The Experts below are selected from a list of 2001 Experts worldwide ranked by ideXlab platform
Simo Kilpelainen - One of the best experts on this subject based on the ideXlab platform.
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flow characteristics in Occupied Zone an experimental study with symmetrically located thermal plumes and low momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
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Flow characteristics in Occupied Zone – An experimental study with symmetrically located thermal plumes and low-momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
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modelling and experimental study of performance of the protected Occupied Zone ventilation
Energy and Buildings, 2014Co-Authors: Kai Siren, Simo KilpelainenAbstract:Abstract The main objective of this study is to develop theoretical models to predict the performance of a new type of air distribution method known as protected Occupied Zone ventilation (POV), and to validate the model by conducting experimental measurements. The goal is to find out experimentally the most effective and efficient way of airflow distribution to protect occupants from infection of epidemic respiratory disease. Experimental measurements were performed under three setup conditions, including exhaust at sidewall, exhaust above the protected Occupied Zone and with partitions in the middle of the room. Two models are developed in this study to predict the transient pollutant concentration in the protected Zone and the polluted Zone. The protection efficiency of POV is defined in this study as well, which varies from 8% to 50% depending on the exhaust location, supply air velocity and the usage of partitions. The calculated results by using the models agree with the measurement results with a slot Reynolds number of 667, 1000 and 1167. The POV can separate the protected Zone from the polluted Zone by up to 2800 ppm. The capacity of a POV system to separate the room into two Zones with different concentration levels of contaminant indicates that the POV may protect people from infection of epidemic respiratory disease via a cross-contaminant inside a room.
Arsen Krikor Melikov - One of the best experts on this subject based on the ideXlab platform.
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The impact of thermal loads on indoor air flow
2020Co-Authors: Risto Kosonen, Arsen Krikor Melikov, Maija Virta, Halton OyAbstract:SUMMARY The potential for draught discomfort and high air velocities in the Occupied Zone are often studied with only cooling design in mind. During the transition season, however, downward flows with high air velocities may occur in the Occupied Zone due to cold window surfaces. Airflow generated by supply air terminal dervices may further enhence the velocity in the Occupied Zone. Furthermore, convection flows caused by thermal loads may significantly affect the air flow conditions in the room as a whole and assist the occurance of high velocity near occupants. Analyses of results from full-scale measurements with chilled beams presented in this paper reveal that installations with possibilities of convection flow oposing the supplied flow should be avoided. Generally speaking, convection flows have less impact on air distribution in rooms with chilled beams installed in lengthwise direction than when installed crosswise in rooms.
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flow characteristics in Occupied Zone an experimental study with symmetrically located thermal plumes and low momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
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Flow characteristics in Occupied Zone – An experimental study with symmetrically located thermal plumes and low-momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
Risto Kosonen - One of the best experts on this subject based on the ideXlab platform.
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The impact of thermal loads on indoor air flow
2020Co-Authors: Risto Kosonen, Arsen Krikor Melikov, Maija Virta, Halton OyAbstract:SUMMARY The potential for draught discomfort and high air velocities in the Occupied Zone are often studied with only cooling design in mind. During the transition season, however, downward flows with high air velocities may occur in the Occupied Zone due to cold window surfaces. Airflow generated by supply air terminal dervices may further enhence the velocity in the Occupied Zone. Furthermore, convection flows caused by thermal loads may significantly affect the air flow conditions in the room as a whole and assist the occurance of high velocity near occupants. Analyses of results from full-scale measurements with chilled beams presented in this paper reveal that installations with possibilities of convection flow oposing the supplied flow should be avoided. Generally speaking, convection flows have less impact on air distribution in rooms with chilled beams installed in lengthwise direction than when installed crosswise in rooms.
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Thermal comfort with radiant and convective cooling systems
2020Co-Authors: Risto Kosonen, Halton Oy, Panu Musta Kallio, Kalin KostovAbstract:The difference in thermal conditions between convective and radiant systems is not significant. Contrary to common awareness air temperature and operative temperature are almost similar in room Occupied Zone with radiant ceiling and chilled beam systems. Experiments with human subjects indicate similar performance of systems with respect to the whole body thermal sensation and acceptability of thermal conditions.
