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Jozef I get very good results if I hot mix the gasses and add a 10% fudge factor to each of the gasses to allow for cooling and gas compressibility. E.g. say I have 80 bar of 18/40 in my set and I want to remix this to 232 bar of 11/60. Theoretically, I add: O2 2.2 bar He 107.4 bar Air 42.4 bar 80+2.2+107.4+42.4 = 232 bar In practice I fill as follows: O2 2.4 bar He 118.1 bar Air 46.7 bar (to 247.2 bar) After the gas cools I'll have around 232 bar and the analysis should be fine. The trick is determining when 10% over pump is reached on a digital gauge since the reading is always dropping. I just stop when the rate of drop slows down. David Shimell Email: shimell@se*.co* <mailto:shimell@se*.co*> Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited, Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF, UK registered in England and Wales under company number: 1999363, registered office as above -----Original Message----- From: Gliviak, Jozef [SMTP:Jozef.Gliviak@co*.co*] Sent: Sunday, January 09, 2000 6:13 PM To: techdiver@aquanaut.com Subject: Real gas and mixing based on ideal gas equations (is it useless ? ??) Hello, As you probably know from my previous mails, I'm currently in phase of building my own home mixing station. During my search I found out very interesting findings about differencies between behavior of ideal and real gas. we all know that this is valid for ideal gas p * V = n*R*T and p1*V1=p2*V2 (if temperature is constant) And on this assumption many of us try to mix their Trimix. But based on Van der Waals findings for real gas it looks like this in reality (p+ (n*n*a/V*V))*(V-nb)=nRT where a,b are gas dependent constants when you use this formula for air and you for example calculate amount of air in 10L bottle you will get interesting results: Temp 20Celsius, Air presure 100Bar 150Bar 200Bar volume 880L 1242L 1562L For 200Bar we've got difference appx. 22% which is HUGE difference. That implies to me that using mixing methods based on ideal gas and part. presures are TOTALY useless. Using oxygen analyser we are able to check and adjust amount of oxygen quite sharp, but we've got no clue how much Nitrogen and Helium is in the mix. So I'd like know, if you are using this method. If not, which method do you use ? If yes, how you deal with these differencies between assumptions and reality ? Regards Jozef Gliviak Slovakia -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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