X-Message-Number: 2109 Date: Thu, 15 Apr 93 01:28:43 CDT From: Brian Wowk <> Subject: CRYONICS Reply to Mike Darwin Thanks to Mike Darwin for taking the time to add thoughtful commentary to the Cold Room discussion. Because Mike is busy (and Lord knows I'm falling behind too) I should delay this reply. However I will not be able to sleep tonight unless I reply! Mike Darwin: > 1) Water is a real problem for underground and above ground > structures. Your comments are well taken. This may have to be examined more closely. Perhaps an above-ground concrete enclosure with access from the second-floor level is more appropriate. This might actually be cheaper to build since minimal or no excavation would be required. > 3) Ethyl alcohol is probably not acceptable for several reasons: > A) It is a fire hazard which will send the fire department into orbit. Well, ethyl chloride/bromide are *worse* fire hazards and have toxic combustion products to boot. (The flash point (minimum temperature at which vapor pressure is high enough to ignite) for ethyl chloride is -50'C versus +12'C for ethanol.) I will scan the CRC further when I have time, but so far all the liquids I have seen that freeze in the -130'C to -110'C temperature range have this problem. The only exceptions are CFCs that are prohibitively expensive and enviromentally hostile. > It will be used against you by the competition because it is > a fire hazard. This assumes that the competition has something better, which they won't. I have heard amazing things said about Alcor over the years by the competetion, including (but not limited to) that we are Nazi's and that our cryoprotective perfusate is "toxic." None of these cheap shots have suppressed the growth of Alcor. I think the same will be true of other criticisms in the future that lack objective merit. > B) No, warming up even a little (more > than a few degrees) is NOT acceptable if you have vitrified rather > than frozen patients. To avoid devitrification we have to make sure we stay safely below TG at all times. If the -115'C melting temp of ethanol is too high, we may have to choose some other (probably more flammable, and more expensive) liquid. > 4) Brian is dead wrong if he thinks that patients stored in LN2 > will be removed to -135*C storage. Agreed. I've taken my lumps for this, and will not suggest it again. > 5) I think others have commented on this but I wish to put my > two cents worth in. Thermal stratification is nontrivial. Agreed. In fact I acknowledged the necessity of fan air circulation a month ago, and have not suggested any convection-driven schemes since them. > 3) Bob Ettinger is absolutely right about using thick blocks of > insulation. Again, from practical experience I can tell you that > once you get out beyond a foot you don't seem to get much for your > (foam) money. Certainly by two feet you are almost certainly wasting > your time. I could be wrong on this, but I don't think so. NO way. I have researched this problem to death. The simple fact is that the insulating power of foam rises in direct proportion to its thickness *provided that the thickness is much smaller than the room size*. If Robert Ettinger is reading this, I'm sure he will back me up, as will Steve Harris, or any cryogenic engineer for that matter. The tricky part is when the insulation thickness becomes comparable to the room size (1m foam vs 5m room size in our case). In these cases there is indeed a case of diminishing returns with increasing foam thickness because the geometry creates a non-uniform thermal gradient. However I have analyzed this issue using a studious and conservative methodology and still conclude you cut your heat flows nearly in half going from 1.5 feet to 3 feet thickness. Perhaps, Mike, your personal experience has been confined to applications where the space to be insulated was only a few feet wide. In cases like that there really would be no value in going beyond 1 foot insulation. However that is not the case now being considered. Finally I would just like to point out that if 1 foot of foam insulation is the best we can do, we might as well go home and forget about ever getting out of dewars. We would never be able to afford it. > 4) This point is my most important: Any attempt to engineer > large scale systems to store frozen patients is PREMATURE in the > extreme. Even if a Cold Room does not prevent frozen (as opposed to vitrified) patients from cracking, there is still the cost issue. I believe I am making a darn good case that patients can be stored more securely *and* more cheaply in a Cold Room than dewars. This case will become stronger as the design becomes more detailed and more costs are pinned down exactly. (I am currently collecting quotations from cryogenic foam suppliers). > 5) Peltier effect? Gentlemen, I doubt it. So do I. (See Thermoelectric Blues posting from last week.) > 6) Brian has once or twice asserted that Queue manufactures a > body-sized -135*C freezer. Not to my knowledge! This was second-hand information. I shall in future refrain from making claims that I do not research myself. > Mechanical systems stink. I hate them. They are nothing but > trouble. They are not as reliable as your household refrigerator. I > don't known anything about the company Brian talks about except that > what he was told makes my skin crawl. No known failure mode, should > run decades.... Mike, perhaps you should change your perspective. I have repeatedly stated that a mechanically refrigerated room would have a simple LN2 backup capability. Instead of thinking of LN2 as backup, think of it as the primary cooling mode. You run your refrigerators to save LN2 whenever you can. Even if your refrigerators work only *half the time* (50% down time-- quite unrealistic) they will still quickly pay for themselves in LN2 savings. Not to malign the manufactures, they just told me the system was "like a household refrigerator." The "mean-time-before-failure measured in decades" line was mine not theirs. The literature I received in the mail today from Polycold actually gives a 50,000 hour (6 year) MTBF, which appears to be consistent with Greg Fahy's Queue freezer experience. Finally, I'll point out that Polycold has hundreds of units out in the field in critical commercial applications. They would not be able to keep selling these things unless they had reasonable up-time, and I'm sure we could verify this by talking to a few customers. > When you put a refrigeration set up in place in the field you > have nothing but quality control problems every step of the way. A Polycold cryocooler ships finished and sealed. You just plug it in, pipe it water for cooling and you're all set. The cold heat exchange coil (if you use theirs) is at the end of an insulated, flexible 8' hose that you stick wherever you want. > In a recent posting Brian Wowk states that there is a $7000 > charge at Alcor for use of a cooldown dewar. Since I do not have a > CRFT in front of me I am unable to cite chapter and verse, but I > believe that Brian is mistaking the dewar space charge for the > cooldown charge. In other words, the 7K is the fraction of the > bigfoot dewar which the patient "buys" when s/he is placed into > suspension: sort of like a condominium charge. This cost is then > replaced out of interest on principal over (I think) a 10 or 15 year > period to allow for "sinking fund" replacement of the equipment at the > end of its most conservatively estimated working life. This would make sense, but then why is this "Dewar Slot" charge listed in the Suspension Charges section separate from the Long Term Storage Costs which lists yet another "Dewar Amortization" charge? These are both big charges (the Dewar Amortization charge equals LN2 expense) and can't both be for storage. If they are, then they should at least be listed together with an explanation for the double charge. I look foward to clarification in the new cost estimates now being prepared at Alcor. In any case, my point was that it's easier to slowly cool below -79'C in a Cold Room than in a dewar. I think it's still a valid point. --- Brian Wowk Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2109