Nanofluid impingement jet heat transfer

Heat transfer enhancement is a critical design parameter in engineering applications. Overheating in micro-scaled electronic devices and photovoltaic (PV) panels due to excessive solar radiation and high ambient temperatures are the main obstacles to the advancement of these applications. The primary goal of this thesis is to develop innovative cooling mechanisms through a combination of advanced working fluids, jet impingement, and other passive cooling techniques catered for next-generation electronic devices and solar systems. Much of the content in this thesis focuses on the application of nanofluids and nano-encapsulated phase change material (NEPCM) slurries as two advanced coolants. These coolants are driven by cutting-edge active cooling mechanisms, i.e., conventional impinging jets (CIJs) and synthetic jets (SJs). The novelty of the cooling module also includes passive cooling techniques such as protrusions and dimples. For this purpose, accurate, comprehensive, and validated computational fluid dynamics (CFD) techniques are employed for the simulation of flow and thermal fields. Single-phase and sophisticated multi-phase models are developed to study the thermal characteristics with the consideration of discrete phase modelling of a moving boundary problem. The plausible results obtained are further deployed with machine learning (ML) and meta-heuristic algorithms for optimisation purposes while reducing computational costs. In-depth parametric studies are conducted to understand the effects of influential parameters. It is found that increasing the nanoparticle concentration enhances heat transfer leading to undesired increased pumping power and pressure drop. The results also confirm that a higher amplitude or frequency of the SJ actuators results in better cooling performance. Augmented heat transfer is achieved with the integration of passive cooling techniques, such as inserts (protrusion/dimple) in MCHSs, which significantly improves convective and conductive heat transfer. Thermal conductivity plays an important role in nanofluid heat transfer enhancement, while NEPCM slurries show a higher effective specific heat capacity than nanofluids. The optimised model considering the drawbacks of different parameters is shown to be able to extend life expectancy and enhance the efficiency and reliability of electronic devices. Following the successful implementation of innovative cooling technologies in electronic devices, a state-of-the-art cooling module with multiple CIJs using nanofluids is explored in the PV panel. The results demonstrate that nanofluids are superior to pure water in the PV cooling system. A larger coolant mass flow rate and lower jet-to-surface distance are proven to significantly enhance PV efficiency. This finding is particularly critical to avoiding degradation of the efficiency of solar PV panels as the temperature increases on hot days. The obtained results in this research are applicable for future solar and electronic products such as PV cells, microprocessors, and microchips and are beneficial for academia and industry partners. In addition, numerical findings can be developed for other applications, including solar collectors, boilers, lubrication, and oil recovery.