What is Adiabatic: Definition and 494 Discussions

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. Entanglement

    Isothermal & adiabatic processes

    I'll start with what I know: when work is done on an ideal gas its internal energy increases and some of the work is used to increase the volume of the container if the walls are movable, and I know that when a gas does work its internal energy decreases by a value equivalent to F.d, I have...
  2. G

    Thermodynamics - Adiabatic Compression

    A monatomic ideal gas that is initially at a pressure of 1.60×105Pa and with a volume of 8.50×10−2m3 is compressed adiabatically to a volume of 4.00×10−2m3 A) What is the final pressure? - 5.63E5 B) How much work is done by the gas during the compression? C) What is the ratio of the...
  3. A

    Why adiabatic process is required in heat engine?

    what is the need of adibatic process in heat engine? We can work only with isothermal process .Please expalin this.
  4. gfd43tg

    Adiabatic Air Compressor: Calculating Shaft Work for Isentropic Process

    Homework Statement A small adiabatic air compressor is used to pump air into a 20-m3 insulated tank. The tank initially contains air at 25°C and 101.33 kPa, exactly the conditions at which air enters the compressor. The pumping process continues until the pressure in the tank reaches 1,000...
  5. C

    Entropy change in a irreversible adiabatic process

    One mole of an ideal monatomic gas initially at 298 k expands from 1.0 L to 10.0 L. Assume the expansion is irreversible, adiabatic, and no work is done. Calculate delta S of the gas and delta S of the surroundings. I know that delta dS = dq/T but q = 0 in adiabatic processes right? So does dS...
  6. G

    The ideal gas law for an adiabatic process

    Homework Statement Hi can someone please have a look at this question and let me know if I am on the right track, thanks. A diesel engine requires no spark plug; instead the air in the cylinder is compresses so highly the fuel ignites spontaneously on injection to the cylinder. Q. If the air...
  7. M

    Adiabatic expansion with temperature dependent heat capacity.

    Homework Statement 1 mole of an ideal gas initially at 100° C and 10 atm is expanded adiabatically against a constant pressure of 5 atm until equilibrium is re-established. Given that the temperature dependence of the heat capacity is CV = 18.83 + 0.0209T calculate deltaU, deltaH and deltaS...
  8. H

    Ideal diatomic gas undergoing adiabatic compression

    Homework Statement A very simple question, but I can't figure it out. An ideal diatomic gas, with rotation but no oscillation, undergoes an adiabatic compression. Its initial pressure and volume are 1.20 atm and 0.200 m^3. Its final pressure is 3.60 atm. How much work is done by the gas...
  9. K

    Thermodynamics- Work done- Adiabatic process

    I have a small doubt regarding the workdone derivation in adiabatic process. Here is the derivation W= (P1V1-P2V2) = mR(T1-T2)/n-1 AS we know R/n-1 = Cv and Cp/Cv=1 also considering m=1 W=Cv(T1-T2) but in textbook it is quoted as...
  10. B

    Thermal Physics Adiabatic Heating Problem

    Greetings all, My first post here on this forum. I'm currently revising for exams and have got stuck on a question where I'm not sure where I'm going wrong...Question: 1g of iron filings at 500 °C are inserted into a sealed 20 litre vessel containing 1 mol of an ideal monatomic gas at a...
  11. M

    Thermal Physics adiabatic and isothermal compressibilty

    Ok so I found something online but I need to understand this problem Prove that the ratio of the adiabatic compressibilty ks to the isothermal compressibility kr is equal to the ratio of the specific heat at constant colume, Cv, to that at constant pressure, Cp Definitions of the...
  12. T

    Thermodynamics Efficiency Of Adiabatic Compressor

    1. 100kg of methane is compressed from 0.5MPa and 300K to 3.0Mpa and 500K in a closed chamber by a compressor. The compression process is assumed to be adiabatic, calculate the efficiency of this compressor. Specific heat capacity of methane under constant pressure is 35.58 kJ/k.mol.K and ideal...
  13. B

    Does the Adiabatic Gas Equation Apply to Liquid Compression at High Pressures?

