While for equipment like abs chillers I tend to err towards my own spreadsheet models wherein I can assure absolute control and depth in the model & develop/QC my own performance curves, in eQuest/doe2 you have the option of setting up a "free" steam meter to supply as much heat as your chiller will use. Regardless of platform, you might want to consider carefully if in fact the entire process of heat transfer from the power exhaust stack is truly "free." In my most recent project, we added duct burners to supplement our generator's HRSGs, allowing for high pressure steam. there are also considerations for nominal energies required to reeturn condensate, and depending on your circumstances you may also need to consider the possibility of what happens when your "free" source ends up short in capacity for whatever number of uses (like CHW generation" you're applying.

Hope that's helpful!