Why must immersion elements always be submerged in liquid when energized?

Immersion heating elements are designed to transfer heat directly to the liquid they are submerged in, and when energized without sufficient liquid, they can generate excessive heat in the area of the heating element. This excessive heat can lead to a situation known as "dry fire," where the element is not cooled by the liquid, causing the temperature of the sheath material to rise significantly.

If the sheath becomes too hot, it can exceed the material limits, potentially leading to melting or failure of the element. The high watt density associated with immersion heaters means that they are particularly susceptible to overheating when not properly submerged, which underscores the importance of ensuring they are always immersed in liquid during operation. This preventative measure not only protects the heater from damage but also ensures efficient heating performance and safety in food processing applications.