Mechanical Engineering - Thermodynamics - Discussion

There is a temperature difference during throttling process. Then how can we say that throttling process is isenthalpic procese?

See Irreversibility= T * (change in entropy).
Now for change in entropy we know.
S = dh- vdp
But dh = 0 ( for throttling)
Now (chng in entropy) = -Rln ( P2/P1).

As asked with an increase in pressure difference the change in entropy value decreases which implies that " Irreversibility" also decreases. U can take any value of P1 and P2 and check eg 2 bars and 5 bar diff 3.

Then 3 bar and 7 bar diff 4, notice then change in entropy is decreasing so Irreversibility decreases.

Throttling is a irreversible process. For example if steam is leakage from a pipeline. Here the heat transfer take place from pipeline to the surrounding, but there is no workdone here. That mean there is no chance to flow the steam in reverse in direction. Hence throttling process is said to be "Irreversible Process ".

Irreversible mean loss in availability due to friction. That is loss in available work done. When the pressure difference is more there is more in loss of work. That mean loss in available energy is decrease. So Irreversibility is Increases.

What is meant by irreversible process?

Throttling process is also irreversible flow process.

Throttling should be an irreversible flow process.

Throttling result in decreases pressure.

Throttling process cannot be irreversible.

Lesser the potential gradient lesser is the irreversibility of the process. For an infinitesimally less (limiting to zero) potential gradient, the process becomes reversible.