DIY Passive Chilled Beam, Condensing

Jim_Sobie

Good evening! I have a question for you, the wise folk of radiant. I have delved into the HVAC sites, forums, PDFs, white papers, and of course done a deep search of The Wall here.

I realize that in actual usage, chilled beams must run above dewpoint, lest they condense and drip water onto folks, and furthermore a laminar flow of air that cold would be most likely uncomfortable at best in, say, an office environment. And that dehumidification must be handled by a DOAS (albeit significantly sized-down to only handle latent heat). Same would apply to radiant ceiling panels like Messana, et al.

But what I would like to know is (and this is strictly theoretical; it's just been bugging me): Supposing I had constructed a chiller capable of delivering, eh, let's say 40-45degF supply water and I wished to pipe it through a series of finned baseboard tubing strung up in my garage. To handle the inevitable condensate, I would rig up a set of drip trays that slope a wee bit and drain harmlessly outside. Sorta, kinda, like the gravity coils I've seen mentioned here for flower shops I think. Putting aside the fact that they would condense like mad and spill plumes of chilly air downwards, I just cannot shake the mental image of coming in from mowing the lawn on a 95deg day and standing under that whilst drinking an icy wobble-pop.

Now. Please do (and I do mean, sincerely) pick this apart and tell me how it wouldn't work. Efficiency, sizing, slow to respond, anything. I actually don't work in HVAC at all (automotive/heavy truck industry) but ever since reading Holohan's books 20 years ago I've been absolutely fascinated by all things heating and cooling, and the weirder the better. Thanks for your time; you all have provided me with so much thinking material over the years!

mattmia2

Most chilled beam systems supply dehumidified air to the beams so they have removed most of the latent heat and have some amount of forced airflow. With a chilled beam the swt is at best around 35f and the air is around 75f so best case delta t is about 40 degrees f. With heating with fin tube or a convector the swt is 150f+ and the air temp is around 70f so delta t is around 70+ degrees f. You would need forced air flow to get an amount of airflow that you would feel. You also would have difficulty getting enough capacity with convection alone especially if you were also trying to remove latent heat with convection alone.

Jamie Hall

Your idea will work -- just not as much cooling as you might want, unless you circulate the air. As @mattmia2 said, the real limitation is the difference in temperature between the cool water and the air. Curiously, the beam will remove as many BTUh as a hot water finned pipe will for the same delta T -- it doesn't care what the actual temperatures are, not which way the heat is flowing -- for convection, but there will be very little radiant heat flow. I like the idea of the drip trays.

pecmsg

Old Meat Aging walk in box’s used gravity coils. Basically fin tub with 2 or 3 fins per inch. These would cover the entire ceiling. So yes it will work but you will need maybe 4 or 5 X the heating liner feet. 

Tim_D

There are several types of valance units that work exactly this way. One consideration with the fin tube is that your convection will likely be lower than in a heating application therefore the performance will be lower.

newamericaUSA

How are there valance systems wired. 

We have a few buildings some have backup elect base bound some Dont some have Honeywell zone valves some have Edward s zone valve. 

What is the wither way to wire them. Do I need a Klix  on or do I need two klix on. Or none ?

ineffable

Did you ever set this up? If so, how was the performance?

I'd like to do the same thing in my house since mechanical air circulation bothers me. Basically heat pump + insulated PEX + commercial valance units (if I can find them -- seemingly hard) or regular fin-tube with plastic covers, cradles, and homemade drip pans. However, I'm not sure how to size the system. (I've have the cooling load from a manual J but that may assume forced air circulation.)

EBEBRATT-Ed

@Jim_Sobie

If you had a chiller I would get a small air handler. Majic Air (and there are others) that make small AHUs with chilled water coils. Or a fan coil unit.