What effect does flue gas temperature have on draft strength?

Higher temperatures strengthen draft because warm air is less dense than cooler air. This principle is crucial in understanding how draft works in chimneys and venting systems. As the flue gas temperature increases, the gases rise more quickly due to their reduced density. This creates a greater pressure difference, which enhances the upward flow of air in the flue. This phenomenon is referred to as the stack effect, where the difference in temperature between the flue gases and the ambient air leads to improved draft performance.

In essence, when flue gases are hotter, they expand and become lighter than the cooler air outside, resulting in a stronger draft. This effect is important for efficient combustion and proper venting in heating systems. A strong draft is essential as it helps remove combustion byproducts from the appliance and ensures that fresh air is drawn in for continued combustion.