Fläkt Woods
3099 US 03.02
18
Specifications are subject to alteration without notice
PUMA (A–F) Rotary heat exchanger
TECHNICAL HANDBOOK
Project design advice
Filters
Experience has shown that the ECONOVENT rotor is
very insensitive to clogging during operation, in spite of
the dense structure of passages. This is due to the fact
that the direction of air flow through the rotor is contin-
ually reversing, which has an excellent self-cleaning
effect. The laminar flow through the rotor is also a con-
tributory factor to the very rare occurrence of clogging of
the rotor.
If either of the air streams has a high dust content, the
particles usually adhere to the rotor surface, and very
rarely settle inside the passages. As a result, the particles
are blown away from the rotor surface when the direction
of air flow reverses.
In many installations, the rotor is stationary during
parts of the year. To protect the rotor from deposits and
clogging, the supply air filter of the system should be
located upstream of the rotor.
If the rotor should become clogged, it can normally
easily be cleaned by vacuum cleaning. Compressed air,
low-pressure steam and certain types of grease solvents
can also be used.
Clogging problems may nevertheless occasionally
occur in practice. In the event of doubt, it is therefore
better to fit a filter rather than determine at a later date
that a filter is needed (see Fig. 11).
In order to prevent fouling and clogging of the rotor
during the construction period, the regular filters should
be in position, and the rotor should always be rotating
when the fans in the system are running.
Insertion loss
∆
Lw, dB
Rotor version
Octave band, mid-frequency, Hz
63
125
250
500
1000 2000 4000 8000
Non-hygroscopic
rotor, aluminium
3
4
4
3
4
5
6
9
Hygroscopic
rotor, aluminium
3
2
3
4
5
6
7
9
Composite rotor
3
3
3
4
5
6
10
14
The fan locations shown in Fig. 9 may give rise to prob-
lems, since it may be difficult to achieve correct pressure
balance.
Question: Is maximum heat recovery desirable?
If the fans are installed as shown in Fig. 10, all of the
power supplied to the exhaust air fan motor and almost
all of the power supplied to the exhaust air fan motor will
be utilized.
The location provides constant pressure conditions in the
building throughout the year.
Maximum heat recovery will be obtained if the fans are
installed so that the heat from the exhaust air fan is
utilized (Fig. 10). This fan location can be used only in
systems in which air recirculation is permissible.
In cases where the exhaust air is polluted and return air
cannot be used, a correct pressure balance must be
obtained on both sides of the rotor.
Pressure conditions: p1 > p4, p2 > p3.
INSERTION LOSS
∆
Lw, dB
Rum
Rum
Room
Room
Fig. 9
Fig. 10
Frånluft
Tilluft
Uteluft
1)
2)
Outdoor air
Fig. 11
Supply air
Exhaust air
1) A basic filter should preferably be installed, particularly if the dust consists
of large particles, or of oily, tacky or adhering particles. If a filter is not
installed, space should be left for installing a filter at a later date.
2) The filter class should be selected to suit the requirements of the
premises.
Inspection facilities
An inspection section or a duct with inspection cover
should be connected to the heat recovery unit to enable
the rotor to be inspected and serviced. However, if unit
sections with good access facilities are connected directly
to the heat recovery unit, these may be used for inspection.
