[time-nuts] OT question about liquid cooling

Peter Gottlieb nerd at verizon.net
Thu Oct 4 00:25:51 UTC 2012


Perhaps, but unless you plan on just draining the water, you need a liquid to 
air heat exchanger (LAHE) to cool the water in your loop. Perhaps for a lab it's 
no big deal, but if you intend to operate where it can get cold (needing glycol) 
or where there is very limited water supply (remote locations) this matters.

I'm installing a 96.5% efficient 9 MVA inverter right now and it needs a minimum 
of 65 GPM through the LAHE of a 40% glycol solution (glycol moves less heat than 
water).  The heat exchanger is *substantial*, much larger than the items + cold 
plates it's keeping cool.


On 10/3/2012 8:14 PM, J. Forster wrote:
> It actually takes supprisingly little water flow to dissipate 5 kW.
>
> Very roughly 5 kW = 1250 cal/sec  (4.18 J/cal)
>
> so, for a 1 C degree = 1.25 liters/sec
>
> at 50C degrees = 25 mL / sec. = 1.5 L/min.
>
> -John
>
> ======================
>
>
>> BWIWY (back when I was young) we needed a dummy load for a supercomputer
>> (think Cray YMP size) that drew many many kw.
>>
>> Our test load was about 250' of 3/4" copper tubing coiled at about 12" dia
>> and 1" spacing. The load was varied by changing where the + and - leads
>> were bolted onto the coil with u bolts.
>>
>> The whole mess was cooled by running water through it. A hose barb on the
>> input connected up to the cold water supply and the output was run into a
>> drain. You had too little resistance dialed in when all thy came out the
>> output end was steam. :)
>>
>> Anyway such a test load could be replicated using 1/4" ice machine copper
>> tubing available at the hardware store, some hose clamps, and or hose
>> barbs.
>>
>> Bob
>>
>> On Oct 3, 2012, at 19:35, Tom Harris <celephicus at gmail.com> wrote:
>>
>>> My day job is large industrial power supplies. The test racks have large
>>> resistive loads with big fans exhausting to the outside. Cheap & simple.
>>> Safety is by several strings of temperature cutouts wired in series. We
>>> usually get work experience students in to wire them up.
>>>
>>> Tip: to make a funny valued power resistor, just get the next value up
>>> and
>>> wrap some nichrome wire around it to bring it down to the correct value.
>>>
>>> I met an engineer who made a battery charger for one of our submarines.
>>> This was tested by putting the load bank in a dumpmaster, and keeping it
>>> filled up with water using a firehose!
>>>
>>> On 4 October 2012 02:01, Javier Herrero <jherrero at hvsistemas.es> wrote:
>>>
>>>> Hello all,
>>>>
>>>> Please excuse me for the OT, but since this list is plenty of very
>>>> knowledgeable colleagues, I'm tempted to ask...
>>>>
>>>> I need to cool several resistive loads, in the order of 5kW, and I plan
>>>> to
>>>> use a cold plate and a liquid-to-liquid heat exchanger like the Lytron
>>>> LCS-20, but this unit is quite big, and an overkill (it has 20kW
>>>> capability).
>>>>
>>>> If someone could suggest me a smaller liquid-to-liquid heat exchanger,
>>>> and
>>>> preferably a rack mount unit (and share any experience), it would be
>>>> most
>>>> welcome.
>>>>
>>>> Since this has not too much to do with time and frequency, please
>>>> answer
>>>> off list.
>>>>
>>>> Thank you very much! Best regards,
>>>>
>>>> Javier
>>>>
>>>>
>>>>
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>>>
>>>
>>> --
>>>
>>> Tom Harris <celephicus at gmail.com>
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