Question about Otto Cycle: Why Does Compression Increase Temperature?

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SUMMARY

The discussion centers on the Otto Cycle and the relationship between compression and temperature increase during isentropic compression. It is established that during isentropic compression, the volume decreases and pressure increases, leading to a rise in temperature due to the principles of thermodynamics. Specifically, the internal energy of an ideal gas is directly proportional to its temperature, and when no heat is added (Q=0), positive external work (compression) results in an increase in internal energy, thereby raising the temperature. The equation for change in internal energy, ΔU = Q + W, is critical in understanding this phenomenon.

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  • Understanding of the Otto Cycle and its thermodynamic processes
  • Familiarity with the ideal gas law (PV = nRT)
  • Knowledge of internal energy and its relation to temperature
  • Basic principles of thermodynamics, particularly isentropic processes
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Students and professionals in mechanical engineering, automotive engineering, and thermodynamics who seek to deepen their understanding of the Otto Cycle and the effects of compression on temperature in gas systems.

kamranonline
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I have a general question about otto cycle. If we heat a gas with constant volume its temperature rise according to PV=mRT. However during Isentropic compression(delta Q and delta S is zero), the volume is becoming less and pressure is increasing but i don't know why the temperature should increase during this process. According to the above equation the temperature can increase or decrease but i don't know why it always increases..
 
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The internal energy of an ideal gas is proportional to its temperature. The change of internal energy in a process is

\Delta U = Q + W

where Q is the heat gained from the surroundings and W is the work of the external forces.
When Q =0, a positive external work (compression) will increase the internal energy, so the temperature will increase, too.

ehild
 
Thanks a lot... failed to think from internal energy's perspective.
 

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