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Heat Engines

Heat Engines. Rev. Robert Sterling and the “Air Engine”. History. R. Stirling minister of church of Scotland Prolific inventor entire life Suffered for the injuries of those in congregation. Invention by Need. 1816 patent for air engine Steam engines inefficient and prone to explosions

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Heat Engines

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  1. Heat Engines Rev. Robert Sterling and the “Air Engine”

  2. History • R. Stirling minister of church of Scotland • Prolific inventor entire life • Suffered for the injuries of those in congregation

  3. Invention by Need • 1816 patent for air engine • Steam engines inefficient and prone to explosions • Called air engines until 1940’s use of other gases

  4. How does it Work? • Sealed cylinder one side hot one side cold • Working gas is moved from hot side to cold side

  5. Two Piston Type • Space above piston heated continuously • Space above cool piston is continuously cooled

  6. Physics Phun • Hot gas expands on piston producing pressure (P= F/A) • Cold gas moves to cold side contracts • Two power pulses per revolution

  7. Model engine

  8. But is it Efficient? • Mid 1800’s Carnot determined maximum efficiency of heat engines • Temp hot side—Temp cold side Temp of hot side X 100 Equals maximum efficiency

  9. Carnot Cycle

  10. Efficiency • Stirling engines theoretically reach 100% • Practical examples reach 50% • Gasoline engines struggle to reach above 30%

  11. Why don’t I drive a Sterling Engine • Does not start instantly, requires extensive warm up • Identical problem occurs in fuel cells • Low fuel prices work against efficient engine that does not start instantly

  12. Used on SS (Swedish Subs)

  13. APU’s • Auxiliary power units for electrical generation on Yachts • Quiet, smooth power • Expensive

  14. Cryocoolers • Stirling engines are reversible • Heat in power out • Power in heat consumed • Extremely cold temp to 10° K

  15. Micro coolers • Manufactured in large numbers to cool infrared chips • Used to cool night vision devices • May have applications for space use

  16. Future? • Extensive research in Europe for efficiency advances • Application specific designs • Manufacturing methodology’s

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