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'''Displacement ventilation (DV)''' is a [[room air distribution]] strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height.<ref name="Chen" />
{{See also|Underfloor air distribution}}

'''Displacement ventilation (DV)''' It is a [[room air distribution]] strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height.<ref name="Chen" />


== System design ==
== System design ==
Line 9: Line 7:


== History ==
== History ==
Displacement ventilation was first applied in an [[industrial building]] in Scandinavia in 1978, and has frequently been used in similar applications, as well as office spaces, throughout Scandinavia since that time.<ref name="Chen" /> By 1989, it was estimated that Displacement ventilation comprised the 50% in industrial applications and 25% in offices within Nordic countries.<ref name="Svensson" /> Applications in the United States have not been as widespread as in Scandinavia. Some research has been done to assess the practicality of this application in U.S. markets due to different typical space designs<ref name="Chen" /> and application in hot and humid climates, as well as research to assess the potential indoor environmental quality and energy-saving benefits of this strategy in the U.S. and elsewhere.
Displacement ventilation was first applied in an [[industrial building]] in Scandinavia in 1978, and has frequently been used in similar applications, as well as office spaces, throughout Scandinavia since that time.<ref name="Chen" /> By 1989, it was estimated that displacement ventilation comprised the 50% in industrial applications and 25% in offices within Nordic countries.<ref name="Svensson" /> Applications in the United States have not been as widespread as in Scandinavia. Some research has been done to assess the practicality of this application in U.S. markets due to different typical space designs<ref name="Chen" /> and application in hot and humid climates, as well as research to assess the potential indoor environmental quality and energy-saving benefits of this strategy in the U.S. and elsewhere.


== Applications ==
== Applications ==
Displacement ventilation has been applied in many famous building such as the [[Suvarnabhumi International Airport]] in Bangkok, Thailand, the NASA Jet Propulsion Laboratory Flight Projects Center building,<ref name="Duderhoff" /> and the [[San Francisco International Airport]] Terminal 2 among other applications.
Displacement ventilation has been applied in many famous building such as the [[Suvarnabhumi International Airport]] in Bangkok, Thailand, the NASA Jet Propulsion Laboratory Flight Projects Center building,<ref name="Duderhoff" /><ref>https://www.energystar.gov/sites/default/uploads/buildings/old/files/50_Flight_Project_508.pdf {{Bare URL PDF|date=March 2022}}</ref> and the [[San Francisco International Airport]]<ref>{{Cite web|url=https://www.usgbc.org/articles/san-francisco-airport-aims-achieve-zero-net-energy-usgbc-northern-california|title = San Francisco Airport aims to achieve zero net energy (USGBC Northern California) &#124; U.S. Green Building Council}}</ref><ref>{{Cite web|url=https://medium.com/the-fourth-wave/zero-energy-green-building-in-a-data-enlightened-era-70c84300df4c|title = Zero-energy green building in a data-enlightened era|date = 12 September 2018}}</ref> Terminal 2 among other applications.


== General characteristics ==
== General characteristics ==


=== Airflow distribution ===
=== Airflow distribution ===
The thermal plumes and supply air from diffusers, which determines the velocity of [[airflow]] at floor level, play an important role in DV systems.<ref name="Cho" /> It is necessary to carefully set the airflow rate from the diffuser to avoid drafts.
The thermal plumes and supply air from diffusers, which determines the velocity of [[airflow]] at floor level, play an important role in DV systems. It is necessary to carefully set the airflow rate from the diffuser to avoid drafts.


=== Conditioning type ===
=== Conditioning type ===
Due to the unique properties of thermal stratification, Displacement ventilation is typically used for cooling rather than for heating. In many cases, a separate heating source, such as a radiator or baseboard, is used in during heating periods.<ref name="Chen" />
Due to the unique properties of thermal stratification, displacement ventilation is typically used for cooling rather than for heating. In many cases, a separate heating source, such as a radiator or baseboard, is used during heating periods.<ref name="Chen" />


=== Space requirement ===
=== Space requirement ===
Displacement ventilation is best suited for taller spaces (higher than 3 meters [10 feet]).<ref name="REHVA" /> Standard mixing ventilation may be better suited for smaller spaces where air quality is not as great a concern, such as single-occupant offices, and where the room height is not tall (e.g., lower than 2.3 meters [7.5 feet]).<ref name="REHVA" />
Displacement ventilation is best suited for taller spaces (higher than 3 meters [10 feet]).<ref name="REHVA" /> Standard mixing ventilation may be better suited for smaller spaces where air quality is not as great a concern, such as single-occupant offices, and where the room height is not tall (e.g., lower than 2.3 meters [7.5 feet]).<ref name="REHVA" />


