[time-nuts] OT question about liquid cooling

[J. Forster]

9 MVA is somewhat bigger than 5 kW.

I was assuming fairly short duration tests, perhaps a few hours, where
open-cycle water is practical.

If you are going to use a water loop, getting rid of the heat is certainly
an issue.

-John

==============

> 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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