Advanced Thermodynamics for Engineers, 2nd Edition

Comparing the power outputs based on the same total resistance, i.e. U

H

A

H

þ U

C

A

C

¼ 2 gives the

following table.

It can be seen that the optimum system is one in which the high- and low-temperature resistances

are equal. In this case the entropy generation (per unit of wor k) of the universe is minimi sed, as shown

in the table below.

U

H

A

H

U

C

A

C

_

Q

H

T

H

_

Q

H

T

1

DS

H

W

_

Q

C

T

2

_

Q

C

T

C

DS

C

W

P

DS

W

1 0.25 þ0.333 þ4.17  10

4

0.333 þ0.5 þ4.17  10

4

þ8.34  10

4

1/2  0.225 þ0.333 þ6.23  10

4

0.333 0.4443 þ6.24  10

4

þ0.00125

2 0.225 þ0.266 þ2.48  10

4

0.266 0.4443 þ10.00  10

4

þ0.00125

6.3 EFFICIENCY OF COMBINED CYCLE INTERNALLY REVERSIBLE HEAT

ENGINES WHEN PRODUCING MAXIMUM ...