== Benefits and Limitations ==
== Benefits and limitations ==


=== Local discomfort: vertical temperature difference and draft ===
=== Local discomfort: vertical temperature difference and draft ===
Displacement ventilation systems are quieter than conventional overhead systems with better ventilation efficiency. Hence, it could enhance indoor air quality and provide desirable acoustic environment. Displacement ventilation systems are appropriate in space where high ventilation is required, such as classrooms, conference rooms, and offices.<ref name="Cho" />
Displacement ventilation systems are quieter than conventional overhead systems with better ventilation efficiency. Hence, it could enhance indoor air quality and provide desirable acoustic environment. Displacement ventilation systems are appropriate in space where high ventilation is required, such as classrooms, conference rooms, and offices.


Displacement ventilation can be a cause of discomfort due to the large vertical [[temperature gradient]] and drafts.<ref name="ANSIASHRAE" /> According to Melikov and Pitchurov's research, sensations of cold caused by vertical temperature difference and draft are usually occurred at the lower leg/ ankle/ feet region, while warm sensations at the head are reported.<ref name="Melikov" /> The research also indicates, that the draft rating model could predict the draft risk with good accuracy in rooms with displacement ventilation systems.
Displacement ventilation can be a cause of discomfort due to the large vertical [[temperature gradient]] and drafts.<ref name="ANSIASHRAE" /> According to Melikov and Pitchurov's research, sensations of cold caused by vertical temperature difference and draft are usually occurred at the lower leg/ ankle/ feet region, while warm sensations at the head are reported.<ref name="Melikov" /> The research also indicates, that the draft rating model could predict the draft risk with good accuracy in rooms with displacement ventilation systems.


There is a tradeoff inherent in these two issues: by increasing the flow rate (and the ability to remove greater thermal loads), the vertical temperature gradient can be reduced, but this could increase the risk of drafts.<ref name="Chen" /> Pairing displacement ventilation with radiant chilled ceilings is an effort to mitigate this problem.<ref name="Loveday" /> According to some studies, displacement ventilation systems can only provide acceptable comfort if the corresponding cooling load is less than about 13 Btu/h-sf or 40 W/m<sup>2</sup>.<ref name="Cho" />
There is a tradeoff inherent in these two issues: by increasing the flow rate (and the ability to remove greater thermal loads), the vertical temperature gradient can be reduced, but this could increase the risk of drafts.<ref name="Chen" /> Pairing displacement ventilation with radiant chilled ceilings is an effort to mitigate this problem.<ref name="Loveday" /> According to some studies, displacement ventilation systems can only provide acceptable comfort if the corresponding cooling load is less than about 13 Btu/h-sf or 40 W/m<sup>2</sup>.


=== Indoor air quality ===
=== Indoor air quality ===
One benefit of displacement ventilation is possibly the superior [[Indoor Air Quality|indoor air quality]] achieved with exhausting contaminated air out of the room. Better air quality is achieved when the pollution source is also a heat source.<ref name="Chen" /><ref name="REHVA" />
One benefit of displacement ventilation is possibly the superior [[Indoor Air Quality|indoor air quality]] achieved with exhausting contaminated air out of the room. Better air quality is achieved when the pollution source is also a heat source.<ref name="Chen" /><ref name="REHVA" />

