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12-07-2007, 11:58 AM #14Guest
- Join Date
- Apr 2005
- where the beer flows like wine
12-07-2007, 06:08 PM #15
The Rowland-Molina hypothesis
In 1974 Frank Sherwood Rowland, a Chemistry Professor at the University of California at Irvine, and his postdoctoral associate Mario J. Molina suggested that long-lived organic halogen compounds, such as CFCs, might behave in a similar fashion as Crutzen had proposed for nitrous oxide. James Lovelock (most popularly known as the creator of the Gaia hypothesis) had recently discovered, during a cruise in the South Atlantic in 1971, that almost all of the CFC compounds manufactured since their invention in 1930 were still present in the atmosphere. Molina and Rowland concluded that, like N2O, the CFCs would reach the stratosphere where they would be dissociated by UV light, releasing Cl atoms. (A year earlier, Richard Stolarski and Ralph Cicerone at the University of Michigan had shown that Cl is even more efficient than NO at catalyzing the destruction of ozone. Similar conclusions were reached by Michael McElroy and Steven Wofsy at Harvard University. Neither group, however, had realized that CFC's were a potentially large source of stratospheric chlorine — instead, they had been investigating the possible effects of HCl emissions from the Space Shuttle, which are very much smaller.)
The Rowland-Molina hypothesis was strongly disputed by representatives of the aerosol and halocarbon industries. The Chair of the Board of DuPont was quoted as saying that ozone depletion theory is "a science fiction tale...a load of rubbish...utter nonsense". Robert Abplanalp, the President of Precision Valve Corporation (and inventor of the first practical aerosol spray can valve), wrote to the Chancellor of UC Irvine to complain about Rowland's public statements (Roan, p 56.) Nevertheless, within three years most of the basic assumptions made by Rowland and Molina were confirmed by laboratory measurements and by direct observation in the stratosphere. The concentrations of the source gases (CFC's and related compounds) and the chlorine reservoir species (HCl and ClONO2) were measured throughout the stratosphere, and demonstrated that CFCs were indeed the major source of stratospheric chlorine, and that nearly all of the CFCs emitted would eventually reach the stratosphere. Even more convincing was the measurement, by James G. Anderson and collaborators, of chlorine monoxide (ClO) in the stratosphere. ClO is produced by the reaction of Cl with ozone — its observation thus demonstrated that Cl radicals not only were present in the stratosphere but also were actually involved in destroying ozone. McElroy and Wofsy extended the work of Rowland and Molina by showing that Bromine atoms were even more effective catalysts for ozone loss than chlorine atoms and argued that the brominated organic compounds known as halons, widely used in fire extinguishers, were a potentially large source of stratospheric bromine. In 1976 the U.S. National Academy of Sciences released a report which concluded that the ozone depletion hypothesis was strongly supported by the scientific evidence. Scientists calculated that if CFC production continued to increase at the going rate of 10% per year until 1990 and then remain steady, CFCs would cause a global ozone loss of 5 to 7% by 1995, and a 30 to 50% loss by 2050. In response the United States, Canada, Sweden and Norway banned the use of CFCs in aerosol spray cans in 1978. However, subsequent research, summarized by the National Academy in reports issued between 1979 and 1984, appeared to show that the earlier estimates of global ozone loss had been too large.-------------------------
CO2 Racks Rock !
12-07-2007, 07:15 PM #16
12-07-2007, 07:17 PM #17
12-07-2007, 09:40 PM #18If you can't learn to do something well, learn to enjoy doing it poorly.
The HVAC-Talk Educational Forums is the best place on the net for your HVAC/R info!!!
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12-07-2007, 09:40 PM #19
what do you know to be wrong with Hot Shoi and One Shot ?PHM
12-07-2007, 10:05 PM #20
My problem is with the misinformation they put on their web site and in their literature regarding application and charging procedures. Their irresponsible statements have misinformed untold thousands of "techs", ruined many a compressor due to improper charging causing high superheat/discharge temps, and cost consumers insane amounts of money to replace equipment due to those mistakes.
Other than that...no biggie.
12-07-2007, 10:10 PM #21
What refrigerant is the best R-12 substitute?
What is the better drop-in for 502 ?PHM
12-07-2007, 10:27 PM #22Regular Guest
- Join Date
- Feb 2004
- Medford Oregon
What refrigerant is the best R-12 substitute?
HT/MT R401A MP-39
LT R401B MP66
What is the better drop-in for 502 ?
there are no drop ins contrary to what HotSh_t may say
the best over all repalcement for R502 is R408 (need AB oil)
These are approved by all compressor mfrs
(the "change oil" issue should not affect your decision, example:
the miscibility of HotS_t to mineral oil same as R401A/B to mineral oil
R401A/B recomemdated oil change to keep within guidelines of Copeland,Tecumseh. HotSh_t ignored these guidelines with "no need to change oil" pitches. (one of the reasons they are not approved)
you get better oil return with AB oil with these gases as well as with HotS_t
you will experience same results if you don't change oil to AB with these gases, incuding HotSh_t but oil return will better with AB oil.
12-07-2007, 10:33 PM #23
k fridge -
Doesn't HT/MT R401A MP-39 LT R401B MP66 require an oil change?
I can't do that.PHM
12-07-2007, 10:37 PM #24
Hot Snot should get an oil change too, regardless of what ICOR says. Especially in a low temp application. Of course you shouldn't be using Hot Snot there anyway. MP-66 is the only R-12 replacement that works well at low temp.
12-07-2007, 10:40 PM #25
Oh and, Rocket is correct. There are no "drop ins", the more correct term is "near drop in."
The term drop-in indicates exact replacement, there are none.
Why does MP-39/66 recommend oil changes and Hot Snot doesn't? One manufacturer tells the truth about it.
(Hint, it isn't ICOR)
12-07-2007, 10:46 PM #26
I still mis just having the big three. life was much simpler then. such is life