Air is compressed from an inlet condition of 100 kPa, 300 K to an exit pressure of 1000 kPa by an internally reversible compressor. Determine the compressor power per unit mass flow rate if the device is (a) isentropic, (b) polytropic with n =1.3, (c) isothermal

(a)

(b)

(c)

Explanation:

Hello,

(a) In this case, since entropy remains unchanged, the constant should be computed for air as an ideal gas by:

Next, we compute the final temperature:

Thus, the work is computed by:

(b) In this case, since is given, we compute the final temperature as well:

And the isentropic work:

(c) Finally, for isothermal, final temperature is not required as it could be computed as:

Regards.