Replies

1. 
   DaveRicheson | Mar 16, 2011 06:01am | #1

   Instead of trying to cool a mass of concrete you might look at using a chilled water coil. Essentially you would use a cooling coil (like you see for an a/c unit) and a fan to push air across it. Chilled water cooling is how many commercial building are cooled, and your 42 degree water is in the range that most of those system use. For your purpose a small pump, cw coil, and fan with a termostatic control would work very well.

   Pump the 42 degree water through the coil and dicharge it back into the stream. With a t-stat controlled fan that would cycle on/off as needed and a super insulated structure you might achieve an inside temp of 50 degrees. Even oversizing the coil wouldn't hurt in your case because it would be a flow through system with no compressor to cause to short cycle.

   Mybe Tim will come along and see your post. He designs systems and I'm sure has some ideas you could use.

1. 
   DanH | Mar 16, 2011 07:23am | #2

   And keep in mind there will be condensation.  If you chill the slab to 42 degrees without some other dehumidification, the floor will be constantly wet.

1. 
   lambranch | Mar 16, 2011 01:43pm | #6

   Thanks!

   Thank you all for the great input.  I had actually considered a coil, but was thinking that it would have to be bringing in outside air, and I figured that would be inefficient.  But I like the idea of a coil suspended in the overhead with a fan, just like the big walk-in coolers I’ve been around.  We actually have been offered a pre-fab insulated structure (8 ft x 8ft) that comes with a refrigeration compressor.  We didn’t like the idea of a loud compressor running all the time (not to mention all the energy it consumes), which is why we are trying to use our most plentiful free resource: gravity fed cold water.  50 deg F is not bad (it’s about what our basement is, which is where we store our veggies now), but it’s not good enough for hanging meat.  We might go ahead with the compressor unit to supplement the chilled water system when necessary.   In the winter when the temps are hovering around zero or lower, the water by itself should be enough to keep it above freezing.  I’m not too concerned about condensation- a wet floor doesn’t bother me, and veggies dry out and shrivel up if the air is too dry anyway.  Can’t wait to get started on this project! 

2. 
   DanH | Mar 16, 2011 07:26am | #3

   Even with an overhead coil there would be no requirement for a pump (though it might be desired, to maintain a given flow rate or allow thermostatic control).  The overhead plumbing would be a "siphon" and would not affect the effective pressure of the water, so long as the discharge is at ground level or below.

2. 
   [email protected] | Mar 16, 2011 10:26am | #4

   Automotive radiator

   I'd use an automotive radiator as a cold water heat exchanger.  They are readily available water to air heat exchangers, that can be bought fairly inexpensively from auto salvage yards. 

   If you use a fan and just let it run it should keep the temperature fairly constant with out any complications.  You might save a little energy with a thermostat on the fan, but your temperature will always be a little above ideal for cold storage of food. 

   A refrigerator is normally run at about 35 to 38-degrees, so you can't over cool anything even if you ran a bunch of radiators in parallel.  And, if you ran it through the winter, you would help keep the internal temperature above freezing. 

1. 
   DaveRicheson | Mar 16, 2011 12:27pm | #5

   j&f

   Good idea.

   I work with HVAC quite a bit, and particularlly chilled water systems. I guess I tend to think in that groove instead of "out of the box", like automotive radiators.