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Peltier water cooling - advice

Discussion in 'Extreme and Water Cooling' started by FoderMe, Jan 29, 2009.

  1. FoderMe

    FoderMe Member

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    Continuing on from the end of this thread.

    First: I'm not planning on using this in my pc. I have played with peltiers many moons ago and discovered very early on that power demands & requirements + condensation make the whole thing too much hassle. As like rowan194, I'm planning to replace the generic aircooling in my peltier fridge, with a water cooling system. However my experience with water cooling is nil.

    Block = cpu/gpu/nb? Reservoir required? Rad size? For these questions I'm not sure where to start, as I obviously neither want supreme-overkill, nor something equal/inferior to aircooling.

    Peltier runs at 55W when on 240v source and 45W on 12v source.. not exactly sure why it gets lowered on the 12v source. Perhaps minimising drain on car battery (as 12v source is cigarette adapter).
    I'm assuming the internal ac-dc converter won't be enough to power a pump? The fan it runs with now is a rather stock 12v .23A noisy 120mm bastard if that helps (there's no other visible info I could find to indicate it's power output).
     
  2. rowan194

    rowan194 Member

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    55W @240VAC versus 45W @12VDC is probably due to the power supply not being 100% efficient...

    If the PSU is internal then see if there's any sort of spec label or at least a model number (perhaps printed on the PCB). Take care if it's an "open" unit as there could still be a lethal or at least painful charge left in the high voltage capacitors. If it's external then there will almost certainly be a label.

    You're looking for 2 things...

    1) The output voltage. Is it 12V regulated or a higher voltage?
    2) The maximum amps it can supply. This will indicate how many extras you can add.

    Just so I'm understanding this right, you want to retain its functionality as a fridge, just improve the heat shedding ability of the hot site of the peltier, by using WC? You could probably see an improvement just by using a better heatsink, like an aftermarket CPU cooler. Either way it sounds like you'll end up with things poking out of the case. :)

    FYI, I've ordered a Thermaltake Aqua Brazing W2 VGA Block to mate with the peltier as it has a more square face than a CPU block (and is sufficient size - the northbridge block would be at least a few mm short in coverage), it's all copper, and it's cheap. I have no idea how well it will work. :)
     
  3. rowan194

    rowan194 Member

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    Another suggestion, posting it here since I'll need to do it myself as well... fit a normally closed thermostat switch (eg Jaycar ST3821, 60 degrees normally closed) inline with the peltier so that it cuts out if the hot side goes above a certain temp. This will save the peltier from burning up if your water stops moving for some reason. Or is it only when both sides are "non sinked" that it self destructs? Anyway, for $5 extra it's worth putting it in...
     
  4. ener

    ener Member

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    sounds like fun :thumbup:

    Rad - 120mm (fit where your fan currently is) although you will probably still need air flow so a nice quiet lowspeed 120 sitting on the outside with a grill might work (not sure how much space is inside some good pictures would help)

    Block - depending on how its connected you could use any type, an old 2nd hand block would be nice, should be cheap.

    pump - there are water cooling options from stores D-Tek dB-1 12V DC would work well, alternatively, a 12v pond pump, if you can find one.

    res - use a closed loop, maybe with a small T-line with a cap in it so you can refill/bleed this every now and then

    but we need pictures of the area's we are working with.

    ps. i also like rowans idea of just an upgrading sink, a mid cfm fan, thats QUITE, and maybe new thermal paste (AS ceramic or something)
     
  5. rowan194

    rowan194 Member

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    If my experiment with WC doesn't work - I have to run at least 4m of tubing each way which may be impractical - I'll try a Zalman 9500 CPU cooler instead. I no longer use it since the water block does a better job of cooling a CPU. :D Imagine this thing sticking out the back of a fridge?

    [​IMG]

    PS: No attach facility on OCAU? Some of the older threads have zero pics because they're all hosted on dead sites... wouldn't happen if we could attach images to msgs...
     
