Drying time after wash down

[Kst8er]

Need help on 2 things:

1 - Best (cost & time) method to dry out a room after it has been thru a washdown process?
2 - How long until room is relatively dry & at design conditions?

Some additional background. Room (40Lx40Wx20H) will be washed down once everyday. Owner would like to have room turned over in 3 hours. The 3 hrs is from time process is shut down until room is back at design conditions (76F DB/60% RH). Room will be sprayed down at 100F. Initial design includes VAV RTU with gas heat, DX coil & terminal reheat coils. RTU to serve multiple rooms with similar processes.

My initial thought is to exhaust the room 100% at 10 ACH with elevated temps (90F/40% RH) for 1-2 hrs. Remaining time would be at 5 ACH @ 60-65F supply air to bring room down to 76F/60% RH.

TIA

 

[MintJulep]

How high is up?

How dry is "relatively dry"? Are you interested in only air humidity, or surfaces also? What are the surfaces?

 

[Kst8er]

Most surfaces are to be dry. The crew will go thru & wipe areas that have drops.

Equipment is stainless steel & floor is an epoxy finish. Elevated temps would be around 90F/35% RH.

 

[MintJulep]

Focus on lowering the absolute humidity of the air supply by removing water vapor rather than reducing relative humidity by heating.

 

[IRstuff]

Is there drainage for the standing water on the floor? That might allow you to use more directed airflow to push the drops into floor drains, if there are any. I'm thinking of the Dyson air blade:

http://airblade.dyson.com/hand-dryers/airblade-mk2/airblade-mk2/features.aspx

How much "equipment" is there? What's the total surface area of those equipment?

How did you determine your ACH? I'm swagging about 46kg of water on the walls and floor/ceiling, and swagging 10% effectivity in each ACH's ability to grab water, given the relatively low 90F temperature, which results in about 38kg of water removed in 2hr. Obviously, my effectivity is a total guess, and if it's higher then there may be sufficient margin.

Starting with 40%RH is not helping. And you only have 6 min to evaporate ~6.5kg of water per air change.


TTFN
faq731-376

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[Kst8er]

I don't have info on equipment. Yes, there is floor drains & I can only assume crew will squeegy the water on the floor to drains.

Ideally, we would like to use a desiccant wheel, but budget won't allow. So, looks like we need to dry the supply air as much as possible & exhaust the vapor out.

 

[chicopee]

High volume fans blowing hot air. Well another method is to freeze the entire room after it's washed and then depressurize it to more than half of the atmospheric pressures. That's what is done to documents and books when let's say a sprinkler system is activated in a library; those books and documents would be frozen in refrigerated trailers and the frozen items taken to an altitude chamber where depressurization would take place.

 

[Latexman]

The water would evaporate faster if it could be hotter. I believe if it's < 140 F there is no fear of scalding anyone if they accidently got wet. So, 120-130 F?

Have you considered sending in someone right after washdown with an industrial strength leaf blower to blow standing water off the areas that pool?

Good luck,
Latexman

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