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4. Menu Q vent.
Wöhler DC 100
PRO
4. Menu „Q vent": Measurement of the ventilation loss
A highly sensitive S-type Prandtl tube connected to the DC 100
permits
PRO
to evaluate the ventilation loss of boilers during the evaluation of the energy
efficiency according to article 8 of the European Building Performance Direc-
tive (EBPD).
Since combustion installations are provided with numerous constructional
measures to avoid ventilation losses (apart from exhaust-gas flaps or air cho-
kes), it is usually not sufficient to check visually whether these components
are present and functioning properly. A direct measurement of the ventilation
loss performed on the spot is more useful in practice. This measurement
takes place 30 seconds after burn-out and comprises a determination of the
flow velocity and of the temperature in the residual core flow. Hot-wire ane-
mometers cannot be used to measure the flow in the hot exhaust-gas outlet,
due to their temperature cross-sensitivity. The combination of the DC 100
PRO
and the Wöhler S-type Pitot tube type has proved as sufficient and durable in
field tests (see fig. 4.1).
statischer Druck
static pressure
temperature
Temperatur
Strömung
flow
Fig. 4.1: Pressure meter with Wöhler S-type Pitot tube and temperature sen-
sor connected to the probe tip
The differential pressure measuring instrument must have a sensitivity of 0.01
Pa or better to ensure a sufficient resolution of the flow velocity of approx. 0.1
m/s.
Figure 4.1 shows the DC 100
with Wöhler S-type Pitot tube and tempe-
PRO
rature sensor connected to the probe tip. A special feature of this patented
measuring tube is its increased measuring sensitivity compared to conventi-
onal Prandtl tubes. In addition, a flap mechanism permits to insert the probe
through a standard measurement opening with a diameter of usually 8 mm.
59
e-Mail: mgkg@woehler.com
http://www.woehler.com
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