LIVE Course for free

Rated by 1 million+ students
Get app now
0 votes
125 views
in Physics by (49.2k points)
closed by

One kg of air is compressed polytropically from 1 bar pressure and temperature of 300 K to a pressure of 6.8 bar and temperature of 370 K. Determine the irreversibility if the sink temperature is 293 K. Assume R = 0.287 kJ/kg K, cp = 1.004 kJ/kg K and cv = 0.716 kJ/kg K

1 Answer

+1 vote
by (44.2k points)
selected by
 
Best answer

Irreversibility I = Wmax – Wact

– Wmax = Change in internal energy – T0 × Change in entropy

– Wmax = (u2 – u1) – T0(s2 – s1) = Wrev

– Wmax = cv(T2 – T1) – T0[cp ln (T2/T1) – R ln (p2/p1)] 

= 0.716(370 – 300) – 293 × [1.005 ln (370/300) – 0.287 ln (6.8/1)]

Wmax = –149.53 kJ/kg = Wrev

(negative sign indicates that work is done on air)

The index of compression ‘n’ is given by

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...