Abstract
One of the primary objectives of the UK’s Climate Change Committee (CCC) is to reduce national carbon emissions and provide guidance to achieve the targets set under Carbon Budgets. In the UK, domestic energy consumption bills contribute over 45% of total energy use. A variety of heating systems are used for domestic heating, with over 77% of households using central heating system [1]. Almost all the heating systems use radiators as radiators are a widely accepted form of heating. The heat transfer of radiator varies with the flow rate and temperature of water flowing in the radiator, both of which influence different geometries of radiator. This raises the need to investigate the effect of different geometries of radiator on heat transfer and overall system performance.Given that domestic space heating accounts for approximately 25–30% of total household energy consumption [2] [3], optimising radiator performance can significantly make measurable impact on national energy efficiency and carbon reduction goals, which target a 68% reduction in greenhouse gas emissions by 2030 relative to 1990 levels and the achievement of net zero by 2050 [4] [5] [6] [7] [8]. Selecting suitable specific radiator geometry is consequently fundamental to conducting a focussed, data-driven investigation, as different designs such as flat-panel, convector, column, or finned-tube radiators exhibit varying convective and radiative heat transfer characteristics resulting in varying levels of thermal efficiency and performance. Prior studies have demonstrated that improving surface area, fin spacing and material conductivity can enhance thermal performance by 15-20% [9], supporting the need to analyse commonly used geometries with proven potential for improved energy efficiency and reduced lifecycle energy consumption. To ensure a focused and data-driven investigation, clarification is required regarding the specific radiator geometries to be examined. Each geometry such as flat-panel, convector, column, or finned-tube radiators represents a unique heat transfer configuration that influences convective and radiative efficiency. Consequently, the selection of radiator shapes for this study should be based on their prevalence in domestic applications and their demonstrated potential for enhanced thermal efficiency and reduced lifecycle energy consumption.
This research explores the optimisation of domestic water-filled stand-alone radiators to improve thermal efficiency and energy performance in residential heating systems. The study focuses on identifying how design-geometry, material properties, surface area and fluid dynamics influence heat transfer and hydraulic behaviour of heating systems. By utilizing computational fluid dynamics simulations, the research aims to find the optimal balance between radiator geometry, heat output and energy consumption. The simulation data of one of the radiators was validated using experimental data to compare optimized design against conventional radiator models. The three main geometries of radiator – circular pipe, rectangular pipe and elliptical pipe radiator were investigated. The selected three geometries of various configurations represent very common configurations in existing radiator system, comparing the performance of each geometry can help gaining a comprehensive understanding of which design features contribute most effectively to heat transfer considering a balance between complexity and practicality. This will help to optimize radiator design. Investigating these innovative concepts can uncover new insights and potentially lead to breakthroughs in radiator technology. The Fluent software of Ansys Workbench 2024 R1 R2 version [10] [11] is used to run simulations for heated flow and cold flow at various velocities. Pressure Drop; Temperature and velocity magnitude were recorded at various parts of the radiator. The data were analysed to determine how pressure drop and temperature distribution vary with flow velocity across the three geometries, using charts, graphs and tables for both cold and heated flow conditions. The results identify how geometry, material conductivity and flow behaviour influence thermal efficiency with optimised designs demonstrating notable improvements in heat output, uniformity and operating temperature. These findings highlight that enhanced radiator designs can reduce household heating energy demand, lower operational costs and contribute directly to achieving the UK’s carbon reduction strategy while maintaining indoor comfort.
The Uniform Heating Metric for Elliptical Pipe Radiator (EPR), Rectangular Pipe Radiator (RPR) and Circular Pipe Radiator (CPR) are 1, 0.98 and 0.94 respectively. Overall Performance Index for CPR, RPR and EPR are 5.67 3.99 and 4.06. Radiator geometry has a clear quantitative impact on hydraulic performance: the CPR shows the lowest friction factor (0.04153), indicating minimal hydraulic losses, while the EPR (0.04179) and RPR (0.04235) geometries exhibit increased turbulence and pumping requirements, with the rectangular configuration incurring the highest losses. These results are further discussed in detail in chapter 9.
The comparative analysis demonstrates that radiator performance varies significantly with geometry: the EPR achieved the most uniform temperature distribution, the RPR delivered the highest heat transfer rates but incurred the greatest pressure losses (friction factor 0.04235), while the CPR provided the most balanced thermal–hydraulic performance with the lowest friction factor (0.04153) and reduced pumping energy demand. By refining key parameters – including surface area geometry, high-conductivity materials such as aluminium with a thermal conductivity of 205 W/m.K compared to 50 W/m.K for steel and flow velocities maintained within the 0.25 to 2.0 m/s, heat transfer can be significantly enhanced without increasing energy demand.
The core findings of this research demonstrate that radiator performance improvements are strongly dependent on geometry. The EPR delivered the highest thermal performance, achieving a 15–20% [9], increase in heat transfer efficiency compared with conventional designs, resulting in operating temperature reductions of 5–10 °C. This improvement translated into a 10–25% reduction in annual household heating energy consumption, yielding measurable cost savings. In contrast, the CPR offered the most balanced thermal–hydraulic performance, maintaining lower pressure losses while still achieving meaningful efficiency gains. Across optimized designs, reduced operating temperatures contributed to a 25–30% [12], extension in component lifespan, improving system reliability and reducing maintenance cost.
Overall, this research highlights that geometry optimization supported by CFD modelling can yield substantial improvements in radiator efficiency, thermal comfort, and system longevity. The outcomes directly contribute to achieving the UK’s net-zero carbon goals by enhancing the sustainability and performance of domestic heating systems while reducing environmental impact and operational costs.
| Date of Award | 2 Mar 2026 |
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| Original language | English |
| Supervisor | Rakesh Mishra (Main Supervisor) & Artur Jaworski (Co-Supervisor) |