From Thermodynamic Properties of Water and Refrigerants

Ideal Gas Properties

Thermodynamic tables are derived by considering all gases or vapors as ideal gas. An equation of state is derived by considering the kinetic theory of gases. Many equations of state are available depending on a particular range of temperature, pressure, and volume. The characteristic gas equations are categorized as theoretical, generalized, or empirical.

Theoretical and generalized relations are based on ideal gas concepts, where pressure, volume, and temperature are correlated through the function of form:

f(P,v,T) = 0

This is called the equation of state, which describes the P-v-T behavior of substances. An equation of state provides a convenient method to relate the P-v-T data of a substance.

For ideal gas, the equation of state is Pv = RT.

Empirical relations are based on actual experiments conducted by scientists and depend on the substance. These relations hold true under the different conditions under which the experiments are performed.

Air consists of N 2, H 2, and O 2, which are permanent gases. Yet, air is considered a pure ideal gas, holding true for the equation state Pv = RT.

Ideal Gas Properties: Air

The Ideal Gas Properties of Air table lists the ideal gas properties, such as specific enthalpy, specific internal energy, and specific entropy of air, at any given temperature varying from 100 k to 1,800 k.

to download an Excel sheet that provides the values of ideal gas properties of air at a given temperature.

Ideal Gas Properties of Air


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