OPEN RESEARCH TOPICS (MASTERS AND PhD) IN THE CLEAN ENERGY RESEARCH GROUP FOR 2018
For more information: Prof JP Meyer, [email protected]
Study leaders: Dr M Mehrabi and Prof JP Meyer
In this project, heat transfer characteristics and pressure drop of different nanofluids [it may include hybrid nanofluids] in microtubes will be modelled numerically by using ANSYS commercial software [student version is available at UP for free usage] as well as Lattice Boltzmann technique. The modelling will cover the influence of Brownian motion, thermophoresis force; lift forces, Van der Waal forces and Double layer forces. After successful compilation of the numerical simulation, the numerical result will be branch marked with experimental result. The last part of the project is using an in-house multi-objective optimization code, to find the best nanoparticle combination to reach the highest heat transfer and lowest pressure drop.
Study leaders: Dr M Mehrabi and Prof JP Meyer
Magnetic materials have been used with grain sizes down to the nanoscale for longer than any other type of material. This is because of a fundamental change in the magnetic structure of ferro- and ferrimagnetic materials when grain sizes are reduced. With the increasing sophistication of pharmaceuticals, the dramatic development of cell manipulation and even DNA sequencing, the possibility of using magnetic nanoparticles to improve the effectiveness of such technologies is obviously appealing. Hence there are proposals for drug delivery systems, particularly for anti-inflammatory agents and also for the use of magnetic separation technologies for rapid DNA sequencing. A further and somewhat surprising application of magnetic nanoparticles lies in the production of controlled heating effects. Each cycle of a hysteresis loop of any magnetic material involves an energy loss proportional to the area of the loop. Hence if magnetic nanoparticles having the required coercivity are remotely positioned at a given site in the body, perhaps the site of a malignancy, then the application of an alternating magnetic field can be used to selectively warm a given area. It has been proposed that this simple physical effect could be used both to destroy cells directly and to induce a modest increase in temperature so as to increase the efficacy of either chemotherapy or radiotherapy.
Study leaders: Dr L Smith and Prof K Craig
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.
Study leaders: Prof JP Meyer and M Everts
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
Study leader: Dr M Moghimi Ardekani and Prof J P Meyer
The principal objective of this project is minimizing the amount of mirror soiling in CSP plants and hence the amount of cleaning water consumed in the current cleaning procedure. Most effective conventional mirror cleaning uses 0.2-1.0 litres of water per m2 of collector area which in terms of a CSP plant area would ends to huge water consumptions. Therefore, implementing wind breaker around the CSP field could be an effective approach to act as dust barrier for the mirror field and reduce water consumption of the field. However, the design of the dust barrier must be carried out in such way to cause larger particles to fall to ground under gravity in the vicinity of the barrier whilst providing sufficient lift to accelerate smaller particles to a height where they are likely to pass over the solar field. To fulfil this goal various dust barrier designs in terms of porosities, shapes and dimensions, must be optimized to find the optimum design that would be appropriate to reduce soiling of glass mirror solar collectors in the solar field of an existing CSP plant. In this Study, ANSYS package (ANSYS Fluent for CFD simulation and ANSYS DX for Optimization) is used to evaluate the number of potential designs and their optimizations for this project.
Study leaders: Prof M Sharifpur and Prof JP Meyer
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.
Study leader: Prof J Dirker
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.
Study leader: Prof J Dirker
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.
Study leaders: Dr WG le Roux and Prof JP Meyer
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.
Study leader: Prof JFM Slabber
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
Study leader: Prof JFM Slabber
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
Study leader: Dr Gazi I. Mahmood
Postgraduate level: MEng preferred (one student).
Short pin-fins are commonly employed in rectangular channels to promote turbulence mixing in the flow and increase channel convective heat transfer coefficients. The applications of pin-fins are seen in cooling channels of gas turbine passages, electronic chips, bearing and electric motor housings, solar cells, and cooling jackets. The geometry of the short pin-fins in such channels is typically cylindrical which introduces large pressure penalty across the cooling channels. The pin-fin geometry is not optimized to provide the optimum heat transfer in the channel with the minimum pressure drop. The large pressure penalty is responsible for the poor thermal performance (high heat transfer accompanied by high pressure losses) of cylindrical pin-fin channel and limits the pin-channel applications as heat transfer enhancer that can accommodate only large pressure drop.
