# Find the work required for the process.

3 kg of steam in a piston -cylinder device at 400 kPa and 175 degree Celsius undergoes a mechanically reversible ,isothermal compression to a final pressure such that the steam becomes just saturated.What is the work required for the process.

\(T=175^{\circ}C

\\v=0.503\;m^{3}/kg

\\S=7.055\;kJ/kgK

\\P=400\;kPa

\\u=2606\;kJ/kg\)

For saturated vapour

\(v=0.216\;m^{3}/kg

\\u=2579\;kJ/kg

\\S=6.622\;kJ/kgK\)

We have

\[q=T\left ( s_{2} -s_{1}\right )\]

\(\\=\left ( 175+273 \right )\left ( 6.622-7.055 \right )

\\=-193.983

\\W=q-\left ( u_{2}-u_{1} \right )

\\=\left ( -193.984-\left ( 2579-2606 \right ) \right )\times 2

\\= -500.94\;kJ\)

Therefore work required for the process is approximately -501 kJ.