33
Planning • Calculation • Units
We reserve the right to make changes to dimensions and design in the interest of technical advances.
Symbol
Unit
Explanation
Q
kW
Heating capacity of air heater
Q = Q
H
+ Q
AL
Q
H
kW
Heating requirement for room to be heated
Q
AL
kW
Heat requirement to heat fresh air to room temperature
Q
AL
= V
AL
· C
PL
·
∆
t
Q
L
kW
Effective heating capacity of air heater with mounted
accessory components
V
m
3
/h
Air volume flow of air heater without mounted
accessory components
V
L
m
3
/h
Effective air volume flow of air heater with mounted
accessory components
V
L
= V
· f
V
V
AL
m
3
/h
Fresh air volume flow
V
AL
= X
· B · L
V
W
l/h
Heating medium volume flow
V
W
=
t
L1
°C
Air inlet temperature at air heater
t
L2
°C
Air outlet temperature at air heater
∆
t
°C
Air inlet/outlet temperature difference at air heater
∆
t =
t
L2
– t
L1
∆
t
W
°C
Heating medium inlet/outlet temperature difference at air heater
∆
t
W
= t
W1
– t
W2
∆
t
°C
Effective air inlet/outlet temperature difference at air heater
with mounted accessory components
∆
t
L
=
∆
t · f
L
C
PL
Specific heat capacity of air at constant pressure
ϕ
L
Dry air density
L
m
Length of room to be heated
W
m
Width of room to be heated
H
m
Height of room to be heated
X
1/h
Number of air changes in room to be heated
f
Q
-
Heat output factor
f
Q
= Q
L
/ Q
f
V
-
Air capacity ratio
f
V
= V
L
/ V
f
L
-
Air heating factor
∆
P
W
kPa
Heating medium resistance (pressure loss on water-side)
∆
P
ST
Pa
Static pressure difference with mounted accessory components
D
-
Pressure difference value with mounted accessory components
kg
m
3
860 · Q
t
W
kWs
———
kg · K
kWs
1 ———
kg · K
