Jorg, Thanks for the the additional details. You addressed all of my concerns. I wish the original article had these details. Unfortunately, I think the original article simplified things a bit to much, and was a bit optimistic about running one of these in a dessert.
-- Prentice On 03/01/2013 05:46 PM, Jörg Saßmannshausen wrote: > Hi all, > > answers are inserted. > > On Donnerstag 28 Februar 2013 Prentice Bisbal wrote: >> On 02/28/2013 05:00 AM, Hearns, John wrote: >>> I think this has been discussed here before, but it is a pretty >>> innovative product: >>> >>> http://www.theregister.co.uk/2013/02/28/wet_servers_cut_cooling_costs_res >>> earch_leeds_university/ >> I really should just save my rants about immersive liquid cooling on a >> web page somewhere so I can just provide a link every time this topic >> comes up. I'd just provide links to my previous rants here in the >> archives, but I'm feeling lazy this morning. >> >> Seriously, this article is both interesting and confusing, and there are >> some stupid/ridiculous statements in the article. >> >> 1. The interesting: >> >> How easy is it to clean this liquid up? Is it oily like mineral oil? If >> it's not slippery and it's easy to clean up, that addresses my biggest >> problem with immersive cooling. The Novec didn't look as thick or >> slippery as mineral oil in the video, but it's hard to tell something >> like that from a web-quality video. > It evaporates easily and it is used as a cleaning agent. > You can dip your mobile into it and it is still working (the mobile, that is). > When you fish it out again you got a clean mobile. You might be surprised how > much grease there is on a mobile ;-) > So it is not like oil, the visosity is lower. > >> 2. The confusing: >> >> Is the Icetope system an immersive cooling system? From the video, it >> looked more like a "direct contact" cooling system where the liquid is >> run through pipes into "direct" contact with the processors, but the >> demo made me think they are talking about immersive cooling. Even for >> direct-contact cooling (if that is the right term) having a >> non-conductive liquid is a better option than water if a leak occurs. > Yes. Motherboard is imersed into the Novac in a sealed Aluminium container > which got a chilled plate on one side. The chilled plate is cooled with water. > So for that you need a pump. The excess heat is removed by an outer loop water > cycle. Here you can use whatever you like, even grey water (with a filter). We > want to use 3 radiators so here we need a heat-pump, the same you get from > your local DIY store for your domestic central heating. Not much noise here. > >> 3. The stupid/ridiculous: >>> Dunking servers in new magic liquid 3M Novec reduces the cooling >>> system's energy use by 80 - 97 per cent, compared to cooling systems >>> that use air. Air cooling is inefficient because it is a poor >>> conductor, produces diffuse general heat and requires energy-chomping >>> high powered fans, said the boffins. >>> 3M Novec is also a thousand times better at conducting heat than >>> water, and one low-powered fan in a chamber of 3M Novec is adequate toJorg, >>> >>> >>> >>> Thanks for the the additional details. You addressed all of my concerns. >>> i wish the original article had these details. Unfortunately, I think >>> the original article simplified things a bit to much, and was a bit >>> optimistic about running on of these in a dessert! >>> chill a server array. >> At some point or system size, you're still going to need pumps to >> circulate the liquid. While natural convection is fine for gases, it's >> usually inadequate for liquids due to their higher viscosity. And if you >> need to transport that liquid horizontally away from the heat source to >> the heat sinks, you're definitely going to need pumps. Liquids might >> have thermal capacities and thermal conductivities that are about 1000x >> that of air, but I think the viscosity of a liquid has got to be at >> least 1000x that of a gas. In this case, the pumps are still probably >> using less electricity than all those fans, but I think these quotes >> distort some of the facts. > See above. The novac will not be pumped around, convection is all you need. > Remember, the nodes are standing upright and are not flat as a normal > installation would suggest. So the transport is vertically and here you got a > 'chimney effect' as well. > So, as mentioned above, you need two sets of pumps for the inner and outer > look of the water (sic!) cooling system. > >>> The fact that this system is completely enclosed raises a host of >>> possibilities. It does not interact with its environment in the way an >>> air-cooled server does, so you could put it in an extreme environment >>> like the desert >> Ummm, no. that heat still has to go somewhere. And that "somewhere" has >> to be at a temperature low enough for there to be a temperature >> difference large enough create the "driving force" necessary for useful >> heat transfer. That's probably not going to happen in the desert. > The outer water cycle has a max. temperature of 50 °C and the return is max 45 > °C. Given it is cold in a dessert at night you might be able to just about do > that. However, I would not really want to have my cluster in the dessert ;-) > >>> It is also completely silent. You could have it on a submarine or in a >>> classroom. >> See my earlier comment about the need for a pump. I guarantee that even >> the smallest production systems will need some kind of circulation pump. >> you can probably locate that pump further away from the system being >> cooled, but it will be producing some level of noise, somewhere. > Think about how noisy a domestic heat pump for your central heating is and you > get an idea how loud the cluster is. I stood next to one and you could barely > hear it. So no big pumps. > >> Overall, if this 3M Novec overcomes the drawbacks of mineral oil, this >> is great, but I feel that this article and this research is more like >> press release for 3M Novec. > Well, 3M is supporting the project. However, to be honest, of all the systems > I have seen so far that seems to be the most intelligent one, specially as you > can harvest the heat and do something with it. > The radiators we are using are too small to heat up the building or the > staircase in the winter, granted. However, it is more to demonstrate the > principle and I only get one rack. I will post my experiences when and if I > get the system installed. At least so far nobody here mentioned a serious > problem which is reassuring. > >> Rant over. You may now return to your regularly scheduled work day. > Not a rant, just some comments :-) > > All the best from a dark London > > Jörg > u _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
