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Illustrating thermodynamic concepts using a hero's engine
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Abstract
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.
Keywords (Audience):
High School / Introductory ChemistryKeywords (Domain):
Chemical EngineeringKeywords (Feature):
Tested DemonstrationsKeywords (Subject):
GasesCiting Articles
Citation data is made available by participants in CrossRef's Cited-by Linking service. For a more comprehensive list of citations to this article, users are encouraged to perform a search in SciFinder.
This article has been cited by 1 ACS Journal articles (1 most recent appear below).
Denitrification as a Model Chemical Process
Gordan GrguricJournal of Chemical Education2002 79 (2), 179Denitrification as a Model Chemical Process
Gordan GrguricJournal of Chemical Education2002 79 (2), 179Bacterial denitrification in seawater facilities such as aquaria and mariculture systems is a process particularly well suited for illustrating important concepts in chemistry to undergraduates. Students can gain firsthand experience related to these ...
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- Received: August 03, 2009
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