Question #150498

A system contains 0.25 m3 of air pressure of 4.8 bars and 160⁰ C. It is expanded adiabatically till the pressure falls to 1.5 bar. The air is then heated at a constant pressure till its enthalpy increases by 80 kJ. Sketch the process on a P-V diagram and determine the total work done. Use Cp=1.005 kJ/kg.K and Cv=0.714 kJ/kg.K

Expert's answer

Volume of system contains= 0.25 m^{3}, Air pressure= 4.8 bars and Temperature T_{1}=160^{0}C. P_{2}= 1.5 bar, h=80 kJ,Cp=1.005 kJ/kg.K and Cv=0.714 kJ/kg.K

"P_1V_1^{\\gamma}=P_2V_2^{\\gamma}"

"\\frac{V_2}{V_1}=\\frac{P_2}{P_1}^{\\frac{1}{\\gamma}}"

"\\gamma=\\frac{C_p}{C_v}=1.41"

"V_2=" .1095 m^{3}

Work done in adiabatic process= "\\frac{P_1V_1-P_2V_2}{\\gamma -1}=\\frac{4.8 \\times .25 - .1095\\times 1.5}{1.41-1}=252.6 kJ"

Work don in constant pressure = Pdv= h=80 kJ

Total work done= 252.6+80=332.6 kJ

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