A thermodynamics problem ...

I know we have several people on this board who know thermodynamics. I've got a good "textbook" problem for you if you feel up to doing one.
I've done some research and managed to figure out the basic equations but what I'm trying to figure seems beyond me and I need help.

I'm considering installing a permanent, passive heatsink in the basement. Digging a trench outside is just not an option. Not only would it need to be ~3' deep (our frost-line here in KC) but the only two places I have to dig it would put the lines to the outside at least 50' away from the computers. With those obstacles I'd rather install one in the basement and insulate as necessary.

My basic idea is to run some type of rectangular copper tubing against the concrete basement wall using it as a heatsink. I could easily grout over and around the copper to help as a sink and then add insulation over that as thick as needed. The basement wall is 6" thick and behind the wall is at least 4' of dirt - mostly clay soil. Cave temps in Missouri run 13-14°C and the basement ambient is ~20°C.

Assume 2000W to cool and hopefully a full 2 GPM after restrictions. I've got an Iwaki MD30RZT pump for the main cooling loop, which will only include the copper in the basement and a 2(?) gallon res upstairs where the computers are. This is for a long-term SETI farm so I want to make sure I have enough extra to last awhile. What I need to know is how much surface area contact would I need against the wall, what spacing between the rectangular runners to avoid heat build-up between them, and how much insulation between the runners and the basement air?


I have another option I would consider but I'd like to see the numbers for this one first since it's the easiest to do, though not necessarily the cheapest.

Any help or useful comments would be appreciated ...

Elevendy!

Heat Loss through Building Elements due to Transmission
http://www.engineeringtoolbox.com/heat-loss-transmission-d_748.html

Perhaps a trip to a library (remember those?) is in order.

One big problem you're going to have is the masive heat dump of that pump.
From: http://forums.procooling.com/vbb/showthread.php?t=10825&highlight=pump+is+too+much
Eheim 1046, adds around 1.5W of heat to the loop
Eheim 1048, adds 3W of heat
Eheim 1250, adds 9W of heat
MCP600, adds 8W of heat
MCP650, adds 15W of heat
Iwaki MD-15R @ 60Hz, adds 22W of heat
Iwaki MD-20RZ @ 60Hz, adds 31W of heat
Iwaki MD-30RZ @ 50Hz, adds 50W of heat
There are many threads on many forums on passive cooling.

Basically, your trying to build a radiator that's attached to the comcrete.
You might be better off just running some fintube just off the floor. With proper baffeling (a big"shroud"?) you could use the "chimney" effect to suck the cooler air off the floor. Then use a low heat dump pump to send the water back upstairs to the farm's rez. Then use, again, a low heat dump pump to run through the blocks.

I've been to that site but it's still a good link. I guess I've been looking at the equations the wrong way. I'll think about it some more and add in a dose of "standard" physics and maybe come up with the answers I need. It's just been awhile since I've done much besides coordinate geometry (polar & rectangular) and basic trig.


The pump(s) for the blocks isn't a problem - those will be "normal" WC loops, which I can handle. I expect to bleed some of the MD-30 pump heat into the concrete in a different location so I wasn't worried about it. I'll look into that a little closer, though.

The reason I wanted to stick with that pump was the option of running a 1/2" line over to my den and using a little of the cooling for my main and project rigs (at least until the farm gets bigger). Otherwise I'll probably need another pump for that res - (2x15W) or (1x50W plus some secondary cooling) ...?

billb said:

Perhaps a trip to a library (remember those?) is in order.

Click to expand...

Library??? We don't need no stinking Library! ...