Draft produced by the difference in weight of a column of flue gases and outside air is called:

Draft produced by the difference in weight of a column of flue gases and outside air is called:

• A. Mechanical Draft
• B. kPa
• C. Natural Draft
• D. MPS

Answer: (C)

Natural draft, driven by buoyancy from the temperature (and density) difference between hot flue gases and outside air, pushes the combustion products up and out of the vertical vent. Heated gases are lighter, so the weight of the gas column is less than that of the same-height column of outside air, creating a pressure difference that draws the gases upward. The effect strengthens with greater height of the stack and a larger temperature difference. Mechanical draft would use a fan or blower to move the gases, not buoyancy, and the other terms are units, not a type of draft.

Natural draft, driven by buoyancy from the temperature (and density) difference between hot flue gases and outside air, pushes the combustion products up and out of the vertical vent. Heated gases are lighter, so the weight of the gas column is less than that of the same-height column of outside air, creating a pressure difference that draws the gases upward. The effect strengthens with greater height of the stack and a larger temperature difference. Mechanical draft would use a fan or blower to move the gases, not buoyancy, and the other terms are units, not a type of draft.