Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

- the most efficient way to navigate the Engineering ToolBox!

Friction Head Loss in Air Ducts - Online Calculator

Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units

Sponsored Links

The major loss, or friction loss, in a circular duct in galvanized steel with turbulent flow can for imperial units be expressed

Δh= 0.109136 q^1.9 / d_e^5.02 (1)

where

Δh = friction or head loss (inches water gauge/100 ft of duct)

d_e = equivalent duct diameter (inches)

q = air volume flow - (cfm - cubic feet per minute)

For rectangular ducts the equivalent diameter must be calculated.

Pressure vs. head

Air Ducts Friction Loss Calculator - Imperial Units

The head loss calculator below is based on formula (1):

Head loss and air flow velocity for some common duct sizes and air flow volumes can be taken from the table below:

Head Loss (inches water gauge per 100 feet duct)
Air velocity (ft/min)
Air Volume (cfm)	Duct Size (inches)
Air Volume (cfm)	4	5	6	8	10	12	16
100	0.65	0.21	0.09	0.02	0.01
100	1146	733	509	286	183
200		0.8	0.32	0.08	0.02	0.01
200		1467	1019	573	367	255
400			1.19	0.28	0.09	0.04	0.01
400			2037	1146	733	509	286
800					0.34	0.14	0.03
800					1467	1019	573
1600							0.12
1600							1146

Air velocity should not exceed certain limits to avoid unacceptable noise generation.

Air Ducts Friction Loss Calculator - SI Units

This pressure loss calculator is based on formula (1) with input and output values modified for SI units.

Pressure vs. head

Air Ducts - Velocity and Friction Loss - Excel Template

This Excel template can be used to calculate velocity and friction loss in air ducts.

Air Ducts - Friction Loss Diagram

The chart below can be used to estimate friction loss in air ducts.

The default values are for air flow 400 cfm (680 m³/h), duct size 8 in (200 mm) and friction loss 0.28 inH2O/100ft (2.3 Pa/m).

Download and print Air Ducts Friction Loss Diagram!

Air Duct Velocity

Sponsored Links

Related Topics

Ventilation - Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more

Related Documents

Air Ducts - Friction Loss Diagram - Major loss diagram for air ducts - SI units
Air Ducts - Friction Loss Diagram - A major loss diagram for air ducts - Imperial units ranging 10 - 100 000 cfm
Air Ducts - Velocity Diagram - Air flow volume, duct size, velocity and dynamic pressure
Duct Sizing - Equal Friction Method - The equal friction method for sizing air ducts is easy and straightforward to use
Duct Velocity - Calculate velocities in circular and rectangular ducts - imperial and SI-units - online calculator
Ducts Sizing - Velocity Reduction Method - The velocity reduction method can be used for sizing air ducts
Ductwork Seal Classes - Ductwork prone to air leakages
Equivalent Diameter - Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI-units
Equivalent Diameter - Rectangular and Circular HVAC Ducts - Equivalent diameter for rectangular and circular ducts - air flows between 100 - 50000 cfm
Hydraulic Diameter - Hydraulic diameter of pipes and ducts
Pressure Classifications of Duct Systems - Duct systems are commonly divided into three pressure classifications
Sizing Circular Ducts - A rough guide to maximum air volume capacity of circular ducts in comfort, industrial and high speed ventilation systems
Spiral Ducts - Dimensions - Standard dimensions of spiral ducts - Imperial units
Typical Air Duct Velocities - Typical air duct velocities in applications like ventilation systems or compressed air systems
Velocity Classification of Ventilation Ducts - Recommended air velocities in ventilation ducts

Tag Search

en: air ducts head friction pressure loss rectangular circular

Sponsored Links

Search the Engineering ToolBox

- the most efficient way to navigate the Engineering ToolBox!

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate this page to

About the Engineering ToolBox!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Advertise in the ToolBox

If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. You can target the Engineering ToolBox by using AdWords Managed Placements.

Citation

This page can be cited as

Engineering ToolBox, (2003). Friction Head Loss in Air Ducts - Online Calculator. [online] Available at: https://www.engineeringtoolbox.com/duct-friction-pressure-loss-d_444.html [Accessed Day Mo. Year].

Modify access date.

close

3D Engineering ToolBox - draw and model technical applications!

2D Engineering ToolBox - create and share online diagram drawing templates!

Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 20

Sponsored Links