Three kg of saturated R-134a inside frictionless piston-cylinder device is at a

Question

Three kg of saturated R-134a inside frictionless piston-cylinder device is at a state (state 1) such that the piston is not moving (equilibrium). The atmospheric pressure around the device is 99.4 kPa and the mass of piston is 2.45 kg. The volume of the system is 90 liters at this state. Heat is then transferred to the system until the internal energy of the system reaches 165 kJ/kg (state 2). The heat transfer will continue until the system T becomes 30 degrees C (state 3). Determine (a) 5 pts. The T(initial) (b) The amount of boundary work done by the system (in kJ) during the process from state 1 to state 2, (c) the phase at state 3 (d) the amount of delta u (in kJ) during the process from state 2 to state 3.

Explanation / Answer

Initial pressure = 99.4*10^3 + 2.45*9.81 / 0.05 = 99880 Pa

Initial specific volume = V/m = 0.09 / 3 = 0.03 m^3/kg

From R-134a properties at 99880 Pa and 0.03 m^3/kg we get T = -26.4 deg C, quality x = 0.152, u = 47.4 kJ/kg

b)

From R-134a properties at 99880 Pa and u2 = 165 kJ/kg we get T = -26.4 deg C, quality x = 0.747, v2 = 0.144 m^3/kg

Boundary work w12 = P*(v2

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