Question

Part II Work out the problems-clearly indicating/labeling final results for each part, show to be considered for partial credit. Point values are shown in parenthesis. 8 final results for each part. Show all your work 1. (15) A horizontal piston-cylinder assembly contains water. The piston is connected to a shaft, which (15) A horie can apply different forces to the piston as the water is expanded or compressed. Initially, the apparatus contains a saturated liquid-vapor mixture of water at 0.9 bar with quality of 80% and volume of 1.0 m'. The shaft is programmed to move following a polytropic process unth the volume doubles and the pressure is 0.7 bar. I (3) For the initial state, calculate the amount of mass present in the vapor phase in kg. il. (3) For the initial state, what percent of the total volume is occupied by vapor? ili. (2) Determine the type of polytropic process (.e., find n when P V-constant). iv. (2) Could kinetic and potential effects be neglected for the system? Why or why not? (5) Determine the amount of heat transfer required to accompany the process in R.

Answer 1

Answer :- Water saturation liquid - vapor mixture PiE , x, = 0.8 o.gbar = Im3 F iii ] polytropic process pun= c o P2 = 0.7bar , V2 =2v . Pivin =P O. 9 x 10 = 0,7%( 2 x )” 9 = (2) 172 0.36 i) Initial state Pia 0.9 bar from steam stable V = 0.001041 m3 1 kg - vg = t. 8691 m3/kg since Vis mu, v= mx, vg 1 mx 0.8 X 1: 8691 m= 0.67 kg

0] U xug = 0.8% 1.8691 via 1.49528 m3/kg Amount of volume occupied 1.49528 vapor percentaze of Total volume occupied by vapor = 80% Water does not be have like an ideal zas, zas equation cannot be applied. at og bar , ht = 605. 2 kJ/kg hg = 62265.7kJ/kg. 62265.7k at 0.7bar, hf = 376.8 kJ/kg hs 2 2 2 3 3 13 / 11 ho = [ ht + x (htg) Jetongbar = 2217.75 kg = 2217.76 ky I bar = 2212 9 @ 0.7 bar, hg = 2660. 1 kg = hz We mche-hu) =0.67*( 2060.1-2217.78) w = 296.37 kJ

The effect of changes in kinetic and potential energy can be neglected in the process as it is a liquid Rapor mixture. Considering appreciable chanzes in kinetic enerzy would convert the problem into a case of compressible flow. This process obeys first law of thermodo Which accounts for inter-chanzable nature of heat and work . Hence, the amount and heat transfer is same as 296.37 kJ as estimated above.
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