Thermodynamics Miscellaneous Moderate Questions and Answers | Page - 1

Thermodynamics Miscellaneous

The current level of the maximum temperature of steam turbine inlet.is much lower than that at gas turbine inlet because

1. The fuel combustion temperature in a steam generator is lower than that in a gas turbine engine
1. Of the corrosive nature of high temperature steam on super heater tubes
1. The materials used for the gas turbine blades are not suitabie for the steam turbine blades
1. Unlike the gas turbine blades the steam turbine blades cannot be cooled

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In gas turbine cooling is provided to blades which keeps the blade material at much lower temperature.

Correct Option: D

In gas turbine cooling is provided to blades which keeps the blade material at much lower temperature.

The INCORRECT statement about regeneration in vapor power cycle is that

1. it increases the irreversibility by adding the liquid with higher energy content to the steam generator
1. heat is exchanged between the expanding fluid in the turbine and the compressed fluid before heat addition
1. the principle is similar to the principle of Stirling gas cycle
1. it is practically implemented by providing feed water heaters

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the principle is similar to the principle of Stirling gas cycle

Correct Option: C

the principle is similar to the principle of Stirling gas cycle

Which one of the following modifications of the si mpl e i deal Rank i ne cycl e i ncr eases t he thermal efficiency and reduces the moisture content of the steam at the turbine outlet?

1. Increasing the turbine inlet temperature
1. Decreasing the condenser pressure
1. Increasing the boiler pressure
1. Decreasing the boiler pressure

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η = f(T_m)
T_m↑ η ↑

Correct Option: A

η = f(T_m)
T_m↑ η ↑

Which of the following statements regarding a Rankine cycle with reheating are TRUE? (i) increase in a average temperature of heat addition (ii) reduction in thermal efficiency (iii) drier steam at the turbine exit

1. only (i) and (ii) are correct
1. only (ii) and (iii) are correct
1. only (i) and (iii) are correct
1. (i), (ii) and (iii) are correct

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With reheat aver age temperature of heat addition increases. Hence, efficiency of cycle also increases. Further, the quality of steam is higher at turbine exit.

Correct Option: C

With reheat aver age temperature of heat addition increases. Hence, efficiency of cycle also increases. Further, the quality of steam is higher at turbine exit.

The density of air in kg/m³ at the nozzle exit is

1. 0.560
1. 0.600
1. 0.727
1. 0.800

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Given: T₁ = 400 K, P₁ = 300 kPa,
P₂ = 50 kPa, R = 0.289 kJ/kgK
v = 1.4, A₂ = 0.005 m²
Process from entrance to exit is isentropic process, therefore
T₁ = P₂ ^γ-1/_γ
T₂ P₁

⇒ t₂ = 400 50 ^0.4/1.4 = 239.5 K
P₁

From the perfect gas equation,
ρ = P
RT

ρ₂ = P₂ = 50 = 0.727 kg/m³
RT₂ 0.287 × 239.5

Correct Option: C

Given: T₁ = 400 K, P₁ = 300 kPa,
P₂ = 50 kPa, R = 0.289 kJ/kgK
v = 1.4, A₂ = 0.005 m²
Process from entrance to exit is isentropic process, therefore
T₁ = P₂ ^γ-1/_γ
T₂ P₁

⇒ t₂ = 400 50 ^0.4/1.4 = 239.5 K
P₁

From the perfect gas equation,
ρ = P
RT

ρ₂ = P₂ = 50 = 0.727 kg/m³
RT₂ 0.287 × 239.5