    Hi all, Hope you can help I am trying to figure out the temperature rise in a liquid subject to high pressures (7000bar in this case) Is the below adiabatic gas equation still suitable? or is there another way of working this out for liquids? T2 = T1(v1/v2)^y-1 P2 = P1(v1/v2)^y Were y =...
  14. M

    Quasi-static, adiabatic problem

    Two moles of a monatomic ideal gas are at a temperature of 0°C and a (dQ = 0) and quasi-static volume of 45 liters. The gas is expanded adiabatically until its temperature falls to - 50°C. What are its initial and final pressures and its final volume? I've been beating my head against a wall...
  15. M

    Decrease in pressure due to adiabatic expansion derivation?

    Homework Statement Show that \frac{dp}{p} =\frac{\gamma}{\gamma-1}\frac{dT}{T} if the decrease in pressure is due to an adiabatic expansion.Homework Equations Poisson equations: Pv^{\gamma} Tv^{\gamma - 1} Ideal Gas Law: Pv=R_{d}T, where R_{d} is the dry air gas constant. Hydrostatic...
  16. S

    Finding Final temp for Adiabatic process

    Homework Statement A nearly flat bicycle tire becomes noticeably warmer after it has been pumped up. Approximate this process as a reversible adiabatic compression. Assume the initial pressure and temperature of the air before it is put in the tire to be Pi = 1.00 bar and Tf 287K . The final...
  17. S

    How Do You Derive Irreversible Adiabatic Work Equations?

    Homework Statement So I came down with something and missed some class and am making it up from others notes which arent entirely clear plus the long weekend for turkey day and I am really hoping someone can help me make some sense of this... I am trying to come up with the derivations for...
  18. S

    C(v,m) vs C(p,m) and adiabatic, reversible work

    Homework Statement A sample of carbon dioxide, mass 2.45g, is allowed to expand reversible & adiabaticly from 500cm3 to 3.00 dm3 What is the work done by the gas Homework Equations dw=-pexdV du=dq+dw du=nCv,mdt The Attempt at a Solution At first i just wanted to say that because...
  19. H

    Adiabatic Expansion: Constant pressure and temperature

    I'm new to the forum, so please be kind. I was reading through my pchem textbook, and I noticed something. We're given the equation: ΔU = q + w For an adiabatic expansion, we're told that q = 0. Fair enough, no heat transfer. But when there is a constant T and change in V, my book...
  20. E

    Does the temperature return to its initial value in an adiabatic cycle?

    In an adiabatic compression/expansion cycle of an ideal gas, does the temperature return to its initial value after the cycle has completed? Or does it increase as the cycles continue?
  21. A

    Adiabatic Process: C_v ≠ 0 Despite dQ = 0

    The low is: dQ=dU+p dV but the specific heat to volumen (in a perfect gas) cte is: C_v = \frac{dQ}{dT} = \frac{dU}{dT} why if in adiabatic proces dQ=0, then C_v \neq 0 ?? http://en.wikipedia.org/wiki/Adiabatic_process#Ideal_gas_.28reversible_process.29
  22. C

    Work done by gas in adiabatic process

    In an adiabatic process PVγ=constant Now I thought the work done by an ideal gas in an adiabatic process was given by the equation here: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/adiab.html But while doing a GRE question the answer was given as PfVf - PiVi / 1 - γ Is this...
  23. S

    Adiabatic expansion, entropy change

    Homework Statement 1 mol of monoatomic ideal gas (temperature T1) is inside a cylinder with a moving piston (all are isolated). The initial external pressure on the piston is P1. at some point the external pressure is changed to (2/3)P1, the gas undergoes (irreversible) adiabatic expansion...
  24. B

    Properties of adiabatic process

    Hello Can we consider the sentence “Adiabatic process cannot decrease entropy” (found for example here) to be true in any circumstances ? Here I do not want to focus on any particular situation. Hence the system is not necessarily a (perfect) gas; the transformation is not necessarily...
  25. J

    What is the adiabatic flame temperature of methane and air combustion?

