A closed system undergoes a cycle consisting of three proces

A closed system undergoes a cycle consisting of three processes. During which is adiabatic, 60 kJ of work is done on the system. During the second process. 190 kJ of heat is transferred to the system while no work interaction takes place. During the third process, the system does 100 kJ of work as it returns to its initial state. Determine the heat transfer during the last process and the net work done and net heat transfer during the cycle.

Solution

As the internal energy U of the system depends only on the state of the system so in a cyclic process the net change of internal energy U will be equal to zero

U = q + w = 0

1st process: (adiabatic)

q1 = 0 ( for adiabatic)

w1 = 60 kJ

u1 = q1 + w1

u1 = 0 + 60 kJ = 60 kJ

2nd process:

q2 = 190 kJ

w2 = 0

u2 = q2 + w2 = 190 kJ

3rd process:

w3 = -100 kJ

(a) change in internal for cylic process = 0

u1 + u2 + u3 = 0

60 + 190 + u3 = 0

u3 = - 250 kJ

And u3 = q3 + w3

-250 = q3 - 100

q3 = - 150 kJ

so 150kJ heat is removed from system.

(B) Net work done = w1 + w2 + w3 = 60 + 0 - 100 = - 40kJ

40kJ work is done by system. .......Ans

net heat transfer = q1 + q2 +q3 = 190 - 150 = 40 kJ

40 kJ heat is transfered to the system. .....Ans