Temp and Rh control year round in northeast

[joecontrol]

I have a 12 X 15 X 12 room that i am trying to control temp to +,- .05°c and +,-5% rh. I have the temp problem undercontrol but the problem i have is reducing the rh in the room and i feel the problem is i cannot get the chilling cold enought to remove enough of the water i am thinking of going with a split system instead of the chilled water system.The problem i have is when winter comes around the head pressure is going to be to high. Is there a system i could chill the compressor coil with water to remove the problem of trying to run in below 20°f.I now use electric heat with constant cooling and the temp controls well. I figure if i could get the coils to remove more of the Rh I could actually get control of the Rh. This is needed to contol the temp and Rh in a dimensional lab. Any suggestions or help would be greatly appericated,Joe

 

[IRstuff]

In most industrial air handling systems, there is a discrete de-humidifier that is used to remove moisture from the air. A smaller version is probably what you need:

http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611764027

TTFN

 

[ChasBean1]

Joe, at what temperature and humidity is the room to be maintained? You gave the variation band but not the actual control values. This bit of info would help.

Thanks, -CB

 

[joecontrol]

It is going to be 68°F and 25 - 30% Rh. Another problem is adding Rh in the winter without effecting the room temp. Uniformity in the room is important so i cannot just put a humidifier in the room. I have heard about steam sprays and other ideas, that are not supposed to add to the room temp.

 

[ChasBean1]

That's a very dry indoor environment for 68°F. If you dehumdify by cooling, the magic number (neglecting internal humidity gain) is 31-35°F, a value to which you would have to cool the incoming air during spring, summer, and fall (all conditions above outside air temperature of 35°F), which I would guess, without looking up ASHRAE bin values represents more than 75% of any given year.

This is not reasonably achievable with conventional chilled water or DX systems. You would need to seek out alternative dehumdification systems - e.g., desiccant dehumidifiers. I don't think Grainger would stock anything for your application because a normal dehumidifier uses a typical refrigeration circuit, which might get a room dewpoint as low as maybe 45°F, not 31-35°F to suit your need.

Search for desiccant (one S, two C's - if the seller can't spell it, it's probably not worth buying from them) and see what you turn up. Regards, -CB

 

[joecontrol]

thanks for your info and the tips. JD

 

[rodger1]

Here, this will dry you out.

http://www.cargocaire.com/