DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)
DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)
(OP)
What is other users experience for gas phase pressure drop in Aspen using the pipe block. And, under deep vacuum ?
We have a system with HX's and Pipework under deep vacuum so the condensation thermo impacts the flow rates etc.. so using aspen is very attrative.
Aspen users the darcy method wherease i'm used to using Bernoulli for relief valve systems in excel..
So, what is users experience with the methods?
i seem to have read that darcy is a modified bernulli and therefore can i assume it is a reasonable method.





RE: DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)
You have to keep in mind that most of your standard tools start with an "incompressible flow" assumption. In vacuum operations you really have to start with a "compressible flow" assumption which puts you in the realm of some very difficult and problematic arithmetic.
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)
As David says, but I'll gently disagree with the %, I have found that you can reasonably use Darcy if the outlet density is no more than about 10% different that the inlet density for MOST compressible flow problems. That is usually good enough.
But... Your situation is different. If I was in your shoes I would use a compressible flow simulator that uses a generalized energy equation and a proper EOS for your particular gas at vacuum conditions. I do not know if Aspen does that but I bet it does given that Aspen costs dang near more than my first house. The documentation will tell you. You might have to use a fancy simulator like one of the NASA ones. Just make sure Aspen and the EOS are applicable to your situation; it may not be.
RE: DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: DP METHOD: Compressible flow Darcy or Bernoulli & in aspen ? (most accurate valid)