Steam and water are widely used as heat transfer media in heating equipment due to their favorable physical and chemical properties, as well as their cost‑effectiveness.

Physical Properties of Steam

1.At room temperature, water exists as a liquid and readily converts to steam when heated.

2.Steam has a high specific heat capacity and high latent heat of vaporization.

3.It offers good heat transfer characteristics, and its volume decreases significantly upon condensation.

4.As pressure increases, the saturation temperature also rises.

Chemical Properties of Steam

1.Steam is non‑corrosive and harmless to humans.

2.It is chemically stable and presents no fire hazard.

Additional Characteristics

After steam expands to do work, the exhaust steam can still serve as a heat source. It can also be used in a cascaded manner, transferring heat from higher to lower temperature levels.

Heating Methods Using Steam as a Heat Carrier

1.Direct Heating
In direct heating, the total heat content of the steam—including both sensible and latent heat—is transferred to the heated material. Both superheated and saturated steam can be used, and steam pressure is not a primary concern. Therefore, reducing steam pressure does not result in energy savings with this method.

2. Indirect heating method
steam is introduced into heating pipes (heat exchangers), and the heated material contacts the pipe surfaces to absorb the latent heat released during condensation. The condensed water is then discharged to atmosphere through a steam trap (see Figure 5). This method utilizes only the latent heat of steam. As noted earlier, higher steam pressure corresponds to lower latent heat but higher sensible heat in saturated water. Therefore, supplying saturated steam at an appropriate pressure to the heat exchanger is an important factor in achieving energy savings.Steam is introduced into the heating pipes (i.e., heat exchangers), and the heated object comes into contact with the surface of these pipes, and the latent heat released by the steam is absorbed by the heated object, so that the heating is realized. The steam emits latent heat and condenses into condensate. This condensate is then discharged into the atmosphere by a steam trap (see Figure 5). The so-called indirect heating is to use only the latent heat of steam. As mentioned earlier, the higher the vapor pressure, the less latent heat, while the sensible heat of saturated water increases; In other words, the supply of saturated steam at the right pressure for the heat exchanger used is the key to energy savings.