The proposed research will experimentally investigate the thermo-fluid performance of a rectangular channel employing short elliptical shaped pin-fins. The drag coefficient in cross-flow over the elliptical body is lower than that over the cylindrical body. Thus, the pressure drop in the channel employing the elliptical pin-fins is expected to be smaller compared to the channel pressure drop employing the cylindrical pin-fins. However, recent investigations show that the elliptical pin-fin channel provides less heat transfer enhancement than the cylindrical pin-fin channel. The objectives of the proposed research project are to optimize the elliptical pin-fin configuration (elliptical geometry and array configuration of pin-fins) to maximize the heat transfer in the channel which is comparable to that provided by the cylindrical pin-fin configuration. Attention will be paid to the elliptical-pin shape to maintain the pressure drop in the channel to the minimum. Thus, the investigation will find an elliptical pin-fin channel geometry which will provide superior thermal performance compared to the cylindrical pin-fin channel.
Research Aims:
Potential outcome: (i) Alternate to the cylindrical pin-fins with higher thermal performance, and (ii) Wider applications of the pin-fins in the cooling channels.
Study leader: Dr. Gazi I. Mahmood
Postgraduate level: MEng or PhD level (one student).
Problem statements & Objectives:
Film cooling of endwall is employed to protect the gas turbine blade and vane passages from the hot combustion gas. However, the strong secondary flows in the blade and vane passages reduce the effectiveness of the film cooling. Location and geometry of the film cooling jets are important for the effectiveness. Strategically located film cooling jets in the endwall may also reduce the secondary vortices in the passages resulting in lower total pressure losses across the passage.
The proposed research will numerically (CFD) and experimentally measure the total pressure losses, endwall convective heat transfer coefficients, and endwall film cooling effectiveness in a 2-D vane cascade employing an upstream 2-D contour endwall and film cooling jets. Coolant jets will be supplied from both continuous slots and discrete holes. The objectives of the investigation are to reduce the secondary flows and increase the endwall film cooling effectiveness in the vane cascade passage. The measurements will be obtained in the 2-D vane cascade facility located in the Wind Tunnel Laboratory at UP. The cascade employs scaled up vane airfoils of a GE-E3 engine 1st stage vane.
Research Aims:
Potential outcome: (i) Coolant hole configuration for higher film cooling effectiveness and lower total pressure losses, and (ii) 2-D contour endwall for higher film cooling effectiveness and lower total pressure losses.
Study Leader: Prof K J Craig
Optimization of novel central tower receiver using impingement heat transfer. Previous work has proposed a candidate geometry for a novel receiver that traps sunlight and uses impingement heat transfer. A previous masters study has developed software to provide an accurate heat flux distribution at the aperture of the receiver using ray tracing and a realistic sunshape and DNI profile. This investigation will use that information to optimize the internal geometry of the receiver in terms of thermal efficiency of the heat transfer fluid (HTF). This includes an optimal receiver size study in terms of CSP plant size. This study focuses on using ray-tracing software, Computational Fluid Dynamics (CFD) and mathematical optimization as software. Molten salt is to be used as HTF and draining under gravity needs to be kept in mind as well. External natural convection losses can be considered as well. The option also remains to analyse thermal stresses of the structure housing the HTF.
General
By participating in these topics, you will work with Ken Craig who has a background in Computational Fluid Dynamics (CFD) and Mathematical Optimization. Before returning to UP in 2012, he spent 5 years in industry (IST Nuclear, PBMR and Westinghouse) as an expert CFD analyst. Prior to that, he was a professor at UP with 14 years academic experience. In his research during his previous time at UP, he applied CFD to a variety of fluid-thermal problems (air pollution modelling, continuous casting, container sloshing, electronics cooling, etc.) and also had some non-linear structures (crash, metal forming) exposure. Key in these applications was the combination of CFD and mathematical optimization, i.e., defining optimization problems and using optimization algorithms with CFD/structures solvers to drive towards an optimal design configuration that meet the specified performance targets. Since 2013, most of his research is focused on solar energy applications.
Study leader: Dr Axel Lexmond
A concentrated solar thermal Rankine cycle is developed to generate small scale (1-10kW) off the grid power without any fuel demand. The critical and least understood step in this process is the solar boiler, which is to be optimised and tested by the student. Boiling heat transfer is a complicated process; the performance of the boiler will be strongly dependant on design parameters (boiler coil size, geometry) and operational conditions (flow rate, back pressure and temperature) Exergy analysis will be used to predict the performance of an irreversible Rankine cycle and to optimise power production.
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