, 35 °C and 45 °C for optimization and the results showed that 8, 18 and 20 PCM packets were needed to provide cooling for the outdoor worker at acceptable comfort level, respectively. At the very high ambient temperature of 45 °C and when increasing the PCM packets number to 32 packets, it was shown that the working duration can be extended from 45 min recommended by labor standards to two hours similar to duration permitted at 28 °C and 35 °C.
Abstract The distribution of phase change material (PCM) packets on a cooling vest worn by active... more Abstract The distribution of phase change material (PCM) packets on a cooling vest worn by active human in hot environments is investigated using an integrated fabric-PCM and bio-heat model. The model considered the effect of added PCM weight and hot environments on the human metabolic rate, and incorporated the effect of condensation to check its occurrence in the vest. The fabric-PCM model predictions of local torso skin temperature were validated experimentally on a thermal manikin operated at constant heat flux mode while its predictions of skin and core temperatures when integrated with the bioheat model were validated with published experimental data on human subjects exercising in hot conditions. The validated model is used in a parametric study to determine the best arrangement of 8 PCM packets distributed on different torso segments to improve sensation and comfort of human performing moderate activity in hot climate. It was found that placing 8 PCM packets on the back resulted in the best overall sensation of 1.38 as compared to 2.69 when no PCM is used using a sensation scale that varies from very cold at −4 to very hot at +4.
Thesis Department of Architecture and Development Studies School of Architecture Lund Institute of Technology Lund University, 2000
This study is on a combined effect of window, the daylighting and the thermal effects, in desert ... more This study is on a combined effect of window, the daylighting and the thermal effects, in desert houses. It is comprised of two complementary studies. In the introduction a historical review on the development of use daylight has been carried out in order to place the case study in a historical perspective. The first study is comprehensive and contains two main parts. In the first part a study was carried out on the people and history of the town of Ghardaia in Southern Algeria. This was done in order to understand the architectural form of that region. The second part is experimental and consists of two field studies carried out in Ghardaia. Their aim was to investigate the influence of daylight level and temperature on the use of residential houses. This investigation included both traditional and "modern" houses, the moderna having relatively large windows similar to those of the northern part of Algeria, the traditional ones having small or no windows. The second study is also experimental consisting of computer parametric studies on windows design from two standpoints, namely daylighting level and thermal effects of windows in desert houses. A typical traditional house is described as it was observed. Then the recorded light values are presented and commented upon. In the second part, three types of modern houses observed in the field studies are presented and compared to the traditional archetype. The comparison especially dwells on the relative effectiveness of the two systems of daylighting. In the third part, focusing on various issues of lighting, the results of interviews with the inhabitants are presented. The thermal and daylighting studies indicate that it is possible to have windows to the east, west or north orientations with still acceptable and daylighting effects as long as they comply with the following recommendations: * For south and north orientations, the absolute surfaces and the fenestsration should be in the medium to high range. * For an east orientation, the absolute surfaces and the fenestration should be in the medium range. * For an orientation to the west, similar recommendations may be appropriate, albeit with more carefully designed solar shading, since the probability for overheating will be higher.
Abstract A cooling vest containing phase change materials (PCM) can help in maintaining the skin ... more Abstract A cooling vest containing phase change materials (PCM) can help in maintaining the skin temperature of the covered parts at a comfortable level. A transient mathematical model of heat and mass transfer through clothing layers containing PCM packets was developed. Two experiments were performed on a clothed heated cylinder in controlled environment to validate the model using two PCMs at different melting temperatures. Good agreement was found between model-predicted and measured temperatures of the microclimate air between the cylinder and the PCM. The validated fabric-PCM model was then integrated with a segmental bio-heat model to provide realistic skin boundary conditions. The predicted core and mean skin temperatures agreed well with published experimental data of a human wearing a PCM-vest in hot environment. The validated integrated bio-heat and fabric-PCM models were used to study the effect of the melting temperature of the PCM and its mass on the vest performance. It was found that a lower melting temperature must be used when a fast cooling effect is desirable. Moreover, it was found that at fixed melting temperature increasing the PCM mass increased the cooling duration.
In order to support mega-events in the near future such as the FIFA 2022 World Cup, the Qatari co... more In order to support mega-events in the near future such as the FIFA 2022 World Cup, the Qatari construction sector is dealing with exceptional opportunities and challenges in the Building Information Modeling (BIM) domain. Big projects based on the use of this advanced new process are currently under development in new economic cluster areas in the country. For this reason, BIM is being implemented using any available method on many large projects despite the absence of any mandated BIM standards and/or government policies. Most companies in Qatar are collating portions of international BIM standards to produce guidelines aimed at resolving problems and overcoming projects constraints. All this raises a need for higher BIM competencies. An assessment in terms of BIM competencies to understand where Qatars construction industry practitioners are and where they are trying to go has become a necessity. Accordingly, this article seeks to provide a local insight of the BIM competencies a...
