Research and development of nanoparticle dispersions for diverse applications
Nanofluids are a simple product of the emerging world of nanotechnology. Suspensions of nanoparticles (nominally 1 to 100nm in size) dispersed in fluids such as water, oils, glycols and even air and other gases can rightly be called nanofluids. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research conducted by our group and others, however, explores the performance of nanofluids in a wide variety of other applications. A recent article, entitled 'Small Particles, Big Impacts' from our group presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.
The importance of heat transfer research
Heat transfer research (like all research) has benefits to society, although the benefits are not always communicated or quantified. Sometimes these benefits are simply training and advancing knowledge on a particular topic. A recent article by our group, entitled, 'Socioeconomic impacts of heat transfer research', looks to quantify which topics in the area of heat transfer are being published, funded, and patented. A rough estimate of the economic returns for breakthroughs in heat transfer technology is shown in the figure (above). It was found that a 10% improvement in all sectors of the United States economy where heat transfer plays an importan role could lead to >100 Billion of annual value added to the US economy! This is huge when compared to the total research funding available for this type of research is well under 1 Billion. The questions now becomes: can researchers achieve these types of enhancements?? Our group hopes to contribute to this challenge!
Research and development of nanoparticle-based cancer treatments
Engineered nano-particles (20-50 nm in size) have been studied as a possible medium for cancer treatment. To accomplish this goal, these particles must first navigate human arteries, then selectively attach to malignant cells in the body. Once positioned, these particles can be activated by near-infrared light or other means - treating the diseased area. Experimental investigation needs to be conducted to validate ongoing modelling efforts and to provide them with necessary inputs. By studying complicated phenomena which are beyond the feasibility of current models providing necessary input parameters and also to study phenomena which are beyond feasibility, we will significantly enhance our fundamental understanding of nano-particle motion and interaction. To carry out this research, a Nanosight nanoparticle tracking instrument will be used. Using simulated in-vitro and modelling conditions, we intend to conduct flow visualization, particle tracking, and particle agglomeration studies for particles of different size, shape, and composition under numerous flow scenarios.
Discover optimized nano-particle mixtures for use as solar harvesters
Nanofluids - one simple product of the emerging world nanotechnology - where nanoparticles (nominally 1-100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.) - have shown to be advantageous in numerous industries. One of the major advantages of going to a system that uses nanofluids is the tunability of the material, size, shape, and volume fraction of the nanoparticles for the operating mode of the system. In this project we are working to determine nanofluid mixtures that will meet tomorrow's solar energy harvesting demands - high efficiencies, selective absorption, increased thermal properties, etc. can all theoretically achieved with nanofluid systems. It is also possible to do this cost-effectively, since low volume fractions of particles can drastically change these outputs.
Scale-up testing/modeling of solar thermal systems
A dish receiver solar thermal test bed is being developed on the UNSW solar and thermal roof-top laboratory. As such, this system is being designed as a test platform for development of high intensity thermal energy carrier fluids. These fluids are any working fluids (e.g. nanofluids, molten salts, ionic fluids, etc.) which are engineered to improve the efficiency of concentrating solar thermal systems. This test bed is being used to determine the performance of these fluids in a real system with the goal of commercialization of fluids developed at UNSW. The test bed is versatile and compatible of testing a wide variety of fluids, solar input levels, and operating conditions (flow rates, temperatures, and pressures).
Hybrid solar photovoltaic/thermal systems
Optical filters are essential in a wide range of applications - optical communications, electronics, lighting, optical sensors, photography and many more. This research aim to design and model nanofluid-based optical filters which can provide an alternative to conventional optical filters. To set some constraints on what could prove to be a very large array of future products, we will design filters specifically for solar energy harvesting. Solar energy conversion is a growing market and the design requirements for these system demonstrate that nanofluid-based filters can be tailored to be selective over a wide range of wavelengths. Initial results indicate that nanofluid-based filters are particularly well suited to hybrid solar photovoltaic/thermal (PV/T) systems where it is possible to utilize much of the unused solar energy of a PV-only system. In such a system, the nanofluid can be employed both as a selective volumetric solar absorber and a heat transfer medium. In addition, these novel filters can be used to create a thermally isolated system - keeping the PV cell as cool as possible while allowing the thermal part to be operated at high temperature. In this work, a wide variety of nanofluid options can be combined and evaluated to reach highly selective filters for five PV cell alternatives. Ultimately, this research demonstrates that nanofluids show excellent potential as spectrally selective filters over any optical wavelength.
High temperature solar materials development and testing
This project consists of the following three parts:
(a) High Temperatures Base Fluids. This is possibly the biggest challenge of this proposal. Even molten salts (which are expected to achieve higher temperatures than organic fluids) become thermally and chemically unstable at temperatures above 600 oC (Coastalchem, 2011; Lovering, 1982). In nitrate salts (above 600 oC) the nitrogen and oxygen decompose and, depending on conditions, form the following gases: O2, N2, NO, NO2, N2O2, N2O3, N2O4, N2O5 (Stern, 1972). On the other hand, there are a vast amount of other molten salts, such as carbonates, halides (fluorides, chlorides, bromides, iodides), sulfates, and others, which are stable at much higher temperatures. Often, though, these salts have high liquidus temperatures. For example, lithium iodide and lithium carbide have melting temperatures of 469 oC and 732 oC, respectively (Kenisarin, 2010). These are simply too high and would require extensive and costly measures to prevent freezing in the system (e.g. heat trace). Fortunately, liquidus temperatures can be depressed by making multiple component eutectic mixtures and by adding impurities (Bradshaw & Siegel, 2008). Some combinations have been proposed (Kenisarin, 2010; Kearney, 2002) and tested (Smith & Chavez, 1988; Bradshaw & Siegel, 2008) in recent years. In this subtask, a software package - FactSageTM - will be used to sort through available molten salt (and possibly other liquid) mixtures and generate phase diagrams for various combinations. (Note: FactSageTM draws on sophisticated thermodynamic equilibrium calculations and a wide variety of material databases to determine results for multi-component mixtures).
