Datasheet
32
WHAT IS VENTILATION?
Ventilation is understood to be the replacement of a por-
tion of air which is considered undesirable (polluted), by
another that provides an improvement both in terms of
purity, and of temperature, humidity, etc.
FUNCTIONS
To maintain the air in an enclosure under suitable condi-
tions of temperature, humidity, pressure, speed and degree
of pollution to ensure the health and wellbeing of people,
or living beings.
FLOW RATE
This is the amount of air displaced in a given unit of time.
(The flow given in the technical specifications is at free
discharge, in other words, with no pressure loss). Flow is
shown as Q and is usually expressed in m
3
/h, although it
is also commonly expressed in m
3
/min, m
3
/sec, l/s, C.F.M
1m
3
/h = 3,6 l/s
1,7 m
3
/h = 1 C.F.M
The FLOW RATE and the section are related as follows:
Q = V * S = m
3
/h
V = Air speed (m/sec)
S = Section (m
2
) of the duct
WHAT IS PRESSURE?
It is the pushing force per surface unit that air needs to circulate
and overcome the resistance of the system (pressure losses).
Pressure is given in: mmH2O and Pa
9,8 Pa = 1 mmH2O
THERE ARE THREE TYPES OF PRESSURE:
Static Pressure (Pe): This is the force of the air in all direc-
tions on the walls of the tube, in a perpendicular direction
to them.
Dynamic Pressure (Pd): Is the force that accelerates the
air from zero to the velocity of the system. It is manifested
only in the direction of the air.
There is a formula that links dynamic pressure and speed:
Pd = (V / 4,04)
2
Speed Table with its Dynamic Pressure (table 3)
Speed (m/s) Dynamic Pressure mmH
2
O
1 0.06
2 0.24
3 0.55
4 0.98
5 1.53
6 2.20
7 3.00
8 3.92
9 4.96
10 6.12
11 7.41
12 8.82
13 10.35
14 12.00
15 13.78
16 15.68
17 17.70
18 19.85
19 22.11
20 24.50
21 27.01
22 29.65
Total Pressure: This is the sum between the static pressu-
re and the dynamic pressure Pt = Pe + Pd
WHAT IS NOISE?
It is the audible sound, that is propagated through the air
and which is unpleasant to the receiver.
The Sound Pressure (Lp) level is what we really hear
and it varies according to the premises and the distance
between the source of the noise (extractor or fan) and the
receiver.
The Sound Power (Lw) level is the amount of sound ener-
gy of a sound source (extractor or fan) every second and it
is constant, in other words, it does not vary according to the
premises or the distance from the sound source.
S=
*
∏
d
2
4
Concepts
BASIC VENTILATION CONCEPTS