This article delves into the core design concepts and frequent mistakes in achieving pressure balance in ventilation duct networks. It covers resistance matching, valve configuration, CFD simulation validation, and online adjustment, providing engineers with actionable guidance to optimize system efficiency and avoid costly design traps.
1. Overview
Ventilation network pressure balance refers to the process of ensuring stable pressure distribution and balanced airflow across multi-branch, multi-fan duct systems by rationally distributing resistance and airflow among each branch. Poor pressure balance may cause certain branches to be over- or under-supplied, lowering overall efficiency and increasing local noise and vibration.
2. Importance of Pressure Balance
Precise Airflow Distribution: Ensures each zone receives the required ventilation and prevents dead spots or wasted airflow.
Reduced Energy Consumption: Proper resistance distribution minimizes ineffective fan output.
Extended Equipment Lifespan: Prevents prolonged high-load operation of fans, reducing vibration and mechanical wear.
Improved Safety: Avoids gas accumulation or hazardous gas retention, ensuring personnel and equipment safety.
3. Key Design Points
System Resistance Matching
Calculate the total resistance for each branch, including duct length, diameter, elbows, and flanges. Draw the system resistance curve according to required airflow, and match it with the fan’s performance curve.
Branch Airflow Distribution
Install constant volume or balancing valves at main-branch intersections. Adjust valve openings to distribute the design airflow precisely for each branch.
Valve and Damper Configuration
Balancing valves should be located at the branch entrance, ensuring a straight pipe section ≥5D after the valve. Use motorized dampers in sensitive areas for centralized remote control.
Online Monitoring and Adjustment
Install differential pressure transmitters, airflow sensors, and other devices for real-time monitoring at each node. Integrate with PLC/SCADA systems for closed-loop PID control.
CFD Simulation Validation
Use CFD simulation in the design phase to visualize network airflow, identify dead zones and short-circuit flows. Optimize duct sizes, valve placement, and fan layout based on simulation results.
4. Common Pitfalls
Over-reliance on Single Fan Performance: Ignoring actual branch resistance causes significant deviation between design and real airflow.
Neglecting Dynamic Operating Conditions: Failing to allow for load changes or adjustment space as production conditions vary.
Underestimating Leakage and Resistance: Overlooking duct leakage or flange looseness leads to higher actual resistance than calculated.
Blindly Increasing Duct Diameter: This may reduce resistance but increases material costs, space requirements, and capital investment.
Lack of Balancing Valves or Online Adjustment: Without fine-tuning mechanisms, operators can only reduce fan speed or use bypasses, wasting energy.
5. Conclusion and Recommendations
Comprehensive Evaluation: Always match fan performance curves with system resistance curves at the initial design stage.
Flexible Adjustment: Equip necessary balancing valves, motorized dampers, and online monitoring devices for operational fine-tuning.
Validation & Optimization: Use CFD simulations and field flow tests to ensure that the design matches real-world conditions.
Regular Calibration: Perform pressure balance calibration every six months and adjust as needed.
By scientifically balancing ventilation network pressure and avoiding common pitfalls, you can achieve efficient, stable, and cost-effective ventilation system operation.