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DIY Passive Chilled Beam, Condensing

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!

Comments

  • mattmia2
    mattmia2 Member Posts: 5,737
    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.
    Jim_Sobie
  • Jamie Hall
    Jamie Hall Member Posts: 19,147
    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.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Jim_Sobie
  • pecmsg
    pecmsg Member Posts: 2,954
    edited June 12
    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. 
    Jim_Sobie
  • Tim_D
    Tim_D Member Posts: 72
    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.
    Jim_Sobie