The key difference between wet dry and superheated steam is that wet steam is at the boiling point of water and contains water droplets, and dry steam is at the boiling point of water but has no water droplets, whereas superheated steam is at a higher temperature than the boiling point of water and it does not contain water droplets.
Steam is water in the gas phase. Steam can form as a result of evaporation or boiling of water. There are three major types of steam as wet steam, dry steam, and superheated steam.
CONTENTS
1. Overview and Key Difference
2. What is Wet Steam
3. What is Dry Steam
4. What is Superheated Steam
5. Wet vs Dry vs Superheated Steam in Tabular Form
6. Summary – Wet vs Dry vs Superheated Steam
What is Wet Steam?
Wet steam is the water vapour, including water droplets. Therefore, it is a mixture of steam and liquid water. This type of steam occurs at a saturation temperature that consists of more than 5% water. We can describe wet steam as a two-phase mixture because it has both gaseous phase and liquid phase in the same system. Moreover, this stem has water droplets that have not yet changed their phase of matter.
Figure 01: Steam Phase Eruption of Castle Geyser
Wet steam typically causes corrosion in vulnerable equipment, including turbine blades, low-pressure steam piping, and heat exchanges.
We can calculate the specific volume of wet steam with the vapour quality (given as “x”) and the specific volumes of saturated liquid water and dry steam (given as Vl and Vs, respectively. Then the relationship between these terms is:
Vwet = Vs .x + (1-x)Vl.
What is Dry Steam?
Dry steam is water vapour without any water droplets. Generally, this type of steam is produced industrially in dry steam power plants where the steam is released from the pressure of a deep reservoir through a rock catcher, which is then passed through the power generator turbines to produce energy. We can define dry steam as a type of saturated steam that has been slightly superheated to remove any water droplets existing in the water vapour. This type of steam is a single-phase system because it only has a gaseous phase; water vapour is in the gaseous phase.
We can use dry steam to safely clean around control panels, conveyors, directly on walls, within the ducts, etc., because it does not cause any corrosion due to the absence of water droplets.
What is Superheated Steam?
Superheated steam is the water vapour at a very high temperature than the boiling temperature at that pressure. This type of steam occurs only when all liquid water has undergone evaporation or removed from the system. This is also a type of single-phase steam because it only has a gas phase in it.
Figure 02: Volume (v), Energy (u), Enthalpy (h), and Entropy (s) versus Temperature (C) for Superheated Steam
Superheated steam can lose its internal energy through cooling (by some amount), which results in a lowering of its temperature without changing the state of matter. Moreover, superheated steam and liquid water cannot occur under thermodynamic equilibrium, so these two phases cannot coexist.
Furthermore, this type of steam is not suitable for sterilization because it is a type of dry steam. In order to perform sterilization with this type of steam, we need to expose the unsterilized object to superheated steam for a long time period to obtain some effectiveness.
What is the Difference Between Wet Dry and Superheated Steam?
Wet, dry, and superheated steam are types of steam produced from water. Wet steam is the water vapour, including water droplets while dry steam is the water vapour without any water droplets. Superheated steam is the water vapour at a very high temperature than the boiling temperature at that pressure. The key difference between wet dry and superheated steam is that wet steam is at the boiling point of water and contains water droplets, and dry steam is at the boiling point of water and has no water droplets, whereas superheated steam is at a higher temperature than the boiling point of water and it does not contain water droplets.
The below infographic lists the differences between wet dry and superheated steam in tabular form for side by side comparison.
Summary – Wet vs Dry vs Superheated Steam
Steam is water in the gas phase. Steam can form as a result of evaporation or boiling of water. There are three major types of steam as wet steam, dry steam, and superheated steam. The key difference between wet dry and superheated steam is that wet steam is at the boiling point of water and contains water droplets, and dry steam is at the boiling point of water and has no water droplets, whereas superheated steam is at a higher temperature than the boiling point of water and it does not contain water droplets.