  6. rowan194

    rowan194 Member

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    Bah, PCCG accepted an order for parts that show as "IN STOCK" and charged my card but they don't actually have stock on hand. Guess I won't be playing with the fridge this weekend. :( They did this "it's ALMOST in stock" trick last order too...
     
  7. ford ftw

    ford ftw Member

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  8. rowan194

    rowan194 Member

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    Some random thoughts on potential cooling "power" if you mate a bong cooler with a peltier fridge...

    A heatsink can't cool to less than ambient, right? My current fridge + heatsink setup seems to maintain a temperature difference (inside of fridge vs. room temp) of about 16C. It could probably do better on air with a better heatsink and fan, but I'll use that as a "best expected" figure for now.

    Based on limited test results so far my outdoor bong cooler can cool its water reservoir to between 7-11C below ambient. (I don't know if an indoor one would work so well since there may be issues with saturation, unless the chimney output is vented or the room air dehumidified...?)

    Now with the hot side of the peltier cooled by water: if the (outdoor) ambient temp is 30C then the water loop temp would be 19-23C, and based on a -16C drop the interior of the fridge would be 3-7C. If the ambient temp is 15C then the peltier will probably start icing up.

    The beauty of using the outdoor bong is that on milder days the water loop temp can be quite a bit below the INDOOR ambient temp... it's unlikely that a human would routinely sit in a room that's 10 or 12 degrees, but the water loop could be that cold or coler. Might need a thermostat to cycle the peltier when the weather gets a bit cooler. :)

    Going further and thinking of the cooling loop (including bong cooler) as a good sink of heat rather than just sitting at a specific temp to subtract the difference from, a two peltier sandwich might be able to consistently get you down to normal (4C ish) fridge temps. The question is then how much it's costing you to run (or even build) versus a compressor based bar fridge. ;)
     
  9. rowan194

    rowan194 Member

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    ^ I should add the above back of the envelope calcs are based on results from a 51W peltier from Jaycar. I presume chilling ability would be better with a higher power peltier, so long as you can sink the extra heat.
     
  10. cvidler

    cvidler Member

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    12V * 0.23A = 2.76W
     
  11. OP
    OP
    FoderMe

    FoderMe Member

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    Yeah, there's two angles I'm looking at it: improving the cooling capacity + lowering noise levels. The stock fan isn't THAT loud, but I wouldn't want to increase it by even a single dB.

    As soon as it isn't god-awful hot, I'll get motivated to disassemble it again and take some photos. Once you see what I'm working worth, I'm sure everyone will agree that my options are limited as far as internal space goes.

    Have you got some photos of your fridge? I'm still trying to figure out how exactly I'd firmly attach a block or new heatsink. There's nothing standard about what's in mine now and with the heat that comes of the peltier, I need to be confident that whatever I put in there doesn't lose contact.
     
  12. rowan194

    rowan194 Member

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    Update on the W2 block... it's 40mm in height, which is what I based my purchase decision on, but unfortunately that's for the rear level; by the time you get to the "chip face" at the front the size is only 31x31mm. This portion is raised by about half a mm so it may be possible to sand it down, in which case the coverage would end up being about 39x35mm. The TEC I have is 40x40mm so I guess I'll need an extra layer of proper sized copper as a heat spreader. (I have NO idea where to buy a flat piece of copper?...)

    OTOH, perhaps the ceramic coating of the TEC is sufficient to spread heat, with only a reduction in overall transfer efficiency because a small part on each side isn't covered? Or is the TEC likely to burn out?

    I have 2 of them (one spare) and another on the way so I guess there's only one way to find out. :)
     
  13. rowan194

    rowan194 Member

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    The fridge has a solid aluminium (?) block that the peltier sits on, the 2 screw holes match up almost perfectly with the W2 mounting grooves. (A couple of nudges at the W2 grooves with some needle nosed pliers fixed that. :D ) I had to ditch one of the spring washers (screw isn't long enough) but apart from that it all seems to fit together nicely. Unfortunately unless I find a matching screw that's longer I won't be able to sandwich two TECs together.