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influence of installation of displacement ventilation diffusers above Occupied Zone on the vertical temperature gradient in simulated office rooms
E3S Web of Conferences, 2019Co-Authors: Panu Mustakallio, Risto Kosonen, Mika Ruponen, Natalia LastovetsAbstract:Displacement ventilation diffusers are typically installed to the Occupied Zone, which can limit the utilization of the displacement ventilation. This paper presents the full-scale test results of two simulated office rooms with installation of displacement diffusers near wall, above the Occupied Zone. Vertical temperature gradients are compared to full-scale tests with installation of displacement diffusers to the Occupied Zone. The full-scale test setup consisted of two displacement diffusers and ceiling exhaust in wellinsulated room with 20.7 m2 floor area and room heights of 5.1 m and 3.3 m. The internal heat loads simulated situations with 10 occupants (simulated with heated cylinders), fluorescent lighting units, solar load on window surface (heated foils in one wall) without/with direct solar load on floor (heated foil on floor). The installation of displacement ventilation diffusers above Occupied Zone influenced on the vertical temperature gradient above the Occupied Zone only slightly. It reduced the vertical temperature gradient in the Occupied Zone. This confirms the operation of the displacement ventilation with this installation. This can be advantageous due to the smaller temperature stratification in the Occupied Zone, still the ventilation efficiency can be slightly lower comparing to the typical installation of the displacement diffusers.
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flow characteristics in Occupied Zone an experimental study with symmetrically located thermal plumes and low momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
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Flow characteristics in Occupied Zone – An experimental study with symmetrically located thermal plumes and low-momentum diffuse ceiling air distribution
Building and Environment, 2018Co-Authors: Sami Lestinen, Simo Kilpelainen, Risto Kosonen, Hannu Koskela, Juha Jokisalo, Arsen Krikor MelikovAbstract:Abstract Airflow interaction between thermal plumes and vertical air distribution may cause significant effects on airflow characteristics such as velocity and temperature fields, turbulence intensity and fluctuation frequency. The flow interaction creates a random flow motion, vortical structures and turbulent mixing that can further yield a draught discomfort in an Occupied Zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m (width) x 3.2 m (height) with symmetrical set-up of cylindrical heat sources that gave a thermal load of 40–80 W/floor-m2. The ventilation air was supplied through a diffuse ceiling with 0.5% degree of perforation. The observations indicate that the mean air speed and the airflow fluctuation increase with thermal load. Furthermore, the results show that a range of length scales increases with thermal load and with mean air speed. The results indicate that it can be difficult to fulfill the standard air velocity criteria for highly Occupied spaces, where the maximum allowable mean air velocity is relatively low, i.e. 0.15–0.20 m/s. This is because the buoyancy flows from heat sources accelerate locally the flow field.
Ying Zhang - One of the best experts on this subject based on the ideXlab platform.
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the impact of ventilation rate and partition layout on the voc emission rate time dependent contaminant removal
Indoor Air, 1994Co-Authors: Fariborz Haghighat, Zheng Jiang, Ying ZhangAbstract:A numerical study has been carried out to predict the indoor air quality in a newly painted partitioned office and to assess the effect of ventilation rate and partition layout on the pre-ventilation time required to allow the contaminant concentration level to drop to an acceptable level. The air-flow pattern, the time history of the average contaminant concentration level in the Occupied Zone, and the pre-ventilation time were computed by a CFD code with a K-e turbulence model. A displacement ventilation system, with different operating conditions, was used to remove contaminants in the office. The VB emission model, developed by Guo and Tichenor (1992), has been improved to include the influence of non-uniform concentration distribution on contaminant emission rate from the paints. The average contaminant (VOC) concentration levels in the Occupied Zone and in each chamber were recorded hourly until the average concentrations in the office were less then 0.0005 g/m3. It has been found that the non-uniform concentration distri- bution greatly influences the decay rate of VOC emissions. The time required for the average concentration in each chamber to reach the threshold level is different, since they are non-uniform. The time differences between the chambers having the highest and lowest concentrations were 3 to 8 hours. The results also show that the time required to reduce the concentration in the Occupied Zone to the threshold level is dependent on the partition layout. For the same ventilation rate, the required time is approximately 4-8 hours longer when using a side layout than when using a central layout.
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The Impact of Ventilation Rate and Partition Layout on the VOC Emission Rate: Time‐Dependent Contaminant Removal
Indoor Air, 1994Co-Authors: Fariborz Haghighat, Zheng Jiang, Ying ZhangAbstract:A numerical study has been carried out to predict the indoor air quality in a newly painted partitioned office and to assess the effect of ventilation rate and partition layout on the pre-ventilation time required to allow the contaminant concentration level to drop to an acceptable level. The air-flow pattern, the time history of the average contaminant concentration level in the Occupied Zone, and the pre-ventilation time were computed by a CFD code with a K-e turbulence model. A displacement ventilation system, with different operating conditions, was used to remove contaminants in the office. The VB emission model, developed by Guo and Tichenor (1992), has been improved to include the influence of non-uniform concentration distribution on contaminant emission rate from the paints. The average contaminant (VOC) concentration levels in the Occupied Zone and in each chamber were recorded hourly until the average concentrations in the office were less then 0.0005 g/m3. It has been found that the non-uniform concentration distri- bution greatly influences the decay rate of VOC emissions. The time required for the average concentration in each chamber to reach the threshold level is different, since they are non-uniform. The time differences between the chambers having the highest and lowest concentrations were 3 to 8 hours. The results also show that the time required to reduce the concentration in the Occupied Zone to the threshold level is dependent on the partition layout. For the same ventilation rate, the required time is approximately 4-8 hours longer when using a side layout than when using a central layout.
