environmentally sound solutions for ventilation
TRANSCRIPT
SINTEF Energy Research
NATO/CCMS Sustainable Building for Military Infrastructure
Environmentally Sound Solutions for Ventilation
Hans Martin MathisenSINTEF Energy Research
Energy Processes2005-09-21
Outline of presentation
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Ventilation principles:NaturalMechanicalHybrid
Heat recoveryCase study of hybrid ventilation
A sustainable solution requires source elimination:
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Pollutions:Emissions from building materials => use low emitting materialsPolluting processes => remove them or encapsulate themEtc.
Heat:Solar irradiation => reduce glazed areas and use solar shadingHeat generating equipment => find another solution or encapsulate
Natural Ventilation
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ghghppp i ρρρ ∆=−=∆+∆=∆ )( 021 where: ∆p1 =∆p2 – pressure difference over opening,h – height difference between openings, m ρ-density, kg/m³ g – gravity, m/s2
Warm air is lighter than cold air:•In the lower part of the building cold outdoor air presses inwards•In the upper part warm indoor air tries to flow out
Natural ventilation
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The Buoyancy Increases With Increased Height Difference
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Availability of Buoyancy , Oslo
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2000 4000 6000 8000
timer
qopp
drift
ID TTghACq /∆=10 meter height difference between inlet and outlet openings. A=1m2
CD=0.6
q buo
yanc
y, m
3 /S
Hours (one year)
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Natural Ventilation, Wind As Driving Force
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Maximum availability of wind, Oslo
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2000 4000 6000 8000
timer
qvin
d
2/pRD CAUCq ∆=
CD – Coefficient for flow resistance through openings.A – Opening’s section, m2
UR – Wind velocity, m/s∆Cp – Wind pressure coefficient for the building
Hours (one year)
q win
d, m
3 /S
∆Cp=0.4, Cd=0.6, A=1m2
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Availability of Buoyancy and Wind
00.5
11.5
2
2.53
3.54
0 % 20 % 40 % 60 % 80 % 100 %
Timer, % av undervisningstid
q=(q
vind
2 +q o
ppdr
2 )0.
5 ,m
3 /s
q is the sum of the air flow rate from buoyancy and wind. 10 meter height difference for buoyancy. Cp=0.4, Cd=0.6, A=1 m2.
Hours, % of one year working hours
q=(q
win
d2 +q b
uoya
ncy2 )
0,5 ,
m3 /s
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Conclusion natural ventilation
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No possibility for efficient heat recovery due to low driving forces ⇒ Higher energy consumptionDifficult to satisfy requirements for airflow rates all the time ⇒From time to time unacceptable air qualityNo possibility for efficient cleaning of outdoor air ⇒ Can only be used in areas with clean outdoor air Natural ventilation generates no noise by itself, but admits noise from outdoor and between rooms. Wind can generate noiseThe conclusion is that natural ventilation can not be recommended for non-residential buildings for northern climates
Mechanical Exhaust Ventilation
Fan
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Mechanical Balanced VentilationHeat recovery
unit
Fans
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Mechanical ventilation, components
Constant air volume - CAV
Variable air volume - VAV
Constant air volume - CAVWater based cooling - Fancoil
Constant air volume - CAVWater based cooling – Chilled suspended ceiling
Hydronic heating
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Energy Use for Fans in Mechanical Ventilation
SFP is defined as:
where V is air volume flow rate in m3/s and P is the sum of all fan power
SFP can simplified be written as:
VP
SFP&
∑=
where is total pressure loss and is the total efficiency
tot
tot
VpVSFPη&&∆
≈
totp∆ totη
Annu
al e
nerg
y us
e (k
Wh/
m2 /y
ear
Energy consumption for fans, operation time 8760 hours/year
Airflow rate[l/s/m2][m3/h/m2]
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Heat Recovery
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Heat
+Hea
t rec
over
y un
itOutdoor air Indoor
Exhaust airOut
Heat coil
16-20 °C
20-24 °C
t t
Liquid Based Heat Exchanger (Run around)
Avtrekkskanal
Tilluftskanal
Varmeveksler luft til glycol
Varmeveksler glycol til luft
Efficiency typically equals 50%Heat exchanger glycol to air
Heat exchanger air to glycol
Exhaust duct
Supply duct
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Liquid Based Heat Exchanger
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Plate Heat Exchanger
AvtrekkskanalTilluftskanal
Varmeveksler
Efficiency typically = 60%
Exhaust ductSupply duct
Heat exchanger
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Plate Heat Exchanger
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Rotary Heat Exchanger
Exhaust duct
Supply duct
Rotary wheel
Efficiency in the range 80 to 90%
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Rotary Heat Exchanger
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Close up of Wheel, Rotary Heat Exchanger
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Complete Mixing Ventilation
.
