Solution.
p1=90⋅103Pa;
T1=293K;
ν2ν1=9;
Q=2100kJ=2.1⋅106J;
T1T2=(ν2ν1)k−1;
T2=T1(ν2ν1)k−1;
T2=293⋅91.4−1=791K;
p1p2=(ν2ν1)k;
p2=p1(ν2ν1)k;
p2=90⋅103⋅91.4=1950⋅103Pa;
Qin=cv(T3−T2)⟹T3=cVQ+T2;
T3=7181.4⋅106+791=2740K;
p3=p2(T2T3);
p3=1950⋅103(7912740)=6754⋅103Pa;
T4=T3(ν4ν3)k−1;
T4=2740⋅(91)0.4=1141K;
Qout=cv(T4−T1);
qout=718(1141−293)=608864J;W=Qin−Qout;
W=1.4⋅106−0.609⋅106=0.791⋅106J;
η=QinW⋅100%;
η=1.4⋅1060.791⋅106⋅100%=56.5%;
Answer: p3=6754⋅103Pa;T3=2740K;η=56.5%.
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