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Dear TRNSYS Community,
Hello Shayan,
See my reply here to another user who also wanted to re-compile Type 1 to produce different outputs and ran into the same problem with the Fprime_function. I assume you are trying to re-compile using TypeStudio? I think, since Type 1 references functions in SolarCalcs.lib, the two files have to be compiled together, which unfortunately is not something TypeStudio allows. I recommend downloading Microsoft Visual Studio with the Intel Fortran compiler to edit and re-compile a version of Type 1 directly within the TRNdll64.dll package. See the second answer here for instructions to download and install Visual Studio and the Intel Fortran compiler. There's also an introduction to compiling TRNSYS Types in Visual Studio in this video: https://www.youtube.com/watch?v=fZ5-zSC094Q.
You are correct, the correction method used by Duffie and Beckman only applies to the 1st order efficiency equation. We did a lot of work about 13 years ago to derive the correct second-order correction factor, which is housed in SolarCalcs.lib and doesn't make its source code available to users. Basically, we follow the same derivation method Duffie and Beckman used for their 1st-order correction factor (beginning from the theoretical equation for the energy balance on a fluid element), only we used an energy balance with 2nd order loss coefficients on the fluid element instead of just the 1st order loss coefficient. We also accounted for the fact that (T_coll - T_amb)^2 in the second order efficiency equation is actually (T_coll - T_amb)*ABS(T_coll - T_amb), else the efficiency trends the wrong direction when the ambient air temperature is greater than the collector temperature.
