Ideal Gas Processes and Polytropic Variants
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Questions and Answers

Which of the following best describes external irreversibility?

  • Irreversibility associated with temperature differences during heat transfer.
  • Irreversibility due to interactions with external forces or environments. (correct)
  • Irreversibility resulting from the compression of gases.
  • Irreversibility caused by fluid friction within the system.

Which condition is NOT required for a process to be considered reversible?

  • No fluid friction affecting the system.
  • No mechanical friction present.
  • A constant temperature difference during heat transfer. (correct)
  • Processes controlled through a series of equilibrium states.

In a constant volume process, which of the following properties remains unchanged?

  • Pressure
  • Specific volume (correct)
  • Temperature
  • Density

What contributes to internal irreversibility in thermodynamic systems?

<p>Presence of fluid friction and mixing effects within the system. (D)</p> Signup and view all the answers

Which of these processes do NOT represent a means of energy transfer?

<p>Allowing heat to flow through an insulated system (C)</p> Signup and view all the answers

What is the relationship between change in enthalpy and change in temperature in an isobaric process?

<p>∆H = mCp∆T (A)</p> Signup and view all the answers

In an isobaric process, the work done in a non-flow case is expressed as which of the following?

<p>Wnf = P∆V (B)</p> Signup and view all the answers

What indicates that a process is isobaric?

<p>Pressure remains constant (A)</p> Signup and view all the answers

How is work defined under steady-flow conditions?

<p>W = -∆PE - ∆KE - ∆PV (B)</p> Signup and view all the answers

In an ideal gas process at constant pressure, what is the work done represented in terms of temperature change?

<p>W = mR∆T (B)</p> Signup and view all the answers

What does the change in entropy formula depend on in an isobaric process?

<p>Heat added and temperature change (B)</p> Signup and view all the answers

For a perfect gas undergoing an isobaric process, if the initial temperature is 100℉, what is required to find the final temperature?

<p>The change in enthalpy (A)</p> Signup and view all the answers

What does the equation ∆U = mCv∆T represent?

<p>Change in internal energy (B)</p> Signup and view all the answers

What is the relationship between pressure and temperature during an isometric process?

<p>Pressure and temperature are directly proportional. (C)</p> Signup and view all the answers

Which equation correctly describes the change in enthalpy for an isometric process?

<p>∆H = mCp∆T (C)</p> Signup and view all the answers

In an isometric process, what is the value of work done for a non-flow process?

<p>Work done is zero. (C)</p> Signup and view all the answers

What does the equation W = -ΔPE - ΔKE - ΔPV imply for an isometric process?

<p>It assumes negligible changes in kinetic and potential energy. (A)</p> Signup and view all the answers

How is the change in entropy calculated for a gas during an isometric process?

<p>∆S = mCvln(T2/T1) (D)</p> Signup and view all the answers

What does the ideal gas equation PV = mRT imply for isometric conditions?

<p>Volume remains constant while pressure changes. (A)</p> Signup and view all the answers

If no heat is transferred in an isometric process, how is internal energy related to work?

<p>Work done is equal to the change in internal energy. (D)</p> Signup and view all the answers

What characterizes an isobaric process?

<p>Pressure remains constant throughout the process. (D)</p> Signup and view all the answers

In an isometric process, how is work defined in relation to pressure change?

<p>W = -V∆P (C)</p> Signup and view all the answers

What effect does adding heat have in an isometric process?

<p>It changes temperature without changing volume. (D)</p> Signup and view all the answers

Flashcards

Isobaric Process

A thermodynamic process occurring at a constant pressure.

Change in Enthalpy (∆H)

The heat added or removed during an isobaric process. It's equal to mCpΔT, where m is the mass, Cp is the specific heat at constant pressure, and ΔT is the change in temperature.

Change in Internal Energy (∆U)

The change in internal energy, equal to mCvΔT, where m is the mass, Cv is the specific heat at constant volume, and ΔT is the change in temperature.

Work (Non-Flow)

Calculated as W = ∫PdV where P is pressure and V is volume. For an isobaric process, where P is constant, this simplifies to W = PΔV.

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Isobaric Process (PV-T Relation)

For an ideal gas, at constant pressure: (V1 / T1) = (V2 / T2) .

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Work (Steady-Flow)

In steady-flow conditions, steady isobaric work is zero (W=0).

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Change in Entropy (∆S)

Change in entropy equals heat over change in temp (i.e., Q/ΔT). For an ideal gas at constant pressure, it equals mCv * ln(V2/V1).

