3. Consider an air-standard dual cycle. Operating data at principal states in th
ID: 2073667 • Letter: 3
Question
3. Consider an air-standard dual cycle. Operating data at principal states in the cycle are given in the table below. The states are numbered as in Fig. 3. If the mass of air is 0.05 kg, determine a. the cutoff ratio. b. the heat addition to the cycle, in kJ c. the heat rejection from the cycle, in kJ d. the net work, in kJ e. the thermal efficiency. State T p (kPa) 95 214.07 300.19 2 862.4 4372.8 643.35 890.89 3 1800 9126.9 1487.2 2003.3 1980 9126.9 1659.52227.1 5 840.3 265.7 625.19 866.41 300 4 Fig. 3Explanation / Answer
a. The cut off ratio
=1980/300
=6.6
b. Heat addition
qin = [Cp (T3 T2) Cv (T4 – T1)]
=1.005(1800-862.4) - 0.718(1980-300)
=942.288+1206.24
=2148.528kJ
c. heat rejection
qout = Cv (T5 – T1)
=0.718(840.3-300)
=387.9354 kJ
d.Net work
wnet = qin qout
=2148.528-387.9354
=1760.9354 kJ
e. Thermal Efficiency
th =
= 1760.9354 / 2148.528
=0.8196
=81.96 %