How to Size a Heat Exchanger

Sizing a heat-recovery device is a four-input problem: you know the airflow, the temperature (and often humidity) difference between the two streams, the effectiveness you need, and the pressure drop your fan can afford. Everything else - core size, face area, plate count - follows from those. This hub is the entry point to our sizing library and turns the selection process into repeatable steps.

If you have not yet chosen a technology, start at the technology comparison hub; if you need the underlying physics, see the basics hub.

The Selection Workflow

1. Define the duty - supply and exhaust airflow (m³/h or CFM), entering temperatures, and climate/process constraints.
2. Set the target effectiveness - driven by energy code (see the standards hub) and payback.
3. Pick the technology - plate, wheel, heat pipe or run-around coil, using the comparison matrix.
4. Size the core - face area and depth from airflow and allowable pressure drop.
5. Verify - commission against the rated condition with a real measurement.

Start With the Selection Guide

Our main reference, Heat Exchanger Selection Guide: Sizing, Airflow, ΔT, Efficiency, works through each input with the formulas and rules of thumb a specifier actually uses.

Effectiveness and Hand Calculation

Before trusting software, learn to sanity-check a result. Calculating Heat Exchanger Effectiveness by Hand shows the Effectiveness-NTU steps, and the Effectiveness-NTU method explained in the basics hub gives the theory.

Application Scenarios

Recovery duty varies enormously by setting. These articles map the technology to the environment:

• Application Scenarios Analysis - a structured overview of where each device fits.
• Common types in agricultural ventilation - humidity and dust considerations.
• Cross-flow heat exchanger applications - where the simpler flow arrangement is the right call.
• Heat Recovery and Building Energy Balance - sizing in the context of the whole building load.

Commissioning and Verification

A size is only correct if it performs. Commissioning and Performance Testing covers how to measure effectiveness on site and reconcile it with the rated value, an essential step referenced by ASHRAE 84 and EN 308.

Per-Industry Walkthroughs

Real selection examples across duty types - use these as templates for your own project:

• Data centers - liquid-coupled recovery cutting cooling costs ~40%.
• Marine & offshore wind - corrosion-resistant cooling solutions for harsh environments.
• Pharmaceutical & herbal drying - energy efficiency with product-quality preservation.
• Textile dyeing & setting - a case study in energy efficiency.
• Industrial coating / VOC lines - VOC exhaust heat recovery.
• Lithium-battery NMP recovery - solvent-vapor recovery for sustainable manufacturing.
• Sludge drying & waste treatment - a comprehensive case study.
• Wood & biomass drying - boosting drying energy efficiency.

Frequently Asked Questions

What airflow do I size to? The design outdoor-air rate from ASHRAE 62.1 or local code - not the peak fan capacity.

How much pressure drop is acceptable? It is a fan-energy trade-off; the selection guide gives typical face-velocity limits. Lower velocity means lower drop but a larger core.

Plate or wheel for my climate? Covered in the comparison hub - plates for clean, non-humid duty; wheels where latent recovery pays off.

Related Hubs

Heat exchanger fundamentals · Compare technologies · Standards and compliance

Send Us Your Duty Data

The fastest route to a correct size is to send us your airflow, ΔT and humidity data. We return a rated selection with the right standard referenced - or use the selection guide to scope it yourself first.