Chimney Draft Calculator

Formula

To calculate the Chimney Draft:

\[ D = h \cdot p \cdot \left(1 - \frac{T_o}{T_i}\right) \cdot g \]

Where:

\(D\) is the chimney draft (pascals)
\(h\) is the height of the chimney (meters)
\(p\) is the density of the air (1.292 kg/m³)
\(T_o\) is the outside temperature (°C)
\(T_i\) is the inside temperature (°C)
\(g\) is the acceleration due to gravity (9.81 m/s²)

What is Chimney Draft?

A chimney draft is a measure of the pressure differential between the inside and outside of a chimney shaft. This pressure differential causes air to move up through the chimney, which helps in removing smoke, gases, and other byproducts of combustion. Proper draft is crucial for the efficient operation of heating systems and to ensure safe venting of combustion gases.

Example Calculation 1

Let's assume the following values:

Height of Chimney (\(h\)) = 10 meters
Outside Temperature (\(T_o\)) = 10°C
Inside Temperature (\(T_i\)) = 150°C

Use the formula:

\[ D = 10 \cdot 1.292 \cdot \left(1 - \frac{10}{150}\right) \cdot 9.81 \approx 10 \cdot 1.292 \cdot 0.9333 \cdot 9.81 \approx 118.73 \text{ Pascals} \]

The chimney draft is approximately 118.73 Pascals.

Example Calculation 2

Let's assume the following values:

Height of Chimney (\(h\)) = 15 meters
Outside Temperature (\(T_o\)) = 5°C
Inside Temperature (\(T_i\)) = 100°C

Use the formula:

\[ D = 15 \cdot 1.292 \cdot \left(1 - \frac{5}{100}\right) \cdot 9.81 \approx 15 \cdot 1.292 \cdot 0.95 \cdot 9.81 \approx 184.62 \text{ Pascals} \]

The chimney draft is approximately 184.62 Pascals.