Demos: 3E-08 Visible Stirling Engine
This is a working version of the Stirling engine. With a small flame from an alcohol burner it will run at 1000 rpm and a small generator will light up a small light bulb. It will also run as a heat pump or refrigerator. It is too small to see from the audience, but can be displayed on the digital projector while illuminated by a portable lamp. A digital thermocouple is available to display the temperatures of the two reservoirs. If it is placed near the engine you can easily move the camera to see one or the other. A good animation to describe the Stirling cycle can be found on the web here: http://travel.howstuffworks.com/stirling-engine1.htm. A figure showing the cycle on a PV diagram is shown below.
If you are going to show the heat pump or refrigerator, do that first. The motor will run on 9 volts (do not exceed 12 V). Reversing the polarity will change the direction of the motor and switch from refrigerator (CW when facing motor side) to heat pump. A thermocouple will show the temperatures of the two reservoirs. The difference in temperatures will be about 10 C for the refrigerator or 14 C for the heat pump.
To operate as an engine, remove the connection to the motor and place the small flame under the end of the glass piston. It takes about a minute to add enough heat to run the engine. You will need to give it a push clockwise (when facing the motor side) to get it started. Once it is running well, you can connect the small light bulb to the generator. This will slow down the motor somewhat.