Vapor Power Cycle

What should be the critical temperature of working fluid for maximum efficiency of vapour power cycle?

• the working fluid should have critical temperature as low as possible

• the working fluid should have critical temperature as high as possible

• the critical temperature does not affect the efficiency of the vapour power cycle

• none of the above

What is the drawback of the steam as a working substance in a power cycle?

• in a vapour power cycle, maximum temperature which can be obtained with best available material is more than the critical temperature of water and requires large superheating

• it allows only small amount of heat addition at the highest temperature

• it requires reheat and reheater tubes are costly

• all of the above

The below diagram is the T-s diagram of the Rankine cycle with reheat. Which process represents the reheat?

• process 1 – 2

• process 2 – 2 ′

• process 2 ′ – 2 ″

• process 2 – 3 ′

How are the effect of reheat and effect of regeneration on the efficiency of steam power plant compared?

• effect of reheat is greater that the effect of regeneration on plant efficiency

• effect of regeneration is greater that the effect of reheat on plant efficiency

• both the reheat and regeneration have same effect on efficiency of steam power plant

• cannot say

Which among the following has the lowest efficiency than the others, when they are operated between same pressures?

• Ideal Rankine cycle

• Ideal regenerative cycle

• Carnot cycle

• None. All of the above have same efficiency

The mean temperature of heat addition ( $T_H$  ) in the Rankine cycle can be increased by

• reheating the steam

• increasing superheat

• increasing pressure ratio between which the cycle works

• all of the above

The reheat cycle allows steam power plant -

• to use higher pressure ratio

• to maintain required quality of steam at the exit of the turbine

• to increase the turbine work

• all of the above

What is the effect of superheated steam on efficiency of Rankine cycle?

• efficiency of Rankine cycle decreases with increase in superheat of the steam

• efficiency of Rankine cycle increases with increase in superheat of the steam

• efficiency of Rankine cycle is not affected by change in superheat of the steam

• none of the above

The maximum efficiency of Rankine cycle (η_Rankine) is the function of

• the mean temperature of heat addition (T_m) only

• the mean temperature of heat addition (T_m) and temperature of steam at the exit of the turbine

• the mean temperature of heat addition (T_m) and temperature of steam at the entry of the turbine

• the mean temperature of heat addition (T_m) and temperature of steam at exit of the condenser

What is the relation between efficiencies of Rankine cycle and Carnot cycle for the same pressure ratio?

• (η_Rankine) = (η_Carnot)

• (η_Rankine) > (η_Carnot )

• (η_Rankine) < (η_Carnot )

• none of the above