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7/30/2019 room pressure
1/13
Dipl. Ing. Andreas Trk
LABCONTROL
TROX GmbH Germany
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Pressure regulation for different requirements
laboratories
operating rooms
clean rooms
quarantine ward
S3/S4 security laboratories
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room pressure
room supplyroom exhaust
Normal room
Volume flow:1000 m/h 5%= 950 1050 m/h
Volume flow:1000 m/h 5%= 950 1050 m/h
room leakage 0.02 m(2 cm gap below one door)
room pressure about 1 Pa(by leakage volume flow 75 m/h)
no problem
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room pressure
room supplyroom exhaust
Volume flow:1000 m/h 5%= 950 1050 m/h
Volume flow:1000 m/h 5%= 950 1050 m/h
room leakage 0.005 m(0,5 cm gap below one door)
room pressure about 20 Pa(by leakage volume flow 75 m/h)
You must use pressure control
Airtight room
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room pressure
room supplyroom exhaust
Volume flow:1000 m/h 5%= 950 1050 m/h
Volume flow:1000 m/h 5%= 950 1050 m/h
room leakage 0.001 m(1 mm gap below one door)
room pressure 500 Pa!(by leakage volume flow 75 m/h)
Walls could be damaged
Very airtight room
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p
=
*
*
2 A
V
According to Bernoulli:
If the area is nearly zero
The pressure will increase nearlyunlimited!
2
Even a lowest volume flowdifference will change the
room pressure
dramatically!
A = Roomleakage
= air density 1,2 kg/m3
= Volume flow difference
= geometric coefficient approx. 0,72
room pressure 500 Pa!
Physical Background
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tightness
Leackagevolume flow
Pressurecontrol
=
**
2 A
Vp
2
Regulation triangle
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0,02 m
0,01 m
0,005 m0,002 m0,001 m
0
5
10
15
20
25
30
35
40
45
50
55
0 20 40 60 80 100 120 140 160 180 200 220 240Leckagevolumenstrom / Leakagevolumelow [m/h]
Raumdruck/Roomp
ressure
[Pa]
approx. 1mm gap
=
**
2 AVp
2
approx. 1cm gap
Room leakage / room pressure
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- 10 Pa- 25 Pa
- 15 Pa
- 15 Pa
- 10 PaP
Reference Pressure
The reference must be
stable / constant pressure
forbidden!!!
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Attention
No pressure variation in reference room
No pressure variation in the ventilation system
In air tight rooms regard the hysteresis of the VAV regulator
every pressure room must be regulated to a reference room
the regulation quality dependents of all installed regulator inthe room, even the non pressure regulator
The pressure is every time a function of the leakage volumeflow
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Controller
Pressure controlled room
Reference pressure
Room pressure / working with damper - only
Cheap solution
Damper will move to extreme positions (Open / Close)
Door switches can not be used in laboratories (Notallowed streamings are possible)
No fast reaction times possible
High pressure jumps after closing doors
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Room pressure / volume flow cascade
Contr.Contr.
Master / Slave
Reference pressure
Pressure Controlled room Defined control areas
No extreme positions of the damper
No door switches needed
Fast control possible
Master / Slave situations possible
High transparency of data
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Thank you for your interrest!
www.trox.de
Halle 6.2 Stand C14/C16
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