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 <[email protected]> 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 <[email protected]> >>>> 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 >>>>> >>>>> >>>>> >>>>> ______________________________**_________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/** >>>>> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> >>>>> and follow the instructions there. >>>> >>>> >>>> -- >>>> >>>> Tom Harris <[email protected]> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> ----- >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1427 / Virus Database: 2441/5308 - Release Date: 10/03/12 >> >> > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
