Experience with water cooled resistors? - Page 1
Forum section: electronics / projects

author: compet17
author_rank: Regular Contributor
timestamp: August 31, 2016, 02:31:49 pm
content: I'm planning to update my UPS tester with some water cooled resistors instead of incadescent lamps... Does anyone have experience with ARCOL HSW600 series resistors?http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/2523016/These resistors can dissipate up to 600W with a water flow of 4L/min@20C and mounted on an aluminum plate.From the appearance it looks like the resistor is wound onto that copper tube and then inserted into the case. That would mean the outside case can get quite hot while the inside is cooled by water... Is the idea to water-cool the mounting plate too?Has anyone used those resistors ?Chris

author: CM800
author_rank: Frequent Contributor
timestamp: August 31, 2016, 03:14:03 pm
content: Quote from: compet17 on August 31, 2016, 02:31:49 pmFrom the Datasheet:QuoteSo by the looks of that, it is solely cooled by the water, a 3mm plate would not do much in the way of cooling.The datasheet also holds the answer to your other question:So there we go, The case temperature will get hot enough to boil water at 500W.You could probibly bump up the power they can take without getting too finger-burny by putting them onThisas well.

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 31, 2016, 05:15:03 pm
content: That's one strange looking resistor... I've not seen (much less used) one like that before. I mostly use plain old chassis mount wirewound resistors for high power loads; either air cooling them or bolting them to a chill plate.I have a bunch of 1kW 1 ohm wirewounds that I wire in series/parallel as needed:http://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/TE1000B1R0J/A105574-ND/2367679For even higher power with a bit of inductance I've made loads out of stainless steel wire rope; and for really obscene power levels with minimal inductance I've used stainless steel sheet folded in a zig-zag suspended over a bank of fans. Granted the tempco isn't exactly on par with the usual wirewound resistor, but when you need to dissipate 200kW+ of continuous power you don't have too many options.

author: LaserSteve
author_rank: Super Contributor
timestamp: August 31, 2016, 05:27:13 pm
content: I've used Hot Water Heater Elements as water cooled ballast resistors. They have a great deal of stray inductance. But the price is right.Steve

author: SeanB
author_rank: Super Contributor
timestamp: August 31, 2016, 06:58:48 pm
content: I used a bedframe, made from steel angle with steel strap supports, as a dummy load for a 28VDC genset. It handled 8kA with only a little heating, only getting to bright cherry red. The 115VAC side used a 200l drum, with 3 stainless steel rods on the lid, going into the drum, filled mostly full with salt water. That made a good boiler.

author: Twoflower
author_rank: Frequent Contributor
timestamp: August 31, 2016, 07:22:15 pm
content: Hmm, something does not add up. According to the data sheet (TCWilliamson posted the interesting part) the temperature supposed to rise linear. But at about 500W the water will boil. And the heat of vaporization of water is rather high. So I would assume that the temperature stays flat for some region. And 2l/min liquid water will generate much steam (3400l/min). Looking at this tiny tubes I assume that this will be an interesting show. Or they assume to use high pressure to prevent the water to boil. Which looks also rather unrealistic looking at these tiny PTFE tubes.What do I miss here?

author: dmills
author_rank: Super Contributor
timestamp: August 31, 2016, 08:00:07 pm
content: Case temperature rise, not coolant delta T.Also those are the hook up wires, the coolant flows in that big copper tube down the middle of the thing.regards, Dan.

author: CM800
author_rank: Frequent Contributor
timestamp: August 31, 2016, 09:07:30 pm
content: Quote from: MagicSmoker on August 31, 2016, 05:15:03 pmI was reading your post wide-eyed, cursing, then I scroll down to someone using a bloody bedframe....:Quote from: SeanB on August 31, 2016, 06:58:48 pmWHAT THE ACTUAL.... *cough* I... well.. that would be some sight to see...Quote from: Twoflower on August 31, 2016, 07:22:15 pmThat is the case temperature, not the internal temperature. The liquid would not be boiling / creating steam... that said It could be a fun project to make an instant vaporizor load. Full mains water in once side and a massive jet of steam out the other... Lets see how much power that would take:30 l/min (twice shower flow rate)=0.5l/sEnergy to turn water into steam: 2.6 MJ/kgso 1.3MJ per second... now to kWAh... 1300 kilowatts....Well there goes my weekend project.

author: calexanian
author_rank: Super Contributor
timestamp: September 01, 2016, 04:47:08 am
content: I think it would be easier and cheaper to use regular HS100 type resistors series and paralleled up on an aluminum sheet with a few PC fans on them. Water cooled is a super messy thing. I have had to use it in some systems and it never works out as you would like because you still have to get the heat out of the liquid and into the air and that requires a radiator and that is not very efficient.

