What does "natural circulation" refer to in the context of a boiler?

Natural circulation in a boiler refers to the process where water movement occurs due to temperature and density differences within the liquid. As water is heated in the boiler, it becomes less dense and rises. This less dense, hotter water moves upward through the boiler, while cooler, denser water descends to take its place. This continuous cycle creates a natural flow of water, allowing for effective heat transfer and steam generation without the need for pumps.

This process is fundamental in many boiler designs because it requires no external mechanical means to circulate the water, making it a simpler and often more reliable system. The interaction between temperature differences and resulting density changes is crucial for the proper function of boilers designed to utilize natural circulation. It's a critical principle that ensures efficient operation and safety in boiler systems.