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.
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.