The effectiveness of displacement ventilation at removing particulate contaminants has been investigated recently.<ref name=":0">{{Cite journal|last1=Woods|first1=Andrew W.|last2=Mingotti|first2=Nicola|date=June 2015|title=On the transport of heavy particles through an upward displacement-ventilated space|journal=Journal of Fluid Mechanics|volume=772|pages=478–507|doi=10.1017/jfm.2015.204|bibcode=2015JFM...772..478M|s2cid=233733115|issn=0022-1120|url=https://www.repository.cam.ac.uk/handle/1810/247941}}</ref><ref name=":1">{{Cite journal|last1=Woods|first1=Andrew W.|last2=Mingotti|first2=Nicola|date=July 2015|title=On the transport of heavy particles through a downward displacement-ventilated space|journal=Journal of Fluid Mechanics|volume=774|pages=192–223|doi=10.1017/jfm.2015.244|bibcode=2015JFM...774..192M|s2cid=53446651|issn=0022-1120|url=https://www.repository.cam.ac.uk/handle/1810/248124}}</ref> Small aqueous droplets containing infectious nuclei are frequently released in hospital rooms and other indoor spaces, and tend to settle through the ambient air at a speed of order 1–10&nbsp;mm/s typically. In cold climates or seasons, sufficiently small droplets are extracted from the top of a displacement-ventilated space if the mean upward air speed exceeds the particle settling speed. However, laboratory experiments have shown that larger droplets may settle faster than the air moves. In this case, the large droplets are not extracted effectively from a space with upward displacement ventilation, and their concentration increases if the ventilation rate is increased.<ref name=":0" /> In warmer climates or seasons, large-scale instabilities in the concentration of contaminants may occur within a space with downward displacement ventilation.<ref name=":1" />


=== Energy consumption ===
=== Energy consumption ===
Some studies have demonstrated that displacement ventilation may save energy as compared to standard mixing ventilation, depending on the use type of the building, design/massing/orientation, and other factors.<ref name="Chen" /> However, for the evaluation of energy consumption of displacement ventilation, the numerical simulation is the main method, since yearly measurements are too expensive and time consuming. Hence, whether displacement ventilation could help with saving energy is still debated.In general, displacement ventilation is attractive to the core region in a building since no heating is needed. However, the perimeter zones require high cooling energy.<ref name="Cho" />
Some studies have demonstrated that displacement ventilation may save energy as compared to standard mixing ventilation, depending on the use type of the building, design/massing/orientation, and other factors.<ref name="Chen" /> However, for the evaluation of energy consumption of displacement ventilation, the numerical simulation is the main method, since yearly measurements are too expensive and time consuming. Hence, whether displacement ventilation could help with saving energy is still debated. In general, displacement ventilation is attractive to the core region in a building since no heating is needed. However, the perimeter zones require high cooling energy.


== Design guidelines ==
== Design guidelines ==
Line 66: Line 66:


{{space|10}}Step 10) Estimate the first costs and annual energy consumption.
{{space|10}}Step 10) Estimate the first costs and annual energy consumption.

== List of buildings using displacement ventilation ==
{| class="wikitable"
!Building
!Year
!Country
!City
!Architects
!Space Type
|-
|[[Jewish Museum, Berlin|Jewish Museum Berlin]]
|1999
|[[Germany]]
|[[Berlin]]
|[[Daniel Libeskind]]
|Exhibit space
|-
|[[Suvarnabhumi Airport|Bangkok International Airport]]
|2006
|[[Thailand]]
|[[Bangkok]]
|[[Helmut Jahn]] of [[Murphy/Jahn Architects|Murphy / Jahn Architects]]
|Airport terminal
|-
|[[Hearst Tower (Manhattan)|Hearst Tower]]
|2006
|[[United States]]
|[[New York City]], [[New York (state)|NY]]
|[[Norman Foster, Baron Foster of Thames Bank|Norman Foster]] of [[Foster + Partners]]
|Large public space
|-
|[[Newseum]]
|2011
|United States
|[[Washington, D.C.]]
|[[Polshek Partnership]]
|Large public space
|-
|Modesto Medical Center
|2008
|United States
|[[Modesto, California]]
|KP Architects
|Health-care
|-
|[[St. John's University (New York City)|St. John's University]], St. John's Hall
|1950s
|United States
|New York City, NY
|unknown
|Teaching environment
|-
|[[Carnegie Hall]]
|1891
|United States
|New York City, NY
|[[William Burnet Tuthill]]
|Theater
|-
|[[Samuel J. Friedman Theatre|Samuel J. Friedman Theater]]
|1920s
|United States
|New York City, NY
|[[Herbert J. Krapp]]
|Theater
|-
|[[National Centre for the Performing Arts (China)|National Center for the Performing Arts]]
|2007
|[[China]]
|[[Beijing]]
|[[Paul Andreu]]
|Theater
|-
|[[Copenhagen Opera House|The Copenhagen Opera]]
|2004
|[[Denmark]]
|[[Copenhagen]]
|[[Henning Larsen]]
|Theater
|-
|[[Prince Mahidol Hall]]
|2014
|[[Thailand]]
|[[Nakornpathom]]
|A49
|Theater
|}

