Lecture 21 PES Su annotated 2011

Lecture 21 PES Su annotated 2011 - ME 200: Thermodynamics I...

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Unformatted text preview: ME 200: Thermodynamics I Lecture 21: Second Law and Irreversibilities Prof. Sojka Summer 2011 7 July 2011M E 2002 In this Lecture We will: Introduce 2 nd Law concepts . Discuss thermal reservoirs . Introduce reversible and irreversible processes . Introductory Comments There are many standard examples to illustrate why the 2 nd Law is important : Spontaneous heating of a hot object in cooler surroundings never happens. Heating a resistorto generate electricity never happens. Transferring heat to a compressor blade will not cause it to rotate. 7 July 20113 ME 200 Introductory Comments We need to make use of the second bit of information that thermodynamics tells us: The 1 st Law gives the magnitude of the energy change. The 2 nd Law gives the direction of the energy change. 7 July 20114 ME 200 Introductory Comments We will find that questions about the direction of energy flow can be answered through use of a new property, entropy (S) , and the 2 nd Law. We will also learn that the Second Law provides information on desirability of energy. It also provides an upper limit on the energy efficiency of devices. July 7 20115 ME 200 Statements of the 2...
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This note was uploaded on 09/26/2011 for the course ME 200 taught by Professor Gal during the Summer '08 term at Purdue University-West Lafayette.

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Lecture 21 PES Su annotated 2011 - ME 200: Thermodynamics I...

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