# Concentration to ppm

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 September 2, 2003, 04:32 Concentration to ppm #1 Soren Guest   Posts: n/a Hi I am new to working with concentration in CFD. I have simulated the dispersion of gas and got the mass concentraion in the unit kg/m^3. How can I convert this to a concentration in ppm ? Thanks in advance. Soren

 September 2, 2003, 05:40 Re: Concentration to ppm #2 Bart Prast Guest   Posts: n/a density_component/density_mixture * molmass_mixture/molmass_component = molecules_component/molecules_mixture multiply this by 1 million and you will have ppm (If this is true, where do I send the invoice to?)

 September 4, 2003, 16:30 Re: Concentration to ppm #3 Pascale Fonteijn Guest   Posts: n/a Bart, Send it to CFX. They have a very large range of units but no ppm yet. Why not implement this one? On the other hand, if you can not do these 'back-of-the-envelope-calculations' yourself, you should not be in a position to perform CFD-calculations. Pascale

 September 5, 2003, 03:44 Re: Concentration to ppm #4 Bart Prast Guest   Posts: n/a It's not simple. I'm just really good. As this is a really simple formula, people can just put it in ccl or an additional variable. For small ppm ranges I think you run into trouble with respect to accuracy (very small massfractions) in CFX. You might have to do it double precision and I've never been able to do this as it requires a little bit too much memory.

 September 5, 2003, 05:54 Re: Concentration to ppm #5 Jan Rusås Guest   Posts: n/a ->Bart, So you give advices that you have not managed to use yourself. You are a true consultant )

 September 5, 2003, 06:00 Re: Concentration to ppm #6 Bart Prast Guest   Posts: n/a Want any more of these advices? I can direct you to our marketing department. They are in the process of selling my skills.

 September 5, 2003, 07:29 Re: Concentration to ppm #7 Jan Rusås Guest   Posts: n/a I am not surpised that it is the marketing department that takes care of selling CFD consultancy. In many cases,(and in many companies)CFD really is only a marketing stunt.

 September 5, 2003, 08:08 Re: Concentration to ppm #8 Bart Prast Guest   Posts: n/a Hmmm, I cannot say that's the case in our company. It's just that they are a hell of a lot better in selling things than the average CFD engineer (myself not included ;-) )

 September 5, 2003, 08:57 Re: Concentration to ppm #9 Bob Guest   Posts: n/a Now theres a scary thought, a marketing department of an engineering company that knows something about engineering !

 September 5, 2003, 08:58 Re: Concentration to ppm #10 Bart Prast Guest   Posts: n/a Now there's a typical engineering cliche

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