Stack or Flue Effect

Stack or flue effect produced when outdoor temperature is lower than indoor temperature

The stack or flue effect produced when outdoor temperature is lower than indoor temperature is due to the difference in weight of warm column air within the building and the cooler air outside.

The rate of air flow can be expressed as

Q = 9.4 A (h (t_r - t_o))^1/2         (1)

where

Q = rate of air flow (ft³/min)

A = free area of inlets and outlets - assumed equal (ft²)

h = height from inlets to outlets (ft)

t_r = average room temperature at height h (^oF)

t_o = outdoor temperature (^oF)

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