Fläkt Woods
3099 US 03.02
16
Specifications are subject to alteration without notice
PUMA (A–F) Rotary heat exchanger
TECHNICAL HANDBOOK
Project design advice
Angle, degrees 1°– 6°
1
2
3
4
5
6
Pressure
Standard foil spacing
4,8
2,0 1,3 0,9 0,7 0,6
differential, p1-p3, in WG Wider foil spacing
2,8
1,0 0,6 0,4 0,4 0,3
Leakage flow rates and fan sizing
Leakage between the supply and exhaust air sides cannot
be entirely eliminated in a rotary heat exchanger. But by
locating the fans as shown in Fig. 5, the carry-over of ex-
haust air to the supply air can be eliminated. The pres-
sure differential between the supply and exhaust air ducts
on both sides of the exchanger should be such that p1 >
p4 and p2 > p3. If necessary, an adjusting damper is
installed as shown in Fig. 5 to achieve this.
Leakage at the seals can be minimized by the pressure dif-
ferential between the supply and exhaust air ducts being
as small as possible. Chart 5 shows the leakage flow across
the seal as a function of pressure differential p1 - p3.
Purging sector – carry-over flow
The purging sector is located on the supply air outlet
side, at the point where the rotor passes from the exhaust
air flow path to the supply air flow path. The sector,
which is adjustable between 0 and 6°, should be set to
suit the pressure differential p1 - p3 in the system (see
table below).
If the purging sector of the heat exchanger is set to 0°, a
certain volume of exhaust air will always be transferred to
the supply air, and a certain volume of supply air will
always be transferred to the exhaust air by carry-over.
However, these volumes are equal and cancel one another
out. If the purging sector is correctly adjusted to suit the
prevailing pressure conditions (see the table), complete
purging of the rotor will take place without any air being
lost. However, a certain amount of supply air will be
transferred to the exhaust air by carry-over. This takes
place at the point where the rotor moves from the supply
air duct to the exhaust air duct as it rotates.
The volume carried over is approximately 3% of the
supply air flow at p1-p3 = 0.4 in. WG, and approximate-
ly 1.5% at p1-p3 = 0.8 in. WG, regardless of
the heat exchanger size (rotor speed = 10 RPM).
Tilluft
Frånluft
p3
p1
Frånluft
p4
Tilluft
p2
Fig. 6.
Purging sector
Chart 5
Leakage flow q1
Fig. 5. Heat exchanger on the suction side of both fans
110 120 135 150
190 200
215
240
265
290
320
350
380
420
300
400
500
1 000
2 000
3 000
200
4.0
1.6
1.2
0.8
Leakage flow q l, CFM
p
1
–
p
3
, IN. WG.
2.0
2.4
3.2
Size 060
170
460
500
095
080
Supply air
Leakage flow ql,CFM
106 148 191 265 371 424 636 848 1272 1696 2120 2756 2968 3392
Size
Supply air
Exhaust air
Exhaust
air
inches WG.