    Hi to all, I want to know the temperature after combustion of methane with air. How will i calculate it? Kindly inform me. Regards, Jaiganesh.S
  26. S

    Change in internal energy due to adiabatic expansion of ideal gas

    what is the change In internal energy of an ideal gas when it is expanded Adiabatically from (p °,v°) to ( p,v )? The relevant equations : dQ= dU+ pdv ; pV^ r = K (constant). r = Cp / Cv. Attempted solution : During adiabatic process dQ=0 ; p= k v ^ -r Th f r : du= -k v^ -rdv Integrating...
  27. djh101

    Irreversible Adiabatic Expansion (Physical Chemistry)

    Homework Statement Consider the adiabatic expansion of .553mol of an ideal monatomic gas with CV,m = 3R/2. The initial state is described by P = 6.25bar and T = 306K. Calculate the final temperature if the same gas undergoes an adiabatic expansion against an external pressure of P = 1.25bar to...
  28. E

    Adiabatic Compression: Pressure & Temperature Change

    I am thinking about the adibatic compression when the gas gets back to Th from Tc... My question is how the p and V gets same as the initial pressure and temperature... Can you prove it?
  29. C

    Is Conservation of Energy Sufficient for Deriving the Adiabatic Process?

    Most of the book using PV=nRT for PV^gamma constant for adiabatic process. However, please refer attachment, proving using conservation of energy will also make sense?
  30. T

    Adiabatic steam turbine - find the second law efficiency

    Homework Statement The Attempt at a Solution So pretty much for this question you want to find the actual work output of the turbine and the reversible work output. To find the reversible (theoretical) work output, you know that s2 = s1, so based on that information you can find what...
  31. T

    Find the max velocity of the steam in a steady-flow adiabatic nozzle

    Homework Statement http://i.imgur.com/4kztfIs.png The Attempt at a Solution According to the solution, the max velocity is when the entropy of state 1 is equal to the entropy at state 2. Why is this the case? My friend says it is because the system is isentropic but I am still very...
  32. T

    Passive Adiabatic Effect: Cold sky reflection on IR imagery.

    I am currently in training to become an analyst using thermal imagery. In the studies I have been introduced to cold sky reflection on thermal imagery, however the instructor explained it as a surface 'reflecting the cold from the sky' which, as far as I'm aware, doesn't fit with the second law...
  33. S

    Isothermal and Adiabatic Compression of a Solid

    Homework Statement A 200g cylinder of metallic copper is compressed isothermally and quasi-statically at 290K in a high-pressure cell. A) Find the change in internal energy of the copper when the pressure is increased from 0 to 12kbar. B) How much heat is exchanged with the surrounding fluid...
  34. T

    Isothermal and Adiabatic piston problems

    Homework Statement This is Problem 12.5 in Blundell's Thermal Physics book. Two Thermally insulated cylinders, A and B, of equal volume, both equipped with pistons, are connected by a valve. Initially A has its piston fully withdrawn and contains a perfect monatomic gas at temperature T...
  35. N

    Adiabatic piston/cylinder problem

    Homework Statement 1, 2, and 3 use the following information: a cylinder is closed at both ends and has adiabatic walls. It is divided into two compartments by a movable, frictionless, adiabatic piston. Initially the pressure, volume, and temperature on both sides are equal and given by P=10.0...
  36. S

    Determine initial and final temperatures, adiabatic expansion?

    Homework Statement A 3.25 mol sample of an ideal diatomic gas expands adiabatically from a volume of 0.1050 m^3 to 0.762 m^3. Initially the pressure was 1.00 atm Determine the initial and final temperatures Homework Equations PVγ= nRT The Attempt at a Solution To get the initial...
  37. N

    Is a Closed, Adiabatic Device Feasible For Work With Steam?

