Question

a) Estimate the value for hfg for R-134a at 80°C using the Clapeyron equation. Compare your answer with the table value. b) Repeat at -30°C (minus 30°C)

Answer 1

the hfg of refrigerant-1349 solution, determined using the clapeyron eq. hig 는 T vigP ) sat. ر") - . from proporttes of stream table for refrigerant 134a table All ufg (vg - VH) M 80'C. (0.006436 0.0010772) 0.005358 m3 lkg = dP Psat 88c Psutusic - - centro) Cena do Sat 80'C bTout 80'C : 85 750 2928,2 2365 85-75 - 56.24 kpalk. Since ST(C) OT(K) substituting we get hfg (353.15 K) (0.005358 m3/kg) (56.24 kpalk). 106.43 kJ Ilg. of hig at at 80'c is The fabulated value 106.35 kJ/kg the small difference is due to approximation used in deteuming ө[o pe of saturation curve at 80'c

Similarly for -30°c. from table uta lug-N+)0-30' (0.22580 0.0007203) : 0.22504 m31kg Psat-32'd -de d gut -3000 su -3000 도 Psat (228.99 (1997) sat@7-30c -32' - (- 28'0). S 76.71 92.76 -32 + 28 4.0125 kpalk Since OTCC) = BTCK) Substituting we get hfg - (243.15) C0.22507)( 4.0125 kPalk ). 219.58 kilkg The tabulated value of hag at -30'c is 219.52 kJ/ keyin