Page 147 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

Example 4.2

What is the highest possible theoretical efficiency of a Carnot cycle with a hot

o
reservoir of steam at 200 C when the cooling water available from condenser is at

o
10 C?

Solution to Example 4.2

From equation 4.8,

T (s ) s −
 carnot = 1− 2 B A ) s −
(s T
1 B A
10 + 273
= 1−
200 + 273

283
= 1−
473
i.e. Highest possible efficiency = 1 – 0.598

= 0.402 or 40.2 %

Example 4.3

A steam power plant operates between a boiler pressure of 42 bar and a condenser

pressure of 0.035 bar. Calculate for these limits the cycle efficiency and the work

ratio for a Carnot cycle using wet steam.

Solution to Example 4.3

A Carnot cycle is shown in the figure given in the next page.
T1 saturation temperature at 42 bar

= 253.2 + 273 = 526.2 K

T2 saturation temperature at 0.035 bar

= 26.7 + 273 = 299.7 K

T

4
526.2 1

299.7 2
3

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