eml 3100 entropy and power cycles

# eml 3100 entropy and power cycles - Thermodynamics Entropy...

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1 Thermodynamics Entropy A thermodynamic property (like h, v, etc.) Entropy per unit mass is an intensive property and has units of kJ/kg K dS =( δ Q/T) int rev Can integrate this to get change in entropy. Note as with energy we concern ourselves with change and not the actual entropy.

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2 Thermodynamics Entropy Can be viewed as a measure of disorder or disorganization. Generating entropy is generating disorder. Efficient people lead low entropy lives. They are organized. They have a place for everything (minimum uncertainty). It takes minimum energy to find something.
3 Thermodynamics Entropy Friction, unrestrained expansion of gases, uncontrolled electron exchange (chemical reactions) result in entropy generation. In the real world entropy is always increasing. (Except for some of those biological things we mentioned before.)

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4 Thermodynamics Entropy In statistical thermo, S = k lnp (Boltzmann relationship) Where k = Boltzmann constant = 1.3806 x10 -23 J/K And p = thermodynamic probability, the total number of possible microscopic states of the system. Consider an expanding gas vs. a perfect crystal at 0 K.
5 Thermodynamics Entropy So what do we do with this entropy? Evaluate the availability to do work based on the source and sink conditions we have Evaluate the economics of process changes Simulate real world processes for analysis (e.g. turbines, compressors)

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6 Thermodynamics Entropy Specifically in this class, we will use entropy as a property. We will take the operation of a turbine, compressor or the process in a diesel or Otto cycle and assume the device behaves in an isentropic fashion (constant entropy across the device) much like we took a throttling valve and assumed its process was isenthalpic (constant enthalpy).
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## This note was uploaded on 09/05/2011 for the course EML 3100 taught by Professor Sherif during the Summer '08 term at University of Florida.

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eml 3100 entropy and power cycles - Thermodynamics Entropy...

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