Aerothermal Propulsion

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Aerothermal Propulsion

• Lecture 2
• Thermodynamics of Flows

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Agenda

• 2nd law of Thermodynamics
• Application To Flows
• Adiabatic Processes

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1st law of Thermodynamics
dE dQ PdV Changes in Energy consist of both
heat dQ addition and work PdV on surroundings
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2nd law of Thermodynamics
dS dQ/T Changes in Entropy consist of heat dQ
transfer at a given temperature (reversible) or
to a lower temperature ( irreversible) Entropy is
tendency of universe to disorder, mixing ,
friction, and uniformity
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2nd law of Thermodynamics
TdS dQ dETdS-PdV dHTdSdPV Entropy cannot
change without a transfer of heat dQ
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Entropy Increase
dQ
T20,000K
T3K rest of universe
Everything useful results from entropy increase
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Ideal Gas Law
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Specific Heats
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Adiabatic Process
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Adiabatic Process
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Adiabatic Process
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Adiabatic Process
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Adiabatic Process
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T vs S graphs
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Adiabatic Process

• Adiabatic processes are the ideal limit of
  compression or expansion processes in flows
• Processes occur so rapidly that heat transfer
  cannot occur
• Non ideal processes in gases lead to ??5/3