Embedded equations in SAM software

Dear team,

I've been looking at how variables are calculated within SAM software. Specifically in CSP parabolic trough model, it uses lookup functions to find the TES fluid density/specific heat as indicated in the help menu.

May I ask where I can find those lookup functions? 

I checked the UI files in SAM/runtime/ui folder, but only find the function names that being called, such as 'substance_density' or 'cspdtr_tes_userhtf'. I couldn't find the definition of those functions. Could you help me locate them? Thanks!

Best,
Zhuoran 

Hi Zuoran,

If the heat transfer fluid is user-defined, SAM uses a lookup function to interpolate between the values provided in a table of fluid properties. For the physical trough model, you can find an example of a user-defined HTF table for the Storage HTF fluid input on the Thermal Storage input page: Choose the user-defined fluid from the list, and then click Edit to see the table.

The lookup function Linear_Interp::linear_1D_interp() interpolates these table values and is defined in tcs/interpolation_routines.cpp: github.com/NREL/ssc/blob/develop/tcs/interpolation_routines.cpp#L65 .
 
For non-user-defined heat transfer fluids, the property functions are in tcs/htf_props.cpp: github.com/NREL/ssc/blob/develop/tcs/htf_props.cpp#L309 .

Functions from the user interface call intermediate functions in the SSC code like the ones here, github.com/NREL/ssc/blob/develop/ssc/cmod_ui_tes_calcs.cpp#L128 , but the final calls are to htf_props.cpp.

Best regards,
Paul.

Thanks Paul! This is what I wanted to find. Really appreciate for your help.

Best regards,
Zhuoran