Hello,
The input variables are described in SAM's Help system, which you can open by pressing the F1 key in Windows, or command-? in OS X.
For example, here is the description for the design loop outlet temperature:
"The temperature of the HTF at the outlet of the loop under design conditions. During operation, the actual value may differ from this set point. This value represents the target temperature for control of the HTF flow through the solar field and will be maintained when possible."
I think that you are referring to the warning message about the HTF temperature being outside of its operating range that SAM displays after running simulations. The Help system shows a table of operating temperature ranges for the HTFs in SAM's fluid library. The message tells you that for at least 50 hours of the 8760 hours in a year, SAM calculated that the field temperature exceeds the maximum operating temperature. That is based on the simulation results, not the design conditions. The design temperature under design conditions (at 950 W/m2 irradiance by default), but the actual temperature calculated during the simulation will vary from the design point as the ambient and operating conditions vary.
Best regards,
Paul.
