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racctor

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- TL;DR Summary
- How can temperature be conserved while pressure drops in non adiabatic expansions/compressions?

Hello!

I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle we see that while the pressure drops to near surrounding levels the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How can energy enter the system that increases the temperature, but not the pressure? Or in other words, how can energy dissipate into kinetic energy of the gas but not increase the pressure?

I think the same problem occurs for me in the compression step of real heat pumps: If i add work to a real system to reach a certain pressure, how come the temperature of real systems is higher than in the ideal isentropic compression?

If we take into account that in those examples we experience some heat loss to the surroundings, wouldn't that just decrease the mechanical Work i can get out of the system, but since heat is lost, the temperature drop should be the same as the pressure drop?

Your help is very much appreciated

kind regards

I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle we see that while the pressure drops to near surrounding levels the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How can energy enter the system that increases the temperature, but not the pressure? Or in other words, how can energy dissipate into kinetic energy of the gas but not increase the pressure?

I think the same problem occurs for me in the compression step of real heat pumps: If i add work to a real system to reach a certain pressure, how come the temperature of real systems is higher than in the ideal isentropic compression?

If we take into account that in those examples we experience some heat loss to the surroundings, wouldn't that just decrease the mechanical Work i can get out of the system, but since heat is lost, the temperature drop should be the same as the pressure drop?

Your help is very much appreciated

kind regards