    There's plenty of room in the fridge since this setup (just a water block, basically) is fairly low profile when compared to the aluminium heatsink and fan that used to be mated to the TEC. Obviously in my case there will be vinyl tubing exiting the side so it won't look completely "stock" ;)

    After all that waiting for PCCG - I ordered "in stock" product 6 days ago but it wasn't shipped until yesterday - I just realised I don't have enough 6mm tubing to run out to the bong cooler. Argghhh!! Time for a run to Bunnings...

    This fridge also has a heating function which reverses the polarity of the TEC. Once everything is hooked up I'm curious to see whether it's able to pull down the temp of the circulating water. If it does anything noticeable then I might look at sandwiching a TEC between a W2 block (cold side) and Zalman CPU cooler (hot side) to use for supplementary pre-cooling of the water.
     
  14. rowan194

    rowan194 Member

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    Finally got the tubing and ran a second exit line out to the bong cooler... (20mm tube in through the window, then split to 4 x 6mm tubes, with each device having its own return to the bong)

    So far it seems to be going reasonably well - no burning smell (the first thing I checked!), the plate inside the fridge feels very cold to the touch, I can feel a little heat around the rear of the TEC but the water block isn't even warm. Temp isn't changing very rapidly but that may be because of the fridge design itself. So far it's fallen from the ambient of about 32C to 23C, but it's only been 5-10 mins. On the stock air heatsink it would have settled around 16C.
     
  15. V8R

    V8R Member

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    hmm, interesting, might look at doing the same to my old mans waeco pelt fridge.. used it for one dry (nt) season in the truck then bought a compressor fridge :)
     
  16. zaz96

    zaz96 (Banned or Deleted)

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    Id like to see someone try putting peltiers on the sides of resovoirs. Should work somewhat like a rad.
     
  17. rowan194

    rowan194 Member

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    One thing I overlooked, I shouldn't be comparing the fridge temp to inside ambient since the TEC is now watercooled... the temp of the water (and therefore the block) should be outside ambient minus a few degrees.

    I ended up reseating the TEC. I can see ice forming from condensation on the aluminium block, and also on the plate inside the fridge. The water block doesn't feel warm, but it also doesn't feel cool as copper normally would. I guess that means it's working fairly well.

    Fridge temp is still falling, I guess it's just taking a while. I'm not sure how much of that is due to the temperature of the bong water dropping as the evening gets cooler...

    After all this work on the fridge my wife is complaining I'll never need to leave the office! ;)
     
  18. rowan194

    rowan194 Member

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    That's something I'm interested in trying. I have a Zalman CPS 9500 cooler which says it's all copper, so I could have a go at dipping it into my reservoir - after removing the fan ;) - and mating the face with a TEC. I'm not sure how heatpipes would work when cooling (I presume they wouldn't?) so I guess it's just the copper edge of the pipe that's "transmitting" cool. Would probably be better if I could find a generic copper heatsink.

    Another option would be to use it on the hot side of the peltier and use a waterblock on the cold side to chill the water that's passing through.
     
  19. rowan194

    rowan194 Member

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    Here's some pics of the setup

    [​IMG]

    The aluminium block between the TEC and the plate inside the fridge is seriously iced up... this is going to get messy when it's turned off...

    (Side note - should I be using thermal grease on the cold side of the TEC, or will it just freeze?)

    [​IMG]

    This is the "cold" plate inside the fridge, it's iced up as well as the surrounding area of the back wall.

    [​IMG]

    7.2C at the rear. I had previously had the thermometer sitting in the door which shows a couple of degrees higher. The fridge is still not achieving a delta of more than about 16-18C, which is really no better than the air cooling setup. I bet a small fan to circulate and equalize the internal air would improve this heaps (modern fridges do this)

    Now for a real world test: I've stuck a room temp drink inside the fridge. So far the temp has wandered up to 12.9C, and it's still climbing. Let's see if it can get back down to the 7's. :D
     
  20. sympozium

    sympozium Member

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    i have to say that looks like fun
     

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