A methodology needs to be developed to conduct safety analysis of optimized core design with mixed cores.
Non-uniform heat flux flow boiling
Fuselage aftbody analysis and optimisation for efficient propulsion integration
Numerical investigation of the potential energy recovery and feasibility of airframe propulsion integration strategies
Investigating the effect of flow on the morphology of a dried albatross wing
Enhancing pool boiling heat transfer through metal 3D printing
Falling film refrigerant evaporator: Experimental heat transfer characterization of boiling on the outside of enhanced tubes
Thermal BioMedical Device
A novel falling film algae photobioreactor: Experimental characterization of mass and heat transfer coefficient
A novel falling film algae photobioreactor: Experimental characterization of mass and heat transfer coefficient
A recently developed 3D printing process allows for copper to be printed at a relatively low cost. A metal 3D printing laboratory at the University of Pretoria is being commissioned that uses this technology to 3D print complex geometry copper parts.
This allows for exciting opportunities in heat transfer, with the manufacture of geometries previously impossible now available with this technology, which can result in more efficient solar water heaters, refrigeration equipment and even nuclear reactors. However, while theory suggests this recently developed low-cost copper 3D printing technology should enhance boiling heat transfer, it is experimentally untested at present.
Boiling heat transfer in particular can benefit from this 3D printing process, as the process produces parts that are somewhat porous, which can actually aide boiling heat transfer.
This study thus aims to 3D print a number of complex copper microstructures and subsequently test them under pool boiling conditions to determine the possible enhancement in heat transfer.
Study Type: This is an experimental study focussed on lab work, with practical use of 3D metal printing and experimental measurement with sensors. The theory covered will focus boiling heat transfer and 3D printing mechanics. Some basic coding will be required to process and analyse the results.
Study Type: This is an experimental study focussed on lab work, with practical use of 3D metal printing and experimental measurement with sensors. The theory covered will focus boiling heat transfer and 3D printing mechanics. Some basic coding will be required to process and analyse the results.
Study Mode: Full Time
Degree Type: Masters or PhD
Experimental funding: Provided
Student funding: The student will have to self fund their studies or secure funding themselves, such as through the UP funding page, DSI-NRF Masters/PhD program, DSI-CSIR program or similar.
Falling film evaporators, such as the one illustrated here by York, are used in some central air conditioning systems to cool water that is then sent throughout the building to wherever cooling is required (i.e. hydronics systems). The water inside the evaporator tubes is cooled by boiling and evaporating the refrigerant that is trickled onto the outside of the tubes. Flooded evaporators are often used in these systems as well, but the falling film evaporators have the advantage of requiring less refrigerant charge and at times improved heat transfer.
Falling film evaporators may be particularly useful in the near future as the shift to less climate damaging refrigerants occurs. These new refrigerants are often slightly poisonous or flammable, and thus the lower refrigerant charge of falling film evaporators means that they pose less of a safety risk. However, the heat transfer characteristics of these falling film evaporators are still not very well understood, particularly with these new generation of refrigerants.
The aim of this study will be to experimentally test and investigate the heat transfer of new tubes and refrigerants in a falling film evaporator. The Falling Film Evaporator Facility will be used, and the study will build on the previous work conducted by students and previous collaborations with MIT and Imperial College. The exact project scope will be determined by the most recent findings in the department.
Some previous studies of this sort conducted within our department with this facility can be found here: [1] [2] [3].
Study Type: This is an experimental study focused on lab work, with experimental measurement with sensors and high-speed camera. The theory covered will focus on the physics of fluid dynamics, two-phase heat transfer, bubble physics and similar. Some basic coding will be required to process and analyse the results. Some image analysis of the high-speed footage may be required.
Study Mode: Full Time
Degree Type: Masters or PhD
Experimental funding: Provided
Student funding: The student will have to self fund their studies or secure funding themselves, such as through the UP funding page, DSI-NRF Masters/PhD program, DSI-CSIR program or similar.
