Water spray atomization humidification

[santu398]

I have seen a Water spray Air Handling Unit used for cooling and humidification and cleaning of air. Cleaning is done when the air passes through the sprays.

Air handling unit consists of air filters, sprays,a pump to circulate the water to the spray header,a heat exchanger to cool the spray water and a blower. this blower sucks the ambient air through the filters and spray.

Controls present : Control valve near the heat exchanger to regulate the temperature of spray water.

I know that the humidification rate depends on
1) temperature of spray water,
2) temperature of ambient air,
3) Rh of the ambient air.

How the duct relative humidity related to spray water temperature?
If the temperature of spray water increases relative humidity increases or decreases?

Thank you

 

[EnergyProfessional]

There are 2 mechanisms to consider:
- warmer water can warm up the AHU air which decrases RH at given water-content
- warmer water will evaporate more, which increases water content.

I would think the latter process is prevailant and RH will increase. Like in your shower, when you use warmer water, it gets steamier.

 

[Compositepro]

If your spray is used for filtering, then you can assume that the air after the spray is saturated (100% RH at water spray temp). Then the absolute humidity stays constant, as reheating this air lowers RH.

 

[berkshire]

This type of installation used to be called an Air Washer, it used to be common in the painting industry for removal of overspray and fumes from spray booths. They also used to be used either for cooling, or for rehumidification in the HVAC industry, the next item in the line would be a moisture eliminator made of sloping plates in the duct to remove any moisture particles carried over from the washer. What is your application?
B.E.

You are judged not by what you know, but by what you can do.

 

[santu398]

Thanks for your reply

The application is we are required to maintain high Rh and low temperature in glass fiber forming.

The water header spray pressure is constant.

@HerrKaLeun

Any different beahviour during winter and summer season?

 

[EnergyProfessional]

i think summer winter differences depend on if that is outside air. Even when inside air, this largely depends on OA.

Your water is probably colder in winter. Your air may be drier in winter. the air leaving your device likely still will be at 100% RH, but at lower temp. So if you want a higehr temp and re-heat, RH will be lower. So you may want to reheat, and then humidify in winter.

but reheating before you have your washer may be bad since all the stuff you try to get out of the air, wills tick to the coil. this depends on what you have in the air. So you may wash, reheat and then wash again to humidify more.

I guess it depends on what exactly you want int he end (T and RH) to discharge.

 

[NegativeZero]

preheat return air> filters> coils> spray..

will help increase RH.