.
•Complete mixing is only used together with mechanical ventilation•Requires relatively high pressure to work•Chilled air can be supplied without draft in the occupied zone•Pollutions is mixed with the room air and diluted
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Displacement Ventilation
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.
.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..........................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .............................................
.... .........
......
...........
......
.. . . . . . . . ..........
.. . . . . . . . .
Entrained air volume up to this height = V
Heatsource
Supplied air volume = V
.
.
•Displacement is used both for hybrid and mechanical ventilation•Pollutions are effectively transported away from the occupied zone
Advantages and Disadvantages of Mechanical Balanced VentilationAdvantages:
Relatively low investment costsGood possibilities for heat recovery from exhaust air with high efficiencyGood possibilities for central coolingGood possibilities for demand controlled ventilation (variable air volume=VAV)
Disadvantages:Uses electrical energy for running fans (Can be reduced by proper design)Fans generates noise (Can be reduced by proper design)Requires operators with technical skills Includes many mechanical and electrical components
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Hybrid Ventilation, Utilizes Both Mechanical and Natural Driving Forces
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Comparison of Natural, Hybrid and Mechanical Ventilation
Principal connection between driving pressure and flow section for a given duct layout, airflow rate, outdoor temperature and height. Pressure loss coefficient varies from 33 to 5 (shown at the bars).
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Case study: Office Building With Hybrid Ventilation (“Nordlåna” at HiNT)
The building is called ”Nordlåna” and is a part of the Nord-Trøndelag University College. The case study concentrated on one part of the building. This wing is called the HiNT-wing.The SINTEF research project was financed by Statsbygg - The Directorate of Public Construction and Property
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Ventilation, PrincipleExhaust fan
Supply air fanFilter, heat recovery and heat coil
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Ventilation, Principle
InntakstårnTilluftskasse med perforert front.Reguleringsspjeld innebygd i kassen.Det er en enhet for hvert kontor/modul.
Kulvert
Filter, vifte, varmegjenvinnerbatteriettervarmebatteri og spjeld kjøring av luftutenom varemebatterier
Supply air terminal device with perforated front. Air volume damper
in the device. One unit per office.Culvert
Air intake tower
Filter, fan, heat recovery exchanger,heating coil. A damper that makes it
possible to bypass heat exchanger at summer time
Demand controlled ventilation:The damper in the air terminal is controlled from a presence detector and the room temperature
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Culvert
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Full Scale Measurements of Office Rooms in “Nordlåna”
Full scale measurements were used to test the chosen ventilation solution:
Air velocitiesTemperature distribution in the room
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The Solution in Practice
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Full Scale Model, Cell office
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Full Scale MeasurementsResults, Temperature Profile
0.00
0.50
1.00
1.50
2.00
2.50
3.00
15.0 17.0 19.0 21.0 23.0 25.0 27.0
Temperatur, °C
Høy
de o
ver g
ulv,
m
Med bokhylleUten bokhylle
More than 3 °C temperature difference between neck and ankles is uncomfortable
Hei
ght a
bove
the
floor
, m With bookshelfWithout bookshelf
Temperature, degrees Celsius
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How they do it!
