http://bura.brunel.ac.uk/handle/2438/8626 2026-04-28T16:22:30Z http://bura.brunel.ac.uk/handle/2438/33217 Title: Development and investigation of CO₂ heat pump for domestic buildings Authors: Qayyum, Usman Abstract: The residential building sector in the UK, is responsible for 25% of energy consumption and 17% of CO2 emissions, with space heating accounting for 65% of this. More than 80% of existing dwellings use gas boilers for space heating and domestic hot water and to decarbonise this energy input, heat pumps are considered to be a key technology. Despite this potential, heat pumps have so far failed to gain wide market penetration in the UK due to high capital and installation costs, inability to provide high enough temperatures to be used with existing radiators in retrofit applications and requirement for thermal energy storage. This project makes a contribution to addressing this challenge by investigating the development of a CO2 high-temperature heat pump and its integration with thermal energy storage. to satisfy space heating requirements for existing and new dwellings, facilitate the use of low tariff electricity and provide demand services to the grid. The investigations involved: i) dynamic simulations of 2 and 3 bedroom semi-detached dwellings to establish space and domestic hot water energy demand; ii) extensive experimental investigations on a CO2 heat pump developed at Brunel to establish operating characteristics; iii) simulation of the heat pump to enable design optimisation; iv) investigations on the performance and integration of the heat pump with a Phase Change Material (PCM) thermal energy storage system. The work has demonstrated that: i) The CO2 heat pump can provide significant flexibility in the provision of different water delivery temperatures from 40 oC to 80 oC to satisfy both domestic hot water and space heating demand and the requirement of different types of heat emitter in existing and new dwellings; ii) Using the performance characteristics of the heat pump, the optimum hot water storage tank size for the 4 bedroom domestic dwelling was determined to be between 200 and 300 litres: iii) Using current domestic electricity and gas prices and CO2 emission factors, the annual running cost of the heat pump was found to be approximately double that of the gas boiler due to the large difference between gas and electricity prices, but offering 40% reduction in CO2 emissions; iv) Heat pump design and optimisation work using a simulation model developed for this purpose is expected to lead to an increase in increase the seasonal COP of the heat pump and its cost effectiveness over gas boilers; v) Integration of the heat pump with a PCM storage tank designed and using Rubitherm RT70HC PCM has shown that the heat pump can charge the storage tank effectively, leading to a 50% reduction in the storage volume required for the same thermal energy storage capacity compared to hot water storage. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/33165 Title: Characterisation and bioiogicai testing of synthetic eiectrospun membranes for organ-on-a-chip appiications Authors: Qiao, Shuai Abstract: BacteriaI vaginosis is the most common compIex muItibacteriaI vaginaI infectious disease among women of chiIdbearing age. It is reIated to vaginaI microecoIogicaI imbaIance and has a high prevaIence and recurrence rate. ReIevant data shows that the risk of infection is as high as 15% to 50%, the disease may increase a woman Is risk of contracting sexuaIIy transmitted infections and Iead to premature birth or miscarriage, seriousIy affecting a womanIs quaIity of Iife. There have been few previous studies on bacteriaI vaginosis systems that mimic the true, in vivo environment incorporating the epitheIiaI Iayers with bacteriaI biofiIms and the response to treatments. This study deveIoped a two-channeI, vagina on a chip that creates an in vitro micro-vaginaI tissue that simuIates the femaIe Iower reproductive tract. The cuIture chambe r contains an eIectrospun ch ito sa n /poIyvinyI aIcohoI scaffoId and vaginaI epitheIiaI ceIIs. A diverse attempt was made on eIectrospinning scaffoIds to expIore the optimaI combination, incIuding comparison of different materiaIs such as chitosan/poIyvinyI aIcohoI, PCL/GeIatin, and expIoration of orientation spinning and co-axiaI spinning. The optimaI poIymer concentration and composition suitabIe for the growth of VK2/E6E7 ceII Iines were expIored through MTT assay; fIuorescence microscopy verified the possibiIity that vaginaI epitheIiaI ceIIs can adhere to the scaffoId; chitosan/poIyvinyI aIcohoI scaffoId and vagina on a chip were assembIed to construct a 3D in vitro vaginaI ceII cuIture pIatform. The vagina on a chip wiII aIIow future cIinicaI appIications to expIore the causes of bacteriaI vaginosis and to test reIated targeted drugs. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/33129 Title: Experimental studies on the performance of low-carbon, high-efficiency heavy-duty dual-fuel combustion engines Authors: Pinto da Mota Longo, Kevin Abstract: This thesis presents an experimental investigation into dual-fuel combustion strategies aimed at decarbonising heavy-duty engines through the use of low- and zero-carbon gaseous fuels. A single-cylinder research engine and its fuelling system were upgraded for dual-fuel operations with hythane and hydrogen. Systematic experiments were performed at a constant engine speed of 1200 rpm and loads of 0.6, 1.2, and 1.8 MPa IMEP, corresponding to 25%, 50%, and 75% of full engine load. The study explored both conventional and advanced combustion strategies by varying effective compression ratio and diesel injection timing to maximise thermal efficiency and minimise engine-out emissions. The diesel-hythane dual-fuel system demonstrated strong potential for short-term decarbonisation. An advanced combustion