Question

In: Physics

10 kg of air occupying a cylinder volume of 0.28 m3 is allowed to expand isentropically...

10 kg of air occupying a cylinder volume of 0.28 m3 is allowed to expand isentropically
behind a piston to a pressure of 30 bar. The air is then heated at a constant volume. Finally, the
air is cooled at a constant pressure back to its initial conditions. The initial pressure is 60 bar.
Calculate the change in entropy, the net work done and the net heat flow. Sketch the cycle on
the p‐v and T‐s diagrams.

Solutions

Expert Solution

The number of moles of air is

The initial temp is

For an ideal gas, an isentropic process is equal to an adiabatic process, therefore we can write

Gamma for air is 1.4

The work done in this process is given by

The following process is at constant volume, this means that the work is zero. The temperature at the end is

The heat in is equal to the change in internal energy:

The last process is an isobaric. The work done on the system is

The change in internal energy

The heat flow is then according to the first Law

The change in entropy over the cycle is zero, the net changes in work and heat are:

genius_generous answered 1 year ago

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