2nd Class Power Engineering (2A3) Practice Exam

Natural circulation in a boiler is critical for maintaining efficient heat transfer and ensuring that water flows properly through the system without the need for mechanical pumps. A key factor influencing natural circulation is the height of the steam drum above the bottom drum.

This height creates a hydrostatic head, which is the pressure difference due to the height of the water column within the system. The greater the height between the steam drum and the bottom drum, the stronger the driving force for circulation. As water is heated in the boiler, it becomes less dense and rises towards the steam drum, while cooler, denser water sinks back down to be heated again. This continuous cycle helps maintain proper flow and effectively transfers heat throughout the boiler system.

While water temperature plays a role in density differences and circulation, the specific impact of the height of the steam drum is a more direct and critical factor influencing the natural circulation process. The type of fuel used and the color of the water do not have a significant impact on the natural circulation mechanism itself.