Thermal Expansion

Ducts made of galvanized steel can be subject to relatively important temperature differences, especially if they are intended for heating or air-conditioning purposes.

The linear expansion due to these temperature changes is in general minimal.

It is not uncommon on larger buildings however to find ducts several hundred meters long.

In such cases thermal expansion must be taken into consideration. 

If one assumes that the duct is used for heating purposes (80°C minus ambient temperature of 20°C makes a temperature difference of 60°C) and that it is 100 m long, then the expansion would be 100m × 60 × 0,000013 = 0,78. The duct would then be 100 m long at 20°C and 100,78 m at 80°C!


Linear expansion coefficients of some materials:

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