Diveblendr - Free, offline, technical tools for diving

[inquis]

For gas blending, I think temperature consideration is critical. I use VdW and adjust the target pressure for measured temperature (estimated with an IR temp gun). I routinely hit within 0.1 of my target mix on the helium fraction. (That fraction is extremely sensitive to the final top-off pressure due to the zero He content in air.)

 

[DoxStuckDox]

Good to see others going beyond the ideal gas approximation. In Subsurface, we found that van der Waals corrections are not much better in the temperature and pressure range relevant for diving. I talked about his in my blog a few times: Real gas – The Theoretical Diver

It turns out, a polynomial fit is much closer to tabulated data, so that is what we use. There is also a blending software based on this. Real Gas Blender Calculator It's open source, so fee free to use the formulas!

Really enjoyed the blog post (and writing style). It is interesting how the tabular approach gets close enough; I mainly implemented the polynomial approach out of a challenge to myself for coding. That said, I'm still not happy with my blender calcs as it doesn't take in to account the RATE of addition; which is sometimes quite variable in South Asia.

I'll take a look at the source code you highlighted and poke around a bit. I will also add your site to my links page on the next update. Cheers .

 

[Arkman]

Do you have any plans to imperial support? I'm working on changing my diving to metric, but I'm not there yet

 

[DoxStuckDox]

Do you have any plans to imperial support? I'm working on changing my diving to metric, but I'm not there yet

Yes - I ca update the libraries to work in Imperial. I'll add some site-wide settings for units in the next week. Cheers!