tHERMO
ENGINEERING
THERMODYNAMICS
Dr. Tamer A. Tabet
Course Code: KC1702 and Mechanical Eng.
Programme, KM21102.
SEMS-1-2011/2012
Lecture 6. Tue. 15 / 10/ 2012
Lecture Room DKP 10
Engineering Thermodynamics
Lecture 6: Evaluating Properties
Using the Ideal gas
OUTLINE:
Real gases, specific heats, internal energy, enthalpy
In this section the ideal gas model is introduced.
The ideal gas model has many applications in engineering practice and is frequently used in subsequent section of this text.
Ideal gas Equation state
From the Generalized compressibility chart show that the state where the pressure p is small relative critical pressure Pc (low
PR), and the temperature T is large relative to the critical temperature Tc (high Tc ).
The compressibility factor Z =Pv/RT , is approximately.
At such state we can assume with reasonable accuracy that Z=1, or: Pv =RT
Known as the Ideal gas equation of state.
Generalized Compressibility chart
Generalized Compressibility chart
Compressibility Factor Equation
Engineering calculations often require a tradeoffs between ease of use and accuracy. The ideal gas equation is very easy to use, but of questionable accuracy for many cases. Virial and cubic equations of state are accurate, but not particularly convenient. A good compromise is a generalized compressibility factor equation.
The "compressibility factor", z, is defined so that
Consequently, z=1 for an ideal gas. There are a wide variety of ways to obtain z -- it is a function of T and P and can be determined from any of the equations of state we have already discussed. Most gas properties depend on composition, but according to the
"Law of Corresponding States" a few properties are the same for all gases when expressed in terms of deviation from the critical point. We do this by using the "reduced temperature" and
"reduced pressure"
Correlations and charts that take advantage of corresponding states
to
THERMODYNAMICS
Dr. Tamer A. Tabet
Course Code: KC1702 and Mechanical Eng.
Programme, KM21102.
SEMS-1-2011/2012
Lecture 6. Tue. 15 / 10/ 2012
Lecture Room DKP 10
Engineering Thermodynamics
Lecture 6: Evaluating Properties
Using the Ideal gas
OUTLINE:
Real gases, specific heats, internal energy, enthalpy
In this section the ideal gas model is introduced.
The ideal gas model has many applications in engineering practice and is frequently used in subsequent section of this text.
Ideal gas Equation state
From the Generalized compressibility chart show that the state where the pressure p is small relative critical pressure Pc (low
PR), and the temperature T is large relative to the critical temperature Tc (high Tc ).
The compressibility factor Z =Pv/RT , is approximately.
At such state we can assume with reasonable accuracy that Z=1, or: Pv =RT
Known as the Ideal gas equation of state.
Generalized Compressibility chart
Generalized Compressibility chart
Compressibility Factor Equation
Engineering calculations often require a tradeoffs between ease of use and accuracy. The ideal gas equation is very easy to use, but of questionable accuracy for many cases. Virial and cubic equations of state are accurate, but not particularly convenient. A good compromise is a generalized compressibility factor equation.
The "compressibility factor", z, is defined so that
Consequently, z=1 for an ideal gas. There are a wide variety of ways to obtain z -- it is a function of T and P and can be determined from any of the equations of state we have already discussed. Most gas properties depend on composition, but according to the
"Law of Corresponding States" a few properties are the same for all gases when expressed in terms of deviation from the critical point. We do this by using the "reduced temperature" and
"reduced pressure"
Correlations and charts that take advantage of corresponding states
to