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Effektförluster från ventilationskanaler

Lindén Johansson, Sigfrid LU (2016) ABK920 20161
Division of Building Services
Abstract
To minimize energy losses becomes more and more important in a world where energy efficiency is a big priority and necessary if we want a future on our planet. The relative impact from ducting losses on the energy performance of the building was earlier so small that it was plausible to ignore them. Nowadays many of the other parts of the losses have been cut which means the air ducts now might stand for such a significant part of the total energy losses that a more thorough investigation of the losses are needed.
In this study, a review of current air ducting systems in commercial and residential buildings were made. The principal ways for energy to leave an air duct were studied and relevant equations were gathered and assembled. The... (More)
To minimize energy losses becomes more and more important in a world where energy efficiency is a big priority and necessary if we want a future on our planet. The relative impact from ducting losses on the energy performance of the building was earlier so small that it was plausible to ignore them. Nowadays many of the other parts of the losses have been cut which means the air ducts now might stand for such a significant part of the total energy losses that a more thorough investigation of the losses are needed.
In this study, a review of current air ducting systems in commercial and residential buildings were made. The principal ways for energy to leave an air duct were studied and relevant equations were gathered and assembled. The mathematical model was tested by comparing calculated temperatures with measured ones from a building where air flows and temperatures could be read through the automation system Swegon SuperWISE.
When the mathematical model was shown to give plausible results it were used to calculate the energy losses from the air duct system divided on floor area. Two office buildings where studied to compare different principals of cooling. One system had cooling by variable on demand ventilation with under tempered air and the other had constant ventilation and comfort modules with waterborne cooling. It was done by simplifying one of the levels of the building and divide the distributing air/water ducts/pipes in to equivalent ducts/pipes that go from the central shaft out to zero flow in the duct/pipe. The model iterates and take in to account the diminishing flow and temperature difference the further from the central shaft it gets. The calculated losses from the air ducts were in the variable air volume building where 0.8 – 1.4 W/m2floor and the combined losses in the building with constant ventilation and water cooling pipes the losses where 1.6 W/m2floor with the majority of the losses from the uninsulated return pipes.
In the variable flow building the calculations indicated up to seven times bigger losses and for the constant air building the calculated losses where a little more than a half time bigger for the cooling distribution compared to what was used in the energy calculations for the different projects. What part of this energy loss that actually leave the buildings were outside the scope of this thesis to answer because of the complexity. One way to move forward in that regard would be to investigate the possibility to do advanced simulations of the building, maybe with a tool developed to work with BIM models, which would be an interesting next step to study. (Less)
Abstract (Swedish)
I en allt mer energieffektiv värld så spelar allt fler av energiförlusterna allt större roll. Tidigare hade man samma förluster som idag från kanalsystemet men de totala förlusterna var större. När man nu har minskat andra förluster i huset får kanalför- lusterna en allt större betydelse i den totala energianvändningen, vilket leder till att det nu finns anledning att ta större hänsyn till dem.
I detta arbete görs en genomgång av nuvarande ventilationskanalssystem i kontor och bostäder. De principiella sätt som energi kan vandra in och ut genom kanalväggarna till omgivningen studeras och de sammanställda formlerna testas mot avlästa flöden och temperaturer från ett kanalsystem i ett kontorshus. Avläst data kommer från Swegons SuperWISE... (More)
I en allt mer energieffektiv värld så spelar allt fler av energiförlusterna allt större roll. Tidigare hade man samma förluster som idag från kanalsystemet men de totala förlusterna var större. När man nu har minskat andra förluster i huset får kanalför- lusterna en allt större betydelse i den totala energianvändningen, vilket leder till att det nu finns anledning att ta större hänsyn till dem.
I detta arbete görs en genomgång av nuvarande ventilationskanalssystem i kontor och bostäder. De principiella sätt som energi kan vandra in och ut genom kanalväggarna till omgivningen studeras och de sammanställda formlerna testas mot avlästa flöden och temperaturer från ett kanalsystem i ett kontorshus. Avläst data kommer från Swegons SuperWISE system som är ett automationssystem för behovsstyrd ventila- tion installerat i huset.
