Le21 - ME 200: Thermodynamics I Lecture 21: Introducing the...

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ME 200: Thermodynamics I Lecture 21: Introducing the 2 nd Law, irreversibilities Reading: Sections 5.1-5.4; SP21, 5.3, 5.8 10/15/2010 1 ME200 Therm I Lecture 21, Prof. Mongia Professor Hukam Mongia Office Hours: MWF 9:30 to 10:30 AM in ME 83 Other times email for appointment; Phone: 765-494-5640 Course Website: https://engineering.purdue.edu/ME200/ Course Secretaries: Diana Akers (ME 84) and Marilyn Morrison (ME 100) Grader: Abhro Pal , abhro.pal@gmail.com
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10/15/2010 ME200 Therm I Lecture 21, Prof. Mongia 2 First law of thermodynamics States conservation of energy principle when transforming one form of energy into other Considers only change in energy (or quantity ) in such transformations Why Second Law? Second law of thermodynamics (considers quality ) 1. Predicting direction of processes 2. Establishing conditions for equilibrium 3. Best theoretical performance of cycle, engines, devices 4. Factors that preclude the attainment of best theoretical performance 5. Defining temperature scale independent of the properties --- 6. Calculating properties (u, h, ---) in terms of easily measurable properties (e.g., temperature, pressure).
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10/15/2010 3 Source: http://www.grc.nasa.gov/WWW/K-12/airplane/drag1.html We use indirectly the 2 nd Law in ‘every thing’ we do
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Source: http://www.grc.nasa.gov/WWW/K-12/airplane/presar.html During steady-state flight with no change in altitude and speed, and no drag (ideal case) 10/15/2010 4 ME200 Therm I Lecture 21, Prof. Mongia Drag Power Drag xVelocityisdissipated asQ
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10/15/2010 FUEL SAVINGS & AERODYNAMIC DRAG REDUCTION FROM RAIL CAR COVERS Bruce Storms, NASA Ames Research Center Kambiz Salari, Lawrence Livermore National Laboratory Alex Babb, University of California Los Angeles Cars measure approximately 3 m wide, 3.4 m high, and 14.6 m long with a gap between cars of 1.7 m. Stodolsky , F., 2002, “Railroad and Locomotive Technology Roadmap,” Argonne National Laboratory, Argonne, IL. DOE’s Effort to Reduce Truck Aerodynamic Drag through Joint Experiments and Computations by Rose McCallen, 2006 / ? Drag amb Will Q T provide moreinsight Drag reduction ~43% Round-trip fuel savings ~9% 5 ME200 Therm I Lecture 21, Prof. Mongia
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10/15/2010 6 Cooling down of a hot body in a room How do I do it?
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This note was uploaded on 01/13/2011 for the course ME 200 taught by Professor Gal during the Fall '08 term at Purdue University-West Lafayette.

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Le21 - ME 200: Thermodynamics I Lecture 21: Introducing the...

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