Meet Harry Mitchell, Katopodis Prize winner

Every year, the Department of Mechanical Engineering awards prizes to recognise the achievements of our PhD students.

The Katopodis prize is awarded for the best PhD thesis within the Thermofluids division. Spyridon ("Spyros") Katopodis was an industrial case student in the Thermofluids division, studying transient emissions from diesel engines. He passed away in 2009.

The current prize holder is Harry Mitchell, let’s get to know him better:

CAn you say a few words on the award you’ve received?

I am deeply honoured to have received the 2024 Katapodis Prize for the best PhD Thesis in the Thermofluids division! My thesis, “Flaming and smouldering hazards in large timber compartments”, contributes to understanding and improving fire safety in modern timber buildings. Reflecting on all the other remarkable research conducted within our division, I feel proud that my work has been held in such high regard.

Why did you decide to study for a PhD?

I decided to do this PhD because I became passionate and fascinated with fire behaviour. It sounds very cheesy, but since I was in the Scouts, starting campfires somewhere in a rainy field in Hampshire, I have always found fire interesting. During my undergraduate studies, Prof. Guillermo Rein was my Heat Transfer lecturer. I asked him after one lecture about summer research opportunities, after which I spent the summer designing and making a fire-tornado rig, which the fire science research group I am a part of, Imperial Hazelab, has used dozens of times for outreach at Imperial and beyond.

It felt like the right path to continue learning and growing – I really like the idea of solving problems that nobody has solved yet and using those findings to help others. Fundamentally, the goal of my research is to understand how fires behave in buildings so that the overall safety of occupants can be improved, hopefully saving lives.

Before the PhD, I was not the most confident person - public speaking, for example, terrified me! However, during the PhD I had the opportunity to prove to myself that I can present my work to hundreds of people, solve exciting and challenging problems, and advance the forefront of human knowledge.

What is your research about, in a nutshell?

Engineered timber, or mass timber, has grown in popularity as a modern building material over the past two decades for several reasons, including a global desire to increase sustainability. With up to 39% of worldwide carbon emissions produced by humans coming from the construction industry, the adoption of engineered timber in modern construction has the potential to mitigate some of this. However, as anyone who has seen a campfire will tell you, timber can burn, posing a unique challenge compared to concrete and steel.

My research identified that the vast majority of fire experiments conducted in timber buildings have been small in size (<100 m²) compared to a lot of the actual buildings we are seeing being constructed (e.g. office spaces >1000 m²), which limits our understanding of how fire behaves in larger designs such as open-plan offices and retail spaces, which can be several thousand square meters. Therefore, I was a part of the largest timber building fire experiments conducted to date, the CodeRed experiments.

The CodeRed experiments were conducted in a 352 m² compartment with a timber ceiling and a wood crib along the floor, which approximated the typical amount of fuel in an office. My thesis studied and characterised three hazardous phenomena that had been largely under-studied in the context of timber buildings:

• 1) Flame spread along the floor and ceiling of timber compartments.
• 2) Smouldering (flameless burning, like the glowing at the end of a campfire!) of timber after the end of flames.
• 3) The ejection of firebrands (embers) from compartment openings during the fire, that can land on and ignite surrounding combustible material (e.g. nearby vegetation and buildings).

How would you describe your experience during your PhD in the department?

I honestly can’t think of a better place to do a PhD. Imperial as a top-ranking university worldwide is a great place to study, with excellent research facilities. The department is full of supportive and knowledgeable people at the top of their fields, whose guidance has been invaluable during my PhD. I truly feel that wherever I end up in my future research career, Imperial and this department has more than prepared me for the challenge.

I am particularly proud to be a part of the Hazelab research group, which is been a world-leader in fire science research across a range of topics, including wildfires, batteries, and buildings. In particular, representing the department and Hazelab at multiple international conferences has been a great experience!

What would you say about the supervision you received?

