Question

A frictionless-piston-cylinder device contains a liquid-vapor mixture of water at 200°C. During a constant- pressure process, 500 kJ of heat is transferred to the surrounding air at 20°C. As a result, part of the water vapor contained in the cylinder condenses. a) Draw a schematic of your system including the boundary and all relevant energy transfer. (2 pts) b) Determine the entropy change of the water, in kJ/K. (3 pts) c) For the extended system (system + surroundings), write an entropy balance including the entropy generated and entropy transfer. (3 pts) d) Determine the total entropy generation during the heat transfer process. (3 pts)

Answer 1

Given Temperature of liquid pour mixture of water - 900°C a 200 1973 = 473 k = Ti Temperature of surrounding q = 20°c a 20 4273 = 293k Heat transfer to the surrounding 500 5 tment Bonvironement 8.500 kg Universe - system of surrounding" teater to usystem Surrounding D T2 AX Heat flow from system a to surrounding entropy of system decrealy and entropy of surrounding increases BS surrounding to a 500 Surrounding 72 993 1 1.706 1915

A Assystem to surrounding 20 when heat flow seversibly at surrounding tempo (fixed) Se bat assystem - - 8 = -500 boc locar 473 's-1.06 ks IK I AX ds = do t (AS) Generation for closed neration system) asa a + (8) generation & Misi a mere (for open system.) and control ustima ( 58 ) 4 (5) prosesin his, - me se fos steady state. atau = 0 (siehen, tis, ne se OR [css) gen. . - (88) - misi time se

12 @ . Sgen = Serem its surrounding -1.06 + 1706 = 0.646 165/K