Kai Siren - One of the best experts on this subject based on the ideXlab platform.
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Evaluating the thermal comfort performance of heating systems using a thermal manikin with human thermoregulatory control
Indoor and Built Environment, 2014Co-Authors: Ehab Foda, Kai SirenAbstract:The evaluation of the local thermal comfort and application of thermal manikins can further assist the design and selection of heating systems. This study aimed at evaluating the thermal comfort performance of different heating systems using a newly developed thermal manikin with an enhanced thermal control. The heating systems for a workstation, included a conventional radiator (convector) mounted under the window, heated floor in the Occupied Zone and an infrared heater mounted to the ceiling. The experiments were conducted in a test room with a facade attached to a climate chamber to simulate outdoor winter conditions. In these experiments, the supplied power for the different systems was kept constant to independently quantify the differences in their thermal comfort performance at same energy consumption. The thermal manikin was deployed in the Occupied Zone to evaluate the local and overall thermal comfort under each system using the equivalent temperature (Teq) approach. The thermoregulatory contro...
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modelling and experimental study of performance of the protected Occupied Zone ventilation
Energy and Buildings, 2014Co-Authors: Kai Siren, Simo KilpelainenAbstract:Abstract The main objective of this study is to develop theoretical models to predict the performance of a new type of air distribution method known as protected Occupied Zone ventilation (POV), and to validate the model by conducting experimental measurements. The goal is to find out experimentally the most effective and efficient way of airflow distribution to protect occupants from infection of epidemic respiratory disease. Experimental measurements were performed under three setup conditions, including exhaust at sidewall, exhaust above the protected Occupied Zone and with partitions in the middle of the room. Two models are developed in this study to predict the transient pollutant concentration in the protected Zone and the polluted Zone. The protection efficiency of POV is defined in this study as well, which varies from 8% to 50% depending on the exhaust location, supply air velocity and the usage of partitions. The calculated results by using the models agree with the measurement results with a slot Reynolds number of 667, 1000 and 1167. The POV can separate the protected Zone from the polluted Zone by up to 2800 ppm. The capacity of a POV system to separate the room into two Zones with different concentration levels of contaminant indicates that the POV may protect people from infection of epidemic respiratory disease via a cross-contaminant inside a room.
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Influence of the floor-based obstructions on contaminant removal efficiency and effectiveness
Building and Environment, 2001Co-Authors: Kim Hagstrom, A. M. Zhivov, Kai Siren, L.l. ChristiansonAbstract:Dimensioning of dilution ventilation is often made using the perfect mixing approximation, assuming uniform contaminant concentration throughout the room space. However, the contaminant removal efficiency and effectiveness of air conditioning system should be accounted for during design. The effectiveness is in this context used as a measure of the contaminant distribution uniformity within the Occupied Zone. Influence of an Occupied Zone obstruction level, air distribution method, air change rate, cooling load and contaminant source non-uniformity on the contaminant removal efficiency and Occupied Zone contaminant concentration uniformity were studied in scale model. The room air distribution method results in contaminant concentration non-uniformity inside the Occupied Zone. A method was developed to take this into account during the design of air distribution system. Contaminant supply non-uniformity was found to have great influence on the concentration non-uniformity with two tested air distribution methods.
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The influence of Heat and Contaminant source Nonuniformity on the performance of three different room air distribution methods
1999Co-Authors: Kim Hagstrom, A. M. Zhivov, Kai Siren, P.e. ChristiansonAbstract:The efficiency of an air diffusion system consists of two factors. The first is the ability of the system to remove heat and contaminants out of the ventilated room. This is most often characterized using temperature removal and contaminant removal efficiency. The second, seldom considered, factor is the uniformity of the temperature and contaminant distribution within the ventilated space. This factor describes how much the maximum contaminant concentration or minimum temperature differs from the average value. In previous studies with uniform sources, significant differences were found in efficiency between three room air distribution methods. The target of this study was to find out how much the nonuniformity of a source influences the efficiencies of the air distribution methods. Scale model experiments were conducted to determine the influence of heat and contaminant source nonuniformities on the Occupied Zone temperature and contaminant distribution and the temperature removal and contaminant removal efficiencies in industrial space. Three room air distribution methods (one mixing and two zonal) were used. The heat and contaminant source nonuniformity and source location were found to have a major influence on the efficiencies of the room air distribution methods studied. For example, the Occupied Zone nonuniformity was fourfold at highestmore » compared to the cases with a uniform source. Analysis of the data shows that with zonal room air distribution methods, both vertical and horizontal zoning are created when the sources are not uniform.« less
