Evaporative Cooling Unit

[Calen Beaune]

I searched the existing topics and found the following question/answer dealing with evaporative cooling.

http://ventsim.invisionzone.com/topic/465-setting-up-a-heat-simulation/?tab=comments#comment-877

Are there any other ways to simulate evaporative cooling (swamp coolers/ atomizers), than by changing the airway wetness fraction? And is there any way to simulate an indirect evaporative cooling system? I saw the update on the new New Ventsim Cooling Feature (5.4.3.0)  but couldn't find a reference on how to access it.

[Craig Stewart]

Hi

Evaporative cooling is easily simulated by just directly adding moisture to the airflow in the airway.  You can do this in the EDIT BOX > HEAT TAB > Moisture which is added in the form of grams/second (for example 100g/second) evaporates 0.1l per second of water into the air.  If you spray too much water for the available airflow to evaporate, the excess will be ignored.

Once the water is evaporated, the ambient (dry bulb) air temperature will reduce in response.  Wet bulb temperatures will remain the same.  The scientific methodology behind this is essentially that sensible heat is being transferred latent heat, resulting in a decrease of sensible heat and an equivalent increase in latent heat.

Indirect evaporative cooling is more complex.  The moisture evaporated is kept separate from the main airflow via a close plate heat exchanger.  In this case, while sensible heat is still being offset by latent heat, the latent heat is no longer being added to the air.  If the heat exchanger was 100% efficient, you could simulate this by observing the sensible and latent heat exchange in the evaporate cooling circuit, and then entering the equivalent =ve sensible heat in the main airstream circuit.