In 2024, Flexigas Pipe Ltd commissioned the project "Innovative underfloor heating pipe design" to address a defined challenge in the building and construction sector. The assignment combined computational fluid dynamics (CFD) and energy and thermal modelling with a decision-focused engineering study. Its purpose was to explain the governing physical behaviour, identify the variables controlling performance, and convert the findings into practical recommendations for design, operation and future development.

We increased floor heating efficiency by enhancing convective and radiative heat delivery from an innovative underfloor heating pipe while controlling pumping power. Computational fluid dynamics and energy and thermal modelling were used to explore pipe cross sections, materials and spacing patterns within typical screed build ups. The study examined flow regime, internal pressure loss, external heat flux distribution and room level comfort metrics under low temperature operation compatible with heat pumps. Metrics included delivered heat per unit pump power, warm up time, surface temperature uniformity and local peak limits for comfort and surface integrity. Mesh and parameter sensitivities on fluid properties and set points underpinned robust comparisons between concepts. A specific cross section and spacing variant improved near surface heat flux uniformity and reduced hydraulic losses at target flow rates, broadening the low temperature operating window. We provided Flexigas with evidence based design rules and a clear path to prototype build and test, plus a reproducible model to accelerate iteration across pipe sizes and room layouts.

The methodology centred on a coupled internal-flow, conjugate heat-transfer and room-level thermal model of the innovative underfloor pipe. The representation retained the pipe cross-section, circulating fluid, wall material, screed and floor layers through which heat reached the occupied space. Boundary and operating conditions covered pipe shapes, materials, spacings, flow rates and low-temperature supply conditions compatible with heat pumps, with material, fluid and equipment properties assigned from the available design information. Resolution was concentrated in regions where steep velocity, thermal, concentration or phase gradients were expected, while the overall model remained efficient enough to compare several credible configurations. This balance allowed system-level performance to be linked to the local mechanisms responsible for it.

The assessment compared cross-section and installation patterns assessed alongside hydraulic and techno-economic considerations. Performance was judged using delivered heat, pressure loss, pumping power, heat-flux and floor-surface uniformity, warm-up time and comfort-related surface limits. Results were reviewed through quantitative summaries and engineering visualisations, such as contours, vectors, streamlines, sections and time histories, selected to suit the physics. Important assumptions and operating uncertainties were considered so that the recommendations relied on repeatable comparative trends rather than a single nominal case.

For Flexigas Pipe Ltd, the principal value was design rules and a calculation toolkit for a more efficient low-temperature underfloor-heating product. The final evidence linked each recommendation to the relevant model or process output, making it suitable for internal design reviews, supplier or contractor discussions and, where applicable, planning, safety or regulatory dialogue. The work also created a reusable baseline that can be updated as geometry, operating data or test results become available, reducing the cost and risk of later design iterations.