At the end of this module, you will be able to:
- Describe the three phases of water
- Define the boiling point of water
- Define "latent heat"
- Define "condensation"
- Define "superheated steam"
- Describe problems with using superheated steam on a paper machine
- Describe the relationship between steam pressure, temperature, and latent heat
- Describe how steam is used in a paper machine drying system
- Identify the flow of steam and condensate through the paper machine
The following key questions are answered in this module:
Why does water boil at lower temperatures at higher elevations?
The phase of water (solid, liquid, or gas) is determined by its temperature and pressure. Atmospheric pressures are lower at higher elevations, and liquid water boils at lower temperatures at lower pressures.
What is condensate?
When water molecules in steam contact a cool surface, they lose energy to that surface and change into a liquid. The resulting liquid water is called "condensate."
What is superheated steam?
Superheated steam is steam that has been heated above its boiling point for the current pressure
How can superheated steam cause problems with the rotary joints on dryer cans?
The moisture in saturated steam lubricates the carbon rings in the rotary joints. Without this lubrication, the rings will wear more rapidly and could even crack if they get too hot.
Why is it important to collect and reuse the condensate from a paper or board machine?
The condensate still contains heat, which is valuable because it lowers the amount of heat needed to produce additional steam.
Below is a transcript of the video sample provided for this module:
Water or H2O, exists in three phases: solid, liquid, or gas. The phase that water takes is determined by its temperature and pressure. There are some significant changes that occur as water goes from the liquid to gaseous phase. This transition is referred to as boiling, and it occurs at 212 degrees Fahrenheit at normal atmospheric pressure, zero PSI gauge pressure. As heat is added to liquid water, it increases in temperature. Each BTU, a unit of energy that is added, increases the temperature of one pound of liquid water by one degree Fahrenheit. Once the water reaches the boiling point, the temperature stops increasing. As even more heat is added, this energy goes toward creating vapor rather than increasing temperature. Once all of the liquid water in a system has turned to vapor or evaporated, the temperature will resume its increase as more heat is added. Steam at a temperature above its boiling point is called super-heated steam.
Use the additional resources and links below to learn more about this topic: