Energy saving is an important topic that we all need to be aware of. This comprehensive technical selection document is based on our many years of experience as a steam trap manufacturer and introduces the operating principles and extensive use cases of various steam trap models. We believe that this information can help you choose the right steam trap to achieve energy saving.
What is water vapor?
Water generates tasteless, odorless, and colorless (invisible) gas when heated. In daily life, boiling water with a kettle generates steam.
Steam generation process
The cycle of steam and water is as follows
Water and steam cycle
① When water is heated under a certain pressure, its temperature rises.
② After reaching the saturated water (boiling water) temperature, the temperature stops rising and the water begins to evaporate and turn into steam.
③ Continue heating, and the evaporation process continues until all the water evaporates and turns into steam. During this process, the temperature remains unchanged. This temperature is called the saturated steam temperature. The steam at this point is called saturated steam, and the pressure at this point is called the saturated steam pressure. Steam is typically used in this state. The amount of water contained is expressed as the percentage of dryness of saturated steam.
④ After all the water has evaporated, if it is heated again, the temperature rises again. This state of steam is called “superheated steam.” ⑤ After releasing heat, the temperature drops and returns to the state of condensed water and water.
The figure below shows the temperature changes of water and steam as the amount of heat is added when 1L (1kg) of water at 0°C is heated at atmospheric pressure.
The state changes of 1 L (1 kg) of water when heated. In this graph, the pressure is kept constant at atmospheric pressure, and the water begins to boil at 100°C. The temperature of the water and steam coexisting at 100°C. Therefore, the saturated steam pressure remains constant, and the temperature remains constant until all the water is converted to steam. This means that since the saturated steam pressure remains constant, the temperature also remains constant, allowing for stable and uniform heating, and adjusting the pressure can control the temperature.
The amount of heat required to heat 1L (1kg) of water at 0°C to 100% steam (gas) at atmospheric pressure is
• Heat required to heat water (sensible heat): 419 KJ/kg
• The amount of heat required to heat water to steam (latent heat): 2,258 KJ/kg
Therefore, the total amount of heat (sensible heat + latent heat = total heat) = 2677 KJ/kg.
* Latent heat is much greater than sensible heat, and saturated steam uses latent heat for heating.
Basic properties of steam
1. Relationship between saturated steam pressure and temperature
As the saturated steam pressure increases, the temperature also increases accordingly. Therefore, when a high heating temperature is required, the steam pressure needs to be increased.
2. Relationship between saturated steam pressure and heat
As the saturated steam pressure increases, the sensible heat increases, the waste heat decreases, and the total heat increases. Therefore, the lower the saturated steam pressure, the more heat is available.
3. Relationship between saturated steam pressure and volume
As the saturated steam pressure increases, the steam volume per unit mass (specific volume) decreases dramatically. Therefore, the higher the saturated steam pressure, the smaller the volume and the smaller the pipe diameter.
