Ventilation Dampers

Overview

Engineering reference data for Ventilation Dampers 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

Damper Classification by Function

Damper Leakage Classification (BS EN 1751:1999)

The leakage class determines the acceptable air leakage through the damper at a 100 Pa pressure difference.

• *Class 0: No requirements
• *Class 1: Less than $0.2 \text{ m}^3\text{/s per m}^2$ valve area
• *Class 2: Less than $0.04 \text{ m}^3\text{/s per m}^2$ valve area
• *Class 3: Less than $0.008 \text{ m}^3\text{/s per m}^2$ valve area
• *Class 4: Less than $0.0015 \text{ m}^3\text{/s per m}^2$ valve area

Air flow rates at 100 Pa are typically available from manufacturer catalogs.

Leakage Flow Rate Calculation

The leakage air flow through a closed damper can be calculated using the pressure difference and manufacturer data at 100 Pa.

$q_l = q_{100} \left( \frac{\Delta p_l}{100} \right)^{1/2}$

Where:

• $q_l$ = actual volume flow per m² valve area (m³/s per m²)
• $q_{100}$ = volume flow at 100 Pa per m² valve area (m³/s per m²)
• $\Delta p_l$ = actual pressure drop through the valve (Pa)

References

• Original Source