The Stirling Engine-Refrigerator: Rich Pedagogy from Applied Physics

A Stirling engine of the type used for demonstration purposes has been outfitted with a pair of sensors that measure pressure and piston displacement when the engine is operating with a small temperature difference between the hot and cold reservoirs. Measured variables are compared against computer generated output based on a simple theory that involves nonlinear equations of motion. Theory and experiment are found to be in reasonable agreement. Temperature dependence of the graph of pressure versus piston displacement, for different directions of flywheel rotation, permits a better understanding of the physics of heat engines and refrigerators in general.