AirHumidifiers 01 2015 V2

with two heating coils

DV Air handling unit

The evaporative process into the Mollier chart

The illustration on page 7 shows an example of the usual

design process for humidification into the Mollier chart

with 2 heating coils (pre- and post heating): Starting from

outside air at –3 °C and 40% RH to achieve air at 22 ºC

and 50% RH.

Pre-heating + humidification + post heating

See illustration with 1-2-3-4 on page 7.

This example has absolute humidity increase from

1.5 g/kg to 8 g/kg.

With two heating coils you can accept a lower starting

temperature before the humidification. The reason is that

if the air temperature is lower after the humidification

than desired, you have the possibility to heat up the air in

order to end up with the desired air conditions.

1. The air is heated up from -3 ºC and 40% RH through

the rotary heat exchanger and furthermore through the

pre-heating coil until the desired temperature is

reached.

Now the air has a RH of 4% and a temperature of 34 °C.

As the air passes through the humidifier, the saturated

pads of the humidifier pass on the moisture to the air.

This changes both the humidity of the air as well at the

temperature.

3. Ending with 17

°C

and 70% RH by following the

enthalpy lines in the Mollier chart.

4. After passing through the post heating coil the tempe-

rature rises to the end conditions of 22

°C

and 50% RH.

How to choose in SystemairCAD

If this is the chosen solution you may have to change the

CelPad thickness of the HU-CELL material. You will also

have the possibility to change the starting temperature to

reach your desired leaving air conditions. Here you will

have the possibility not only to change the humidifier

thickness but also the temperatures. This solution ensures

you more possibilities. However, it is also more demand-

ing for the control system. The selection can be made in

the SystemairCAD and calculated instantly to find the

leaving air conditions of the AHU.

| Air Humidifiers