Fläkt Woods
3099 US 03.02
14
Specifications are subject to alteration without notice
PUMA (A–F) Rotary heat exchanger
TECHNICAL HANDBOOK
14
Efficiency
For a hygroscopic rotor (B, D and F rotor):
The temperature efficiency for a given rotor size and a
given supply air flow is obtained from the design chart
on page 16. At maximum speed and for equal supply and
exhaust air flow rates:
η
tt =
η
tf
where
η
tt = supply air temperature efficiency and
η
tf = exhaust air temperature efficiency.
At maximum speed and at different supply and exhaust
air flow rates, the supply air efficiencies are linked, and so
are those of the exhaust air.
η
tt
≈ η
xt
η
tf
≈ η
xf
How the temperature efficiency changes at different flow
rates is shown in the design chart on page 16.
Chart 3
Temperature and moisture efficiencies at different rotor
speeds
Temperature and moisture recovery
The temperature efficiency ht and the moisture efficiency
hx at different rotor speeds are shown in Chart 3. The
chart is valid for normal changes in condition in climate
systems and at an air velocity v = 3 m/s through the
rotor.
Definitions:
Efficiency
Supply air temperature efficiency
η
tt =
t2-t1
t3-t1
Supply air moisture efficiency
η
xt =
x2-x1
x3-x1
Supply air enthalpy efficiency
η
ht =
h2-h1
h3-h1
Exhaust air temperature efficiency
η
tf =
t3-t4
t3-t1
Exhaust air moisture efficiency
η
xf =
x3-x4
x3-x1
Exhaust air enthalpy efficiency
η
hf =
h3-h4
h3-h1
t = temperature (°F)
x = water content per lb of dry air (gr)
h = enthalpy (Btu/lb)
A common feature of all hygroscopic aluminium rotors is
that when the rotor speed is reduced, the moisture effi-
ciency also drops below the temperature efficiency.
However, with the ECONOVENT F rotor of composite
material, the difference between the two efficiencies on a
drop in speed is appreciably smaller.
0
10
20
30
40
50
60
70
80
90
0
20
40
60
80
100
Verkningsgrad
η
%
100
% av max. varvtal
η
t
η
x
Hygroskopisk rotor
Kompositrotor
t4, x4, h4
t3, x3, h3
t1, x1, h1
t2, x2, h2
q1
Tilluft q2
q4
Frånluft q3
Rum
Composite rotor
Hygroscopic rotor
% of max. speed
Efficiency
η
%
Room
Fig. 4
Supply air q2
Exhaust air q3