[enuano]

Hi there!

I'm doing my master's thesis and need to modelate model R-245fa for a turbine expansion (Ansys CFX). I want to model it as a real gas, because the pressures for this work are not so low. I have problems setting some of its properties:

1. Boiling temperature. At which pressure? I read it should be 15ºC and it makes sense if it refers to the reference pressure of 1bar.

2. Setting the fourth order polynomial parameters of specific heat at constant pressure. For my range of pressures, which is 0.85-0.35 MPa, I just consider Cp constant with a value of about 1067 kJ/kgK, so I calculate just the first coefficient (17,203) and set all others so that they don't influence. The problem is when running the simulation, it goes out of range and gives error.

Do any of you have experience in simulating R-245fa and can tell me which coefficients to use?

Thank you very much!

[Medison]

I've modeled some cases with R-245fa but in my cases i used coefficients for variable Cp0.
1. You need to define normal boiling temperature i.e. at 1 atm
2. Don't forget to divide your polynomial coefficients by the specific gas constant (as shown in the theory guide).
If you are interested my coefficients for R-245fa were:
a1 = 5.34674
a2 = 1.41302E-02
a3 = 1.11188E-04
a4 = -2.75001E-07
a5 = 2.16421E-10

Hope it help