In 1763 james watt was asked to repair a newcomen

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In 1763, James Watt was asked to repair a Newcomen steam engine. Watt’s discovery, a separate condenser , produced more efficient steam engine making him a very wealthy man . Eng. discoveries may precede theory by 100’s of years. Steam Engines
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13 Consider a frictionless weightless piston sitting as shown wedged between two stops, # 1 and #2. Heat is received from a reservoir at 100 o C and there is no heat sink. Note: Saturation vapor temperature at 1bar is 99.63 o C. The system is isolated from the surrounding except for interaction with the heat reservoir. It is not possible to achieve the state 3. See details on next slide. 1 kg water 1bar 1 1 kg water 1bar 2 1 kg water 1bar 3 1 2 100 w kJ 1 2 2522.15 kJ q kg Not Possible 2 3 100 , 0 cycle w kJ w 2 3 1334.31 kJ q kg Internally reversible? Externally irreversible?
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 14 From State 1 to 2 3 3 1 2 1 2 1 1 2 2 3 1 2 1 2 1 2 1 2 0.694 , 1.694 20 , 99.63 83.95 2506.1 100 (1.694 0.6940) 2506.1 83.95 1 100 2522.1 00 5 o o f g v m v m T C T C kJ u u kg kJ u u kg w kPa m w q q kJ kJ kg From State 2 to 3 3 3 3 3 3 3 2 2 3 3 2 3 0.694 1.0432 10 1.694 0.409, 1271.79 1271.79 2506. 100 1 10 0 1334.31 0 cycle v m x x x kJ x u kg q w kJ w kJ q kg I can’t reject heat from 99.63 o C to 100 o C hot temp. reservoir.
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10/15/2010 15 Thermal Reservoir W cycle 1 st Law of Thermodynamics: W cycle = Q cycle Q cycle Kelvin-Planck statement of the 2 nd Law It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of work to its surroundings while receiving energy by heat transfer from a single thermal reservoir W cycle ≤ 0 (single reservoir) Reversible system, W cycle =0, otherwise irreversible ME200 Therm I Lecture 21, Prof. Mongia
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 16 Equivalence of the Clausius and Kelvin-Planck Statements Cengel & Boles, 2011
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 17 Clausius’s first dispute was with Thomson Kelvin over a result of Joule that he had quoted in his 1850 papers. Clausius was insisting that a German not the Englishman, Joule was the first to establish the result. Clausius was dragged into a controversy on who proposed first the equivalence between heat and work- James Prescot Joule or Julius von Mayer ? Julius Robert von Mayer enunciated during 1841 one of the original statements of the conservation of energy: “Energy can be neither created nor destroyed.”
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 18 Perpetual Motion Machines violating the 2 nd Law Cengel & Boles, 2011
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 19 Perpetual Motion Machines violating the 1 st Law Cengel & Boles, 2011
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 20 Examples of irreversibilities 1. Heat transfer through a finite temperature difference 2. Unrestrained
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