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

\(v=0.216\;m^{3}/kg
\\u=2579\;kJ/kg
\\S=6.622\;kJ/kgK\)

 

 

Asked on 29th September 2019 in Propulsion.
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  • 1 Answer(s)

    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.

    Answered on 29th September 2019.
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