A novel thermal sensation device is being developed to aide in the screening and diagnosis of peripheral neuropathy. Peripheral neuropathy describes the condition of damaged nerves in the arms and legs, most commonly a result of diabetes or HIV. The thermal sensation device hopes to provide a lower cost and portable device that is able to detect this damage.
This project is a collaboration between the Department of Mechanical and Aeronautical Engineering and the Department of Physiology
Study Type: Experimental study where prototypes will be analysed, built, tested and improved. The project will integrate electronics, coding, prototyping and sensing and measurement. In particular, I would not recommend this project to students who are uncomfortable with electronics (or unwilling to learn).
Study Mode: Full Time or Part Time
Degree Type: Masters
Experimental funding: Yes.
Student funding: No. The student will have to self fund their studies or secure funding themselves, such as through the UP funding page, DSI-NRF Masters/PhD program, DSI-CSIR program or similar.
Collaborators: Department of Physiology
Algae are an exciting possible crop to grow for a variety of reasons, such as biofuels, protein for animal feed or niche biochemical compounds. However, algae production is largely still too expensive for many of these products to be cost competitive.
The Department of Mechanical Engineering is currently developing a novel falling film photobioreactor that hopes to reduce the costs of algae production. This reactor’s heat and mass transfer characteristics need to be quantified to determine its technical capabilities so that it can be compared to current reactors on the market and its competitiveness can thus be quantified.
The student will thus conduct an experimental campaign to measure the mass and heat transfer characteristics across a range of atmospheric conditions as well as a number of design parameters of the falling film photobioreactor.
Study Mode: Full Time
Degree Type: Masters
Experimental funding: Provided
Student funding: The student will have to self fund their studies or secure funding themselves, such as through the UP funding page, DSI-NRF Masters/PhD program, DSI-CSIR program or similar.
Biodigesters convert waste organic mass largely into methane and CO2, with the organic mass able to act as fertiliser for plants once the biodigester is done with it.
Coupling biodigesters to greenhouses offers great synergistic potential. The fertiliser from the biodigester can be used for the plants in the greenhouse, and if the methane is used to in a generator, electricity for the greenhouse can be produced. The exhaust gases from the generator can then lastly be used as a heat and CO2 source for the plants.
This project will tackle this idea through a technoeconomic analysis of this system to determine if and when it is viable.
Study Type: This is a desktop study focused on modelling and analysis of the various design configurations developed during the study. The theory covered will touch on heat transfer and thermodynamics through the analysis of the biodigestor, the generator, the plants in the greenhouse and the greenhouse itself. Coding and numerical analysis will be required to develop the model of the system, but it is envisaged to be largely a first principles model.
Study Mode: Full Time or Part Time
Experimental funding: Not required. Open-source software will be used.
Student funding: The student will have to self fund their studies or secure funding themselves, such as through the UP funding page, DSI-NRF Masters/PhD program, DSI-CSIR program or similar.
Efficiently integrated airframe propulsion systems offer the potential to maximise aircraft performance and reduce noise emissions. This contributes to one of the ambitious targets for environmental impact of aviation to explore new technologies to reduce emissions, fuel consumption and noise pollution. Installing the propulsion units on the back of the fuselage the propellers can ingest the fuselage boundary layer and thereby reducing the effective drag of the fuselage, all while improving the propulsive efficiency of the power plant. Such a close integration of the propellers into the airframe lowers nacelle drag and reduces external noise radiation. Analysis and optimisation of this integration and the interaction of these systems will be the core focus of this work.
Supervisor(s): Dr Lelanie Smith & Dr Drew Sanders (Cranfield University)
In the last two decades, major research initiatives around the world have been working on new aircraft configuration development, under the priority heading of “The Green Aircraft”. The most well-known of these initiatives is the National Aeronautics and Space Administration (NASA)’s Environmentally Responsible Aviation (ERA) project, the European Commission’s New Aircraft Concepts Research (NACRE) and the Clean Sky project. Spurred by the growing consensus that the current dominant aircraft configuration will have to be substituted, the search is intensifying for a superior new configuration as the pressure of the growing aviation industry on the environment demands substantially better flight efficiency.
