Question

(a)

  (i) For a power cycle, the heat transfers are Q_in=60 kJ and Q_out=40 kJ. Determine the net work, in kJ, and the thermal efficiency.

  (ii) A refrigeration cycle operates with a coefficient of performance β=1.5. For the cycle, Q_out=500 kJ. Determine Q_in and W_cyele each in kJ.

(b) 

A gas within a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes:

Process 1-2: Compression with p V= constant, from p₁=1 bar, V₁=1.6 m³ to V₂=0.2 m³, U₂-U₁=0.

Process 2-3: Constant pressure to V₃=V₁.

Process 3-1: Constant volume, UI-U₃=-3549 kJ.

There are no significant changes in kinetic or potential energy. Determine the heat transfer and work for the three processes, in kJ. Is this a power cycle or a refrigeration cycle?

Answer 1

in the process U1-U3 =-3549 kJ =>U1

Internal energy is function of temperature , thus T1