I'm currently working on a project that requires me to model depressurization of a gas through an outlet. I need to find the time for complete depressurization of a pressurized chamber as a function of opening cross-sectional area A. I scoured the forums, and found the extremely helpful link pointing to the Rasouli and Williams model. (http://air-dispersion.com/feature2.html) The only problem I now have is determining the coefficient of discharge C. The material we're using for the chamber will either be steel or a type of polyethylene. To determine C, I'd like to perform this experiment: http://mysite.du.edu/~jcalvert/tech/fluids/orifice.htm My only question is this, if the actual area of the opening for the chamber has yet to be determined, would I still yield an accurate result for C using an arbitrary area in the experiment? That is, would the value of C yielded by the experiment apply to any sized opening so long as the material used remains constant? Also the chamber is being designed for air, but using water in the experiment should be fine as there is made no reference specifically to the type of fluid, correct? Thank you for any help, it is greatly appreciated.