author: Berni
author_rank: Super Contributor
timestamp: September 01, 2016, 05:16:56 am
content: There is also the poor mans watercooled ballast of putting a bunch of thin wire in to a bucket of water. Eventually the water in there will get hot but you do get a few minutes of operation before you have to change the water. Usually its enough to test a high power PSU.As people have said for continuous operation then water cooling might not be the best idea. All that heat that was put in to the water has to be dissipated and if you are looking at dissipating kW of power then you will be looking at car radiators and similar. But water cooling does have the benefit of being able to move that heat out of the room provided you put your radiator outside and run a hose trough the window. Dissipating a few kW in a room for an hour is going to make it get pretty toasty in there unless said room is a warehouse or a server room.If keeping the heat inside the room is not a problem then its far simpler to just buy a crap ton of cheep ceramic power resistors, create a frame to hold them in a grid and hang it all in front of a powerful fan. If you want to save cost you could also just get resistance wire and wind that back and forth on a insulating frame. By spreading the power out over a large surface it makes simply blowing air over the whole thing very effective.(Look at how much power they can dissipate in the tiny heating coils of a hair drier)

author: Fungus
author_rank: Super Contributor
timestamp: September 01, 2016, 07:25:14 am
content: Quote from: SeanB on August 31, 2016, 06:58:48 pmThat's the best thing I've read all week.

author: MosherIV
author_rank: Super Contributor
timestamp: September 01, 2016, 09:35:04 am
content: QuoteI have not used the water cooled resistors that you are talking about.I have worked with water cooled bearings/motors/industrial control.You are suppose to use a closed loop, pressure sealed system with cooling for the water, ie some kind of radiator or better still a water chiller unit.

author: tszaboo
author_rank: Super Contributor
timestamp: September 01, 2016, 09:55:57 am
content: I did some investigation for high power resistors. For dissipating 40KW. Right, so:Nothing beats air cooling for price/performance. You only want water cooling if youa) dont have space for the dissipating elementb) want to evacuate the heat from the room10W cement resistors are some 10 cents in high quantity, so you get 1KW for 10 money units (EUR/CHF/USD, whatever). And you need some fans, and that is it.Now water cooled resistors are very expensive, and usually you are better, if you can make standard resistors watercooled. My best concept was IMS PCB with a bunch of very cheap 1206 resistors mounted on a aluminium water block, both sides used, stacked.And there are some Chinese and Taiwanese manufacturers, who make very cheap directly watercooled resistors, which might end up cheaper, and I think might be better for one off projects.

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 01, 2016, 10:24:04 am
content: Quote from: TCWilliamson on August 31, 2016, 09:07:30 pmAye, the kludges I've had to come up with because the pointy-haired bosses were too cheap to spend money on proper testing equipment have been epic... and ugly; but they've worked.That said, if you get a quote for a 200kW load bank capable of 1kA+ you'll probably come to agree with me that folding up some stainless steel sheet isn't such a bad idea after all.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 02, 2016, 04:19:56 am
content: Any reason not to just use a few hair dryers?

author: technotronix
author_rank: Regular Contributor
timestamp: September 02, 2016, 05:15:08 am
content: I used it before few months for my small project, it provides direct cooling without heat sink and 1 single supply for several functions. Even Electric vehicle braking resistor is suitable for industrial applications.

author: Twoflower
author_rank: Frequent Contributor
timestamp: September 02, 2016, 05:54:13 pm
content: Quote from: dmills on August 31, 2016, 08:00:07 pmAh, yes of course! The water runs so fast through the resistor it won't start to boil. How could I miss this...

author: babysitter
author_rank: Frequent Contributor
timestamp: September 02, 2016, 10:45:00 pm
content: Regarding bed frame:One of the local hams back where I from was chief of the tram/bus company. He once described something resembling something similar as a "brake resistor". Normally the electric tram was timed so that at the main hill, one tram was going down, "recuperating" into the net to brake, and another one was climbing the same hill using the excess power. If something went wrong and there was way more power available than used, that device was attached to the power supply with a satisfying "clonk".

author: calexanian
author_rank: Super Contributor
timestamp: September 03, 2016, 04:34:23 am
content: I still would use standard power resistors and heat sinking. Water cooling is just a pain. You have to have pumps, and pumps do go bad let me tell you. I am always having cooling problems with diffusion pumps and from the sound of it you will be operating in the same flow/wattage range. Once you get the heat into the water you have to get rid of it and that requires either a big open pocket of water with ice or radiators, and now your radiator requires a fan. Why not just put a fan on a hear sink with a power resistor on it and call it a day?