Question

Refrigerant 134a in a piston cylinder assembly, from 180 psi and 140 F to 30 psi. The mass of refrigerant is 0.5 lb. During the process heat transfer to the refrigerant from its surrounding is 1.2 Btu while the work done by the refrigerant is 4.32 Btu. There are no significant kinetic and potential energy effects. • Determine the final temperature of the refrigerant in F •Determine the initial and final specific volume. • Diagram sketch of the P-v include critical point data

Answer 1

From R134a Propertiz At 180 psi and 140°F V = 0.28231 H / dbm 4,=124:17 Btullbm W = 4.32 Btu 8 = -1.2 Blu Q - DU+W Q = m (U2 -41) +W -102=0.5 (42-124:17) + 4.32 U2 = 113.13 Btulabm At 30 psi and U2 = 113.13 Btuldbm 13.13 - 110.35 Thus - 118.35 x 11.7338-116528) & = 1.6528 + -> T2 = 50.238 °F V = 1.70919 fflubm 113.13-110.35 Tz = 407 114.45-110:35 Fimal temperature T2 = 50.2330F mitial Specific volume 10,= 0.28231 fez/dom final specific volume [ ₂ = 1.70919 ft3/ebm

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