Mis vahe on adiabaatilisel ja pöörduval adiabaatilisel protsessil?


Vastus 1:

Pööratavat ja adiabaatilist protsessi nimetatakse adiabaatiliseks pöörduvaks protsessiks. Adiabaatiline protsess on termodünaamiline protsess, kus puudub soojusülekanne. Mõiste "adiabaatiline" tähendab sõna otseses mõttes läbimatut või läbitungimatut.

Adiabaatilised süsteemid on soojusisolatsiooniga süsteemid, nii et need ei lase protsessi käigus välja ega lase kuumusel. Pööratav protsess on protsess, kus ülekantud soojuse kogus on otseselt võrdeline süsteemide entroopia muutusega. Kuna entroopia muutusi ei toimu, on ülekantud soojus null. Seega on see protsess adiabaatiline pöörduv protsess. Neid protsesse nimetatakse ka isoentroopilisteks protsessideks.

Soojusülekandega seotud protsessi nimetatakse diabaatiliseks protsessiks. Lisaks on isobatalist protsess adiabaatiline protsess, mis on pöördumatu. See protsess ei kata tööd. Adiabaatilises pöörduvas protsessis dQ = TdS = 0. See tähendab, et entroopia muutus on null. Arvestades, et adiabaatilises pöördumatus protsessis ei ole dQ = 0 võrdne TdS-iga (TdS> 0). Entroopia muutus on suurem kui null.


Vastus 2:
  • Inirreversibleprocessmoreworkhastobegivenorlessworkwouldbeobtainedcomparetoreversibleprocessbecauseofirreversibilities(suchasfriction,rapidexpansionofgasetc.).Reversibleandirreversibleprocessesareidentifiedbyatermwhichisknownasentropygeneration(Sgen).Entropygeneration([math]Sgen)[/math]istheentropygeneratedwithinthesystemboundarybecauseofirreversibilities.In irreversible process more work has to be given or less work would be obtained compare to reversible process because of irreversibilities (such as friction, rapid expansion of gas etc.).Reversible and irreversible processes are identified by a term which is known as entropy generation (S_{gen}). Entropy generation ([math]S_{gen})[/math] is the entropy generated within the system boundary because of irreversibilities.

Entroopia tasakaalu võrrand suletud süsteemis -

ΔSsystem=ΔQT+Sgen(1)\Delta S_{system} = \displaystyle \frac{\Delta Q}{T} + S_{gen} \ldots (1)

Nii saab iga suletud süsteemi jaoks entroopiat muuta soojusülekande ja entroopia genereerimise abil.

ΔQT=Entropychangedbyheattransfer\frac{\Delta Q}{T} = Entropy changed by heat transfer

Sgen=EntropygenerationinsidetheboundaryofthesystemS_{gen} = Entropy generation inside the boundary of the system

  • Soforanadiabaticsystem,ΔQ=0and1sttermineq(1)vanishes.Therefore,So for an adiabatic system, \Delta Q = 0 and 1st term in eq(1) vanishes. Therefore,

ΔSsystem=Sgen\Delta S_{system} = S_{gen}

AndforanyirreversibleprocessSgen>0.ThenAnd for any irreversible process S_{gen} \gt 0. Then-

adiabaatilise pöördumatu protsessi jaoks -

ΔSsystem>0\Delta S_{system} \gt 0

  • Butforreversibleadiabaticsystem,1sttermaswellas2ndtermvanish.Becauseforreversibleprocess(slowandfrictionlessprocess)Sgen=0andBut for reversible adiabatic system, 1st term as well as 2nd term vanish. Because for reversible process (slow and friction less process ) S_{gen} = 0 and

ΔSsystem=0(2)\Delta S_{system} = 0 \ldots (2)

Accordingtoeq(2)entropychangeiszeroinreversibleadiabaticprocesssoitisknownasIsentropicprocess.Butreverseisnottruei.eisentropicprocessisnotareversibleadiabaticprocess.Becauseentropygeneration(inirreversibleprocess)canbecompensatedbyentropyreductionduetoheattransferfromthesystem(ΔQ<0).According to eq(2) entropy change is zero in reversible adiabatic process so it is known as “Isentropic” process. But reverse is not true i.e isentropic process is not a reversible adiabatic process. Because entropy generation (in irreversible process) can be compensated by entropy reduction due to heat transfer from the system (\Delta Q < 0).

Niisiis, kui adiabaatiline protsess on pöörduv, siis on see isentroopiline protsess.


Vastus 3:
  • Inirreversibleprocessmoreworkhastobegivenorlessworkwouldbeobtainedcomparetoreversibleprocessbecauseofirreversibilities(suchasfriction,rapidexpansionofgasetc.).Reversibleandirreversibleprocessesareidentifiedbyatermwhichisknownasentropygeneration(Sgen).Entropygeneration([math]Sgen)[/math]istheentropygeneratedwithinthesystemboundarybecauseofirreversibilities.In irreversible process more work has to be given or less work would be obtained compare to reversible process because of irreversibilities (such as friction, rapid expansion of gas etc.).Reversible and irreversible processes are identified by a term which is known as entropy generation (S_{gen}). Entropy generation ([math]S_{gen})[/math] is the entropy generated within the system boundary because of irreversibilities.

Entroopia tasakaalu võrrand suletud süsteemis -

ΔSsystem=ΔQT+Sgen(1)\Delta S_{system} = \displaystyle \frac{\Delta Q}{T} + S_{gen} \ldots (1)

Nii saab iga suletud süsteemi jaoks entroopiat muuta soojusülekande ja entroopia genereerimise abil.

ΔQT=Entropychangedbyheattransfer\frac{\Delta Q}{T} = Entropy changed by heat transfer

Sgen=EntropygenerationinsidetheboundaryofthesystemS_{gen} = Entropy generation inside the boundary of the system

  • Soforanadiabaticsystem,ΔQ=0and1sttermineq(1)vanishes.Therefore,So for an adiabatic system, \Delta Q = 0 and 1st term in eq(1) vanishes. Therefore,

ΔSsystem=Sgen\Delta S_{system} = S_{gen}

AndforanyirreversibleprocessSgen>0.ThenAnd for any irreversible process S_{gen} \gt 0. Then-

adiabaatilise pöördumatu protsessi jaoks -

ΔSsystem>0\Delta S_{system} \gt 0

  • Butforreversibleadiabaticsystem,1sttermaswellas2ndtermvanish.Becauseforreversibleprocess(slowandfrictionlessprocess)Sgen=0andBut for reversible adiabatic system, 1st term as well as 2nd term vanish. Because for reversible process (slow and friction less process ) S_{gen} = 0 and

ΔSsystem=0(2)\Delta S_{system} = 0 \ldots (2)

Accordingtoeq(2)entropychangeiszeroinreversibleadiabaticprocesssoitisknownasIsentropicprocess.Butreverseisnottruei.eisentropicprocessisnotareversibleadiabaticprocess.Becauseentropygeneration(inirreversibleprocess)canbecompensatedbyentropyreductionduetoheattransferfromthesystem(ΔQ<0).According to eq(2) entropy change is zero in reversible adiabatic process so it is known as “Isentropic” process. But reverse is not true i.e isentropic process is not a reversible adiabatic process. Because entropy generation (in irreversible process) can be compensated by entropy reduction due to heat transfer from the system (\Delta Q < 0).

Niisiis, kui adiabaatiline protsess on pöörduv, siis on see isentroopiline protsess.