==See also==
*[[Underfloor air distribution]] (UFAD)


== References ==
== References ==
Line 71: Line 161:
<ref name="REHVA">REHVA. (2002). Displacement Ventilation in Non-Industrial Premises. Federation of European Heating and Air-conditioning Associations.</ref>
<ref name="REHVA">REHVA. (2002). Displacement Ventilation in Non-Industrial Premises. Federation of European Heating and Air-conditioning Associations.</ref>


<ref name="Schiavon">{{cite journal|last=Schiavon|first=Stefano|last2=Bauman|first2=F.|last3=Tully|first3=B.|last4=Rimmer|first4=J.|title=Room air stratification in combined chilled ceiling and displacement ventilation systems|journal=HVAC&R Research|year=2012|url=http://www.escholarship.org/uc/item/40r2b5xq|accessdate=9 December 2012|volume=18|issue=1|pages=147–159}}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
<ref name="Schiavon">{{cite journal|last1=Schiavon|first1=Stefano|last2=Bauman|first2=F.|last3=Tully|first3=B.|last4=Rimmer|first4=J.|s2cid=55305722|title=Room air stratification in combined chilled ceiling and displacement ventilation systems|journal=HVAC&R Research|year=2012|volume=18|issue=1|pages=147–159|doi=10.1080/10789669.2011.592105 |url=https://escholarship.org/uc/item/980931rf }}</ref>


<ref name="Svensson">{{cite journal|last= Svensson |first=A.G.L.|date=1989|title= ordic Experiences of Displacement Ventilation Systems| journal= ASHRAE Transactions| volume =95|issue=2 }}</ref>
<ref name="Cho">{{cite web |url=http://www.researchgate.net/publication/26899313_Literature_Review_of_Displacement_Ventilation|title=Literature Review of Displacement Ventilation|last1=Cho|first1=Soolyeon|last2=Im|first2=Piljae|last3=Haberl|first3=Jeff S.|date=May 2005|website=ResearchGate|publisher=Energy Systems Laboratory Texas A&M University System|access-date=November 2015}}</ref>


<ref name=" Svensson ">{{cite journal|last= Svensson |first=A.G.L.|date=1989|title= ordic Experiences of Displacement Ventilation Systems| journal= ASHRAE Transactions| volume =95|issue=2 }}</ref>
<ref name="Chen">{{cite book|last1= Chen|first1= Q. |last2= Glicksman |first2= L.|date=1999|title= Performance Evaluation and Development of Design Guidelines for Displacement Ventilation| location=MA.|publisher= ASHRAE}}</ref>


<ref name="Duderhoff">{{Cite web|url=http://www.edcmag.com/Articles/Web_Exclusive/BNP_GUID_9-5-2006_A_10000000000000933412|archive-url=https://archive.today/20130122224613/http://www.edcmag.com/Articles/Web_Exclusive/BNP_GUID_9-5-2006_A_10000000000000933412|url-status=dead|archive-date=22 January 2013|title=NASA's Out of this World Green Building - Web Exclusives - EDC Magazine|work=edcmag.com|access-date=9 December 2010}}</ref>
<ref name="Chen">{{cite book|last= Chen|first= Q. |last2= Glicksman |first2= L.|date=1999|title= Performance Evaluation and Development of Design Guidelines for Displacement Ventilation| location=MA.|publisher= ASHRAE}}</ref>

<ref name="Duderhoff">{{Cite web|url=http://www.edcmag.com/Articles/Web_Exclusive/BNP_GUID_9-5-2006_A_10000000000000933412|title=NASA’s Out of this World Green Building - Web Exclusives - EDC Magazine|work=edcmag.com|accessdate=9 December 2010}}</ref>


