What is Compressibility: Definition and 59 Discussions

In thermodynamics and fluid mechanics, the compressibility (also known as the coefficient of compressibility or, if the temperature is held constant, the isothermal compressibility) is a measure of the relative volume change of a fluid or solid as a response to a pressure (or mean stress) change. In its simple form, the compressibility



κ


{\displaystyle \kappa }
(denoted β in some fields) may be expressed as




κ
=



1
V






V



p





{\displaystyle \kappa =-{\frac {1}{V}}{\frac {\partial V}{\partial p}}}
,where V is volume and p is pressure. The choice to define compressibility as the negative of the fraction makes compressibility positive in the (usual) case that an increase in pressure induces a reduction in volume. The reciprocal of compressibility at fixed temperature is called the isothermal bulk modulus.

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  1. N

    [Thermo] Derivation of compressibility factor vs reduced pressure

    Homework Statement derivation of compressibility factor vs. reduced pressure I am supposed to derive the graph by solving equations Homework Equations Van der Waals equation of state compressibility factor, Z = (Pv)/(RT) reduced pressure = P/critical pressure Z = f(Tr, Pr) The...
  2. P

    Coefficients of expansion and compressibility

    Homework Statement I need to derive the following relation: \alpha_{S}=\alpha_{P}\frac{1}{1-\frac{\kappa_{T}}{\kappa_{S}}} Homework Equations Hopefully you can see that my notation |P means at constant pressure, I could not find a better way to do this, any ideas...
  3. B

    Why water compressibility is neglicable

    can anyone help me to have simple definition for compressibility and oil compressibility and why water compressibility is neglicable and for synthetic oils what is the effect of compressibilit on them compared to wter and diesel
  4. F

    Oil Compressibility - Bulk Modulus of Oil (API 30-40) 0-3000 psi & 10-20°C

    Could anybody provide information on the bulk modulus of oil (say API Gravity 30-40) in the range of pressure 0-3000 psi and in the range of temperature 10-20 degrees C? Many thanks Filippo Librino
  5. F

    What is the Compressibility of Diesel Fuel at 10 Degrees Celsius?

    Could anybody advise the compressibility of Diesel fuel at 10 degrees Celsius? Thanks Filippo
  6. S

    Compressibility and divergence-free flow

    Hi there, I'd like to know if, under the conditions of thermal flows (viscous, conductive) and low Mach numbers (< 0.3), it is formally/conceptually correct to affirm that "non-divergence is only necessary condition for incompressibility" Thank you very much in advance S.
  7. T

    How Does Piston Movement Affect Gas Compression in a Cylinder?

    Here is my problem: A cylinder with 0.4m radius and 0.5m depth is filled with air at 20C and 1atm. A 20.0 kg piston is lowered into the cylinder, compressing the air inside. Finally a 75 kg man stands on the piston further compressing the air which remains at 20C. how far down does the...
  8. T

    What is the compressibility module and why is it important in fluid mechanics?

    Hello everyone ! I'm currently working on a problem in Eugene Hecht's Physics book. It's about static fluid and the "compressibility module". I'm not sure this traduction makes sense, because my book is translated into French and I can't find the correct English expression. For those who have...
  9. A

    Isothermal compressibility & Volume expansitivity

    I need equations for Isothermal compressibility & Volume expansitivity in terms of temperature and pressure. Please help. It is for refrigerants in both liquid but especially gaseous phase. Ade:wink:
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