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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which of the following enters the super heater of a boiler ?
Cold water
Hot water
Wet steam
Super-heated steam.
Wet steam
The superheater in a thermal power plant is designed to increase the temperature of steam above its saturation point to increase the overall cycle efficiency and prevent moisture damage in the turbine. It receives wet steam directly from the boiler drum, where evaporation is incomplete, and heats it to a superheated state.
The superheater in a thermal power plant is designed to increase the temperature of steam above its saturation point to increase the overall cycle efficiency and prevent moisture damage in the turbine. It receives wet steam directly from the boiler drum, where evaporation is incomplete, and heats it to a superheated state.
Qin=m⋅cp⋅(Tsuper−Tsat) — Heat added in the superheater
ηthermal=1−ThotTcold — Carnot efficiency principle improvement via superheating
The wet steam (mixture of liquid water and steam) leaves the boiler drum and passes through the tubes of the superheater, which are exposed to hot flue gases. During this process, the sensible heat is added to the saturated steam, evaporating any remaining moisture and increasing its temperature well above the saturation temperature (Tsat).
Superheaters convert 'wet' steam into 'dry' or 'superheated' steam.
Prevents erosion of turbine blades caused by water droplets at high velocities.
Enhances the thermal efficiency of the Rankine cycle by increasing average heat addition temperature.
The process occurs at constant pressure in a primary superheater.
Improved thermal efficiency of the power plant
Reduced risk of erosion in turbine blades
Increased work output per unit mass of steam
Requires high-grade, heat-resistant materials (alloys)
Increases the complexity and cost of the boiler unit
Thermal power plants
Industrial process steam systems
Wet steam contains liquid droplets; passing it through a turbine would cause pitting and mechanical failure of blades.
Options A and B are incorrect because water must be converted to phase-changed steam in the drum before reaching the superheater.
Option D is incorrect because steam that is already superheated does not 'enter' to become superheated; it has already passed that stage.
C is correct — Wet steam, which contains moisture, enters the superheater to be converted into dry superheated steam.
Always remember that superheating strictly increases the quality of steam; it is the final stage of steam preparation before entering the high-pressure turbine.