What is Isentropic: Definition and 57 Discussions

In thermodynamics, an isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no net transfer of heat or matter. Such an idealized process is useful in engineering as a model of and basis of comparison for real processes. This is idealized as reversible processes do not occur in reality; thinking of a process as both adiabatic and reversible would show that the initial and final entropies are the same, thus, the reason it is called isentropic (entropy does not change). Thermodynamic processes are named based on the effect they would have on the system (ex. isovolumetric: constant volume, isenthalpic: constant enthalpy). Even though in reality it is not necessarily possible to carry out an isentropic process, some may be approximated as such.
The word "isentropic" can be interpreted in another way, since its meaning is deducible from its etymology. It means a process in which the entropy of the system remains unchanged, as mentioned this requires the process to be both adiabatic and reversible. However, this could also occur in a system where the work done on the system includes friction internal to the system, and heat is withdrawn from the system in just the right amount to compensate for the internal friction, so as to leave the entropy unchanged. However, in relation to the universe, the entropy of the universe would increase as a result.

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  1. R

    Enthelpy and Isentropic compression/expansion

    In a certain thermodynamics textbook, specific work done by an isentropic compressor/pump in an ideal rankine cycles, is given by the following; Wpump = h2 - h1 Wpump = v(P2 - P1), where v = v1 When I carry out these two calculations between any two states, I get vastly different answers...
  2. bardia sepehrnia

    I How can a process be isentropic but not reversible or adiobatic?

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  3. bardia sepehrnia

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  4. yecko

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  5. WhiteWolf98

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  6. Kushwoho44

    I Isentropic Process, General Results for dU and dH

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  7. A

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  8. M

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  10. AGiantGolden49er

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  11. F

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  12. M

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  13. M

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  14. M

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  15. T

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  16. yangshi

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  17. jdawg

    Isentropic efficiency of a pump

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  18. y2j

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  19. AEGIS

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  20. mfig

    I Why do we see the claim that an isentropic process is adiabatic and reversible?

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  21. J

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  22. jdawg

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  23. Rumo

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  24. S

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  25. M

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  26. ajayguhan

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  27. B

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  28. S

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  29. Y

    Determination of the equation of isentropic processes

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  30. S

    Thermodynamics - Isentropic Compression

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  31. K

    Isentropic Nozzle Behavior Explanation

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  32. S

    Thermodynamics ( steam tables ) isentropic

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  33. J

    Isentropic Relations for Real Gas in Converging-Diverging nozzle

    Hello, I am looking at a problem concerning flow through a converging-diverging nozzle. The governing equations are relatively straight-forward for gasses that closely follow the ideal gas law. However I am looking at an unusual gas which is certainly not represented by the ideal gas...
  34. F

    Thermodynamic Properties; Isentropic Expansion

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  35. E

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  36. O

    Calculating quality of steam after isentropic expansion

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  37. R

    Need help with a tricky thermodynamics question involving isentropic efficiency

    Homework Statement An engine operates on an air cycle consisting of the following non-flow processes in succession: 1-2 isentropic compression from an initial state of 80 kPa, 27°C and the volume of 0.071 m 3 through the volume compression ratio of 17.75; 2-3 reversible heat...
  38. C

    Temperature change in an isentropic flow of an ideal gas

    I am a bit confused by the definition of an isentropic process in the flow of an ideal gas. isentropic implies reversible & adiabatic. for a process to be reversible, there are no losses to friction (viscosity in this case), for a process to be adiabatic, there is no heat transfer with...
  39. B

    Isentropic Effeciencies of steam turbines

    Hi, I'm have big problems calculating the Isentropic Effeciencies of steam turbines. There is a HP, IP and LP turbine in the system. I know the calculation is (h1 - h2)/(h1 - h2'), i have the temperatures and pressures in and out for the first two turbines so i can easily get h1 and h2 from the...
  40. J

    Thermodynamics: isentropic efficiency and ideal gas model

    Air at 1175 K, 8 bar enters a turbine operating at steady state and expands adiabatically to 1 bar. The isentropic turbine efficiency is 92%. Employing the ideal gas model with k=1.4 for the air, determine (a) the work developed by the turbine, in kJ per kg of air flowing, and (b) the...
  41. B

    Isentropic Specific Enthelpy HELP

    Hi guys, I'm struggling with some equations regarding the enthalpy change over a compressor in a vcc system. I'm currently working on a model for the whole system and I think I've got all equations except the one describing the enthalpy difference betweeen the inlet and outlet of the...
  42. R

    Can Realistic Assumptions Help Design an Efficient Air Acceleration System?

    I came up with my own design problem, after completing a refrigeration design problem on the completion of my thermo I class. My design problem is this: I want to accelerate air to 56m/s via a compressor and then a nozzle. I'm trying to do a cost analysis of how much power I would save if the...
  43. C

    Calculating Power Output of Isentropic Steam Turbine | Helpful Guide

    I know the answer is 6328kW, I just not sure on how the book came up with that answer. Can anyone help? An isentropic steam turbine processes 5 kg/s of steam at 4MPa,which is exhausted at 50 kPa and 100oC. 5% of this flow is diverted for feed water heating at 700kPa. Determine the power...
  44. S

    Calculate Work, Isentropic Head & Efficiency of a Centrifugal Gas Compressor

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  45. C

    Paradox in isentropic expansion? (statistical mechanics)

    If I have a container containing a liquid mixed with some other substance that has much a higher boiling point (i.e. water and salt). This liquid will be in equilibrium with its vapor (the salt vapor pressure is negligible). Now I quasi-statically adiabatically expand this vapor. Isentropic...
  46. kandelabr

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  47. N

    Isentropic Process and Reversible Process

    Hi all, Will like to check if my below thoughts are right: 1) For a totally reversible process, it has to be both internally and externally reversible. And the definition of externally reversible means heat transfer between a system and reservoir where the temperature are the same. 2)...
  48. J

    Isentropic efficiency vs polytropic efficiency of a gas turbine

    definition wise i got the difference between these two efficiencies. but in practice how does these two differ? i was referring to this book: Jet propulsion: a simple guide to the aerodynamics and thermodynamic design ... By N. A. Cumpsty he has mentioned this: "using polytropic...
  49. A

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    Homework Statement I have a system u =Av-2exp(s/R) N moles of this substance initially at T0 and P0 are expanded isentropically until the pressure is halved. What is the final temperature? Homework Equations du = \partialu\partials ds + \partialu\partialv dv du = Tds - Pdv...
  50. K

    Determine the isentropic efficiency of a turbine

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