What is steam

Industrially, steam is sometimes used as a heating source.

Although it is rare to heat with steam at home, the water oven “Hercio” developed by Sharp has a catchphrase of “bake with water” cooking with overheated steam, deoiling, reducing salt, and keeping vitamins. . Reduce calories and salt content, and enjoy delicious healthy cooking! ”
It is characterized by cooking with superheated steam heated to 300 degrees or more instead of cooking with microwaves like a microwave oven. I am promoting that It can do it.

The industrial definition of steam ( Water vapor ) is H2O gas.

Ice is (solid H2O).
Water is also (liquid H2O).
Similarly, steam is (gaseous H2O).

Steam is the one that looks white when water particles are mixed in the steam.
In industry terms, it is called “wet saturated steam”.

The absence of water particles in the steam is called “dry saturated steam” in industry terms.

Superheated steam is steam obtained by further heating saturated steam.

Sterilization drying and heat treatment of food
Wood heat treatment
Drying concrete products
Waste treatment
It is used for etc.

Heating is the transfer of thermal energy. It is called “heat transfer”.
Steam “heats” in two ways.

Convective heat transfer of steam

The high-temperature steam contacts the object to be heated and heats it.
The specific heat of superheated steam (1.33 cal / g / ° C) is about twice that of air (0.24 cal / g / ° C).
In other words, it has twice the heat.

Condensation heat transfer of steam

The conversion of a gas into a liquid is called condensation.
The amount of heat radiated when high-temperature steam comes into contact with the object to be heated and returns to water is 539 cal / g, which is about 2200 heat of air.
In addition, superheated steam has the property of condensing preferentially in low-temperature parts, and has the property of suppressing uneven heating.

【 Advantages of steam heating 】

Heat is large compared to air (approximately 5.5 times), and the heating effect is high.
There is condensation heat transfer, and uneven heating is suppressed.
It is colorless, transparent, tasteless and odorless, and does not discolor the object to be heated.
Since the object to be heated is heated in a low oxygen atmosphere, there is little change in the heating object.
Remains harmless to humans even if left in contact.
Does not self-burn and does not ignite heating objects.
Safe to leak.
Materials are easily available.
Difficult to dry even when heated.

【 Disadvantages of steam heating 】

It becomes water when it cools
Requires a large device (boiler).
Requires two materials: electricity, fuel and water.

【 Control equipment for steam 】

Steam heating is an area of wide application and potential.
To control the temperature of steam, a combination of an automatic control valve and a temperature controller is required.
As an example, “Azbil top guide type single seat control valve CV3000 Alphaplus (AGVB / AGVM)” is introduced.

The CV3000 Alphaplus (AGVB / AGVM) small high-performance control valve is configured with a flow path shape with low pressure loss, has a large valve capacity, and a high-range, high-precision flow characteristic that operates from low pressure to high pressure.
The valve plug has high vibration resistance held by the top guide with a large sliding area and shutoff performance conforming to IEC standards.
The operation unit uses a small high-power multi-spring type.
As described above, the compact, lightweight, high-performance single-seat control valve can be widely used for process control that emphasizes high reliability control and shut-off performance.