Stirling Engine Experiment

[stan.hornbaker]

An Experiment for Coffee Cup Stirling Engines

Purpose: To show that heat flows through the engine from the hot side
to the cool side and that energy (in the form of heat) is converted to
mechanical energy (in the form of a spinning crankshaft turning the
propeller).

Equipment: 1. A large coffee cup or similar container that can be
easily insulated. (4@ dia.) Insulate with Styrofoam insulation
around sides and bottom if possible and seal joint at top with
silicone sealant. An insulated thermos may also work well.
2. A MM-1 or MM-5 Coffee Cup Stirling Engine (CCSE).
3. A thermometer (dial type with long stem) up to 212 F or 100 C.
These are often sold for making candy.

Procedure: For each run fill the coffee cup with boiling water from a
teakettle, or fill the cup and microwave it until boiling just starts
Boiling water can burn you so be very careful.

Observations and Data:
Run Number One:
1. Record the surface temperature of the top of the engine from the
surface decal thermometer on the CCSE. Feel the top of the engine with
two fingers and record your subjective impression of how warm or cold
it is. Also take and record the temperature of the hot water.
2: Place your CCSE on a coffee cup. Do Not Start engine. Every five
minutes for an hour record the temperature shown by the surface
thermometer and the subjective temperature with two fingers.
3. At the end of the hour, set the CCSE aside to cool to room
temperature, and take the temperature of the water, before reheating
the water and proceeding.

Run Number Two:
1. Note surface decal thermometer on the CCSE and record temperature
and subjective temperature of top of engine with two fingers. Also
take and record the temperature of the hot water.
2: Place the CCSE on coffee cup and flip flywheel (propeller), noting
the speed increase as the engine warms up. Note the time and the
temperature indicated by surface thermometer. Repeat every five
minutes, for an hour recording the temperature and time.
3. Feel the top surface. What do your fingers tell you.
4. Take the temperature of the hot water.

Explain why the top did not warm up appreciably during run 1 but did
heat up during run 2.
Did any energy flow through the engine during run 1?
How did that energy flow compare with run 2?

It's a good idea to keep the engine out of the sun during this
experiment and away from any moving air currents caused by heating or
air conditioning systems.