Not sure if this should be posted in the general physics forums or in the hw/coursework section. I'm in my second semester of general physics and have to do a class project. For my project I built an alpha type Stirling engine. In the paper I need to write I need to explain how it works using physics. I'm am stuck on the second law of thermodynamics and finding the efficiency (real and ideal) of a Stirling heat engine. I also need to compare the Stirling engine to the carnot engine. I know the efficiency of a carnot is effc= 1-(Tc/Th). What formula is used to calculate the the real efficiency of a Stirling heat engine?