One of the strategies for future generation subsonic fixed-wing aircraft is integrating the propulsion into the airframe. Integrating propulsion into the fuselage and potential advantages of Boundary Layer Ingestion (BLI) become complex to quantify with conventional methods of thrust/drag bookkeeping. Drela (2009) developed the Power Balance Method (PBM) in order to redefine the performance measurements of an aircraft with integrated propulsion, by measuring the mechanical flow power and change in kinetic energy rates. This method has not been widely validated, other than some recent work (Mutangara et al., 2021; nd) show some basic cases and modifications of the PBM in order to capture subsonic steady flow over a flat plate, 2D airfoil, 3D body and a virtual disk. Some work has been done towards basic 2D compressible steady flow cases with some success Odendaal et al.,(2022). Odendaal et al., (nd) also conducted a fuselage optimisation study and used the PBM to quantify performance and the potential energy recovery of optimised designs.
This Masters work will continue to expand on the existing body of work through a couple of potential avenues.
All these are preliminary steps towards setting up and finding an ideal airframe propulsion integration strategy.
All the projects are CFD based and rely on an interest in programming and CFD. Commercial software Star-CCM+ is preferred and strongly supported through training opportunities.
References:
Drela, M. (2009) ‘Power Balance in Aerodynamic Flows’, AIAA Journal, 47(7), pp. 1761–1771.
Mutangara, N. E., Smith, L., Craig, K. J., & Sanders, D. S. (2021). Potential for Energy Recovery ofUnpowered Configurations Using Power Balance Method Computations. Journal of Aircraft,58(6), pp. 1364 - 1374.
Mutangara, N.E., Smith, L., Sanders, D.S. and Craig, K.J. (no date) Potential for Energy Recoveryfrom Boundary Layer Ingesting Actuator Disk Propulsion. Journal of Aircraft. In review.
Odendaal, D., Smith, L., Craig, K.J., Mutangara, N.E. & Sanders, D. (2022). Validation cases studiesof a numerical approach towards optimisation of novel fuselage geometries, In review.
Odendaal, D., Smith, L., Craig, K.J., Mutangara, N.E. & Sanders, D. (no date). Fuselage OptimizationStudy for Improved Recoverable Energy, In preparation for publication.
The modern aviation industry, no matter how far we’ve come, has its roots in the study of avian flight.
Despite the continued development of manufacturing techniques, fixed-wing aircraft are still the easiest to manufacture and therefore still dominate the commercial market. However, the industry is now one of the most polluting and wasteful industries and engineers are once again looking to birds for inspiration. There is still much to be learnt from seabirds, the gliders of the avian world, to improve existing designs. Extracting aerodynamic information from seabirds, the most threatened of all bird groups, remains challenging.
This study aims to produce detailed aerodynamic information of a species of albatross that has to date been neglected in aerodynamic investigations in literature, the grey-headed albatross (Thalassarche chrysostoma). The fastest travelling speeds have been recorded for the grey-headed albatross (Catry et al., 2004), which has a maximum wing span of around 2.2 m and weighs up to 3.8 kg (Pennycuick, 1982; Warham, 1977).
Previous work on the grey-headed albatross (GHA) wings, included wind tunnel measurements at a range of airspeeds and angles of attack. Modern optical and laser scanning techniques have been used to produce scans (3D point clouds) of the wings under wind load in the wind tunnels, but flow separation (indicated by feathers lifting up from the wing) has hampered the accurate extraction of a usable aerofoil and 3D CAD.
It is thus hypothesised that a combination of wind tunnel and computational techniques can provide a geometry that can be used for continued aerodynamic investigation. Processed static scans (i.e., air off) of the GHA wing are available and smoothed/cleaned aerofoils have been extracted at different spanwise locations on the GHA wing. Static scans are, however, not a true representation of the birds in flight – the wing structure and feathers are pliable and the geometry changes with changes in airspeed even in a fixed gliding configuration (this has been proven in wind tunnel tests). We thus propose that applying fluid-structure interaction simulations to the static aerofoil, at varying speeds and angles of attack, may provide aerofoils that mimic that of the GHA in flight. The fluid-structure interaction simulations will form the main part of this study, while small experiments may be required to compile the necessary input values for the CFD code.
