Adiabatic Definition and 498 Threads

In thermodynamics, an adiabatic process (from the Greek adiábatos, meaning “impassable”) is a type of thermodynamic process which occurs without transferring heat or mass between the system and its surroundings. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work. It also conceptually supports the theory used to explain the first law of thermodynamics and is therefore a key thermodynamic concept.
Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings.
In meteorology and oceanography, adiabatic cooling produces condensation of moisture or salinity, oversaturating the parcel. Therefore, the excess must be removed. There, the process becomes a pseudo-adiabatic process whereby the liquid water or salt that condenses is assumed to be removed upon formation by idealized instantaneous precipitation. The pseudoadiabatic process is only defined for expansion because a compressed parcel becomes warmer and remains undersaturated.

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  1. kelvin490

    Why dU may not equals dW in free expansion?

    From a video lecture, it is mentioned that "dU≠dW in Joule's free expansion if the process is irreversible and adiabatic" Mentioned in around 36:00-38:00 in the video: What I would like to ask is why in this irreversible adiabatic process, dU≠dW? Is it because the W here doesn't include other...
  2. S

    Adiabatic Free Expansion and Reversible Isothermal Path

    Homework Statement Consider an ideal monatomic gas that undergoes an adiabatic free expansion starting from equilibrium state A with volume 500 cm3, pressure 40 kPa and temperature 300K to state B, which has a final equilibrium volume of 1000 cm3. Construct an reversible isothermal path that...
  3. O

    Why does the total temperature not change in adiabatic flow?

    Hi guys, I have a question to you that has been bothering me for a while now. It is about adiabatic flow in a duct or more specifically in the air intake of a jet engine. In lectures and textbooks it is always stated that the total temperature in an adiabatic flow does not change. Hence the...
  4. T

    Relation between adiabatic approximation and imaginary time

    Regarding interacting green's function, I found two different description: 1. usually in QFT: <\Omega|T\{ABC\}|\Omega>=\lim\limits_{T \to \infty(1-i\epsilon)}\frac{<0|T\{A_IB_I U(-T,T)\}|0>}{<0|T\{U(-T,T)\}|0>} 2. usually in quantum many body systems...
  5. E

    Calculating Adiabatic Cooling at 1000 Meters Using Atmospheric Law

    Homework Statement A pocket of air rises 1000 meters. Estimate how much it cools. Use the atmospheric law to determine pressure at 1000 meters. Homework Equations P = P0 * e-Mgz/RT PVγ = constant TVγ-1 = constant The Attempt at a Solution Using the atmospheric law, I found the pressure at...
  6. R

    Irreversible adiabatic expansion in which P_ext=0

    Homework Statement In an adiabatic irreversible expansion of ideal gas , if Pext = 0 then which is true, A. T2=T1 B. Q=0, C. P1V1= P2V2 D. P1V1γ= P2V2γ Homework Equations ΔU = Q - W For ideal gas, PV= nRT[/B] ΔU ∝ ΔT The Attempt at a Solution I know Q= 0, Work done is zero, So ΔU = 0, hence...
  7. K

    Extended Surfaces (Fins) Adiabatic Tip

    Homework Statement Please see images - full problem statement given. Summary: I have to calculate TL for an adiabatic tip extended surface I found all the equations for points 1-6 but cannot figure out 7. Homework Equations 1st BC: θ(0) = Tb - T∝ 2nd BC: x=L The Attempt at a Solution If it is...
  8. S

    Is work done in adiabatic process quasi static or not?

    Is work done in adiabatic process quasi static or not?
  9. M

    Polish Physics Olympiad: Proving Adiabatic Reversible Process

    Homework Statement (56th Polish Olympiad in Physics, 2007) We have a tube of mass ##M##, consisting of two segments of diameters ##d_1, d_2##. The pistons (see the picture http://www.kgof.edu.pl/archiwum/56/of56-2-1-R.pdf) have mass ##m_1, m_2##. At the start the air inside had pressure...
  10. Y

    Adiabatic vs. Isocurvature cosmological perturbations

    Dear everyone, Now, I'm reading some papers on the "Curvaton Mechanism"(eg.http://arxiv.org/abs/hep-ph/0110002v2 as the original literature.) Here I have some confusion on this topic. (1) Why the primordial perturbation of curvaton field is initially isocurvature-type? When the inflation driven...
  11. I

