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ENGINEERING THERMODYNAMICS

ENGINEERING THERMODYNAMICS. Dr. M.R.SWAMINATHAN Assistant Professor Internal Combustion Engineering Division Department of Mechanical Engineering ANNA UNIVERSITY CHENNAI-25. LIMITATIONS OF I LAW.

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ENGINEERING THERMODYNAMICS

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  1. ENGINEERING THERMODYNAMICS Dr. M.R.SWAMINATHAN Assistant Professor Internal Combustion Engineering Division Department of Mechanical Engineering ANNA UNIVERSITY CHENNAI-25.

  2. LIMITATIONS OF I LAW The first law of thermodynamics is simple, general, but does not constitute a complete theory because certain processes it permits do not occur in nature!

  3. Examples of processes which are not prohibited by the first law, but cannot happen in a real world. • Perfect machine • Transfer heat from cold to hot subject • Gas expansion

  4. IRREVERSIBLE PROCESSES A battery discharges through a resistor, releasing energy. The reverse process will not occur. Two gases, initially in separated adjoining chambers, will mix uniformly.

  5. A free expansion of gas (in Gay-Lussac-Joule experiment) Heat flows from a high temperature body to a low temperature reservoir in the absence of other effect

  6. STATEMENTS OF THE SECOND LAW OF THERMODYNAMICS: Kevin-Planck Statement: It is impossible to construct a device that operates in a cycle and produces no other effects than the performance of work and the exchange of heat with a single reservoir.

  7. Model Heat Engine Qhot= W+Qcold or Qhot-Qcold=W (what goes in must come out)

  8. II LAW OF THERMODYNAMICS

  9. EFFICIENCY OF HEAT ENGINE

  10. Even the most efficient heat engines reject almost one-half of the energy they receive as waste heat.

  11. It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work.

  12. Clausius Statement: It is impossible to construct a device that operates in a cycle and whose sole effect is to transfer heat from a cooler body to a hotter body.

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