A heat exchanger only saves energy if the recovered heat exceeds the extra electricity needed to push air through it. That trade-off is governed by pressure drop.
What Drives Pressure Drop?
- Face velocity (higher speed = steeper rise)
- Core depth and plate count
- Surface corrugation and coating thickness
- Dust or fiber loading on fins
Reading a Performance Curve
Manufacturers publish pressure drop vs airflow. A good design operates on the flatter part of the curve — typically 2–3 m/s face velocity for plates. Beyond that, fan power rises faster than recovered heat.
Calculating Net Savings
Net savings = recovered thermal energy − extra fan energy. As a rule of thumb, keep added pressure drop under 100–150 Pa for ventilation applications unless efficiency gains are large.
Design Tips
- Use EC plug fans to capture part-load efficiency.
- Add pre-filters to keep the core clean.
- Provide access for periodic cleaning.
- Model the full year, not just design day.
Put pressure drop next to recovered energy early in the selection, not after. Apply the fan affinity laws when forecasting part-load savings: halving flow roughly quarters the fan power, so variable-speed control pays back fast on duty with wide load swings. Track specific fan power, the watts per cubic meter per second of air moved, as a single figure of merit across competing cores. Use the published performance curve rather than a single point, and model the annual load profile so the design sits on the efficient part of the curve for most hours. Pre-filtration and a cleaning plan protect that position over time. Our performance methodology explains how effectiveness and pressure drop trade off in practice.
Frequently Asked Questions
Is a bigger core always better?
Not always. A deeper core raises efficiency but also pressure drop; optimize the combination.
How often should I clean?
Inspect quarterly in dusty duty; clean when pressure drop rises 15–20 % above baseline.