Flash calculation and Mehra's acceleration

protosurge@gmail.com · science forum beginner Joined: 09 Apr 2006 Posts: 4

I'm trying to improve the speed of a VLE flash routine I've written.
The routine is essentially an inner loop that solves for the
liquid/vapor fraction (via Rachford-Rice) and outer loop that updates
K-values by K(i) = K(i)*(fugacityLiquid[i]/fugacityVapor[i]) for each
component. This procedure works well but sometimes takes 200-300
iterations of the outer loop (average 2-3 of the inner loop) to
converge. I found a reference to an acceleration procedure by Mehra
(from the early 80's) but unfortunately the closest library doesn't
seem to have an electronic or paper copy of the journal. I was
wondering if someone could outline the steps to calculate the
acceleration factor or point me towards an alternate source of the
algorithm (A more recent journal publication or book). Thanks in
advance for the all help.

Mehra, R.K., Heidemann, R.A., and Aziz, K.,: "An Accelerated
Successive
Substitution Algorithm", Can. J. of Chem. Eng., 61,590, (1983).

Kiran

Torben Laursen · science forum beginner Joined: 05 Jun 2005 Posts: 5

Hi Kiran

There are 2 much better methods
#Dominant eigenvalue method
#Full newton

If you are going to spend some time on this I suggest that you get this
book:
http://www.tie-tech.com/pub/publications.htm

Regards Torben Laursen
VLXE

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