References:
Catry, P., Phillips, R. A., & Croxall, J. P. (2004). Sustained fast travel by a Gray-headed Albatross (Thalassarche chrysostoma) riding an Antarctic storm. The Auk, 121(4), 1208–1213.
Pennycuick, C. J. (1982). The flight of petrels and albatrosses observed in South Georgia and its vicinity. Philosophical Transactions of the Royal Society, 300(1098), 75–106.
Warham, J. (1977). Wing loadings, wing shapes, and flight capabilities of procellariiformes. New Zealand Journal of Zoology, 4(1), 73–83. https://doi.org/10.1080/03014223.1977.9517938
The Clean Energy Research Group over the past ten years did extensive work on heat transfer in the transitional flow regime (the flow regime between laminar and turbulent flow). The work was experimental in nature and four state-of-the-art experimental set-ups were developed. On all four of these set-ups experiments were conducted that improved our fundamental understanding of heat transfer and pressure drop in the transitional flow regime. The work has drawn a lot of international attention. Two students will complete their studies at the end of this year or beginning of 2018. The experimental set-ups of these two students will be available for new follow-up projects. The exact details of the project will be determined by the outcomes of the existing projects. It will probably be necessary to implement some minor changes on the set-ups, however, it will be possible to start producing results relatively quickly. Examples of recent work are available on: https://drive.google.com/open?id=0B_HYfQIIW4eLcnhmOWEwZ2l1V1U
The fluids which usually use as heat transfer working fluids have limited capacity to remove the heat in the various thermal systems in different industries such as power generation (especially nuclear power plants), automotive, petrochemical processes, solar-thermal systems, fuel/chemical production, air-conditioning, micro-electromechanical systems (MEMS), and microelectronics. The progression of the technology has resulted in an explosive growth of thermal management problems in compact space. Nanofluids which are solid-liquid composites show higher thermal conductivity and higher convective heat transfer performance than traditional liquids in certain conditions. Therefore, by using nanofluids, the heat transfer process can be optimized. The nanoparticle materials could be ceramics, oxides, metals, bio-materials and nanotubes. The size of the nanoparticles is usually between 1nm and 100nm. The most important parameters in thermal-fluid analyses of the nanofluids are; effective thermal conductivity, effective viscosity and the conditions and situations which improve the convective heat transfer by using nanofluids. On the other hand, magnetic nanofluids show more efficient in the presence of a proper magnetic field. Therefore, different projects are defined in the nanofluids area in this research group, they include (but not limited to):
All the projects mentioned above may involve experimental investigation, mathematical modelling and CFD simulations. For each candidate, concerning his/her background and the priorities of available research grants, a specific project will be defined.
Flow boiling is an important heat transfer mechanism. In thermal solar energy systems, such as direct steam generation plants or solar driven desalination plants, the working fluid is heated in collector tubes exposed to focused solar irradiation. Several types of collector tube and solar reflections systems exist, but they all result in circumferentially non-uniform heat flux conditions on the outer surface of the collector tube. Because most flow boiling literature is for fully uniform heat flux conditions, relatively little is known about what impact the heat flux distribution has on the internal heat transfer performance (heat transfer coefficient). In this investigation the influence of the heat flux distribution is to be investigated experimentally. For this purpose one or more horizontal test sections are to be constructed with specially designed heating elements with which different solar heat flux distribution conditions can be mimicked in a laboratory environment. Test are to be conducted at different mass flow rates, heat flux distributions and heat flux levels. Wall temperature heat flux measurements are to be made and processed into heat transfer coefficients. Relevant correlations are to be developed to describe the impact of the investigated parameters.
