Page 108 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

( 2070x 10 3 . 0 x 014 − 207x 10 3 . 0 x 077 )
 Work done =
. 1 35 − 1

3
= 37.3 x 10 Nm
3
= 37.3 x 10 J
= 37.3 kJ

3.6 a) For a polytropic process,
n
n
p 1 V = p 2 V
1
2
In the given case
n
1 x 0.06 = 9 x 0.011 n

 . 0 06  n
   = 9
 . 0 011

n = 1.302

p V − p V
W = 1 1 2 2
n − 1

1 ( x 10 5 . 0 x 06 ) − 9 ( x 10 5 . 0 x 0111 )
=
. 1 302 − 1

= -13.2 kJ

The negative sign indicates that work energy would flow into the system

during the process.

b) The non-flow energy equation gives

Q – W = U2 – U1

Q – (- 13.2) = ( 370 x 0.07 ) – ( 200 x 0.07 )
 Q = - 1.3 kJ

The negative sign indicates that heat energy will flow out of the fluid

during the process.

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