Heat Engines; Curie Effect, Nitinol and BiMetal
Curie Effect Magnetic Heat Engine
Curie Point Magnetic Heat Engine – How it works
The heat engine uses a principle of magnetism discovered by Pierre Curie. He studied the effects of temperature on magnetism. Ferromagnetism covers the field of normal magnetism that people typically associate with magnets. All normal magnets and the materials that are attracted to magnets are ferromagnetic materials. Pierre Curie discovered that ferromagnetic materials have a critical temperature at which the material loses its ferromagnetic behavior. This is known as its Curie Point.
As an example, a piece of iron (Fe) at room temperature is strongly attracted to a magnet. Heat the iron to a temperature of 770 C, which is its Curie Point, it loses its ferromagnetism behavior and it is no longer attracted to a magnet. If we let the iron cool, it regains its ferromagnetic behavior and is attracted to the magnet again.
We can use this property to construct a small swinger type heat engine. The heat engine uses a nickel alloy wire that has a low Curie Point, see drawing to right. When the wire is at room temperature it is attracted to the magnet, and swings close to the magnet. In this position, labeled B in the drawing, it is heated by the flame of a small birthday cake candle. When the material temperature reaches its Curie Point, it loses it ferromagnetism and falls away from the magnet, to position A, and out of the candle flame. As the wire cools it regains its ferromagnetism and is attracted to the magnet again, where it swings back up toward the magnet to position B and back into the candle flame. This process repeats, swinging the nickel alloy wire back and forth.
Heat Engine Kit (requires assembly) HE-01 - $35.96
Pictures and videos of the heat engine functioning. Click on picture to view video.
Brass Candle BC-01 - $14.95
Components sold separately to build your own heat engine
DiscMagnet-01 - $7.95
1" diameter neodymium disc magnet
N-Wire-01 - $4.95
6" Low Curie Point Wire
Nitinol Heat Engine Kit
Nitinol Heat Engine - powered by hot and cold water.
The Heat Engineis a very special kind of heat engine that demonstrates
the conversion of heat energy into mechanical energy. Based upon the
work of Dr. Alfred Johnson who was granted a patent on this type of heat engine in 1977 patent # 4,055,955.
It uses the unique property of Nitinol alloy to generate mechanical motion from heat. Nitinol has trained into a shape at high temperature (about 600° C) and allowed to cool to room temperature, where it can be easily deformed and welded into a loop.
When heated above a transition temperature (in this application about 50° C to 70° C) the Nitinol object abruptly returns to its high-temperature shape with a substantial force that is able to drive the pulleys and thus create motion.
HE-02N - $65.95
Nitinol Heat Engine
This fully assembled Nitinol Heat Engine works like an engine without any visible power source. As a shape memory alloy, the Nitinol wire reacts to small changes in temperature converting low temperature thermal energy into mechanical energy and driving the engine as it tries to return to its "remembered shape".
The wheels of the Thermobile will continue to spin as long as it remains heated. To start the engine, simply immerse the edge of the smaller pulley into a water bath between 45 and 90 degrees Celsius and spin the larger pulley.
8" long x 1" thick, 4 oz.
Clear acrylic handle with aluminum pulleys and looped Nitinol wire.
Operating Temperature: 45 - 90 degrees Celsius. (105 - 200F)
BiMetal Heat Engine Kit
SeeSaw Heat Engine driven Candle
The spiral spring is the engine of the see-saw. It is made of a bimetal,
two metals, which expand differently when heated.
The spiral spring twists over the candel and moves the sphereical weight to the other side. Causing the see-sae to tip to the other side.
The pulls the spiral spring away from the heat, causing the bimetal to cool and contract. When the spiral spring contracts it swings the weight causing the see-saw to tip to its original position, where the cycle repeats.
Video 1: SeeSaw Engine Running (6 Mb)
SeeSaw - $52.95