Adiabatic Process

An adiabatic process is one in which no heat is gained or lost by the system. The first law of thermodynamics with Q=0 shows that all the change in internal energy is in the form of work done. This puts a constraint on the heat engine process leading to the adiabatic condition shown below. This condition can be used to derive the expression for the work done during an adiabatic process.

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Adiabatic Process

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Adiabatic Process

For an ideal gas consisting of n = moles of gas, an adiabatic process which involves expansion from

=
to = =
at initial temperature = K

With the initial volume and temperature specified, the initial pressure is determined:

Using, = kPa = x10^ Pa

The detailed behavior of the pressure and volume depends upon the specific heats of the gas:

Constant pressure = J/mol K
Constant volume = J/mol K
The specific heats determine the ratio, =

and then the adiabatic condition can be applied to determine the constant K .

=

The work done can then be determined:

= J = x10^ J

The final pressure for the process can be determined from the adiabatic condition:

= kPa = x10^ Pa

and the final temperature can be obtained from the ideal gas law.

= K
The specified initial temperature for the work calculation must be in Kelvins, so it must be converted from the other temperature scales.
= K = °C = °F
Discussion of adiabatic process
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