    Calculating the End Temperature of Adiabatic Compression for an Ideal Gas

    Homework Statement Air is compressed at room temperature from atmospheric pressure to ##\frac{1}{15}## of the initial volume. Calculate the temperature at the end of compression assuming the process is reversible and adiabatic.Homework Equations ##pV^\gamma = constant \Longleftrightarrow T...
  12. S

    Work done isothermal, adiabatic ideal gas

    Problem statement, work done, and relevant equations: One mole of ideal gas is initially at 1 atm and has a volume of 5L. a) Calculate the work done on the gas during an isothermal, reversible compression to a volume of 2L. ##W_isothermal = - \int_{v_i}^{v_f} p dv = - \int_{v_I}^{v_f}...
  13. S

    Thermodynamics adiabatic diffuser question

    An adiabatic diffuser is employed to decrease the velocity of an airstream from 220 to 30 m/s. The air enters the diffuser at a rate of 8 kg/s with a temperature of 300c and a pressure of 100kpa. Determine the exit area of the diffuser if the exit pressure is 125kpa. Answer is 0.37 m^2 Guys I...
  14. B

    What Changes During Free Adiabatic Expansion of a Real Gas?

    Homework Statement Which of the following changes during the free adiabatic expansion of a real gas? (I) internal energy (II) temperature (III) pressure Homework Equations PV=nRT; ΔU= q + w The Attempt at a Solution For ideal gases under adiabatic conditions, we know that there is no heat...
  15. R

    Adiabatic irreversible expansion

    This example is taken from the wikipedia page describing irreversible processes. I just want to make sure I understand correctly why the initial state can't be reached anymore. I assume the transitions to be quasi-static, but there is friction between the piston and the cylinder. If so...
  16. J

    Entropy increase in adiabatic irreversible compression

    Hi there, I was wondering if you could help me, I think I may have some concepts wrong or incomplete. Homework Statement We have an adiabatic cylinder of volume ##V_1## filled with a gas of pressure ##p_1## and temperature ##T_1## in thermal equilibrium, closed with a piston. All of a suden...
  17. W

    Need clarification on adiabatic process and heat capacity

    In class we're currently learning about reversible and irreversible adiabatic processes. For reversible process, we got dq=0, so dU = dw = -P*dV = Cv*dT. What I don't get is where did the Cv*dT come from? I remember q=C*dT, but dq = 0 so I'm not sure what that means? Also, where does Cv*dT...
  18. L

    Reversible adiabatic expansion proof

    Homework Statement Prove the relationship between the pressure, P, and the temperature, T, for an ideal gas with a reversible adiabatic expansion. Base the proof on the first law of thermodynamics and the ideal gas law. The relationship is: T^(Cp,m/R)/P = constant Where R is the gas constant...
  19. C

    Should Adiabatic Work Include VdP?

    My textbook says, basically, for an adiabatic process... All three variables in the ideal gas law—P, V, and T—change during an adiabatic process. Let’s imagine an adiabatic gas process involving an infinitesimal change in volume dV and an accompanying infinitesimal change in temperature dT. The...
  20. F

    Adiabatic Process in cloud Formation

    I am going to report about Adiabatic process, specifically in cloud formation. Can someone help me some important points to consider?Im more concerned in cloud formation only since my topic is limited in that matter. 1. What is the science behind the adiabatic process in clouds? 2. Some...
  21. E

    Work done by product gas in reversible adiabatic expansion

    I am having trouble calculating the work done by a product gas in reversible adiabatic expansion, and in calculating the final temperature. pV gamma = constant, Cv = constant (assume), gamma = cv + nR / Cv. anyone who can help me out?
  22. L

    Adiabatic condition and equation of state

    Homework Statement 8.02 × 10−1 moles of nitrogen gas ( γ= 1.40) is contained in a volume of 2.00 × 10−2 m3 at a pressure of 1.00 × 105 Pa and temperature of 300 K. The sample is adiabatically compressed to half its original volume. IT behaves as an ideal gas. (i) What is the change in...
  23. S

    Are "isentropic" and "adiabatic" same?