Efter att formlerna visat sig ge beräknade temperaturer på tilluften vid tilluftsdonen som ser ut att följa de avlästa temperaturerna görs beräkning av effekten från venti- lationskanalerna per kvadratmeter lokalyta. Detta görs i två kontorshus som har olika principer för kylning av arbetsplatserna, det ena behovsstyrd varierande ventilation med undertempererad luft och det andra konstant ventilation och kyla via vätskesy- stem och kylbafflar. Genom att formulera en förenklad modell över ett våningsplans hela tilluftskanalsystem och beräkna dess energiförlust med hänsyn till minskande flöden och temperaturdifferens ju längre ut i kanalsystemet man befinner sig och sen summera kanalernas förluster och fördela dem på hela planets golvarea fås en effekt från kanalerna på 0,8 – 1,5 W/m2golv i huset med behovsstyrd ventilation. I huset med konstant ventilation görs motsvarande förenklade beräkningar även för köldbä- rarrören där effekt från tilluftskanaler landar på 0,1 W/m2golv och från köldbärarrören hamnar på 1,5 W/m2golv.
I huset med behovsstyrd ventilation visar beräkningarna ca fem gånger högre energi- förlust från kanalsystemet per kvadratmeter lokalyta jämfört med den som använts vid energiberäkningen för projektet. I huset med konstant ventilation var det beräkna- de värdet drygt en halv gång högre än det som använts i den energiberäkningen. Hur stor andel av den energi som lämnar kanalerna som sedan lämnar huset visar sig stå utanför denna studies förmåga att besvara då komplexiteten är allt för stor. Ett sätt att gå vidare skulle kunna vara att göra en mer omfattande studie med avancerade simuleringar av hela byggnaden, samt att utveckla verktyg som kan använda sig av BIM-modeller, något som vore intressant att studera närmare. (Less)
Please use this url to cite or link to this publication:
author
Lindén Johansson, Sigfrid LU
supervisor
organization
course
ABK920 20161
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Ventilationskanaler, Effektförluster, Kanalisolering, VAV, Behovsstyrd ventilation, Köldbärarör, CAV, Konstantflöden
report number
5058
other publication id
TVIT
language
Swedish
additional info
Examinator: Dennis Johansson
id
8891947
date added to LUP
2017-06-09 15:31:04
date last changed
2017-06-09 15:31:04
@misc{8891947,
  abstract     = {To minimize energy losses becomes more and more important in a world where energy efficiency is a big priority and necessary if we want a future on our planet. The relative impact from ducting losses on the energy performance of the building was earlier so small that it was plausible to ignore them. Nowadays many of the other parts of the losses have been cut which means the air ducts now might stand for such a significant part of the total energy losses that a more thorough investigation of the losses are needed.
In this study, a review of current air ducting systems in commercial and residential buildings were made. The principal ways for energy to leave an air duct were studied and relevant equations were gathered and assembled. The mathematical model was tested by comparing calculated temperatures with measured ones from a building where air flows and temperatures could be read through the automation system Swegon SuperWISE.
When the mathematical model was shown to give plausible results it were used to calculate the energy losses from the air duct system divided on floor area. Two office buildings where studied to compare different principals of cooling. One system had cooling by variable on demand ventilation with under tempered air and the other had constant ventilation and comfort modules with waterborne cooling. It was done by simplifying one of the levels of the building and divide the distributing air/water ducts/pipes in to equivalent ducts/pipes that go from the central shaft out to zero flow in the duct/pipe. The model iterates and take in to account the diminishing flow and temperature difference the further from the central shaft it gets. The calculated losses from the air ducts were in the variable air volume building where 0.8 – 1.4 W/m2floor and the combined losses in the building with constant ventilation and water cooling pipes the losses where 1.6 W/m2floor with the majority of the losses from the uninsulated return pipes.
In the variable flow building the calculations indicated up to seven times bigger losses and for the constant air building the calculated losses where a little more than a half time bigger for the cooling distribution compared to what was used in the energy calculations for the different projects. What part of this energy loss that actually leave the buildings were outside the scope of this thesis to answer because of the complexity. One way to move forward in that regard would be to investigate the possibility to do advanced simulations of the building, maybe with a tool developed to work with BIM models, which would be an interesting next step to study.},
  author       = {Lindén Johansson, Sigfrid},
  keyword      = {Ventilationskanaler,Effektförluster,Kanalisolering,VAV,Behovsstyrd ventilation,Köldbärarör,CAV,Konstantflöden},
  language     = {swe},
  note         = {Student Paper},
  title        = {Effektförluster från ventilationskanaler},
  year         = {2016},
}