#homecmos IRC log for Tuesday, 2012-07-31

berndjheh, "shrink to the 12.5µ node" has surely not been heard in 30 years20:35
berndjazonenberg, what will you do about contacts? won't you need to futz with tungsten and the like?20:37
berndjSync: how's your grasp on thermodynamics?20:37
azonenbergberndj: unknown at this point20:37
azonenbergMy first goal is to get litho working reliably at the 12.5um node20:37
azonenbergonce i can do patterning, i'll take it from there20:38
Syncberndj: first rule of thermodynamics, you do not talk about thermodynamics20:38
berndjthat must be the -1th law :)20:38
Syncwhat's the problem?20:39
berndjjoule expansion. besides eliminating moving parts, what's the advantage?20:39
berndjisn't adiabatic expansion hugely more efficient?20:39
berndjyou're the one working on DIY cryo, aren't you?20:40
Syncyes adibatic expansion is more efficient but it has drawbacks20:41
berndjfor a small liquefier it's no issue of course, you go for the fewest-moving-parts method. but if you're doing tonnes a day i'd expect energy costs to start mattering20:42
SyncI'm currently waiting for some gasses to arrive then I can investigate some autocascading systems20:42
Syncyes but then your are doing it differently20:42
Syncbah -r20:42
berndjactually i though J-T expansion was how the commercial air separation plants worked. i may be mistaken20:43
Syncthat depends20:43
Syncthere are some that use adibatic expansion20:43
Syncbut yes the majority ist J-T20:43
berndjmaybe the plant predates the green revolution20:44
SyncI guess the idea is to have highly optimized compressors for your load20:44
Syncalso most processes are low pressure now20:45
berndjah. i can see adiabatic expansion being a lot more sensitive to load variations than a J-T system20:45
berndjyou're [going to be] running at ~100bar IIRC/20:46
Syncyes, but plans are slowly changing20:46
Syncthe cascade cooling system is far too large if I run at that pressure20:47
SyncI can get much smaller with advanced cooling concepts20:47
berndjwhy was it necessary to run at such a high pressure in the first place?20:47
berndjis the cooling just plain not enough at lower pressure?20:47
Syncbecause you need a high pressure differential to get enough temperature drop20:48
berndjin general, or to have a system that can start up? (as µ rises as air gets cooler)20:48
Syncthat is a good question20:49
SyncI do not know how startup in larger air destillation plants works20:49
SyncI'd say they prime them20:49
berndjclassic bootstrap problem20:49
SyncI now plan to run the N2 at something managable like 25bar but chill it using an autocascading system20:50
Syncthus eliminating the need for huge compressors20:50
Syncbut that is a long term project now that I have LN2 on tap20:51
berndjby the way, what do you think of http://chemistry.stackexchange.com/questions/785/why-does-oxygen-not-condense-onto-open-dewers-of-liquid-nitrogen20:52
berndjif you cool air, do you get a mixture of N2 and O2, or one or the other, or what?20:52
Syncyou get a mixture20:52
Syncand you need to destill the o2 off20:52
berndji'm still not 100% confident of my reasoning in the answer i gave to that Q20:53
Syncalso most dewars are capped off when filled20:53
berndjdistillation, yet another major project20:53
Syncso they have a ever so slight amount of nitrogen coming out20:53
Syncthat replaces all oxygen20:54
Syncyou can indeed make LO2 with LN2 :P20:55
Syncbeen there done that20:55
Syncfun stuff20:55
berndjjust using the LN2 as heat sink to condense the O2?20:55
berndjthat's what i'm unsure about in my Q; the way i read O2's vapour pressure graph, it only just starts to condense out of air at LN2's boiling point20:56
berndj*in my A to that Q20:57
Syncjust look at the standard condition points20:58
berndjyeah, then it's 90K as opposed to N2's 77K20:59
berndjbut oxygen isn't at 1atm in the air20:59
SyncI'm not so sure if the PPO2 is important there20:59
Syncfor condensing out O2 from the air probably, but for liquifiying O2 from the bottle not so much21:00
berndjwell, the ambient temperature is under 100C, yet it isn't raining21:00
berndjah, sure, out of the bottle it'd be at or (way) above 1atm21:00
SyncI think you are right, the BP at the PPO2 in air is so close to the BP of N2 that it barely condenses out21:01
berndji guess that's why you get a mixture when you liquefy air21:02
Syncthat is just because you have both gasses in the air21:02
Syncthe pressure differential is enough to liquify both21:03
berndjif PPO2 were a bit higher, you'd first get O2 condensing out though, wouldn't you?21:03
Syncgah I should go to sleep21:03
berndji guess it depends on just how big the T drop is in the expansion21:04
Syncwhen I'm liquifying air the PPO2 just determines what I end up with21:04
Synccondensing out from the air is different21:05
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