    Isentropic means a process where entropy remains constant. Now formula for entropy is ΔS = ΔQ/T now in an isentropic process, ΔS=0...so that means ΔQ = 0 ...right? but if ΔQ = 0, that is an adiabatic process. so are isentropic and adiabatic processes are...
  24. K

    Adiabatic Process | Plotting V-P Diagram

    Homework Statement A gas of volume 1400[liter] and pressure 2.33[atm] expands in an adiabatic process to 2240[liter] and 1.2[atm]. plot the process on a V-P diagram. I shorten the question, only this interests me. the number of moles is given. Homework Equations Equation of state: ##PV=nRT##...
  25. D

    Is the universe an adiabatic system?

    Hello everyone, I wanted to ask you if the universe is an adiabatic system where the energy it can't be transmited outside itself. If is an adiabatic system, what happened with the information and energy inside a black hole? How the universe started with a 0 entropy state? Could be the...
  26. mukul

    Adiabatic effusion and violation of energy conservation

    when the gas effuse out of an insulated container, its velocity is given by \sqrt{\frac{2\gamma RT}{(\gamma-1)M}} (irodov's problem 2.42) This leads to the result that every mole of leaking gas has an energy of \frac{\gamma RT}{(\gamma-1)} whereas we know the energy contained in 1 mole of gas...
  27. S

    Adiabatic Lapse Rate Explained: Work, Energy, & Temperature

    I Think I understand this, but when I look it up, I keep reading about work done and energy used, which puzzles me. The simple way I have always thought about it is, when you expand a gas you also expand the heat it contains, so while it contains the same amount of heat, it's concentration...
  28. A

    Why are isothermal process values higher than adiabatic ones?

    why are isothermal process values higher than adiabatic process ones? I know that the volume is powered by gama in adiabatic process ones, and this has an effect. but how can I explain it ?! http://www.popsolving.com/Thermodynamics/Problem2.4_Freebody.jpg
  29. A

    Adiabatic process of monatomic gas problem

    Homework Statement By how much does the temperature of an ideal monatomic gas change in an adiabatic process in which 4.0kJ of work are done on each mole of gas? By how much does the temperature of an ideal diatomic gas (with molecular rotation but no vibration) change in an adiabatic process...
  30. MexChemE

    Exothermic reaction in adiabatic reactor

    Homework Statement One mole of gas A, two moles of gas B, and one mole of inert gas I are fed into an adiabatic reactor of variable volume and constant pressure at 25 °C. At this temperature, the reaction yielding liquid R proceeds normally as: \textrm{A} (g) + \textrm{B} (g) \rightarrow...
  31. AdityaDev

    Expansion of a Helium-Filled Balloon: Exploring Thermodynamic Processes

    If I heat a rubber balloon filled with helium slowly and if the balloon is fully expandable and (the balloon) can be assumed to require no energy in its expansion,what type of thermodynamic process is taking place? Is it isobaric? Since the balloon expands the pressure exerted by the gas on...
  32. I

    Restricting exhaust flow causing temperature increase?

    We have a situation. Someone modified the exhaust pipe from a diesel fired equipment. Exhaust gas flows out through a 30mm internal dia pipe. The modification carried out was to reduce the diameter of the pipe to 20 mm internal dia. The Exhaust outlet temperature from the equipment was 400 deg...
  33. MexChemE

    Adiabatic expansion against constant pressure

    Homework Statement a) For a certain ideal gas CP = 8.58 cal mol-1 K-1. We have 2 moles of said gas at 293.15 K and 15 atm. Calculate the final volume and temperature when the gas expands adiabatically and reversibly until it reaches a pressure of 5 atm. (Answers: V = 7.45 L; T = 227.15 K) b)...
  34. B

    Adiabatic Flame Temperature Calculation for Methane Combustion

    < Moderator Note -- Thread moved here to Homework Help forum > One volume of CH4 is mixed with V volumes of air (78 vol.% N2,21 vol.% O2,1 vol.% Ar) at 1 atm and 25°C; then the mixture is ignited. Find the temperature of adiabatic combustion (the adiabatic flame temperature). The volume of air...
  35. P

    Adiabatic evolution and floquet theorem

    Hello everybody, I'm trying to understand if is possible to say something about the Floquet exponents, in the limit of a very slow changing on time. I try to explain. Given the differential equation $$ \dot{\vec{v}}(t) = A(t) \vec{v}(t) $$ with $$ A(t+T)=A(t) $$ a monodromy matrix is given...
  36. K

    The first law of thermodynamics and the dry adiabatic lapse rate

    Say there is a parcel of air rising and cooling, what is going? Is it that the net kinetic energy (Temperature) of the parcel is distributed over the (new and larger) area/volume? Or Is it that the parcel is undertaking work as it presses outwards and so looses a corresponding amount of kinetic...
  37. T

