Design and installation of air duct systems (Duct Design)

Design and installation of air duct systems (Duct Design) Design air ducts for air conditioning systems. Why do you need to "reduce the size of the duct"? Solving doubts in an easy to understand way If you are wondering about designing and installing an air duct system (Duct Design), why do engineers have to design the air duct to get smaller and smaller with distance? Simple principles to remember For this matter, "When the air decreases, the pipe must be smaller." The main reason is because when the air is distributed separately according to the nozzle...

Design air conditioning ducts. Why do you need to "reduce the duct size"? Solving doubts in an easy to understand way

If you are wondering about the design and installation of duct systems (Duct Design), why do engineers have to design ducts to become smaller and smaller?

By distance? Simple principles to remember For this matter it is "When the wind decreases, the pipe must become smaller".

The main reason is because when the air is distributed through different heads (Diffuser) at various points, the air volume or CFM (Cubic Feet per Minute)

inside the main pipe will decrease If we do not reduce the size of the air duct according to the amount of air lost Will result in the wind speed being too low. Wasted budget

and cause the air distribution system to be unbalanced

5 An important reason why air duct design must "reduce duct size"

Properly reducing duct size (such as using the Equal Friction method) will have the following benefits for the overall HVAC system:

Maintain the appropriate air speed: Helps the air to circulate well. Not too slow until the wind doesn't reach its destination. And not too fast until it causes loud noises.

Maintain constant Friction Rate (Equal Friction): Make the pressure loss (Pressure Loss) per meter similar. Helps to balance the pressure drop across the entire system.

Cost savings: When the pipe size is smaller It will use less steel sheets and insulation. Lighter system weight This results in savings in both material costs and installation costs.

Reduced installation space above the ceiling: smaller pipes allow for higher ceiling heights. and avoid problems with air ducts colliding with other system work (such as water pipe work, electrical work)

Balanced air distribution (Air Balance): allows air to be delivered to every point in the area appropriately. Easy to balance the system and control the operation of the air conditioner (AHU) efficiently

Clear comparison: reducing pipe size VS not reducing pipe size

1. Wind speed (Velocity)

Reduce the pipe size (correct method): The air speed is within the appropriate range (e.g. 5 - 9 m/s for the main air pipe).

Does not reduce pipe size (Incorrect way): The wind speed has decreased a lot. When reaching the end of the air pipe, the speed is too low.

2. Friction Rate: Pa/m

Reduce pipe size (correct method): Uniform constant value (e.g. 0.90) Balanced pressure drop throughout the system.

Does not reduce pipe size (Incorrect method): Unstable value, unbalanced voltage drop.

3. Air distribution

Reduce pipe size (correct way): Air is distributed evenly to all points properly.

Does not reduce pipe size (Incorrect method): The wind is distributed unevenly. In some spots the wind is light. It takes a lot of time to adjust the system balance settings.

4. Area and budget

Reduce pipe size (correct way): Save costs (reduce materials) and save installation space above the ceiling.

Does not reduce pipe size (incorrect method): wasteful of expenses The material is heavy. The pipe is large and takes up space. and may collide with other system tasks

💡 Compare the picture: Air pipes are like water pipes.

Imagine plumbing. When water flows from the source and the water is turned on continuously, the flow rate (LPM)

will be reduced, so the size of the water pipe must be "reduced" as well (for example, from 4 inches reduced to 3 inches, 2.5 inches, and 2 inches, respectively).

Air ducts use the same principle.

Recommended air speed range for duct work (Guidelines)

In designing air ducts, air velocity (Air Velocity) will vary according to the position of the duct. In general, the recommended criteria are as follows:

Main Duct: 5 - 9 m/s

Branch Duct: 4 - 7 m/s

Sub-main pipe: 3 - 6 m/s

End Duct: 2 - 5 m/s

(Note: The appropriate wind speed value may be changed. Depends on the type of building and design standards chosen)

📌 Short summary for air conditioning system work.

Good air duct design The basic rule must be remembered: "Reduced air -> smaller pipe". This will help achieve the correct air speed.

Consistent pressure drop Save on installation costs Easy to install on site and make the air conditioning system work at its fullest potential

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Source catalog reference. Confirm site conditions and the manufacturer’s instructions before applying this information.

Design and installation of air duct systems (Duct Design)

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