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Saturated steam occurs when steam and water are in equilibrium. If you have a closed container of water and heat it, above 100 celsius the steam pressure will start to rise, and as the temperature continues to rise, the pressure will go on rising. What is happening is that steam is being evolved to match the temperature (steam tables will give this relation) and the steam conditions are said to be saturated because if the pressure is raised by external means, some of the steam will start to condense back to water.
If the steam pressure is held at a lower level than that achieved at saturation, by taking steam off to feed a turbine or other steam usage, there is effectively an excess temperature for that pressure, and the steam is said to be superheated. It in fact then becomes dry, and behaves as a gas. The amount of superheat can be quantified as so many degrees of superheat (celsius or fahrenheit). Turbine designers want steam to be superheated before reaching the turbine, to avoid condensation causing blade erosion, and steam producing boilers in power plants are designed to produce superheated steam.
Wiki User
∙ 14y ago
Wiki User
∙ 13y agoSaturated steam occurs when steam and water are in equilibrium. If you have a closed container of water and heat it, above 100 celsius the steam pressure will start to rise, and as the temperature continues to rise, the pressure will go on rising. What is happening is that steam is being evolved to match the temperature (steam tables will give this relation) and the steam conditions are said to be saturated because if the pressure is raised by external means, some of the steam will start to condense back to water.
If the steam pressure is held at a lower level than that achieved at saturation, by taking steam off to feed a turbine or other steam usage, there is effectively an excess temperature for that pressure, and the steam is said to be superheated. It in fact then becomes dry, and behaves as a gas. The amount of superheat can be quantified as so many degrees of superheat (celsius or fahrenheit). Turbine designers want steam to be superheated before reaching the turbine, to avoid condensation causing blade erosion, and steam producing boilers in power plants are designed to produce superheated steam.
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What is a desuperheater?
HiSuperheated steam is steam that is at a temperature higher than the saturation temperature for the steam pressure. For example, steam at a pressure of 3 bar g has a saturation temperature of 143.762°C. If further heat were to be added to this steam and the pressure remained at 3 bar g, it would become superheated.So, desuperheating is the process by which superheated steam is restored to its saturated state, or the superheat temperature is reduced.The idea behind desuperheating is that saturated steam has a better energy exchange capacity (U coefficient) than superheated steam.Superheated steam must cool down before condensing, therefore it is less efficient than saturated steam in appliances such as heat exchangers.Also, superheated steam is a thermal insulator, just like air.
Is the expansion of superheated steam isothermal?
Expansion of steam in either the saturated or superheated state is generally not isothermal. When steam expands from a high pressure to a lower pressure the temperature will be reduced, unless energy is added during the process. When steam expands in an engine such as a steam turbine, the temperature reduction is greater than during free expansion
Which type of steam is imparted on the blades of turbine?
Superheated steam.
Why is superheated steam preferred in a turbine?
among other things, to improve thermal efficiency and minimize ( transmission losses) as the steam cycles through the turbines, these are often l00% Heavy Duty cycles as in Powerhouse service and Nuclear submarines. turbines use superheated steam in order to avoid condensation inside, and, as a result, erosion of the blades. Superheated steam also contains more potential energy (expressed as an enthalpy).
What is the Temp of 30 psi steam?
30 PSIG is about equal to 45 PSIA. Saturation temperature from the steam tables at 45 PSIA is about 274°F. So the steam would be 274°F, or hotter if superheated.
What is the difference between dry steam and wet steam to clean?
DRY steam is superheated There is a temperature below which steam will start to condense into water droplets. This is called the saturation temperature, and it varies with the pressure of the steam. Steam that is exactly at its saturation temperature is called saturated steam. Steam that is below its saturation temperature contains droplets of moisture and is called wet steam. Steam that is above its saturation temperature is called superheated steam.
Why saturated steam is used in exchangers frequently rather then superheated?
The heat transfer coefficient of superheated steam is poor. Saturated steam has a better heat transfer coefficient, and also most of the heat transferred from steam occurs because of the condensation phase change.
What is a Binary Vapour Cycle?
A binary vapour cycle is a representation of a mercury cycle and a steam cycle on a same scale.In this vapour cycle there is comparison between the mercury cycle and steam cycle. In mercury cycle there occurs isothermal expansion of saturated water from boiler into dry saturated steam followed by isentropic expansion followed by condensation of steam and at last heating of steam and thus mercury has completed the cycle in 4 way process. In steam cycle first ther is isothermal expansion which results in converting of saturated water into dry saturated steam followed by superheated process where the steam is superheated followed by isentropic expansion of superheated steam followed by condensation of exhaust steam and at last heating of steam thus completing the cycle.
