6.16 One kilogram of air initially at 0.8 MPa and 17 C changes to 0.4 MPa...

 

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6.16 One kilogram of air initially at 0.8 MPa and 17 °C changes to 0.4 MPa and 51 °C by three reversible non-flow process 1-a-2 consists of constant pressure expansion fol- lowed by constant volume cooling. Now, consider the process 1 - b - 2 which is an isothermal expansion followed by a constant pressure expansion process and 1-c- 2 which is an adiabatic process followed by constant volume heating. Determine the change of internal energy, enthalpy and entropy for each process. Also find work transfer and heat transfer. Take Cp 1.005 kJ/kg K; cv 0.718 kJ/kg K. As- sume constant specific heat cp and cy. Take pu= 0.287T for air, where the pres- sure p is in kPa; v is the specific volume in m³/kg and temperature T is in K. Ans: 24.412 kJ/kg; 34.170 kJ/kg; 0.311 kJ/kg K; 56.29 kJ/kg; 81.75 kJ/kg = = 6.17 Twenty grams of water at 20 °C is converted into ice at -20 °C at constant atmospheric pressure. Assuming specific heat of liquid water to remaining constant at 4.2 J/K and that of ice to 50% of this value and taking the latent heat of fusion of ice at 0 °C to 335 J/g, find the total entropy change of the system. Ans: 2.21 J/K 6.16 One kilogram of air initially at 0.8 MPa and 17 °C changes to 0.4 MPa and 51 °C by three reversible non-flow process 1-a-2 consists of constant pressure expansion fol- lowed by constant volume cooling. Now, consider the process 1 - b - 2 which is an isothermal expansion followed by a constant pressure expansion process and 1-c- 2 which is an adiabatic process followed by constant volume heating. Determine the change of internal energy, enthalpy and entropy for each process. Also find work transfer and heat transfer. Take Cp 1.005 kJ/kg K; cv 0.718 kJ/kg K. As- sume constant specific heat cp and cy. Take pu= 0.287T for air, where the pres- sure p is in kPa; v is the specific volume in m³/kg and temperature T is in K. Ans: 24.412 kJ/kg; 34.170 kJ/kg; 0.311 kJ/kg K; 56.29 kJ/kg; 81.75 kJ/kg = = 6.17 Twenty grams of water at 20 °C is converted into ice at -20 °C at constant atmospheric pressure. Assuming specific heat of liquid water to remaining constant at 4.2 J/K and that of ice to 50% of this value and taking the latent heat of fusion of ice at 0 °C to 335 J/g, find the total entropy change of the system. Ans: 2.21 J/K

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1616 Process 1a2 Internal Energy change 24412 kJkg Enthalpy change 34170 kJkg ... View the full answer