The efficiency of Carnot cycle is ____ the efficiency of Rankine cycle.

Which of the following statements are correct regarding the Rankine cycle? For a given set of operating pressure limits of a Rankine cycle, superheating the steam beyond the saturation temperature at the boiler pressure will result in: a. an increase in the moisture content of steam leaving the turbine b. an increase in thermal efficiency of the Rankine cycle c. an increase in the mean temperature of heat addition d. a decrease in the amount of heat rejected in the condenser

A

b and c

B

a and d

C

a and b

D

c and d

Group I shows different heat addition processes in power cycles. Likewise, Group II shows different heat removal processes. Group III lists power cycles. Match items from Groups I, II and III. Group I Group II Group III P. Pressure constant S. Pressure constant 1. Rankine cycle Q. Volume constant T. Volume constant 2. Otto cycle R. Temperature constant U. Temperature constant 3. Carnot cycle 4. Diesel cycle 5. Brayton cycle

A

P – S – 5, R – U – 3, P – S – 1, Q – T - 2

B

P – S – 1, R – U – 3, P – S – 4, P – T - 2

C

R – T – 3, P – S – 1, P – T – 4, Q – S - 5

D

P – T – 4, R – S – 3, P – S – 1, P – S - 5

If Stirling cycle with regenerative arrangement and Carnot cycle operate within same temperature limits, then the thermal efficiency of Carnot cycle will be ___________

A

same

B

half

C

twice

D

none of the mentioned

The cycle of evaporation and rain in nature can be assumed to be a kind of Carnot cycle. If ocean water instead of evaporation are boiled by the heat of Sun at a constant temperature of 100 deg C and the condensation of steam into water droplets within the clouds occur at constant temperature of -20 deg C. Find the thermal efficiency of Carnot cycle of nature?

A

0.2777

B

0.3030

C

0.3333

D

0.50

If Tm be the mean temperature of heat addition in Rankine cycle as shown in diagram, what will the formula for efficiency of Rankine cycle?

A

(ηr) = (T3 / Tm)

B

(ηr) = 1 – (T3 / Tm)

C

(ηr) = 1 – (T2 / Tm)

D

(ηr) = (T2 / Tm)

Why is the efficiency of Rankine cycle less than that of Carnot cycle?

A

Because of the working fluid

B

Because of the turbines

C

Because all the heat is not supplied at upper temperatures

D

Because all the heat is supplied at upper temperatures

If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle

A

More

B

Less

C

Equal

D

Depends on other factors

If Carnot cycle has maximum possible thermal efficiency, then why don’t the steam turbine power plants run on Carnot cycle?

A

Because boiler can’t be maintained at constant pressure in Carnot cycle

B

Since work consumed by compressor is approximately equal to work produced by turbine

C

As mean temperature of heat addition is quite low in case of Carnot cycle

D

Because the process of heat addition is at constant temperature

If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle is?

A

more

B

less

C

equal

D

none of the mentioned

Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of C.O.P. of reversed Carnot Cycle?

A

1.25

B

0.8

C

0.5

D

0.25

The efficiency of Carnot cycle is ____ the efficiency of Rankine cycle.

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