<ref name="ANSIASHRAE">''ANSI/ASHRAE Standard 55 (2002). Thermal Environmental Conditions for Human Occupancy</ref>
<ref name="ANSIASHRAE">''ANSI/ASHRAE Standard 55 (2002). Thermal Environmental Conditions for Human Occupancy</ref>
<ref name=" Loveday ">{{cite journal|last= Loveday|first= D.L.|last2=Parsons|first2=K.C.|last3=Taki|first3=A.H.|last4=Hodder|first4=S.G.|date=July 2002|title=Displacement ventilation environments with chilled ceilings: thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate| journal= Energy and Buildings|url= http://www.sciencedirect.com/science/article/pii/S0378778802000075 |accessdate=11 November 2015| volume = 34| issue =6| pages =573–579|doi=10.1016/S0378-7788(02)00007-5}}</ref>
<ref name="Loveday">{{cite journal|last1= Loveday|first1= D.L.|last2=Parsons|first2=K.C.|last3=Taki|first3=A.H.|last4=Hodder|first4=S.G.|date=July 2002|title=Displacement ventilation environments with chilled ceilings: thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate| journal= Energy and Buildings| volume = 34| issue =6| pages =573–579|doi=10.1016/S0378-7788(02)00007-5}}</ref>

<!--<ref name=" Li ">{{cite journal|last= Li|first=Y.|last2=Sandberg|first2=Mats|last3=Fuchs|first3=Laszlo|date=December 1, 1992|title= Vertical Temperature Profiles in Rooms by Displacement: Full-Scale Measurement and Nodal Modelling | journal= Indoor Air|url= http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0668.1992.00005.x/abstract |accessdate=11 November 2015| volume = 2| issue =4| pages =225–243|doi=10.1111/j.1600-0668.1992.00005.x}}</ref>-->

<!--<ref name="Mundt1994">{{cite journal|last=Mundt|first=E|title=Contamination Distribution in Displacement Ventilation -- Influence of Disturbances|journal=Building and Environment|year=1994|volume=29|issue=3|pages=311–317|doi=10.1016/0360-1323(94)90028-0}}</ref>

<ref name=" Mundt1995">{{cite journal|last= Mundt |first= Elisabeth|date=January 1995|title= Displacement Ventilation Systems -- Convection Flows and Temperature Gradients| journal= Building and Environment|url= http://www.sciencedirect.com/science |accessdate=11 November 2015| volume = 30| issue =1| pages =129–133|doi= 10.1016/0360-1323(94)E0002-9}}</ref>

<ref name=" Mundt2001">{{cite journal|last= Mundt |first= Elisabeth|date=August 2001|title=Non-buoyant pollutant sources and particles in displacement ventilation| journal= Building and Environment|url= http://www.sciencedirect.com/science/article/pii/S0360132301000087 |accessdate=11 November 2015| volume = 35| issue =7| pages =829–836|doi= 10.1016/S0360-1323(01)00008-7}}</ref>-->

<!--<ref name=" Nielsen1995">{{cite journal|last=Nielsen|first=Peter V.|date=1995|title= Vertical Temperature Distribution in a Room with Displacement Ventilation| journal=Indoor Environmental Technology|url= http://www.sciencedirect.com/science/article/pii/S0360132301000087 |accessdate=11 November 2015| volume =R9509|location=Aalborg|issn= 0902-7513|doi=10.1016/S0360-1323(01)00008-7|pages=829–836}}</ref>-->

<!--<ref name=" Nielsen1996">{{cite journal|last=Nielsen|first=Peter V.|date=1996|title= Temperature Distribution in a Displacement Ventilated Room| journal=Indoor Environmental Technology|url= http://www.sciencedirect.com/science/article/pii/S0360132301000087 |accessdate=11 November 2015| volume =R9659|location=Aalborg|doi=10.1016/S0360-1323(01)00008-7|pages=829–836}}</ref>-->


<ref name="Novoselac">{{cite journal|last=Novoselac|first=Atila|first2= Srebric|last2= J. |title=A critical review on the performance and design of combined cooled ceiling and displacement ventilation systems|journal=Energy and Buildings|date=June 2002|volume=34|issue=5|pages=Energy and Buildings|doi=10.1016/S0378-7788(01)00134-7}}</ref>
<ref name="Novoselac">{{cite journal|last1=Novoselac|first1=Atila|first2= Srebric|last2= J. |title=A critical review on the performance and design of combined cooled ceiling and displacement ventilation systems|journal=Energy and Buildings|date=June 2002|volume=34|issue=5|pages=Energy and Buildings|doi=10.1016/S0378-7788(01)00134-7}}</ref>