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Measurements in “Nordlåna”
When the building was finished and occupied the autumn 2002, measurements were started to study the energy use
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Nordlåna’s Façade Towards East
HiNT office wing
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Energy Consumption per Month
-
5 000
10 000
15 000
20 000
25 000
30 000
6 7 8 9 10 11 12 1 2 3 4 5
Ener
gi, k
Wh Varmegjenvinner
Varmebatteri
Radiatorer
Elektrisitet
Heat exchangerHeat coilRadiatorsElectricity
Ene
rgy,
kW
h
Month
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Energy Use for the HiNT-wing of “Nordlåna”
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Electricity Hydronic Total
Energy consumption, kWh 39 673 88 192 127 865
Heated area, m² 792
Specific energy use, kWh/m² 50 111 161
Comparison With Energy Consumption in Norwegian Office Buildings
Fra: Bygningsnettverkets energistatistikk Årsrapport 2001
HiNT-fløyenHiNT-wing
kWh/
m2
heat
edar
ea
Source:
The average age of these office buildings are 40 years
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LCC for hybrid and mechanical, HiNT-wing, annual costs
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Hybrid MechanicalBuilding work (fan room, exhaust tower etc) 14 289 15 964Culvert 31 489Other ducts (from culvert to rooms) 25 610 19 800Mechanical equipment, fans and VAV-dampers
31 963 32 352
Control equipment/room sensors 5 660 5 685Total, exclusive energy 109 011 73 800
Hydronic energy 29 913 12 000
Electric energy 1000 5200
Total, inclusive energy 139 924 91 968
Weaknesses of the Chosen Solution
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There is a heat loss from the ducts between culvert and the office rooms. Temperature sensors for supply air is placed above the air intakes in the culvert. Temperature stratification makes it difficult to control the supply air temperature.
The Impact of Increasing the Control Range for the Room Air Temperature
0
100
200
300
400
500
600
700
800
900
1000
22.3 23.0 24.0 25.0
Settpunkt
kWh Ventilasjon
Romoppvarming
Set point
VentilationSpace heating
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The Impact of Improving the Efficiency of the Heat Recovery Unit
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
900.00
1000.00
45 % 55 % 80 %
Virkningsgrad
kWh Ventilasjon
RomoppvarmingVentilationSpace heating
Efficiency
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Room Temperature and Damper Opening
10
15
20
25
30
03.6.30 0:00 03.7.1 0:00 03.7.2 0:00 03.7.3 0:00 03.7.4 0:00 03.7.5 0:00 03.7.6 0:00 03.7.7 0:00
Dag og klokkeslett
Tem
pera
tur,
°C
0
20
40
60
80
100
120
Påd
rag
Spj
eld,
%
RomtemperaturPådrag spjeld
Date and time
Damper openingRoom temperature
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Outdoor Temperature, Temperature in Culvert Before Heat Coil (after fan and filter) and Temperature in Culvert after Heat Coil
10.0
15.0
20.0
25.0
30.0
03.6.30 0:00 03.7.1 0:00 03.7.2 0:00 03.7.3 0:00 03.7.4 0:00 03.7.5 0:00 03.7.6 0:00 03.7.7 0:00
Dag og klokkeslett
Tem
pera
tur,
°C
UtetemperaturTemperatur inntak kulvert før varmegjenvinnerTemperatur kulvert etter varmebatteri
Date and time
Outdoor temperature
Temperature air intake in culvert in front of heat recovery unintTemperature in culvert after heat coil
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Airflow Due to Fan and Buoyancy (working hours, average per month)
0
1000
2000
3000
4000
5000
6000
5 6 7 8 9 10 11 12 1 2 3 4
Måned
Luftm
engd
e, m
³/h
Luftmengde oppdriftLuftmengde vifteAirflow rate buoyancyAirflow rate fan
Month
Airf
low
rate
, m3 /h
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