You make some very interesting points!
Allright, down to basics. Basics are good. I have a 18 x 10.5 x 9” compartment (1701"Â³) made of 1mm thick metal. Cooling units will have to be placed on a single 18 x 10.5" side. I have a real big heatsink lying around of the same size that will easilly draw heat away. I want to cool that compartment to around 4Â°C within a reasonable amount of time, and I want to spend as little money on TECs & PSUs as possible to do it, (don't we all). A thermostat will regulate the temperature by turning the PSU on & off when needed.
I already have 10x TEC1-12706 units from a few years ago that I'm not using for anything, but if it's better to get something larger then so be it.
What TECs & PSUs would you suggest for this purpose?
What goes in the box ? Does it generate heat or once it's cool will it stay cold ?
Can you install a fan in the box ?
My suggestions based on what I know so far....
1) It might be OK to setup your PC PSU for a more permanent use for this project, in view of the low cost required. Having said that though, TEC setups often finally cost a fair bit more than you initially envisaged.
It will all depend on your final power requirements.
2) Your metal box is relatively small and if you could seal it from outside air and install a fan for circulation TEC's can can quite efficiently cool air directly. So long as there is nothing reheating the air, air is much easier to chill than water but conversly the air will heat up much easier too.
3) I don't see any reason why you could not use the 12706s that you have. Most commercial TEC cooled minifridges use small TECs like this usually only one but as you have several at your disposal you can make a more efficient chiller. I am assuming here that what you place in the box does not generate heat.
4) Basically you want a large heatsink with the coldsides of the TECs mounted on the flat side. The fin side of the heatsink should be closed off except for apertures for the fan. Leave the ends open. You mount the fans to blow into the heatsink and exhaust out the ends. Obviously you then have another fan/ heatsink combo on the hotside. With the low wattages involved standard PC fans will do but since you aiming the fans into the heatsink ones with a higher static pressure will work better.
5) Ideally you would have a cutout for the TECs so the hotside is outside the box and the coldside is inside.
6) I assume you plan to insulate the outside.
7) With the thermostat if you can...it would be better to use it to shut down the TECs rather than the PSU. If your using the PC one so long as you have solder the 10ohm 10w resister on it will be still be under load when the TECs shut down. Depending on your thermostat you may need a relay to do this.
On the point of using PC PSUs attached are some pretty awful shots of my first PSU I "devised" for TECs using a PC PSU....
I went well overboard but it was a fun project...if I had to buy all parts new I would not of bothered...the case I got really cheap and most of the other bits were laying around. I have done absolutely nothing to the original case of the PSU (which sits inside to the left as you look at the front.) all I have done is re-appropriated the wires.
Unfortunately the pillars are a little dense and getting to the inner ones is awkward. On the back I mounted the 10w resister over the exhaust fan it can get hot with continued use The molex is so that I can attach a board with the fan headers on so I can run the fans to cool the TECs.
It made a respectable looking, useful PSU which I used a lot initially. Instructions for doing this are 10 a penny on the internet but some are far better than others.
I havent used it for ages as I normally mess about undervolting and I need better control of the voltage, the unit I normally use is fully variable between 4 and 16v.
unfortunately they keep going up in price the original one I got for Â£50.
Edited by zipdogso - 3/7/10 at 7:09pm