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2000
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In the Classroom
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Tested Demonstrations
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Illustrating Thermodynamic Concepts Using a Hero's Engine
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submitted by: Pedro L. Muiño and James R. Hodgson
Department of Chemistry, Kansas State University, Manhattan, KS 66506
checked by: Sheldon Knoespel
Department of Chemistry, Michigan State University, East Lansing, MI 48824-1322
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May 2000
Vol. 77 No. 5
p. 615
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| Abstract |
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A modified Hero's engine is used to illustrate concepts of thermodynamics and engineering design suitable for introductory chemistry courses and more advanced physical chemistry courses. The engine is a boiler made of Pyrex with two off-center nozzles. Upon boiling, the vapor exits the nozzles, creating two opposite, off-center forces that result in a circular motion by the engine around the vertical axis. The engine is suspended from a horizontal bar by means of two parallel threads. The rotation of the engine results in the twisting of the threads, with two important effects: the engine is raised vertically, and potential energy is stored in the coiling of the threads. When the engine is raised, it is removed from the heating source. This stops the boiling. The stored potential energy is then released into kinetic energy; that is, the threads uncoil, and the engine rotates in the opposite direction. This lowers the engine into the flame, so the water resumes boiling and the engine can be raised again. This cycle continues until all the liquid water is vaporized. This demonstration is suitable to illustrate concepts like gas expansion, gas cooling through expansion (Joule-Thompson experiment), conversion of heat to work, interconversion between kinetic energy and potential energy, and feedback mechanisms.
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| More Information |
 Citation |
Muiño, Pedro L.; Hodgson, James R. J. Chem. Educ. 2000 77 615.
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Keywords |
Chemical Engineering; Demonstrations; Gases; Physical Chemistry; Thermodynamics; Teaching / Learning Aids
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History |
Created:
Last Updated: |
March 31, 2000
April 15, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
2000
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May
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615
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