What is the difference between saturated steam and Superheated steam?
Saturated steam occurs when steam and water are in equilibrium. If you have a closed container of water and heat it, above 100 celsius the steam pressure will start to rise, and as the temperature continues to rise, the pressure will go on rising. What is happening is that steam is being evolved to match the temperature (steam tables will give this relation) and the steam conditions are said to be saturated because if the pressure is raised by external means, some of the steam will start to condense back to water.If the steam pressure is held at a lower level than that achieved at saturation, by taking steam off to feed a turbine or other steam usage, there is effectively an excess temperature for that pressure, and the steam is said to be superheated. It in fact then becomes dry, and behaves as a gas. The amount of superheat can be quantified as so many degrees of superheat (celsius or fahrenheit).Turbine designers want steam to be superheated before reaching the turbine, to avoid condensation causing blade erosion, and steam producing boilers in power plants are designed to produce superheated steam. In plants where no turbines are used, only satured steam is normally generated.In heating applications, saturated steam is preferable, because it has a better energy exchange capacity. Superheated steam must cool down, and become saturated steam, before condensing in a heat exchanger. Also, superheated steam is a thermal insulator, like air.That is why it is necessary to direct superheated steam through a desuperheater before using the steam in heating applications.
Is superheated steam suitable for air heaters instead of saturated steam?
No, superheated steam gives off little energy. Most of the heat given off by steam is the latent heat of condensation as it undergoes a phase change from vapor to liquid. Superheated steam could first be "desuperheated" by adding water until it reaches the saturation point, then used for heat transfer processes.
What is a desuperheater?
HiSuperheated steam is steam that is at a temperature higher than the saturation temperature for the steam pressure. For example, steam at a pressure of 3 bar g has a saturation temperature of 143.762°C. If further heat were to be added to this steam and the pressure remained at 3 bar g, it would become superheated.So, desuperheating is the process by which superheated steam is restored to its saturated state, or the superheat temperature is reduced.The idea behind desuperheating is that saturated steam has a better energy exchange capacity (U coefficient) than superheated steam.Superheated steam must cool down before condensing, therefore it is less efficient than saturated steam in appliances such as heat exchangers.Also, superheated steam is a thermal insulator, just like air.
Is the expansion of superheated steam isothermal?
Expansion of steam in either the saturated or superheated state is generally not isothermal. When steam expands from a high pressure to a lower pressure the temperature will be reduced, unless energy is added during the process. When steam expands in an engine such as a steam turbine, the temperature reduction is greater than during free expansion
Why is superheated steam used in power plant?
because if the steam is not superheated the remaining water droplets reduce efficiency and can cause corrosion and pitting. +++ Nearly! Saturated steam, as non-superheated steam is called, is really only steam at the pressure and temperature in the boiler. Once it starts to expand as a gas in doing its work, the pressure and temperature fall and condensation will set in, leaving less and less useful water-vapour to act as a gas. Hence, as you say, the efficiency falls.
What the device used to increase the temperature of the saturated steam without increasing its pressure is called?
There is a small problem with the question: if you increase the temperature of saturated steam without increasing pressure, it will no longer be saturated - it will be superheated. With this in mind, it should be no surprise that the device that does this is normally called a "superheater". The picture accompanying this question is an example of a superheater.
In order for a high temperature boiler or steam engine to produce superheated steam?
In order for a high temperature boiler or steam engine to produce superheated water, or steam?
How is heat generated?
When water is heated, there is a relation between temperature and pressure at which the water and steam are in equilibrium. This applies up to 374 degC at which the corresponding pressure is 222 bar abs or 3220 psi abs. Beyond this temperature liquid water cannot exist and the steam is said to be supercritical. At any temperature between 100 degC and 374 degC there will therefore be a pressure at which steam is just formed and this is said to be dry saturated steam. It is saturated because if the temperature drops even slightly at the same pressure, steam will condense. If at this same pressure the steam is further heated, it is said to be superheated because it is at a temperature higher than dry saturated steam would be. Superheated steam is desirable for use in steam turbines, because it prevents formation of water droplets as the steam is expanded through the turbine-the droplets could damage the turbine blades. In the supercritical region above 374 degC steam will always exist whatever the pressure, so the concept of superheat does not apply here.
Which type of steam is imparted on the blades of turbine?
Superheated steam.
