What is Compressibility factor: Definition and 11 Discussions
In thermodynamics, the compressibility factor (Z), also known as the compression factor or the gas deviation factor, is a correction factor which describes the deviation of a real gas from ideal gas behaviour. It is simply defined as the ratio of the molar volume of a gas to the molar volume of an ideal gas at the same temperature and pressure. It is a useful thermodynamic property for modifying the ideal gas law to account for the real gas behaviour. In general, deviation from ideal behaviour becomes more significant the closer a gas is to a phase change, the lower the temperature or the larger the pressure. Compressibility factor values are usually obtained by calculation from equations of state (EOS), such as the virial equation which take compound-specific empirical constants as input. For a gas that is a mixture of two or more pure gases (air or natural gas, for example), the gas composition must be known before compressibility can be calculated.
Alternatively, the compressibility factor for specific gases can be read from generalized compressibility charts that plot
Z
{\displaystyle Z}
as a function of pressure at constant temperature.
The compressibility factor should not be confused with the compressibility (also known as coefficient of compressibility or isothermal compressibility) of a material, which is the measure of the relative volume change of a fluid or solid in response to a pressure change.
A cylindrical tube (diameter = D, width = L) is completely filled with a liquid (density = ρ). A pump pressurizes the system with a pressure P. Consequently, 1) the solid tube is compressed and deformed according to Hooke's law (σ = ε.E), and 2) the liquid is compressed and deformed, following...
I was reading about thermodynamics in my textbook wheni came across the following thermodynamics constants:
However, i don't understand why did we define 1/V inthe constants. What is the point in doing this?
There's a huge volume of data on NIST database:
https://webbook.nist.gov/cgi/fluid.cgi?T=293.15&PLow=10&PHigh=1000&PInc=10&Applet=on&Digits=5&ID=C7727379&Action=Load&Type=IsoTherm&TUnit=K&PUnit=bar&DUnit=mol%2Fl&HUnit=kJ%2Fmol&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&RefState=DEF
I'm interested...
Homework Statement
Please consider ethylene at 152oF and 126 atm. Please determine the molar volume (ft3/lbmole) if Z is determined by Corresponding States Theory.
Homework Equations
Z=PVm/RmT
Vm= Molar volume
R=Rm/M
M= molecular weight
Rm=1545(ft*lbf)/(lbmol*oR)
Zc=(Pcvc)/(R*Tc)
Tc=283 K...
Homework Statement
Why is it that when considering the compressibility factor of a gas Z we see the value decrease at first and increase as value for Pr increases for an isotherm Tr=1?
Homework Equations
z=1+(Pb/RT)-(a/VRT)
The Attempt at a Solution
It is my understanding that as Pr is low...
The pressure exerted on the walls of the container by a real gas is less compared to an ideal gas. This is due to the attractive forces of the gas pulling the molecules back towards the rest of the gas molecules. However, there is also a relationship whereby at lower temperatures, the z is even...
At low temperatures, z falls below 1 and the reason for that is because the intermolecular interactions cause the pressure exerted to be lesser than expected. PVm/RT=z and since P is less than expected z drops below 1.
However, as the pressure increases z increases to be above 1 because as P...
What is the correct type of pressure (static or total) used in the compressibility factor, KP, when calculating fan power? Howden's Fan Engineering book seems to indicate total pressures should be used, but I also have a PDF from Howden that indicates static pressures should be used. Online...
Homework Statement
Find the volume of 2 kg of ethylene at 270 K, 2500 kPa using Z
Homework Equations
Method to Solve for Z, Using Tr and Pr
PV = ZnRT
The Attempt at a Solution
Tr = 0.9561
Pr = 0.496
Z found to be approx. 0.75
R given on a table at 0.2964 kJ/kg K
From...
Homework Statement
Determine the volume, in m^3, occupied by 20 kg of hydrogen (H2) at 1170 kPa, 2220°C.
Homework Equations
Z=pv/rt, Pr=P/Pc, Tr=T/Tc, and for hydrogen M = 2.016 (kg/kmol) Tc = 33.2 (K) Pc = 13.0 bar Zc=pc*vc/(RTc)
The Attempt at a Solution
I know if I find Z then...
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...