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Ideal Gas Equation

The relationship between pressure (P), volume (V), mass (m), ideal gas constant (R), and temperature (T) for an ideal gas: PV = mRT.

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Ideal Gas Process

A process where energy transfer (heating/cooling, compression/expansion) depends on both the process itself and the initial/final states.

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External Irreversibility

Irreversibility (loss of efficiency) that occurs outside the system, like friction in moving parts.

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Constant Volume Process (Isometric)

A process where the specific volume and density remain constant; volume is fixed/incompressible.

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Reversibility Conditions

Conditions for a process to be considered reversible: equilibrium states (no friction), no temperature differences during heat transfer, and no diffusion.

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Internal Irreversibility

Irreversibility caused by fluid friction within the system, or by internal events (e.g., mixing gases), which are irreversible themselves.

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PV-T relation (isometric)

In an isometric process, the ratio of initial pressure and temperature equals the ratio of final pressure and temperature.

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Internal Energy (isometric)

Change in internal energy (∆U) is directly proportional to the change in temperature (∆T) and specific heat at constant volume (Cv).

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Enthalpy (isometric)

Change in enthalpy (∆H) is directly proportional to the change in temperature (∆T) and specific heat at constant pressure (Cp).

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Non-flow work (isometric)

Non-flow work in an isometric process is zero (W = 0).

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Steady-flow work (isometric)

Steady-flow work in an isometric process is determined by subtracting the changes in potential energy, kinetic energy, and pressure-volume.

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Change in Entropy (isometric)

Change in entropy is calculated using specific heat at constant volume and the initial and final pressure.

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Constant Volume Process

A thermodynamic process in which the volume remains constant.

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Study Notes

Ideal Gas Processes

  • Thermodynamics processes involve energy transfer, like heating/cooling, compression/expansion, stirring/pumping
  • Energy transfer amount depends on the process and final/initial states (properties)

Special Cases of Polytropic Process

  • Isometric: Constant volume, PVn = C
  • Isobaric: Constant pressure, PVn = C
  • Isothermal: Constant temperature, PVn = C
  • Isentropic: Constant entropy, PVn = C
  • Special Polytropic (1 < n < k), PVn = C

External Irreversibility

  • Irreversibility external to the system, such as friction on moving parts (pistons, cylinders), friction between atmosphere and rotating members.
  • Heat flow through containing walls is also a form of external irreversibility (adiabatic wall is theoretical)

Internal Irreversibility

  • Irreversibility caused by fluid friction within a system.
  • Internal events like mixing or diffusion of multiple gases (e.g., turbulence, whirlpools, eddies) are irreversible.

Constant Volume Process (Isometric)

  • Process occurs under incompressibility constraints
  • Specific volume and density remain constant
  • PV/T = C if V = constant

Isometric Process (Detailed)

  • PV-T relation: PV/T = C, if V is constant
  • Change in Internal Energy: ΔU = mCvΔT
  • Change in Enthalpy: ΔH = mCpΔT
  • Non-flow Work: Wnf = 0
  • Steady-flow Work: Wsf = -ΔPE - ΔKE - ΔPV
  • Change in Entropy: ΔS = mCvln(T2/T1) = mCvln(P2/P1)

Constant Pressure Process (Isobaric)

  • Process where pressure remains constant
  • Can be reversible or irreversible, non-flow or steady-flow
  • PV/T = C if P is constant
  • PV-T relation: PV/T = C, if P is constant; V1/T1 = V2/T2
  • Change in Internal Energy: ΔU = mCvΔT
  • Change in Enthalpy: ΔH = mCpΔT
  • Non-flow Work: Wnf = PΔV
  • Steady-flow Work: Wsf = -ΔPE - ΔKE - ΔPV; Wsf = -VΔP or Wsf = 0 if pressure is constant
  • Change in Entropy: ΔS = mCpln(T2/T1) = mCpln(V2/V1)

Problems (Example)

  • Problems involving perfect gases, values for R and k, heat transfer at constant volume/pressure, finding final temperature, enthalpy, entropy, internal energy, and work. (Specific details are provided in the included problem statements).

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Description

Explore the principles of ideal gas processes, including various thermodynamic methods such as isometric, isobaric, isothermal, and isentropic processes. This quiz will also cover concepts of external and internal irreversibility in thermodynamic systems. Test your understanding of these critical concepts in thermodynamics!

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