I n s t r u c t i o n S h e e t
012-06870B
Low Delta T Stirling Engine
SE-8576A
800-772-8700
www.pasco.com
®
Introduction
The PASCO SE-8576A Low Delta T Stirling Engine is a
jewel-like engine. Because of its precision components and
careful construction, it can operate on temperature differ-
ences as small as four degrees celsius (4 °C).
For example, when the room temperature is 22.2 °C (72 °F)
or cooler, the heat from a warm hand is enough to power the
engine.
Stirling engines can be very efficient with some designs
attaining efficiencies up to 50% of the Carnot Cycle effi-
ciency. The Carnot Cycle determines the maximum theoreti-
cal efficiency of a heat engine according to the formula:
where the temperature is measured in absolute degrees
(kelvin (K) or rankine).
Operation
The Low Delta T Stirling Engine operates as follows:
The bottom plate of the engine along with the clear acrylic
cylinder, the top plate, and the graphite power piston make
up a sealed system. When the air inside this system changes
temperature, so does the pressure.
Inside the clear acrylic cylinder is a large white foam
dis-
placer
. This displacer looks like a piston, but it has a
3.125 mm (1/8” inch) gap around its outer edge. Air never
pushes on the displacer; it flows around the displacer.
The engine can begin working when either the bottom plate
or the top plate is heated or cooled to a temperature at least
4 °C warmer or cooler than the other plate. A gentle spin on
the flywheel is needed to start the engine.
As the foam displacer moves away from the warm side of the
engine, air flows around the edge of the displacer toward the
warm side and is heated. When the air is heated, it expands,
which increases the pressure inside the entire engine. This
increase in air pressure pushes up on the graphite power pis-
ton.
Next, the energy stored in the flywheel moves the displacer
closer to the warm side of the engine, and the air once again
flows around the edge of the displacer toward the cool side
of the engine.
When the air is cooled, it contracts, and the pressure drops
throughout the engine. The pressure inside the engine
becomes less than the pressure outside, and the graphite
power piston is pushed down. The displacer moves back
toward the cool side, the air is displaced toward the warm
side, and the cycle starts all over again.
The foam displacer only moves the air back and forth from
the warm side to the cool side of the engine. It does not do
any work on the crankshaft. In other words, the connecting
temp hot - temp cold
temp hot
--------------------------------------------------
% efficiency
=
Flywheel
Crankshaft
Graphite
power piston
Foam
displacer
Connecting
rod
Connecting
rod
IMPORTANT:
Do Not Oil