<ref name="Melikov">{{cite journal|last=Melikov|first=Arsen|last2= Pitchurov|first2= G. |last3= Naydenov|first3= K. |last4=Langkilde|first4= G.|title=Field study of occupants’thermal comfort in rooms with displacement ventilation|journal=Indoor Air|date=June 2005|volume=15|issue=3|pages=205–214|doi=10.1111/j.1600-0668.2005.00337.x}}</ref>
<ref name="Melikov">{{cite journal|last1=Melikov|first1=Arsen|last2= Pitchurov|first2= G. |last3= Naydenov|first3= K. |last4=Langkilde|first4= G.|title=Field study of occupants'thermal comfort in rooms with displacement ventilation|journal=Indoor Air|date=June 2005|volume=15|issue=3|pages=205–214|doi=10.1111/j.1600-0668.2005.00337.x|pmid=15865620|doi-access=free}}</ref>


<ref name="Chen2003">{{cite book|last=Chen|first=Q|last2=Glicksman|first2=L.R|date=January 1, 2003|title=System performance evaluation and design guidelines for displacement ventilation|url=https://books.google.com/books/about/System_Performance_Evaluation_and_Design.html?id=Q9EmAAAACAAJ&hl=en|location=Atlanta|publisher=American Society of Heating, Refrigerating, and Air-conditioning Engineers, Inc|isbn=1931862427}}</ref>
<ref name="Chen2003">{{cite book|last1=Chen|first1=Q|last2=Glicksman|first2=L.R|date=January 1, 2003|title=System performance evaluation and design guidelines for displacement ventilation|url=https://books.google.com/books?id=Q9EmAAAACAAJ|location=Atlanta|publisher=American Society of Heating, Refrigerating, and Air-conditioning Engineers, Inc|isbn=978-1931862424}}</ref>


}}
}}
Line 107: Line 183:


[[Category:Ventilation]]
[[Category:Ventilation]]
[[Category:Heating, ventilating, and air conditioning]]
[[Category:Sustainable architecture]]
[[Category:Sustainable architecture]]
[[Category:Environmental design]]
[[Category:Environmental design]]

Latest revision as of 07:47, 23 May 2024

Displacement ventilation (DV) is a room air distribution strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height.[1]

System design

[edit]

A typical displacement ventilation system, such as one in an office space, supplies conditioned cold air from an air handling unit (AHU) through a low induction air diffuser. Diffuser types vary by applications. Diffusers can be located against a wall ("wall-mounted"), at the corner of a room ("corner-mounted"), or above the floor but not against a wall ("free-standing").[2] The cool air accelerates because of the buoyancy force, spreads in a thin layer over the floor, reaching a relatively high velocity before rising due to heat exchange with heat sources (e.g., occupants, computers, lights).[3] Absorbing the heat from heat sources, the cold air becomes warmer and less dense. The density difference between cold air and warm air creates upward convective flows known as thermal plumes. Instead of working as a stand-alone system in interior space, displacement ventilation system can also be coupled with other cooling and heating sources, such as radiant chilled ceilings[4] or baseboard heating.[1]

History

[edit]

Displacement ventilation was first applied in an industrial building in Scandinavia in 1978, and has frequently been used in similar applications, as well as office spaces, throughout Scandinavia since that time.[1] By 1989, it was estimated that displacement ventilation comprised the 50% in industrial applications and 25% in offices within Nordic countries.[5] Applications in the United States have not been as widespread as in Scandinavia. Some research has been done to assess the practicality of this application in U.S. markets due to different typical space designs[1] and application in hot and humid climates, as well as research to assess the potential indoor environmental quality and energy-saving benefits of this strategy in the U.S. and elsewhere.

Applications

[edit]

Displacement ventilation has been applied in many famous building such as the Suvarnabhumi International Airport in Bangkok, Thailand, the NASA Jet Propulsion Laboratory Flight Projects Center building,[6][7] and the San Francisco International Airport[8][9] Terminal 2 among other applications.

General characteristics

[edit]

Airflow distribution

[edit]

The thermal plumes and supply air from diffusers, which determines the velocity of airflow at floor level, play an important role in DV systems. It is necessary to carefully set the airflow rate from the diffuser to avoid drafts.