The use of PCMs is a viable method of storing thermal energy collected from solar sources to be utilized at night. Liquid-solid PCM’s support high energy concentrations and do not suffer as much from a high volumetric contraction and expansion as is the case with vapour-liquid PCM’s. The phase change temperature is important and should match the requirements of the application. For solar power thermal storage this limits the list of suitable materials. These include for instance inorganic salts and metal alloys. Inorganic molten salts are already used in some solar power plant types as the heat transfer fluid (only in its liquid phase), but has not yet been fully considered as a phase change material in, for instance, possibly simpler type direct steam generation plants, where water is used as the heat transfer fluid directly. A draw-back of inorganic salts are that they have relatively low thermal conductivities which result in a significant thermal barrier during the charging (solidifying) and discharging (melting) modes of thermal storage modules.
In this numerical optimization topic, a commercial numerical software package is to be used to model a thermal storage module where heat transfer rates between (to and from) the heat transfer fluid and (a) selected phase change material(s) is to be maximized during the charging as well as discharging modes. The model is to be validated against experimental data obtained from literature before optimization can commence. Optimization design variables include the thickness of the phase change material plate layers, the length of the plate layers and the number of phase change plate layers.
South Africa has one of the best solar resources in the world. The small-scale solar thermal Brayton cycle consists of a solar dish which concentrates solar power onto a solar receiver in which air is heated before being expanded in a turbine for electrical power generation. A recuperator is also used which allows for higher system efficiency and also a lower compressor pressure ratio. The turbo-machine of the small-scale solar thermal Brayton cycle can consist of a turbine and a radial compressor mounted onto the same shaft. Turbo-machines like these, using air as working fluid, are available off-the-shelf from the motor industry at competitive prices. A 4.8 m diameter solar dish and tubular cavity receiver has been investigated experimentally in recent work, but experimental testing of a prototype solar thermal Brayton cycle is the main objective of this research and therefore, more than one research topic can be accommodated. To approach a prototype, further research can be done analytically and numerically using tools such as Flownex as well as further testing and improvement of the efficiency of the high-temperature solar receiver, while also improving the efficiency of the proposed cycle. Furthermore, experimental testing of a high-temperature recuperator can be performed as well as the selection and testing of micro-turbines.
The field of study combines the 3-dimensional reactor physics analysis of a large number of random groupings of fuel elements with a wide variety of operational histories, that are placed in the fixed geometry of the spent fuel pool at the Koeberg Nuclear Power Station [4]. The study will identify the probability of an accidental super-critical geometry being created and the resultant heat production and removal by natural convection heat transfer mechanisms in the surrounding water of the spent fuel pool.
In general the project requires existing knowledge of reactor physics coupled to heat transfer phenomena [2]. The novelty of the project is to determine the extent of the random groupings of the packings coupled to the burn-up history of the fuel elements and to determine the risk, in terms of overheating and fission product release that such an accidental criticality event will pose.
The proposed cooperative research project will investigate the risk of super criticality and boiling in the SFP. This proposed framework will utilize risk informed approaches to identify parameters necessary to ensure that risks of super criticality and boiling in the SFP are minimized. According to the definition risk is a probability multiplied by consequences. The proposed assessment will utilize probabilistic risk assessment (PRA) methods combined with deterministic studies in the areas of thermal hydraulics, and reactivity (criticality) to evaluate consequences [1]. This framework will form a technical foundation to be used to devise mitigation strategies and provide input to developing regulatory changes by NNR.
The tools to be used in this project consist of MCNP6 [4], SCALE-6.2 [5], COBRA-SFS [2] and MCNP6/CTF [3-6]. MCNP will be utilized to carry out analysis of criticality safety while SCALE-6.2 will be used to confirm independently the MCNP criticality calculations, perform depletion calculations when needed, and conduct uncertainty analysis and propagation. COBRA-SFS, a thermal-hydraulic code developed for steady-state and transient analysis of multi-assembly spent-fuel storage will be used to model important physical behavior governing the thermal performance of SFPs, with internal and external natural convection flow patterns, and heat transfer by convection, conduction, and thermal radiation. Of particular significance is the capability for detailed thermal radiation modeling within the fuel rod array. The multi-physics code MCNP6/CTF, developed at NCSU, will help investigate criticality (reactivity) and boiling in SFPS taking into account complete modeling of all feedback effects involved. The proposed project will develop models for the Koeberg nuclear power plant spent fuel pool for the computation tools involved in the project: MCNP6, SCALE-6.2, COBRA-SFS and MCNP6/CTF.
