12
PA W
PA
04
W2
Air temperature af
ter heater [°C
]
Air flow through the heater [m
3
/h]
Air speed inside the water heating coils [m/s]
Wa
ter flow through the water heating coils [l/s]
Water pressure drop [kP
a]
External air temperature [°C
]
Coil heating capacity [kW
]
Water heater parameters calculation example Air Speed.
Starting from 3500 m
3
/h on the air flow scale draw a vertical line (1) till the air speed axis which makes 3.48 m/s.
Supply air temperature.
Prolong the line (1) of air flow up to the point where it crosses the outside air temperature (blue curve), e.g. -20°C;
then draw a horizontal line (2) from this point to the left till crossing water in/out temperature curve (90/70). From this p
oint draw a
vertical line (3) to the supply air temperature axis on top of the graphic (+22 °C). Heating coil capacity.
Prolong the line (1) up to the point where it crosses the outside air temperature -20°C (red curve) and draw a
horizontal line (4) from this point to the right until it crosses water in/out temperature curve (90/70), from here draw a vert
ical line (5) up to
the scale representing the heating coil capacity (55.0 kW). Water flow.
Prolong the line (5) down to water flow axis at the bottom of the graphic (6) (0.68 l/s).
Water pressure drop.
Draw the line (7) from the point where line (6) crosses the black curve to the pressure drop axis. (9.2 kPa).
Fig. 8. Calculation of water heater parameters
Performance chart for the water heater parameters of the unit PA 04 W2 is shown in fig. 8.
V43EN-03.indd 12
11.09.2015 8:34:19