Conditioning type

[edit]

Due to the unique properties of thermal stratification, displacement ventilation is typically used for cooling rather than for heating. In many cases, a separate heating source, such as a radiator or baseboard, is used during heating periods.[1]

Space requirement

[edit]

Displacement ventilation is best suited for taller spaces (higher than 3 meters [10 feet]).[2] Standard mixing ventilation may be better suited for smaller spaces where air quality is not as great a concern, such as single-occupant offices, and where the room height is not tall (e.g., lower than 2.3 meters [7.5 feet]).[2]

Benefits and limitations

[edit]

Local discomfort: vertical temperature difference and draft

[edit]

Displacement ventilation systems are quieter than conventional overhead systems with better ventilation efficiency. Hence, it could enhance indoor air quality and provide desirable acoustic environment. Displacement ventilation systems are appropriate in space where high ventilation is required, such as classrooms, conference rooms, and offices.

Displacement ventilation can be a cause of discomfort due to the large vertical temperature gradient and drafts.[10] According to Melikov and Pitchurov's research, sensations of cold caused by vertical temperature difference and draft are usually occurred at the lower leg/ ankle/ feet region, while warm sensations at the head are reported.[11] The research also indicates, that the draft rating model could predict the draft risk with good accuracy in rooms with displacement ventilation systems.

There is a tradeoff inherent in these two issues: by increasing the flow rate (and the ability to remove greater thermal loads), the vertical temperature gradient can be reduced, but this could increase the risk of drafts.[1] Pairing displacement ventilation with radiant chilled ceilings is an effort to mitigate this problem.[12] According to some studies, displacement ventilation systems can only provide acceptable comfort if the corresponding cooling load is less than about 13 Btu/h-sf or 40 W/m2.

Indoor air quality

[edit]

One benefit of displacement ventilation is possibly the superior indoor air quality achieved with exhausting contaminated air out of the room. Better air quality is achieved when the pollution source is also a heat source.[1][2]

The effectiveness of displacement ventilation at removing particulate contaminants has been investigated recently.[13][14] Small aqueous droplets containing infectious nuclei are frequently released in hospital rooms and other indoor spaces, and tend to settle through the ambient air at a speed of order 1–10 mm/s typically. In cold climates or seasons, sufficiently small droplets are extracted from the top of a displacement-ventilated space if the mean upward air speed exceeds the particle settling speed. However, laboratory experiments have shown that larger droplets may settle faster than the air moves. In this case, the large droplets are not extracted effectively from a space with upward displacement ventilation, and their concentration increases if the ventilation rate is increased.[13] In warmer climates or seasons, large-scale instabilities in the concentration of contaminants may occur within a space with downward displacement ventilation.[14]

Energy consumption

[edit]

Some studies have demonstrated that displacement ventilation may save energy as compared to standard mixing ventilation, depending on the use type of the building, design/massing/orientation, and other factors.[1] However, for the evaluation of energy consumption of displacement ventilation, the numerical simulation is the main method, since yearly measurements are too expensive and time consuming. Hence, whether displacement ventilation could help with saving energy is still debated. In general, displacement ventilation is attractive to the core region in a building since no heating is needed. However, the perimeter zones require high cooling energy.

Design guidelines

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Different guidelines have been published to provide guidance on designing displacement ventilation systems, including:

  • Skistad H., Mundt E., Nielsen P.V., Hagstrom K., Railo J. (2002). Displacement ventilation in Non-Industrial Premises. Federation of European Heating and Air-conditioning Associations.[2]
  • Skistad, H. (1994). Displacement ventilation. Research Studies Press, John Wiley & Sons, Ltd., west Sussex. UK.
  • Chen, Q. and Glicksman, L. (2003). Performance Evaluation and Development of Design Guidelines for Displacement ventilation. Atlanta: ASHRAE.[1]

Among guidelines listed above, the one developed by Chen and Glicksman are aimed specifically at fulfilling U.S. Standard. Below is a brief description of each step of their guideline.[15]

          Step 1) Judge the applicability of displacement ventilation

          Step 2) Calculate summer design cooling load.

          Step 3) Determine the required flow rate of the supply air for summer cooling.

          Step 4) Find the required flow rate of fresh air for acceptable indoor air quality.

          Step 5) Determine the supply air flow rate.

          Step 6) Calculate the supply airflow rate.

          Step 7) Determine the ratio of the fresh air to the supply air.

          Step 8) Select supply air diffuser size and number.

          Step 9) Check the winter heating situation.

          Step 10) Estimate the first costs and annual energy consumption.

