(a) The final pressure and temperature of air after mixing
M=RTPV
MA=0.287∗375800∗4=29.73kg
MB=0.287∗498450∗4=12.59kg
(MAcvTA+MBcvTB)=(MAcv+MBcv)TF
(29.73∗0.718∗375+12.59∗0.718∗498)=(29.73∗0.718+12.59∗0.718)TF
30.38576(29.73⋅0.718+12.59⋅0.718)TF=30.3857612506.53326
TF=30.3857612506.53326=411.59190C
PFVF=MFRTF⟹PF=8(29.73+12.59)∗0.287∗411.59=624.89kPa
(b) The amount of entropy generation
ΔS=ΔSA+ΔSB=(mA(CplnTATF−RlnPAPF))+(mB(CplnTBTF−RlnPBPF))
ΔS=(29.73(1.005ln375411.59−0.287ln800624.89∗103))+(12.59(1.005ln498411.59−0.287ln450624.89∗103))
ΔS=(29.73∗0.1645)+(12.59∗−0.2858)
ΔS=1.2924kJ/kg.K
(c) the irreversibilities in the process
dU=TdS−dW=1.2924∗300−300∗0.2858=301.98kJ
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