Question
solve 55 please
(a) Sketch the cycle on a p - V diagram. (b) Calculate the network for the cycle, in kJ. (c) Calculate the heat transfer for process 2-3, in kJ. (d) Calculate the heat transfer for process 3-1, in kJ. Is this a power cycle or a refrigeration cycle? As shown P2.55, a gas within a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes in series: Compression with U_2 = U_1. Constant-volume cooling to p_3 = 120 kPa, V_3 = 0.03 m^3. Constant pressure expansion with W_31 = 9.5 kJ. For the cycle, W_cycle = -7.5 kJ. There are no changes in kinetic or potential energy. Determine (a) the volume at state 1, in m^3, (b) the work and heat transfer for process 1-2, each in kJ. (c) Can this be a power cycle? A refrigeration cycle? Explain. For a power cycle operating as in Fig. 2.17a, the heat transfers are Q_n = 50 kJ and Q_ = 35 kJ. Determine the net work, in kJ, and the thermal efficiency.
Explanation / Answer
1) w 31 = 9.5kJ = p(v1-v3)
v1 = 9500/120000+0.03
v1 = 0.109 m^3
2) w tot = w12+w23+w31
w12 = -7.5-9.5 = -17kJ
Q = -w12 = 17 kJ
3) power cycle
