When developing Lepido, we had a clear goal: to create the world’s most resilient heat exchanger – a solution that can handle dirty exhaust air without pre-filters, without extensive cleaning, and without operational disruptions.

But words alone aren’t enough. It needs proof.

That’s why we subjected Lepido to a long-term test in one of the most challenging ventilation environments imaginable: the exhaust duct of a commercial kitchen – specifically, a Burger King restaurant in Malmö, Sweden. Open-flame grilling creates an air stream filled with grease, particles, moisture, heat, and dirt.

Photo from the ventilation system of a fast food restaurant (not Burger King)

If Lepido can handle this – it can handle anything.

The Challenge: Where other systems fail
Dirty exhaust air is the enemy of ventilation systems. Grease, soot, lint, and dust clog conventional heat exchangers, causing high pressure drops, costly maintenance, and eventually – total system failure.

In many operations, heat recovery is therefore avoided altogether because the maintenance costs outweigh the energy savings.

The Solution: A new type of heat exchanger
Lepido is unlike any other heat exchanger. Instead of dense fins, we use a patented geometry with open coils and a large free area – specifically designed to withstand dirty airflows. The construction is made for direct duct installation, with no need for filters.

Behind the design:

Patented coil geometry with high free area

100% counterflow operation

Multiple liquid channels

Designed to match the heat transfer performance of conventional systems – but without their vulnerabilities

Test Environment: A kitchen filled with grease, smoke, and heat

In autumn 2020, Lepido was installed in the exhaust duct of Burger King Malmö – a location where hot, dirty air containing grease and particles flows 16 hours a day. A real-world test, with no compromises:

No pre-filter

No maintenance or cleaning of the Lepido

Operation: 22 months continuously

Kitchen airflow: 1020 l/s, average temperature 34°C

System performance was monitored every minute via a central control system

Photo from the ventilation system of a fast food restaurant (not Burger King)

The Results: Proof of extreme durability

After 22 months of continuous operation, the results are clear:

Operational disruptions: 0

Pressure drop increase: Only about 50 Pa (equivalent to 25 Pa/year)

Efficiency loss: Just -1% in thermal effectiveness

Energy recovered: approx. 86,000 kWh/year

Yes – there is some buildup on the coils (see image). But the impact on performance is negligible, and the system has delivered stable and efficient heat recovery without a single interruption.

Image of the Lepiod after 22 months in operation with no cleaning

Conclusion: A new level of robustness in energy technology

We set up the test to prove that Lepido can do what no other heat exchanger can. And the results speak for themselves:

Lepido is demonstrably built to withstand the harshest environments – without compromise.

This opens the door to profitable and trouble-free energy recovery in:

Commercial kitchens

Drying facilities

Foundries

Food processing plants

Industrial laundries

Wood and biomass industries

Any environment where dirty exhaust air has previously been a barrier

Want to learn more or have a project with dirty exhaust air?
Get in touch – we’ll assist with everything from calculations to project planning.