CoolProp/Matlab/error message

[eduard...@gmail.com]

Hello coolprop-users,

I am a novice in area of the thermodynamics with CoolProp and have a question. Entropy and pressure is known. It is possibly to determine the temperature and Enthalpie with the help of " CoolProp.PropsSI” ? With which command?

I get an error message when I type the following:

Fluid ='R134a';

h_2 = (CoolProp.PropsSI('HMASS', 'P', p_2, 'S' ,s_1, Fluid))

Warning: unable to solve 1phase PY flash with Tmin=169.849, Tmax=311.144 due to error:
HSU_P_flash_singlephase_Brent could not find a solution because Smolar [0.183209 J/mol/K] is below the minimum
value of 41.997410967 J/mol/K
> In CoolProp.PropsSI (line 2)
  In heat_pump (line 50)
Error using CoolPropMATLAB_wrap
Fatal error.

Error in heat_pump (line 50)
h_2 = (CoolProp.PropsSI('HMASS', 'P', p_2, 'S' ,s_1, Fluid))/10^3; % Enthalpie nach dem Verdichter

Can somebody help me?

Thanks in advance.

Best regards

Eduard

[Ian Bell]

Are you sure your entropy is valid?  Is this a question of reference state for entropy/enthalpy?  How did you generate this entropy?  

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[eduard...@gmail.com]

Am Donnerstag, 6. Juli 2017 16:10:38 UTC+2 schrieb Ian Bell:

Are you sure your entropy is valid?  Is this a question of reference state for entropy/enthalpy?  How did you generate this entropy?  

On Thu, Jul 6, 2017 at 5:17 AM, <eduard...@gmail.com> wrote:

Dear Ian,

 

This example I try to recreate.

 

Theoretically is s1 = s2

Overheated area 1:

s_1 = (CoolProp.PropsSI('SMASS', 'P', 2.01, 'T', 273.15+10, 'R134a'))

s_1 = 2.7451 kJ/kgK   (I understand but not this value. According to table for overheated area the value is “1,7952”)

h_2 = (CoolProp.PropsSI('HMASS', 'P', 9.63, 'S' ,s_1, 'R134a'))

 

Error in heat_pump (line 53)

h_2 = (CoolProp.PropsSI('HMASS', 'P', 9.63, 'S' ,s_1, 'R134a'))

 

Best regards

Eduard

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[Philip Bell]

Hi Eduard, 

Looking at the list of units here, pressure should be in Pa and not bar. It appeared to fixed the problem for me but I only use CoolProp in Excel. 

Regards, 

Phil

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[eduard...@gmail.com]

Dear Phil,

 

Thanks for your tip. It works.

 

 

Best regards

 

Eduard

[Ian Bell]

Also, the key point is that entropy and enthalpy have a reference state that you need to take into account.  This is the #1 FAQ for CoolProp: https://github.com/CoolProp/CoolProp/blob/master/FAQ.md

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