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esercizio 1 T1 20 °C 293 K T3 1200 °C 1473 K P1 1 bar 101325 Pa Beta 5 P2 5 506625 rend is compress 0.9 rend is espansione 0.9 T fredda 20 °C 293 K T calda 1400 °C 1673 K Mm 28.8 R* 288.6805556 J/kgK cp 1010.381944 J/kgK T2 is =T1*(Beta)^R*/cp 464.1 K T4 is = T1*T3/T2is 930.0 K rend is compress = (T2 is -T1)/(T2 r -T1) T2 r = (T2 is -T1)/ rend is compr + T1 483.1 K rend is espansione = (T3 -T4 r)/(T3 -T4 is) T4 r = T3 - (T3- T4 is)*rend is esp 984.3 K rendimento I°P= (cp(T3-T4)-cp(T2-T1))/(cp(T3-T2)) 0.3 rendimento ideale con riferimento alle sorgenti termiche = 1- Tfredda/Tcalda 0.8 rendimento II°P= rend I°P/rend id 0.37 irreversibilità interne ed esterne=-qc/Tc + qf/Tf=-cp(T3-T2)/Tc + cp(T4-T1)/Tf 1786.119 esercizio 2 T ingr acqua calda T1 80 °C 353 mpunto ingr acqua calda m1 0.5 kg/s T ingr acqua fredda T2 20 °C 293 T uscita T3 42 °C 315 P 250 kPa L 0 J m1+m2=m3 m1h1 + m2h2=m3h3 m1h1+m2h2=(m1+m2)h3 m1h1+m2h2 = m1h3+m2h3 m2(h2-h3)=m1(h3-h1) m2=m1(h3-h1)/(h2-h3) h ingr acqua fredda h2 hl@T=T3 83.915 h ingr acqua calda h1 hl @T=T1 335.02 h uscita h3 hl @ T=T2 175.894 m2=m1(h3-h1)/(h2-h3) 0.9 esercizio 3 A 400 m2 s 18 cm 0.18 m k 3 W/mK Ts 10 °C 283 K epsilon 0.8 T aria 5 °C 278 K h 8.552 W/m2K Tcielo -10 °C 263 K sigma 5.67E-08 W/K Qpunto conv=hA(Ts-Taria) 17104 W Qpunto irr =epsilon*sigma*A*(Ts^4-Tcielo^4) 29572.86 W Q punto cond=Qpunto conv+Qpunto irr 46676.86 W Q punto cond =DeltaT/Rcond R cond=s/(k*A) 0.00015 K/W Delta T=Q punto cond*Rcond 7.001529 K/W T int= Ts+Delta T 17 °C J/kgK