# Simscape Two-phase Fluid Constant Pressure Specific Heat

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Tech Logg Ding on 1 Sep 2020
Commented: Rohan Kokate on 7 May 2022
In the two_phase_fluid.ssc domain file (located in: C:\Program Files\MATLAB\R2020a\toolbox\physmod\simscape\library\m\+foundation\+two_phase_fluid) does not include the fluid specific heat as a fluid property. Therefore, the tablelookup() function can not be used to find the fluid specific heat. The webpage: https://au.mathworks.com/help/physmod/simscape/lang/two-phase-fluid-domain.html shows that it is available but the domain file does not. The nu_TLU array in the two_phase_fluid.ssc file is not the specific heat but rather the kinematic viscosity as shown below.
nu_TLU = {[
], 'mm^2/s'}; % Kinematic viscosity table

Sarah McElman on 18 Nov 2020
Edited: Sarah McElman on 18 Nov 2020
Hello,
You are correct that nu_TLU represents the kinematic viscosity, and not the specific heat, in the two-phase fluid property file. Our documentation team has been made aware of this.
In the two-phase fluid domain, users must supply the fluid specific heat for both library and custom blocks. You can calculate it based on the Prandtl number in your system:
,
where is the specific heat, μ is the dynamic viscosity, and k is the thermal conductivity. This should be defined for both the liquid and the vapor of the two-phase fluid.
Best,
Sarah
Rohan Kokate on 7 May 2022
Hello Sarah,
Thanks for the suggesting a way to calculate the specific heat. However, when I tried implementing it in my code, it causes discontinuites as the phase changes (probably because of the difference in the vapor and liquid viscosities). Is there a way you can suggest to avoid the discontinuities? I am using the specific heat for calculating the NTU of a two-phase heat exchanger.
Regards,
Rohan Kokate.

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