strategy using early diesel injection combined with Miller cycle delivered significant improvements in thermal efficiency by up to 4% at low load and reduced CO₂ emissions by up to 40% relative to conventional diesel combustion. Total GHG emissions were lowered by approximately 25%, and NOx and soot emissions were reduced by as much as 89% and 69%, respectively, compared to diesel-only operation. The diesel-hydrogen system, while facing limitations in diesel substitution due to combustion phasing constraints, achieved the highest CO₂ and GHG reductions – by up to 56% – when operated with a lower effective compression ratio. Although NOx levels increased under the baseline configuration, mitigation strategies such as external EGR, water injection, and leaner mixtures were shown to effectively reduce NOx without compromising efficiency. Notably, green hydrogen use allowed the diesel-hydrogen powertrain to exceed the EU’s 2030 CO₂ reduction target. A comparative assessment across diesel-CNG, diesel-hythane, and diesel-hydrogen systems confirmed that while methane-based fuels offer substantial NOx reduction, their GHG benefits are limited by methane slip. Hythane emerged as the best short-term solution due to its balance of efficiency and emissions performance, while green hydrogen showed the greatest promise for long-term decarbonisation, provided that NOx control strategies and injection optimisation are fully implemented. Overall, this research confirms that dual-fuel combustion with hythane and hydrogen – when paired with advanced engine strategies – can significantly lower the carbon and pollutant emissions of heavy-duty diesel engines. The findings provide a solid foundation for the further development of clean, efficient dual-fuel systems aligned with upcoming emissions regulations and climate targets. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/32734 Title: Producing a novel alumina reinforced aluminium matrix composite from aluminium machining waste Authors: Uka, Jetmira Abstract: This study explores an innovative approach to producing alumina-reinforced aluminium matrix composites (AMCs) directly utilising aluminium alloy machining waste as the primary raw material. By leveraging the machining waste, this research addresses material sustainability and aligns with circular economy principles, minimising resource wastage and promoting environmental sustainability. The focus is on enhancing the naturally occurring alumina on the swarf surface through specific treatments to improve the composite's overall properties. The research methodology employs a multi-technique analysis to monitor and adjust the processing conditions, ensuring optimal material characteristics. Initially, the aluminium swarf is subjected to high-temperature treatment, followed by Equal Channel Angular Pressing (ECAP) to consolidate the material into a dense, uniform composite. X-ray diffraction (XRD) analysis identifies the phase composition, revealing the transformation of alumina polymorphs under different thermal conditions. Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) maps the elemental and phase distribution, assessing the interaction between alumina reinforcement and the aluminium matrix. Polarised light observation and Electron Backscatter Diffraction (EBSD) are utilised to evaluate grain refinement, microstructure, and texture, providing insights into the composite's mechanical behaviour. Key findings indicate that heat treating the aluminium swarf at 650 °C for 2 hours results in the formation of gamma alumina only on the surface. Increasing the temperature to 850 °C transitions the alumina to the alpha phase, known for its superior mechanical properties. Four passes of ECAP using route C effectively consolidate the treated swarf into a composite with no visible macro-porosity, although microporosity around the alumina particulates is still observed. This suggests that while 4 passes, ECAP successfully breaks alumina films and welds adjacent swarfs, this number of passes fails to remove microporosity that could influence the composite's mechanical properties. The composite's performance is further evaluated through tensile and hardness tests, confirming the significant impact of processing conditions on the material's mechanical behaviour. The presence of alpha alumina, achieved through precise heat treatment and the composite's consolidation via ECAP, contributes to enhanced tensile strength and hardness compared to composites with gamma alumina or those processed under less rigorous conditions. This research contributes to the field of materials science by providing a novel method for repurposing aluminium machining waste into high-value composite materials. By optimising the processing conditions, particularly the heat treatment temperature and the application of ECAP, it is possible to produce AMCs with improved mechanical properties suitable for various high-performance applications. Moreover, this study highlights the potential of using advanced material characterisation techniques to understand the microstructural evolution of composites, guiding the development of more sustainable and efficient manufacturing processes. In conclusion, this study presents a sustainable approach to manufacturing alumina-reinforced AMCs using aluminium machining waste enhanced by high-temperature treatment and ECAP. The findings underscore the importance of processing conditions in determining the composite's microstructure and mechanical properties, offering insights into developing new materials contributing to the circular economy. Future research could explore the long-term performance of these composites in real-world applications and further refine processing techniques to minimise microporosity and enhance material properties. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London 2024-01-01T00:00:00Z