Workers in hot environment experience high heat stresses that affect their productivity and worki... more Workers in hot environment experience high heat stresses that affect their productivity and working intervals. A cooling vest containing phase change material packets (PCMs) is used as a passive body cooling method to remove body heat for a relatively long duration. The aim of this work is to improve the design of the PCM-vest by making its weight lighter if possible or choosing a suitable melting temperature of the PCMs without jeopardizing the duration of its applicability. The study uses a validated transient mathematical model of heat and mass transfer through clothing layers containing PCM packets (fabric-PCM model) and integrated with a segmental bio-heat model to perform a parametric study on the effect of the melting temperature of PCM packets and their mass on trunk skin temperature and heat loss. The bio-heat model divides the torso into upper and lower segments to allow the incorporation of non-uniformity in skin temperature of torso as an interacting boundary for the PCM-vest. A parametric study is performed to investigate the effect of the mass of the PCM packets and PCM melting temperature on the upper and lower torso segments. The cooling duration of the cooling vest and cooling rate are determined and a number of recommendations are developed on desired PCM mass as well as melting temperature for maintaining lowest trunk skin temperature for the longest period in given environmental conditions and activity level. It is found that a lower melting temperature is favored when fast cooling is needed. Moreover, the mass of the PCM affects directly the total duration of melting but not the cooling rate. 2016 Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc.. All rights reserved.The authors would like to acknowledge the financial support of the Qatar National Research Funds (a member of the Qatar Foundation), Grant #NPRP 7 - 486 - 2 - 185, State of Qatar.Scopu
Abstract The addition of fixed external shading devices to glazed surfaces reduces the space load... more Abstract The addition of fixed external shading devices to glazed surfaces reduces the space loads and sensations of visual discomfort caused by excessive day-lighting. The slat-to-slat separation distance of the brise-soleil blinds is crucial in controlling the beam and diffuse solar radiation penetration into the space. In this study, a model of an office space with fully-glazed facade and shaded with brise-soleil was developed to quantify its corresponding daylight glare index and space load. Results were successfully validated experimentally. Then, a parametric study was carried out on the slat separation-to-width of the validated model to find the ratio that ensures no occupant discomfort caused by glare and results in maximum possible energy savings for both south and east oriented fully-glazed facade offices in Qatar. The selection of slat separation-to-width ratio should ensure total blockage of beam solar radiation. Consequently, the sun altitude determines the ratio that yields no discomfort glare; due to the country's latitude, this ratio has to be less than unity in south orientations and slightly larger than the sine of the slat inclination angle in east orientations. The proper selection of separation-to-width ratio leads to significant energy savings which, if integrated with lighting control for internal electric lights, may reach 39.5% and 36.6% in south and east-oriented Clear glazed facade offices, respectively. For a country with high greenhouse gas emissions, this simple energy-conservation measure also provides a cheap technique that is able to reduce CO2 emissions by up to 52.7 kg/m2/year.
Abstract This study investigates the application of the evaporatively-cooled window system in hot... more Abstract This study investigates the application of the evaporatively-cooled window system in hot and humid climates and assesses its seasonal performance and benefits in terms of energy savings. The validated system is a hybrid combination of solar chimney, window and evaporative cooler that induces a natural buoyant flow originated by direct solar radiation application. As proper solar radiation data is critical in applying solar-driven technologies, an on-site weather station was established in Qatar for the measurement of several meteorological parameters for the entire year of 2016. The measurements represent actual validated data recordings in the city of Doha, mimicking harshly hot and humid weather conditions. The simple application of the evaporatively-cooled window on a typical office space subjected to such driving weather conditions was found to save 8.8% of the space total annual energy demand. During the summer, the performance of the system was enhanced by saving 11.3% of the space total daily heat gain. However, the benefits of the system diminished and were sometimes unfavorable during the winter due to its limited cooling performance caused by high humidity.
Abstract Energy efficiency in buildings is crucial for the design of sustainable cities, especial... more Abstract Energy efficiency in buildings is crucial for the design of sustainable cities, especially in hot climates where demands are high. This study investigates the impact of the shading optical properties on the space energy demands when brise soleil is installed in offices with one fully-glazed facade in four different orientations. The criteria for the selection of best shading property are an office with minimal possible total energy demand and maximum outdoor view without any occupant sensation of visual discomfort caused by glare at any time of the year. In addition, this study examines the feasibility of integrating light dimming control to these offices. A simulation model of an office space with external shading on a fully-glazed facade in one pre-selected orientation was developed and validated. Parametric studies on the shading reflectance and transmittance properties were conducted and their effects on spaces energy demands were observed for Qatar's climate, mimicking a developing country with harshly hot weather conditions. In south-oriented offices, savings caused by the addition of brise soleil reach 36.3%; unreflective or barely transmissive slats are recommended and light dimming control is unjustified. Moreover, unreflective opaque shading without light dimming control is found to be optimal in east and west-oriented offices as it saves 37.2% of the space overall energy demand. In contrary, installing highly-transmissive shadings with light dimming control is justified in north-oriented offices as it keeps full outdoor visual sight and still saves energy of up to 11.6%.
