Velocities Ventilation Ducts

Reference data and engineering information about velocities ventilation ducts for hvac systems applications.

velocitiesventilationducts

Overview

Engineering reference data for Velocities Ventilation Ducts in HVAC systems.

Key Formulas

Sensible Heat

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

Latent Heat

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

COP (Cooling)

$COP = Q_c / W$

Coefficient of performance.

Variables

Symbol	Description	Unit
$Q$	Heat transfer	W
$\dot{m}$	Mass flow rate	kg/s
$c_p$	Specific heat of air	J/(kg·K)
$\Delta T$	Temperature difference	K

The duct velocity in air conditioning and ventilation systems should not exceed certain limits to avoid unnecessary noise generation and pressure drop. The limits depend on the application, as background noise levels vary between public and industrial buildings.

8 rows

Recommended Maximum Air Velocities in Ventilation Ducts
Service	Public Buildings (m/s)(m/s)	Public Buildings (ft/min)(ft/min)	Industrial Plant (m/s)(m/s)	Industrial Plant (ft/min)(ft/min)
Air intake from outside	2.5 - 4.5	500 - 900	5 - 6	1000 - 1200
Heater connection to fan	3.5 - 4.5	700 - 900	5 - 7	1000 - 1400
Main supply ducts	5.0 - 8.0	1000 - 1500	6 - 12	1200 - 2400
Branch supply ducts	2.5 - 3.0	500 - 600	4.5 - 9	900 - 1800
Supply registers & grilles	1.2 - 2.3	250 - 450	1.5 - 2.5	350 - 500
Low level supply registers	0.8 - 1.2	150 - 250
Main extract ducts	4.5 - 8.0	900 - 1500	6 - 12	1200 - 2400
Branch extract ducts	2.5 - 3.0	500 - 600	4.5 - 9	900 - 1800

Source: engineeringtoolbox.com

Duct Velocity Classifications

Duct systems are classified based on air velocity to guide design and noise control:

Low Velocity Systems: Air velocities up to 2000 fpm (10 m/s)
Medium Velocity Systems: Air velocities in the range 2000 to 2500 fpm (10 - 13 m/s)
High Velocity Systems: Air velocities greater than 2500 fpm (> 13 m/s)

References

Original Source

Source: engineeringtoolbox.com