Short Answer:

The latent heat of steam is the amount of heat energy required to convert water into steam at a constant pressure and temperature without changing its temperature. It is also known as the latent heat of vaporization, and its value is very high for steam—about 2257 kJ/kg at atmospheric pressure.

This heat plays a very important role in steam generation, energy transfer, and thermal efficiency of power plants. Because of this high latent heat, steam can carry a large amount of energy, which makes it very effective for use in turbines, heaters, and industrial processes.

Detailed Explanation:

Latent heat of steam

When we heat water, its temperature rises until it reaches the boiling point. At this point, even if we continue to add heat, the temperature does not increase until all the water turns into steam. The heat added during this phase change is called the latent heat of vaporization or latent heat of steam. This is the hidden heat that changes the state from liquid to vapor, without raising the temperature.

The value of latent heat is very high for steam, which makes it a very efficient energy carrier. This heat is stored in the steam and released when the steam condenses back into water. This property is extremely useful in thermal power generation, industrial heating, chemical processes, and heating systems.

Significance of Latent Heat of Steam

1. Efficient Heat Transfer

Steam can carry a large amount of energy in the form of latent heat. When it condenses, this energy is released, which is why steam is commonly used in heating applications.

2. Power Generation

In steam turbines, the steam produced in the boiler carries both sensible heat (temperature rise) and latent heat (phase change). The high latent heat increases the energy available for expansion, resulting in more power output.

3. Constant Temperature Energy Transfer

Latent heat allows the transfer of large amounts of energy at a constant temperature, which is ideal for controlled heating, especially in sterilization, food processing, and chemical reactors.

4. Improved Efficiency in Boilers

Knowing the value of latent heat helps in calculating boiler efficiency and fuel requirements. Boilers are designed to supply exactly the amount of heat needed to convert water into steam, which includes the latent heat.

5. Steam Condensation Systems

In condensers, the steam gives up its latent heat to cooling water and turns back into liquid. This process is essential for the Rankine cycle used in thermal power plants. Without understanding latent heat, condensers and cooling systems cannot be properly designed.

6. Energy Storage and Release

Steam’s ability to store and release latent heat is also useful in energy storage systems and thermal batteries, where heat needs to be absorbed and released at steady temperatures.

Real-Life Applications

1. Thermal Power Plants
   Steam turbines use high-pressure steam carrying latent heat to rotate and generate electricity.
2. Industrial Heating
   Textile, paper, and chemical industries use steam to transfer heat during processes.
3. Sterilization in Hospitals
   Steam is used in autoclaves for sterilization, where the latent heat kills microorganisms.
4. Steam Cooking
   In large kitchens and food factories, steam is used to cook food quickly and evenly.
5. District Heating Systems
   Steam is transported through insulated pipes to heat buildings, using its high energy content.

Example Calculation

At 100°C (1 atm), the latent heat of steam is about 2257 kJ/kg. This means:

• To convert 1 kg of water to steam, we need to add 2257 kJ of energy just for phase change (excluding heating from room temperature to 100°C).

This huge amount of energy carried by just 1 kg of steam shows how powerful and useful steam is in thermal applications.

Conclusion

The latent heat of steam is the hidden energy needed to change water into steam without temperature change. It is very important in power plants, boilers, heating systems, and many industrial processes because it allows steam to store and deliver large amounts of energy. Understanding latent heat helps engineers design efficient thermal systems and improve the performance of energy transfer equipment.