Recommended distance in between duct branch take-offs 2

[Fuzzylogic14]

Hi Everyone,

I am sizing an air supply ductwork system and need to know where can I find recommendations as per standard for recommended distance (of equivalent diameters) in between two subsequent branch take-offs on a main straight duct.

I am following the CIBSE guide, but cannot find where it mentions the distance in between branches that we should abide by for reducing the pressure losses.

Can someone help me?

Thanks. Please find the link to my workings.

 

[EnergyProfessional]

I would say 3 diameters since that is a rule of thumb for fans. but I wouldn't sweat it if maintaining this distance would cause awkward duct routing somewhere else.

I often see 2 lateral take-offs right at the same place (left and right). Maybe having the disturbance once is better than having 2 disturbances.

The theory is, you want to have flow stabilize again after a change.

Probably a good idea to not have a transition after every take-off if you have the clsoe to each other. Transitions introduce turbulences, and cost $. Better to keep the duct large for a few feet longer to catch the next take-off.

 

[LittleInch]

IO don't think there is one.

If you want lowest pressure drop then put them next to each other on the same size main duct.

Is this an exhaust or delivery system? With an AHU and a filter i would assume delivery of cold air, so can't see this being your main source of pressure loss.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Fuzzylogic14]

Thanks,@EnergyProfessional and @littleInch for your inputs.

In fact, I am supplying a room with fresh air for an incubation room.

There are 3 incubators in series with each other and the 3 branches are in front of the respective incubators where there are openings and dampers (from the middle of the incubators on top ) which control the air needed via a control system. Whenever air is needed, the damper opens and admits air in the room inside the incubators.

However, the duct system in the picture needs to supply continuous air to the incubation room as recommended by books.

That is why I cannot put the branches in lateral.

Also, the system's total air flow requirement is 1.03 m3/s. Adding a Hepa filter to this system will be where the highest pressure loss will be concentrated. but I do not have the choice as I need to remove dust particles like Aspergillus Fumigatus ( a fungi spore) which are sizes from 1-5 microns.

Thanks for the help.