Cooling vests incorporating phase change material (PCM) packets are used to improve comfort of wo... more Cooling vests incorporating phase change material (PCM) packets are used to improve comfort of workers in hot environments. This work aims to investigate by modeling and experimentation the effect of dividing the working duration into two bouts, where different PCM melting temperatures are used in each bout. An integrated bio-heat and fabric-PCM model predictions of physiological and subjective votes are validated via active human subject testing at hot conditions. A parametric study is performed to select, at two conditions (40°C and 45°C), the optimal PCM melting temperatures of the two bouts that would result with similar thermal comfort and sensation to the optimal single-bout case. The optimal case achieves most reductions in energy use for PCM regeneration, PCM carried weight and material cost. The results of the parametric study showed that heat storage is reduced in the second bout due to wearing the second vest with lower PCM melting temperature, thus thermal comfort and se...
The diffusion of BIM practices and the increasing connotation of BIM contributed to the emergence... more The diffusion of BIM practices and the increasing connotation of BIM contributed to the emergence of several BIM-based specialist roles within the Architectural, Construction, Engineering and Facility Management (AEC-FM) sector. Both the competencies of each specialist role and the potential areas of competency overlap across these roles are not clearly identified in both academic and industry literature. Addressing this gap is important for: creating vocational and tertiary learning opportunities; supporting performance improvement of individuals and potential certification schemes; and defining roles within contract and on projects, and drafting recruitment profiles. The paper aims to identify the competencies for four key BIM specialist roles – selected based on their citation frequency – and analyze their competency overlap. Three knowledge sieves are used to identify the BIM roles and their competencies: academic literature; national BIM guides and specifications from the UK, U...
Abstract This study aims at evaluating experimentally phase change material (PCM) cooling vest pe... more Abstract This study aims at evaluating experimentally phase change material (PCM) cooling vest performance when incorporating two types of PCM with different melting temperatures with varied PCM placement on the lower, upper, front and back of the torso. Experiments on a thermal manikin were conducted to assess cooling rate observed with the various PCM arrangements while experiments on six male subjects were conducted to assess associated physiological and comfort votes after exercising for 45 min. The main findings of manikin testing were that an improved cooling effect can be achieved by covering the upper torso with PCM packets at 28 °C melting temperature while covering the lower torso with the 18 °C packets. Human subject testing established that similar improvements in thermal comfort and sensation levels could be attained when covering the back or lower torso segments with 18 °C instead of covering all the torso. In addition, a maximum reduction in local skin temperatures of 5.45 ± 1 °C was achieved accompanied with a reduction of 64 W in body heat storage. Covering the chest and upper back segments with the 18 °C packets suppressed sweat production and improved wetness sensation. Finally, 16% lower vest weight might be possible with prolonged working periods of two hours at 35 °C.
Abstract Shading devices installed on windows are designed to reduce solar radiation transmission... more Abstract Shading devices installed on windows are designed to reduce solar radiation transmission into the space by absorbing and reflecting radiation rays. This study investigates the effect of shading and day-lighting controls when applied on fully-glazed facades on the annual energy savings in hot climates. For this reason, a dynamic simulation model of a space containing brise soleil and venetian blinds added to the facade exterior surface was developed on EnergyPlus and validated experimentally for office spaces located in Doha, Qatar. Comparison between the experimental and simulation models showed maximum discrepancies of 11.8% and 13.5% in surface temperature and peak space thermal load, respectively. Upon validation, the simulation model was used to evaluate the annual energy savings associated with the use of shading devices on both south and north-oriented facades in Qatar. For the south-oriented facade, brise soleil and fixed blinds with 90° with the vertical were found to save 18.6% and 20.6% of the space energy demands respectively, while mitigating glare risks. As for the north facade, the addition of brise soleil and blinds saves 7.7% and 9.1% of the space total energy demands respectively and removes all risks associated with glare. The adoption of a shading control for the blind angle and day-lighting control for the electric lights was found to save 26.1% of the space total energy without compromising the comfortable glare limit. This control strategy allows the occupants to benefit from the fully-glazed facade while still upholding the indoor space requirements in terms of outdoor visual comfort and day-lighting entrance.