(b) Dispersion Stability. Several one-step and two-step methods are possible for fabrication of stable nanofluids. It should also be noted that a method that works well for one particle/fluid combination is not guaranteed to work for another since the particle/fluid interactions can be significantly different between different nanoparticle dispersions. The resultant stability of the dispersion can be determined qualitatively by observation and quantitatively by measuring the zeta potential in a dynamic light scattering system (available in Chemical Engineering at UNSW). Large absolute values of zeta potential indicate a stable nanofluid. Unfortunately, there are several limitations to zeta potential measurements (i.e. temperature, particle concentration), so observations of settling and other degradation in a temperature controlled furnace might be the most reliable indication stability.
(c) UV Stability. For many materials this is a well studied phenomenon, but not necessarily for the fluids of interest. If data is unavailable, a furnace in the Willis Annex will be fitted with an intense UV light source to test the fluids. Periodic testing of these samples for changes via UV degradation of the optical and thermal properties will be conducted.
Undergraduate/Master's Projects
1) INSTALLATION, MODELLING, AND TESTING OF A CONCENTRATING SOLAR THERMAL DISH COLLECTORBrief summary: In one hour enough solar energy hits Earth to meet global energy demand for the entire year! A major challenge facing society is how to take advantage of this energy. One way to do this is in the form of solar thermal energy - i.e. converting solar energy to heat. In this project, the student(s) will develop models which can predict the performance of a 2.5m diameter parabolic concentrating solar dish system. Further, the student(s) will help install dish components and the data acquisition system (temperature and flow). Lastly, experimental tests of the performance of the solar system will be conducted.
Requirements: Enrolled or completed Engineering Experimentation and Advanced Thermofluids
2) DESIGN, AND FABRICATION OF A VERY HIGH TEMPERATURE SOLAR RECEIVER
Brief summary: Most solar thermal power plants use steam to turn turbine blades which in turn generate electricity. However, not all steam is created equal! Higher temperature steam has more available energy for thermal cycles. Traditional solar thermal systems operate at a maximum temperature of 600 oC. These relatively low temperatures preclude the possibility of using advanced Rankine, supercritical CO2, and Brayton cycles - which are more efficient. In this study the student(s) will model, design, and fabricate a solar receiver which can withstand very high temperatures (up to 1000oC) and temperature gradients. In this project a high temperature alloy receiver will be designed and fabricated for installation into a parabolic dish solar thermal collector.
Requirements: Completed or enrolled in: Fluid Mechanics, Advanced Thermofluids
3) FEASIBILITY STUDY, DETAILED DESIGN, AND (IF FEASIBLE) PROTOTYPING OF AN UNMANNED, SOLAR DRIVEN, AGRICULTURAL VEHICLE
Brief summary: Currently agricultural processes in the western world are carried out mostly by heavy machinery. Ultimately, this means that a lot of energy (in the form of petroleum) goes into growing food. For example, many tractors put out powers in excess of 100kW. Some agricultural process, however, could be done with orders of magnitude less power input - which could theoretically come from solar photovoltaics. Planting seeds, weeding, harvesting of selected products, and pest removal could be done with small, low power, autonomous vehicles. The student(s) involved in this project will first conduct an engineering feasibility study of the potential of this idea. This will be followed by a detailed design of the machine and its control systems. If feasible, a prototype will then be developed which can accomplish at least one (hopefully more) automated agricultural process.
Requirements: Completed or enrolled in: Modelling and Control of Mechatronic Systems
4) MODELLING, DESIGN, AND FABRICATION OF A THERMAL STORAGE BATTERY
Brief summary: Electric vehicles (EVs) are likely to become a major part of future transportation systems. Currently, a large barrier to widespread adoption of these vehicles is range - many consumers would like a range of up to 500 km. Vehicle range can be severely limited if air conditioning (heating or cooling) is demanded of the EV's battery. One way to avoid using the EV's electrical battery for this purpose is to develop a thermal battery which can be used as the energy source to heat or cool the vehicle's occupants. A reversible, portable, latent or sorption thermal packaged product will be designed by the student to meet this challenge. The resulting design will be fabricated and tested in the heat transfer laboratory.
Requirements: Completed or enrolled in: Advanced Thermofluids
5) SUNSWIFT DESIGN PROJECTS
Brief summary: Sunswift is a university student-led solar racing team. Thirty students from the Faculties of Engineering, Science, and Business at the University of New South Wales volunteer their time and skills to design, build and race a state-of-the-art solar-powered car. Selected design projects available for next race season.
Requirements: Only high achieving, 'self-starter' students from UNSW's SPREE or MECH Eng. will be accepted.
Upcoming Projects...
Several further funding proposals are currently under preparation or review. More updates will be made if/when funding for these topics is awarded.