Professor Guillermo Rein has been my academic supervisor and mentor throughout the PhD. He has been extremely generous with his time, feedback, and investment in me becoming the best researcher I could be. One thing that I have particularly valued is that Guillermo has given me exceptional opportunities to grow and learn beyond my PhD research. For example, I was the lead teaching assistant for his Master’s-level combustion course for four years, where I quickly learned how challenging and rewarding teaching is. He has supported me in presenting to hundreds of people at international conferences (and reminded me to “have mercy on my audience”!), got me involved in exciting consultation projects, and given me the guidance and support I needed to become a well-rounded researcher. Due to the wide research scope of Hazelab, I have also got involved in other research collaborations, including the WUI-NITY project, which focuses on modelling tools for wildfire spread and evacuation.

Arup provided me with an incredible opportunity to be a part of the largest building fire experiments ever conducted. Dr. Panos Kotsovinos, the leader of the CodeRed experiments, was a brilliant link into the fire safety industry, making sure that the research we produced together was developed and disseminated in a way that would be beneficial to fire safety engineers, and actually result in safer buildings.

What were the most difficult challenges?

A PhD, as you would expect, is not without its challenges. One of my biggest challenges was that the experiments I was involved in were conducted just outside Paris at the height of the pandemic, meaning that travelling was a challenge. I travelled to France four times, which involved numerous Covid tests, multiple weeks in self-isolation at home and in a hotel in the French countryside, and plenty of croissants consumed.

One of the biggest technical challenges was designing camera protection that could survive in a fire. We were using around 30 action cameras per experiment but had to design a camera housing that could be assembled in a hotel room, and ensure that no data was lost during an experiment that could reach up to 1000°C! In our first experiment, only around 12% of the cameras and data survived, but through careful iteration, by the final experiment over 93% survived.

What did you enjoy most about the experience?

The obvious highlight is setting fire to a building four times – an incredible set of experiments to be a part of, with some truly important findings for building safety! One of my favourite parts of the PhD has been sharing my research with others. My research topic was posed to fundamentally address an engineering challenge, so one of the key steps is sharing the findings with the engineering community to ensure that it is actually going to benefit people by helping to make modern timber buildings more fire-safe.

I also have really enjoyed the opportunity to travel and attend conferences in amazing places, including Chile, Washington, Oslo, Barcelona, and Japan. Being able to travel to amazing places and meet and learn from other interesting researchers has been a privilege, particularly considering I had not even been on an international flight before starting the PhD!

What are you planning to do now and in the future?

I am a Postdoctoral Research Associate in Hazelab, studying a new challenge: smouldering wildfires in arctic peatlands. I’m enjoying conducting some fundamental and challenging experiments in the lab looking into new and exciting fire science challenges.

My broader research interests are on how fire can be a challenge to sustainability and net-zero. Therefore, in the next few years, I will be broadening my research horizons to other fire science challenges such as Lithium-ion batteries and wildfires. From here, I will aim to grow my own research expertise to eventually form my own research team on fire safety as an academic in a UK engineering department!

What are your interests beyond Engineering?

When I am not setting things on fire, I am a Warden in one of the Imperial student halls – I have been a part of the wardening system for five years now, and I have found it really fulfilling to support young engineers and scientists through one of the steepest learning curves (both academically and personally) that they will likely experience. It is truly rewarding to welcome students on their first day at Imperial, and see them leave having become more confident and motivated individuals.

I also really enjoy teaching, which is something I was lucky enough to get quite involved in during my PhD. Due to the restrictions of COVID, some of the undergraduate labs needed to be redesigned to be carried out virtually. Therefore, along with Peter Johnson, Guillermo, and Alexander Maclaren, I redesigned the Heat Transfer lab as a “Lab-in-a-box” session, which is now still a part of the course four years later.

In my free time I am an avid video-gamer, whether it is action or strategy games, anything that is a bit of a challenge! Like a lot of scientists, I'm a bit of a geek - I love watching science-fiction films and TV shows (Doctor Who, Black Mirror, and Christopher Nolan films, just to name a few), and playing board games with my friends.