List of buildings using displacement ventilation

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Building Year Country City Architects Space Type
Jewish Museum Berlin 1999 Germany Berlin Daniel Libeskind Exhibit space
Bangkok International Airport 2006 Thailand Bangkok Helmut Jahn of Murphy / Jahn Architects Airport terminal
Hearst Tower 2006 United States New York City, NY Norman Foster of Foster + Partners Large public space
Newseum 2011 United States Washington, D.C. Polshek Partnership Large public space
Modesto Medical Center 2008 United States Modesto, California KP Architects Health-care
St. John's University, St. John's Hall 1950s United States New York City, NY unknown Teaching environment
Carnegie Hall 1891 United States New York City, NY William Burnet Tuthill Theater
Samuel J. Friedman Theater 1920s United States New York City, NY Herbert J. Krapp Theater
National Center for the Performing Arts 2007 China Beijing Paul Andreu Theater
The Copenhagen Opera 2004 Denmark Copenhagen Henning Larsen Theater
Prince Mahidol Hall 2014 Thailand Nakornpathom A49 Theater

See also

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References

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  1. ^ a b c d e f g h i Chen, Q.; Glicksman, L. (1999). Performance Evaluation and Development of Design Guidelines for Displacement Ventilation. MA.: ASHRAE.
  2. ^ a b c d e REHVA. (2002). Displacement Ventilation in Non-Industrial Premises. Federation of European Heating and Air-conditioning Associations.
  3. ^ Novoselac, Atila; J., Srebric (June 2002). "A critical review on the performance and design of combined cooled ceiling and displacement ventilation systems". Energy and Buildings. 34 (5): Energy and Buildings. doi:10.1016/S0378-7788(01)00134-7.
  4. ^ Schiavon, Stefano; Bauman, F.; Tully, B.; Rimmer, J. (2012). "Room air stratification in combined chilled ceiling and displacement ventilation systems". HVAC&R Research. 18 (1): 147–159. doi:10.1080/10789669.2011.592105. S2CID 55305722.
  5. ^ Svensson, A.G.L. (1989). "ordic Experiences of Displacement Ventilation Systems". ASHRAE Transactions. 95 (2).
  6. ^ "NASA's Out of this World Green Building - Web Exclusives - EDC Magazine". edcmag.com. Archived from the original on 22 January 2013. Retrieved 9 December 2010.
  7. ^ https://www.energystar.gov/sites/default/uploads/buildings/old/files/50_Flight_Project_508.pdf [bare URL PDF]
  8. ^ "San Francisco Airport aims to achieve zero net energy (USGBC Northern California) | U.S. Green Building Council".
  9. ^ "Zero-energy green building in a data-enlightened era". 12 September 2018.
  10. ^ ANSI/ASHRAE Standard 55 (2002). Thermal Environmental Conditions for Human Occupancy
  11. ^ Melikov, Arsen; Pitchurov, G.; Naydenov, K.; Langkilde, G. (June 2005). "Field study of occupants'thermal comfort in rooms with displacement ventilation". Indoor Air. 15 (3): 205–214. doi:10.1111/j.1600-0668.2005.00337.x. PMID 15865620.
  12. ^ Loveday, D.L.; Parsons, K.C.; Taki, A.H.; Hodder, S.G. (July 2002). "Displacement ventilation environments with chilled ceilings: thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate". Energy and Buildings. 34 (6): 573–579. doi:10.1016/S0378-7788(02)00007-5.
  13. ^ a b Woods, Andrew W.; Mingotti, Nicola (June 2015). "On the transport of heavy particles through an upward displacement-ventilated space". Journal of Fluid Mechanics. 772: 478–507. Bibcode:2015JFM...772..478M. doi:10.1017/jfm.2015.204. ISSN 0022-1120. S2CID 233733115.
  14. ^ a b Woods, Andrew W.; Mingotti, Nicola (July 2015). "On the transport of heavy particles through a downward displacement-ventilated space". Journal of Fluid Mechanics. 774: 192–223. Bibcode:2015JFM...774..192M. doi:10.1017/jfm.2015.244. ISSN 0022-1120. S2CID 53446651.
  15. ^ Chen, Q; Glicksman, L.R (January 1, 2003). System performance evaluation and design guidelines for displacement ventilation. Atlanta: American Society of Heating, Refrigerating, and Air-conditioning Engineers, Inc. ISBN 978-1931862424.