    2. A closed, adiabatic device claims to derive useful work by expanding 1 kg of steam from 500 C and 20 bar to 100 C and 1 bar. Do you believe this claim? Assume steam is a real fluid following the steam tables in Appendix A.III.
  38. F

    Adiabatic compression of ideal diatomic gas

    Homework Statement An ideal diatomic gas, with rotation but no oscillation, undergoes an adiabatic compression. Its initial pressure and volume are 1.9 atm and 0.30 m3. It's final pressure is 2.9 atm. How much work is done by the gas? P0 = 1.9 atm = 1.93e5 Pa V0 = 0.30 m3 P = 2.9 atm =...
  39. M

    Constant term in the adiabatic equation

    Hi there! I am working on a project that requires some idea of adiabatic processes. I know the basics of the said topic and I'm currently stuck with the reversible adiabatic equation PV^(gamma)=constant.. and want to know what is the constant term i.e. on what parameters it depends and what is...
  40. K

    Helium balloon problem adiabatic process

    Homework Statement A large research balloon containing 2000 m^3 of helium gas at 1.00 atm and a temperature of 15.0 celsius rises rapidly from ground level to an altitude at which the atmospheric pressure is only 0.900 atm (the figure (Figure 1) ). Assume the helium behaves like an ideal gas...
  41. H

    Thermodynamics of a adiabatic system with degrees of freedom

    In an adiabatic process 16 J of work are done on each mole of a gas. If the gas has 5 degrees of freedom, how much does its temperature change? Answer in terms of R I know the answer is 6.4/R (K), but don't quite sure understand the the theory or math behind it.
  42. S

    Adiabatic expansion; confusion

    Homework Statement We start with an ideal gas confined to half a container. Then, without heat flow, the gas flows into the other half as the partition is punctured. Find the new temperature after the expansion. Homework Equations Since there is no heat flow, I assume the process is...
  43. O

    Joule free adiabatic expansion dT=0?

    In that experiment , the internal energy is zero , volume increase , pressure of system decrease, then temperature will constant ? Thanks
  44. Z

    (THERMO) - Adiabatic Expansion - known P1, P2, and T1

    Question: in a bicycle pump the preasure increases from [p1 = 10^5] to [p2 = 30^5]. If the process is adiabatic ant the air starts at [T1 = 293 K], find the maximum temperature of the air in the pump. (Assuming air can be treated as an ideal gas) Attempt: So using the 1st Law and given...
  45. M

    Adiabatic gas Compression of Piston after Critical Point

    Hello there, Sorry, if there's a thread about this already. Let's say if i have Piston which is fully insulated because as mentioned, it is an adiabatic compression. The pressure will increase as the volume of decrease. But what really happened when the system is compressed over the...
  46. A

    Essentially comparison of isothermal and adiabatic transformations

    Homework Statement Two identical samples of ideal gas are initially at P1 and V1. The first sample undergoes an isothermal transformation to P2, V2 and second sample undergoes an adiabatic transformation to P3, V2. If P3<P2, is V2 higher or lower than V1? Explain Homework Equations...
  47. M

    How Does Adiabatic Expansion Affect an Ideal Gas in a Closed Cycle?

    Homework Statement A 4.00-L sample of a diatomic ideal gas with specific heat ratio 1.40, confined to a cylinder, is carried through a closed cycle. The gas is initially at 1.00 atm and at 300 K. First, its pressure is tripled under constant volume. Then, it expands adiabatically to its...
  48. M

    Specific heat capacity for adiabatic & isothermal process

    Can we define specific heat capacity for an adiabatic process ?? Would it always be zero since dQ is 0 for an adiabatic process? Also, can we define specific heat capacity for isothermal processes ? Would it be infinity in all cases? Just want to verify if I am thinking along the...
  49. M

    Heat capacities, adiabatic processes, etc

    I am confused why the heat capacity at constant pressure can be different from the heat capacity at constant volume. I am also having difficulties absorbing the material regarding the kinetic theory of gases, such as keeping all the ΔE_int changes with what processes etc. Why can adiabatic...
  50. T

    Explanation of Isothermal vs Adiabatic Cooling

    Hey all, I was wondering if someone could explain the difference between isothermal and adiabatic processes. I know that in isothermal process, there is no temperature change in the system, and in adiabatic process, there is no heat transfer. However, can someone explain to me what each one is...
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