Abstract The objective of this work is to optimize the arrangement of Phase Change Material (PCM)... more Abstract The objective of this work is to optimize the arrangement of Phase Change Material (PCM) packets in a cooling vest by targeting torso segments that can trigger comfort when cooled. An integrated fabric-PCM and bio-heat simulation model is used in the optimization to predict human segmental core and skin temperatures to determine overall human thermal comfort during moderate activity in hot environment over a specified working period. The variables of the optimization were the number of PCM packets on the upper and lower front and back torso segments. The constraints to be met were: a core temperature not to exceed 38 °C, a comfort level not to be less than −1.4 on a comfort scale varying from very uncomfortable at −4 to very comfortable at +4 and a PCM melted mass fraction between 0.85 and 1.0. Three environmental conditions were considered at 28 °C, 35 °C and 45 °C for optimization and the results showed that 8, 18 and 20 PCM packets were needed to provide cooling for the outdoor worker at acceptable comfort level, respectively. At the very high ambient temperature of 45 °C and when increasing the PCM packets number to 32 packets, it was shown that the working duration can be extended from 45 min recommended by labor standards to two hours similar to duration permitted at 28 °C and 35 °C.
Abstract The distribution of phase change material (PCM) packets on a cooling vest worn by active... more Abstract The distribution of phase change material (PCM) packets on a cooling vest worn by active human in hot environments is investigated using an integrated fabric-PCM and bio-heat model. The model considered the effect of added PCM weight and hot environments on the human metabolic rate, and incorporated the effect of condensation to check its occurrence in the vest. The fabric-PCM model predictions of local torso skin temperature were validated experimentally on a thermal manikin operated at constant heat flux mode while its predictions of skin and core temperatures when integrated with the bioheat model were validated with published experimental data on human subjects exercising in hot conditions. The validated model is used in a parametric study to determine the best arrangement of 8 PCM packets distributed on different torso segments to improve sensation and comfort of human performing moderate activity in hot climate. It was found that placing 8 PCM packets on the back resulted in the best overall sensation of 1.38 as compared to 2.69 when no PCM is used using a sensation scale that varies from very cold at −4 to very hot at +4.
Thesis Department of Architecture and Development Studies School of Architecture Lund Institute of Technology Lund University, 2000
This study is on a combined effect of window, the daylighting and the thermal effects, in desert ... more This study is on a combined effect of window, the daylighting and the thermal effects, in desert houses. It is comprised of two complementary studies. In the introduction a historical review on the development of use daylight has been carried out in order to place the case study in a historical perspective. The first study is comprehensive and contains two main parts. In the first part a study was carried out on the people and history of the town of Ghardaia in Southern Algeria. This was done in order to understand the architectural form of that region. The second part is experimental and consists of two field studies carried out in Ghardaia. Their aim was to investigate the influence of daylight level and temperature on the use of residential houses. This investigation included both traditional and "modern" houses, the moderna having relatively large windows similar to those of the northern part of Algeria, the traditional ones having small or no windows. The second study is also experimental consisting of computer parametric studies on windows design from two standpoints, namely daylighting level and thermal effects of windows in desert houses. A typical traditional house is described as it was observed. Then the recorded light values are presented and commented upon. In the second part, three types of modern houses observed in the field studies are presented and compared to the traditional archetype. The comparison especially dwells on the relative effectiveness of the two systems of daylighting. In the third part, focusing on various issues of lighting, the results of interviews with the inhabitants are presented. The thermal and daylighting studies indicate that it is possible to have windows to the east, west or north orientations with still acceptable and daylighting effects as long as they comply with the following recommendations: * For south and north orientations, the absolute surfaces and the fenestsration should be in the medium to high range. * For an east orientation, the absolute surfaces and the fenestration should be in the medium range. * For an orientation to the west, similar recommendations may be appropriate, albeit with more carefully designed solar shading, since the probability for overheating will be higher.
Abstract A cooling vest containing phase change materials (PCM) can help in maintaining the skin ... more Abstract A cooling vest containing phase change materials (PCM) can help in maintaining the skin temperature of the covered parts at a comfortable level. A transient mathematical model of heat and mass transfer through clothing layers containing PCM packets was developed. Two experiments were performed on a clothed heated cylinder in controlled environment to validate the model using two PCMs at different melting temperatures. Good agreement was found between model-predicted and measured temperatures of the microclimate air between the cylinder and the PCM. The validated fabric-PCM model was then integrated with a segmental bio-heat model to provide realistic skin boundary conditions. The predicted core and mean skin temperatures agreed well with published experimental data of a human wearing a PCM-vest in hot environment. The validated integrated bio-heat and fabric-PCM models were used to study the effect of the melting temperature of the PCM and its mass on the vest performance. It was found that a lower melting temperature must be used when a fast cooling effect is desirable. Moreover, it was found that at fixed melting temperature increasing the PCM mass increased the cooling duration.
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