What is the term for the draft produced by the difference in weight of flue gases within a chimney?

The correct term for the draft produced by the difference in weight of flue gases within a chimney is natural draft. This phenomenon occurs due to the buoyancy of hot gases, which are lighter than the cooler air outside the chimney. As the hot gases rise, they create a pressure difference that pulls more gases from the combustion process up through the chimney, ensuring efficient venting of exhaust.

Natural draft is commonly found in applications where the design allows for gravity to aid in venting, such as in traditional chimneys or venting systems for appliances. The effectiveness of natural draft can be influenced by factors such as chimney height, temperature difference, and the overall design of the venting system, but its fundamental principle relies solely on the physical characteristics of the gases involved.

On the other hand, the other terms refer to different methods of creating draft: mechanical draft involves devices like fans or blowers to induce airflow, induced draft refers specifically to a system where exhaust fans are used to pull gases out of the combustion area, and forced draft describes a system where a fan pushes air into the combustion chamber to enhance airflow. Each of these methods is engineered for specific applications and can enhance performance where natural draft might be insufficient.