Answer:
Part A) 3899 kPa
Part B) 392.33 kJ/kg
Part C) 0.523
Part D) 495 kPa
Explanation:
Part A
First from the temperature at state 1 the relative specific volume and the internal energy at that state are determined from:
= 214.07 kJ/kg
= 621.2
The relative specific volume at state 2 is obtained from the compression ratio:
=
=621.2/ 8
= 77.65
From this the temperature and internal energy at state 2 can be determined using interpolation with data from A-17(table):
= 673 K
= 491.2 kJ/kg
The pressure at state 2 can be determined by manipulating the ideal gas relations at state 1 and 2:
=
= 95*8*673/300
= 1705 kPa
Now from the energy balance for stage 2-3 the internal energy at state 3 can be obtained:
= 1241.2 kJ/kg
From this the temperature and relative specific volume at state 3 can be determined by interpolation with data from A-17(table):
= 1539 K
= 6.588
The pressure at state 3 can be obtained by manipulating the ideal gas relations for state 2 and 3:
= 3899 kPa
<u>Part B</u>
The relative specific volume at state 4 is obtained from the compression ratio:
= 52.7
From this the temperature and internal energy at state 4 can be determined by interpolation with data from A-17:
=775 K
= 571.74 kJ/kg
The net work output is the difference of the heat input and heat rejection where the heat rejection is determined from the decrease in internal energy in stage 4-1:
<u>Part C </u>
The thermal efficiency is obtained from the work and the heat input:
η=
=0.523
<u>Part D </u>
The mean effective pressure is determined from its standard relation:
MEP=
=
=
=495 kPa