A long-term collaboration between Dext Heat Recovery and Sheffield Hallam University has turned big ideas into food industry firsts, creating greener and more efficient commercial kitchens.

Heat recovery has always been challenging for the food sector, due to the difficulty of handling dirty air streams. Lancashire firm Dext had an idea about how to tackle this issue, but it needed a technical partner to explore what was feasible.

Between 2009 and 2012, the collaboration made its first technological breakthrough in heat recovery. Using state-of-the-art modelling techniques, Hallam academics helped Dext to develop a radiative heat recovery panel that could be installed close to cookers and chargrills in the form of a splashback.

The DexTherm heat recovery panel absorbed waste heat and transferred it into a sealed water circuit, which was then circulated through a coil in a cylinder, providing hot water for the kitchen and substantial energy savings. The system had the advantage of performing well in difficult operating circumstances, as well as being effective, robust, relatively low-cost and easy to clean.

Today, this innovative splashback is used in more than 400 Nando’s restaurants across the UK.

The next project was to develop a bigger, more powerful heat recovery system that could sit within a kitchen’s extract duct. Dext secured a knowledge transfer partnership in 2013 to employ a graduate mechanical engineer to work with Hallam’s expert academics to make this vision a reality. So successful was the partnership, that engineer Dr Gareth Evans has since become Dext’s Technical Director, integral to the ongoing development of the company.

The team scoped out an experimental manufacturing solution, which resulted in a prototype heat exchanger and heat pump plant. The plant needed to recover the waste heat from the kitchen air extractor and provide hot water, space heating and cooling for the entire restaurant. In 2014, the system was successfully installed in a restaurant to evaluate its performance.

Dext joined forces with Hallam’s National Centre of Excellence for Food Engineering (NCEFE) in 2015 to set up a consortium with the William Jackson Food Group and DCI Refrigeration. They successfully secured £600,000 through the competitive Innovate UK ‘Improving Food Supply Chain Efficiency’ fund to develop a new fully-fledged heat recovery system based on the prototype.

The project brought together all the previous experiments and prototype testing to create a full scale, no-stone-unturned development project to develop the DexThermic ‘Dirty Air Heat Exchanger’ (DAHX).

Initially, small-scale prototypes were tested and validated against computational fluid dynamics models, and as the science stacked up, the ambition for the project increased.  In 2018 – the final year of the UKRI project – the third scale prototype became a reality.

The result was an efficient and cost-effective system made from aluminium and stainless steel using a technically advanced design and manufacturing process. The design allowed for the unit to be fitted to the existing air handling system and showcased its resistance against grease build up.

The product proved its ability to recover enough waste heat from the cooking process, and from the body heat of diners in the restaurant, to provide space heating and hot water for the entire restaurant.

Neil Bracewell, Dext Commercial Director said: “An idea, however good it may be, can only come to successful fruition if you can prove its worth, and Sheffield Hallam University gave Dext that opportunity. We were able to turn an idea into a real, robust, ready-for-market product thanks to the academic team and the facilities made available to us. Where else would we get our hands on a full-scale specially built environmental wind tunnel? Now our sustainable heat exchange system is taking the UK catering industry by storm and we have all the data to prove its merit.”

The collaboratively created and academically tested sustainable innovation ‘DexThermic’ is the result of vision, passion and engineering expertise being focused on the hospitality sector with amazing results.

This success story was first published in NCUB’s showcasing booklet, Making Small Mighty. To read about more case studies between UK universities and small and medium sized businesses (SMEs), download the booklet here.