Page 82 - Entrophy Analysis in Thermal Engineering Systems

74 Entropy Analysis in Thermal Engineering Systems

In the next step, we calculate the entropy generation rate associated with
the operation of the Novikov’s model.

_ _ 1 1
Φ ¼ Q (6.18)
H T EH T H
Notice that the cold-end side temperature of the engine is the same as the
low-temperature thermal reservoir’s temperature. Substituting Eq. (6.2) into
Eq. (6.18) yields

1 1
_
Φ ¼ K h T H T EH Þ T EH T H (6.19)
ð
_
Solving ∂Φ=∂T EH ¼ 0 leads to (T EH ) opt ¼T H . This result reveals that the
minimum entropy generation rate takes place when T EH !T H , which
would give a zero finite time power.

6.4 Modified Novikov’s engine
Let us now consider a modified model of Novikov’s engine, in which
the finite time heat exchange only takes place at the cold-end side of the
engine (see Fig. 6.5). Thus, the efficiency and the power output of the

Fig. 6.5 Modified Novikov’s engine on a T-s diagram.