Real World Trials


The findings of the KTP project were applied to a prototype extract/exhaust heat recovery system at Nando’s Aylesbury. The prototype system was designed in collaboration with DCI Group using a cutting edge and incredibly complex CO2 heat pump.

The project used findings from the KTP project to create the very first DAHX (dirty air heat exchanger) prototype, and the system – for all its complexity – functioned well. However, it was expensive and had some capacity control issues due to it using a combination of a new primary heat exchanger (the DEXT prototype) and relatively new CO2 heat pump technology.

A prototype dirty extract heat recovery unit at Nando’s Aylesbury

The findings were, basically, that there were too many new things trying to work together, and this project was good, but it could be much better.

The working concept was right in front of us – but this was a turning point where we saw that the product concept would need to be more fully developed from the ground up, with a complete research and engineering project to unlock the potential of such a system and reduce its complexity.


  • DEXT was the first to successfully implement a novel extract heat recovery system that was resistant to fouling and friendly to new specific fan power requirements (restaurant plant energy requirements).
  • Discovered the value in performance mapping the new heat exchanger and, per the standard practice in heat exchanger design, this would enable the product to be appropriately tuned to the connected refrigeration plant and restaurant/industrial site.
  • The ‘Apollo’ project provided a strong and encouraging business case to invest in a full R&D path forward.
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