The proposed work will require use of high performance computing facilities. The Virtual Computing Laboratory at NCSU (https://vcl.ncsu.edu/) will be utilized. The Office of Information Technology (OIT) High Performance Computing (HPC) services provide NCSU students, faculty high performance computing resources, and consulting support for research and instruction. Campus Linux Cluster, henry2 has 1192 dual socket servers with Intel Xeon Processors (mix of single-, dual-, quad-, six-, and eight-core), 2-4GB per core distributed memory, dual gigabit or 10Gb Ethernet interconnects. Also integrated into henry2 are a number of nodes with 16 cores and up to 128GB of memory. These nodes are intended to support shared memory (OpenMP) jobs or other jobs with large memory requirements. The HPC services are available allowing for running jobs up to 128 processor cores up to 48 hours. The number of nodes can also be expanded on demand to accommodate higher computational requirements. In addition, the Reactor Dynamics and Fuel Modeling Group (RDFMG) at NCSU, led by Dr. Avramova, has the fowling computational resources
The proposed cooperative research project will investigate the risk of super criticality and boiling in the SFP. This proposed framework will utilize risk informed approaches to identify parameters necessary to ensure that risks of super criticality and boiling in the SFP are minimized. According to the definition risk is a probability multiplied by consequences. The proposed assessment will utilize probabilistic risk assessment (PRA) methods combined with deterministic studies in the areas of thermal hydraulics, and reactivity (criticality) to evaluate consequences [1]. This framework will form a technical foundation to be used to devise mitigation strategies and provide input to developing regulatory changes by NNR. METHODOLOGY The tools to be used in this project consist of MCNP6 [4], SCALE-6.2 [5], COBRA-SFS [2] and MCNP6/CTF [3-6]. MCNP will be utilized to carry out analysis of criticality safety while SCALE-6.2 will be used to confirm independently the MCNP criticality calculations, perform depletion calculations when needed, and conduct uncertainty analysis and propagation. COBRA-SFS, a thermal-hydraulic code developed for steady-state and transient analysis of multi-assembly spent-fuel storage will be used to model important physical behavior governing the thermal performance of SFPs, with internal and external natural convection flow patterns, and heat transfer by convection, conduction, and thermal radiation. Of particular significance is the capability for detailed thermal radiation modeling within the fuel rod array. The multi-physics code MCNP6/CTF, developed at NCSU, will help investigate criticality (reactivity) and boiling in SFPS taking into account complete modeling of all feedback effects involved. The proposed project will develop models for the Koeberg nuclear power plant spent fuel pool for the computation tools involved in the project: MCNP6, SCALE-6.2, COBRA-SFS and MCNP6/CTF. The proposed work will require use of high performance computing facilities. The Virtual Computing Laboratory at NCSU (https://vcl.ncsu.edu/) will be utilized. The Office of Information Technology (OIT) High Performance Computing (HPC) services provide NCSU students, faculty high performance computing resources, and consulting support for research and instruction. Campus Linux Cluster, henry2 has 1192 dual socket servers with Intel Xeon Processors (mix of single-, dual-, quad-, six-, and eight-core), 2-4GB per core distributed memory, dual gigabit or 10Gb Ethernet interconnects. Also integrated into henry2 are a number of nodes with 16 cores and up to 128GB of memory. These nodes are intended to support shared memory (OpenMP) jobs or other jobs with large memory requirements. The HPC services are available allowing for running jobs up to 128 processor cores up to 48 hours. The number of nodes can also be expanded on demand to accommodate higher computational requirements. In addition, the Reactor Dynamics and Fuel Modeling Group (RDFMG) at NCSU, led by Dr. Avramova, has the fowling computational resources
Copyright © University of Pretoria 2024. All rights reserved.
Virtual Campus
Get Social With Us
Download the UP Mobile App