water cooled resistors - Page 1
Forum section: electronics / beginners

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 16, 2021, 02:01:22 am
content: https://www.reo-usa.com/us_en/products/resistors/watercooled-resistors.htmlDo these resistors require a water pump - like in a hydroponics system?These resistors they say are kilowatt resistors, so then I imagine a water cooled transistor would be able to have a thru power of maybe a megawatt, not that you would ever need that much power unless you were making an electrostatic flying saucer, or some giant land collossus.

author: amyk
author_rank: Super Contributor
timestamp: October 16, 2021, 02:18:23 am
content: Those are basically water heaters. If you need to dissipate that much power continuously, then yes, you'll need a fully active cooling system and possibly a radiator as well.

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 16, 2021, 03:17:36 am
content: If you water cool the resistance wire, and then you air cool the water, (for evaporative swamp cooling.) that might be a good combination.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 16, 2021, 04:26:50 pm
content: You can use deionised water or pure glycol (water free) as a coolant and you will need a pump and a radiator and maybe a fan too.Tap water will ruin it.Still, what motor are you trying to stop?

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2021, 04:47:56 pm
content: The data sheet for the 60 kW version has explicit requirements for cooling on the last page. Note that the inlet temperature (into the resistor) is rated at 25oC and the outlet temperature at 45oC, with a flow rate of 10 liter/min for design operation. Also, it explicitly calls out good and bad liquids for circulation. Other operating conditions require re-calculation.The heat exchanger back to ambient air must therefore reduce the liquid temperature by 20 Coat that flow rate; heat exchangers have that data in their literature, showing how much air flow is required as a function of temperatures and liquid flow rate.The physical basis for all this includes the heat capacity of water (or whatever fluid). Water has 4184 Joule/(Kelvin liter) heat capacity, which is 4184 Watt/(Kelvin liter/sec) = 245 kW/(Kelvin liter/min). If you dump 60 kW of power into a water flow of 10 liter/min = 600 liter/sec, the temperature rise inside the resistor should be within the 20 K temperature rise specification. Other fluids have lower heat capacity and will have higher temperature rise for a given power and flow rate.

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 17, 2021, 12:06:33 am
content: Quote from: Terry Bites on October 16, 2021, 04:26:50 pmI'm not doing it for real, But what I was theorizing about was a high watt dc->ac converter, It's a cool idea, because once I hit ac, then I can use capacitors instead of resistors to resist current much more efficiently after the initial water cooled resistor stage.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 17, 2021, 10:42:51 am
content: A very expensive solution?Maybe we should have an idle curiousity section.....

author: m3vuv
author_rank: Super Contributor
timestamp: October 17, 2021, 12:02:50 pm
content: ive used 100 ohm 50 watt resistors many times to drop ebike cell banks down in voltage ,normaly put those in a tub of water otherwise they get red hot.