[PATCH] Re: New Bug Reports/Feature Requests

Robert Helling helling at atdotde.de
Fri Feb 26 01:02:47 PST 2016


Hi,

> On 26.02.2016, at 00:54, Rick Walsh <rickmwalsh at gmail.com> wrote:
> 
> Introducing an improved equation that considers temperature raises the question of what temperature should be used.  As the temperature of the gas in the cylinder isn't monitored, there's no correct answer.  Your patch uses dive->airtemp, which I assume is the surface temperature (I'm at work now and not looking through the code to check).  At the start of the dive that is reasonable, unless the cylinder has just been filled, but after a few minutes, it's probably much closer to the water temperature.  Diving here in summer, the difference can be significant (say 35 C on the surface, 17 C in the water).


I totally agree but I think you are just rephrasing of of the ways in which “real volume” is ill-defined. You could also argue that the gas is cooler than the ambient water when you breath it due to the Joule-Thompson effect, but hey, I don’t really care.

I only included it since the formula I found in Wikipedia (which somewhat matches the empirical values, maybe I should post the mathematica notebook that I used when I get back to my laptop) has the temperature in it, so it needs to get _some_ value. First I thought about hard coding 300K but then realized, we typically have some temperature around so it does not hurt much to use that. So that’s what I did. But it does not really matter as we are talking here about a correction to a correction to an ill-defined concept.

Best
Robert

--
.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO
Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics
                      Scientific Coordinator
                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik
                      Phone: +49 89 2180-4523  Theresienstr. 39, rm. B339
                      http://www.atdotde.de

Enhance your privacy, use cryptography! My PGP keys have fingerprints
A9D1 A01D 13A5 31FA 6515  BB44 0820 367C 36BC 0C1D    and
DCED 37B6 251C 7861 270D  5613 95C7 9D32 9A8D 9B8F





-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.subsurface-divelog.org/pipermail/subsurface/attachments/20160226/7d31bc6b/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 495 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://lists.subsurface-divelog.org/pipermail/subsurface/attachments/20160226/7d31bc6b/attachment-0001.sig>


More information about the subsurface mailing list