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NatVent project,WP3/A3.3
Natural ventilation with heat recovery
Heat recovery
Why & target
Driving forces
Norwegian Building
Research Institute
2 Systems
NBI’s system
Measuring
Conclusions
More ...
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P.O.Box 123 Blindern
Forskningsveien 3B
0314 Oslo
Norway
 +47 22965500
 +47 22965725
Contact persons:
J.T. Brunsell ([email protected])
P. Blom ([email protected])
E. Skaaret ([email protected])
T. Hestad ([email protected])
Energy recovering from natural
ventilation systems
Heat recovery

Why & target
Driving forces
Because of two reasons in moderate and cold climate:
 1.To recover energy
 2.To supply preheated air
2 Systems
NBI’s system
Measuring
Conclusions
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Work content WP 3.3
Natural ventilation with heat recovery
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Requirements of a system with heat recovery for an office
building.
Evaluate the energy saving potential.
Develop advanced systems with heat recovery
Laboratory testing of system.
Distribution of natural driving forces
1200
Heat recovery
Why & target
2 Systems
NBI’s system
Measuring
Conclusions
Frequency (hours)
Driving forces
1000
More ...
800
London
Belgia
St.holm
Oslo
Copenhagen
600
400
200
NatVent
55
50
45
40
35
30
20
15
25
Driving force (Pa)
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10
5
0
Internal air supply - system 1 (1...)
Heat recovery
Why & target
Driving forces
2 Systems
NBI’s system
Measuring
Conclusions
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Internal air supply - system 2 (2|)
Heat recovery
Why & target
Driving forces
2 Systems
NBI’s system
Measuring
Conclusions
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NBI’s NatVent system
with heat recovery (1...)
Heat recovery
Storey
Why & target
5
Driving forces
c= 114,1
4
2 Systems
ø500
NBI’s system
3
Measuring
Conclusions
2
ø400
ø315
Lab.hall
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ø315
ø400
1
Test-room
ø500
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c=100,30
NatVent
0
System outdoors (2...)
Heat recovery
2000
1000
Why & target
ø500
Automatic closing
shutters 776x776
on 4 sides
Driving forces
2 Systems
NBI’s system
1000
Assisting fan
vol.controller
Measuring
2400
Conclusions
1400
600
Door
600
Cooling
- coil
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ca300
285
115
1000x1000
580x860
ca500
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Insulation
Opening for filter
ø500
200
ø500
System Indoors (3|)
Heat recovery
Rounded outlet
ø500
Door
Why & target
H.coil
Driving forces
+
2 Systems
NBI’s system
Measuring
500
280
El.filter
600
Inlet chamber
ø500
150
1800
Conclusions
Changeable plate
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600
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Drainage
NatVent
700
500
50 mm insulation
Measurements
Heat recovery
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Temperatures
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Why & target
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Driving forces
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2 Systems
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Outdoor
Indoor
Outgoing air
Incoming air
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Conclusions
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Across the filter
Across both sides of the
heat recovery
Total for the system
including ducts and
terminals
In the ducts, gives the air
flow
Wind
Driving forces
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Pressure drops
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Velocity
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NBI’s system
Measuring
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Natural
– Temp. dif.
– Wind
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Assisting fan
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Filter efficiency
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Heat recovery efficiency
Pressure losses
at design value: 400 l/s
Heat recovery
Why & target
Driving forces
2 Systems
Component
outlet to atmosphere
heat exchanger
extract duct and terminals
Total sum
Pa
1,2
3,1
8,4
12,7
Extract
side
NBI’s system
Measuring
Conclusions
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Component
intake and vertical duct
filter
heat exchanger
supply ducting and terminals
Total sum
NatVent
Pa
11,3
1,0
6,5
19,4
38,2
Supply
side
Measurement modes
Heat recovery
Why & target
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Without any fans
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With extract fan (most of the time)
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With both extract and supply fan
Driving forces
2 Systems
NBI’s system
Measuring
Conclusions
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Temperatures & air flow
(without fans)
Driving forces
2 Systems
NBI’s system
Measuring
Conclusions
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40
300
q exhaust
30
200
q supply
20
10
100
t exhaust
t supply
0
wind
0
-100
t out
-10
01.03.98
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-200
03.03.98
05.03.98
Airflow (l/s)
Why & target
Temp. (°C), wind (m/s)
Heat recovery
Air Flow vs Natural Driving forces
350
Why & target
300
Driving forces
2 Systems
NBI’s system
Measuring
Air flow (l/s)
Heat recovery
Conclusions
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q extract
250
200
q supply
150
Linear (q extract)
100
Linear (q supply)
50
0
10
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15
20
Natural driving forces (Pa)
25
Temperatures & air flow
(extract fan running)
25
Why & target
2 Systems
NBI’s system
Measuring
Conclusions
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Temp. (°C), wind (m/s)
Driving forces
20
q extract
450
350
t extract
15
250
t supply
q supply
10
5
150
50
wind
0
-5
-50
t out
-10
06.03
NatVent
Air Flow (l/s)
Heat recovery
-150
07.03
08.03
09.03
-250
10.03
Extract & supply fan
(without pump running)
Heat recovery
30
2 Systems
NBI’s system
Measuring
Conclusions
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450
q extract and q supply
25
20
15
10
5
400
t extract
350
t supply
300
250
t out
Wind
0
01.06
200
150
03.06
05.06
07.06
09.06
Air flow (l/s)
Driving forces
Temp. (°C), wind (m/s)
Why & target
Fan power & natural driving forces
(pump turned off)
Heat recovery
NBI’s system
Measuring
Conclusions
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18
90
P supply
16
80
70
14
12
60
Temp. diff. inside - outside
10
50
8
40
6
4
30
P extract
20
Wind
2
10
0
01.06
0
03.06
05.06
07.06
09.06
Fan Power, P, (W)
2 Systems
Temp. (°C), wind (m/s)
Driving forces
100
20
Why & target
Extract fan power vs nat. driving force
(regulating at 400 l/s)
Heat recovery
40
Why & target
35
Driving forces
NBI’s system
Measuring
Conclusions
Dates:
30
Fan Power (W)
2 Systems
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6.3-31.3
1.4-2.4
14.4-23.4
Trend
25
20
15
10
regulator
5
0
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0
10
20
30
Wind and Thermal Driving Force (Pa)
40
Conclusions
Heat recovery
Why & target
Driving forces
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2 Systems
NBI’s system

Measuring
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Conclusions
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Heat recovery should be considered in natural ventilated
office buildings in cold climates
Practical concepts existed and have been further developed
Concepts must involve a close integration with the building
design
Heat recovery may require assisting fans for stabilising air
flows.
Assisting energy efficient fans may act as efficient flow
controllers
Measured heat recovery efficiency is 0,5 but can be further
improved
Natural ventilation with heat recovery is economic and
technical competitive with traditional systems today
More information...
Heat recovery
You can fin more information on:
Why & target
Driving forces
2 Systems
NBI’s system
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Heat recovery and the work carried out in the
framework of Task 3.3. in the document ‘3.3_heat
recovery.pdf’ in the directory
\Reports\ Technological solutions
Measuring
Conclusions
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You can read and print pdf-files with the Acrobat® Reader
®3.0. Program. This program is free.
Download it from the Acrobat web site: www.adobe.com OR
run the installation file ar32e301(1).exe in the directory
\Installation