    Books on adiabatic elimination

    Hi, What books/book chapters are good for learning adiabatic elimination in great depth? Thank you.
  38. J

    Adiabatic gas cooling/heating: Explaining Conceptually

    Hi, this is my first post on here. My question relates to adiabatic cooling/heating of a gas. I am trying to grasp the idea conceptually rather than being able to explain it mathematically per se... When gas escapes rapidly from a pressurised cylinder the rapid expansion of the gas is...
  39. S

    Frustrated with Adiabatic compression problem

    Homework Statement In a diesel engine air is adiabatically compressed to autoignition temperature (287oC) of diesel. Given C/nR=2.78 for air, and the room temperature is 27oC, what is the compression ratio where diesel vapor is added for ignition.Homework Equations PV=nRT PV=NkT C=(dU/dT) The...
  40. H

    How do I calculate adiabatic work done by a gas during expansion?

    Homework Statement Hi, I did a lab experiment where I took a 5L vessel made of some material that isolates gas inside and thus behaves like an isolated system (adiabatic). I then pumped gas from ~90kPa to up to 150 kPa... recorded the temperature, then let the gas 'expand' by opening the...
  41. M

    Non-uniform adiabatic gas compression

    I would like some insight on a problem I have been working on. I have a seal container of air where the outside chamber has a slight temperature differential between top and bottom. I understand this causes a density variation in the air between the top and bottom of the chamber. Now I am...
  42. le@rner

    Can Adiabatic Processes Be Irreversible?

    Please help me qualitatively in the following points : 1) If in a system(consider a cylinder) fixed with a piston , if the piston is moved suddenly then how can a process be adiabatic. 2) I understood that the process would be irreversible but, if the process is adiabatic then is the relation...
  43. M

    Exploring Adiabatic Experiments & dU Path Dependence

    (1) Exact form of U exists because of the results of experiments in adiabatic work, what are such experiments which gives proof for above statement? (2) Is differential of Internal energy dU path dependent?
  44. PhizKid

    How can adiabatic pressure variations be used to determine specific heat ratio?

    1. Homework Statement The following describes a method used to measure the specific heat ratio ##\gamma = c_p/c_V## of a gas. The gas, assumed ideal, is confined within a vertical cylindrical container and supports a freely moving piston of mass ##m##. The piston and cylinder both have the...
  45. J

    Calculating work done on a gas- Adiabatic process PV diagram.

    Homework Statement As per attachment. Part iii How would you do this question by integrating the work? Homework Equations W = - ∫P dV PV^gamma = constant The Attempt at a Solution So I integrated the work with P= constant/ V^gamma and came up with this: W = constant* (...
  46. S

    Discover the Gas with the Lowest Adiabatic Index at Room Temperature

    Hello, to the best of your knowledge, what is 1) the gas with the lowest adiabatic index ##\gamma=\frac{c_p}{c_v}## at room temperature 2) a very common, non-flammable, non-toxic gas with the lowest adiabatic index at room temperature Many thanks
  47. J

    Adiabatic, Isothermal and Isochoric Processes

    Homework Statement An ideal gas with Cv = (5/2)R, and Υ = 1.40 undergoes an adiabatic expansion until it has a pressure of 1.0*10^5 Pa and a volume of 2.0m^3. It then undergoes an isothermal contraction of T=300K until it has a volume of 1.0m^3, and then undergoes an isochoric (constant...
  48. R

    Entropy and Enthelpy for adiabatic process

    1) What is the reason why dH!=0 for an adiabatic(q=0) reversible process? The mathematical argument is irrefutable and it is clear that it has to do with the process not being isobaric: ΔH=ΔU+PΔV+VΔP , ΔU=work=−PΔV Therefore, ΔH=VΔP and this is not 0. However, I do not understand it...
  49. George Jones

    Meaning of "adiabatic" in Britain?

    I recently have discovered that the thermodynamics term "adiabatic" seem to be used slightly differently in Britain than it is in North America. What does "adiabatic" mean in Britain?
  50. N

    Why is entropy zero in an adiabatic process?

    No heat exchange is facilitated during an adiabatic process. Change is heat is zero. How does this relates to the entropy being zero? ∫dQ/T? But this could really just mean that the integral is of any constant.
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