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Unformatted text preview: ). ), However, we don’t like to use
in engineering; instead, we like to use mass (
that case, the equation can be reformatted into: where is the molecular mass of the gas (in kg/mol), m is the mass (in kg) and
the gas constant, which is different for different gas. ). In is Example: molecular weight for air is 29g/mol (0.029kg/mol), R for air is: Divide volume ( ) from each side of the state equation: This is the most often used gas state equation in aerodynamics. SHU Fall 2012 1 Thermodynamics (Review) LEC 2 Internal Energy
The energy of a molecule is the sum of translational, rotational, vibrational and electronic
energy. Internal energy ( ) is the sum of the energy of all the molecules in the substance.
In aerodynamics, we usually interested in the specific internal energy, which is the
internal energy per unit mass (
). As we mentioned before, a simple compressible
system only has two independent properties, thus,
, and:

For ideal gas,   , (this is proved in any thermodynamics book, not here), heat capacity at constant volume is defined to be  , therefore Enthalpy
Enthalpy is defined as:
It is apparent that ,
. For air,
are co...
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This note was uploaded on 09/03/2013 for the course AE 339 taught by Professor Wei during the Fall '12 term at NMSU.
 Fall '12
 Wei

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