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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. 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.
What else can I help you with?
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.
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?
What is steam in thermodynamics?
Saturated steam is gas-phase water in equilibrium with liquid water at the same temperature and pressure. If the temperature is above the saturation point and/or the pressure is below the saturation pressure, the steam is "superheated steam". In either case it is a gas. There are some conventions where saturated steam along with some fraction of liquid water in equilibrium with it is still referred to as steam even if not all of it is gas, as long as at least some of it is gas.
What happens when superheated steam pressure is reduced?
steam quality increase
Why is heat trasnfer coefficient of saturated steam is higher than superheated steam?
when steam is at its saturation point for a given pressure, any heat removed will cause liquid water to form. So when saturated steam is used to heat something else, the heated object/substance receives the condensation heat of the steam. The latent heat of condensation/evaporation is 970 But/lb @ 0 psig. On the other, superheated steam only gives up about 10 BTU/lb if it is cooled 20 degrees F. That means that much more steam would be used to transfer the equivalent amount of heat. The liquid water interface also improves the heat transfer.
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.
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
Difference between saturated 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.
Why not super heated steam used in nuclear power plant?
Superheated steam is not used in nuclear power plants because it can cause corrosion in the turbines. Additionally, using saturated steam allows for better control over the temperature and pressure in the system, enhancing safety and efficiency. Nuclear power plants typically operate with saturated steam to avoid these issues.
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.
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 are the advantages of superheated steam?
Superheated steam offers several advantages, including increased thermal efficiency and the ability to transfer more energy than saturated steam, making it ideal for power generation and industrial processes. It reduces the risk of condensation in pipes and turbines, improving equipment reliability and performance. Additionally, superheated steam can operate at higher temperatures and pressures, enhancing process flexibility and enabling more efficient heat exchange in various applications.
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?
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.
Which type of steam is imparted on the blades of turbine?
Superheated steam.
