Flat or Round

[tanto]

Hi folks,
not been on here in a long time but looking for some advice. Needing to replace the flexi-hose on our shower fan as it is fairly well clogged with fluff. Have a total run of around 3m from end to end with an inline fan roughly 2m from the outlet. What would give me the best airflow, round or flat solid ducting? Or is there much difference between the 2 of them. Flexi hose seems to collect a lot of fluff due to it not being smooth internally and also appears to go a bit rigid over time. 100mm fan and ducting.

thanks,
Dave.

 

[KenGMac]

tanto, good evening.

The smooth internal surfaces of the square or rectangular plastic ducting is far more efficient at moving the air than the circular [ribbed] ducting.

As an aside, cleaning the Plastic Square / Rectangular ducting is easier than the circular ribbed ductwork.

If you look at an industrial ducting system they are a smooth pressed steel, Square / Rectangular the circular ducting lengths are kept to a minimum because of the surface resistance on the circular at times called "Elephants Trunking" and the associated internal ribbing, anything that causes air flow turbulence will reduce flow rates and increase load on the fan.

Ken.

 

[tanto]

cheers Ken,
that is the reason for changing from the ribbed hose. Just wondered what would give me the best flow rate, solid round or solid flat ducting.
Dave.

 

[endecotp]

The rectangular plastic ducting is sold for use where you need to fit between joists above a ceiling. If you don't need to do that, get the round stuff.