Input pair variable is invalid Error, For incompressible fluid 'Therminol Vp1'

[Iman Fakhari]

Hi, i want to Find Temperature of Therminol VP1 and i have quality (x=0) and its enthalpy (h) so i coded like this:

T(3) = CoolProp.PropsSI('T' ,'Q',X(3),'H',h(3),'INCOMP::TVP1')

and i get this error:

Warning: Input pair variable is invalid and output(s) are non-trivial; cannot do state update

And i know quality and enthalpy are enough to find temperature of therminol. so whats wrong?  and how can is solves this?

Regards

[Matthis Thorade]

Hi,

saturated liquid enthalpy and saturated liquid entropy should be unique, but saturated vapour enthalpy is not unique. I believe this input pair is just not implemented. So, what you can do is use PQ, or TQ as input pair, or write a small function in whatever wrapper language you are using to find the saturated liquid state. Saturated liquid enthalpy is monotonous between triple point liquid and critial liquid, so any 1D root finding algorithm should work (bisection, Brent, bounded Newton).

Best, Matthis

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Matthis Thorade
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[Iman Fakhari]

Thanks for your response
But i just have H and Q of this state. How can i find P or T?

[Iman Fakhari]

I'm Using matlab. how can i implement this pair of input?