Question

A supply of 10 lbm/s ammonia at 80 lbf/in.², 80 F is needed. Two sources are available one is saturated liquid at 80 F and the other is at 80 lbf/in.², 260 F. Flows from the two sources are fed through valves to an insulated mixing chamber, which then produces the desired output state. Find the two source mass flow rates and the total rate of entropy generation by this setup. 

Answer 1

C.V. mixing chamber + valve. Steady, no heat transfer, no work. 

State 1:  h₁ = 131.68 Btu/lbm, s₁= 0.2741 Btu/lbm R

State 2:  h₂ = 748.5 Btu/lbm, s₂ = 1.4604 Btu/lbm R

State 3: h₃= 645.63 Btu/lbm, s₃ = 1.2956 Btu/lbm R

As all states are known the energy equation establishes the ratio of mass flow rates and the entropy equation provides the entropy generation.