Optimization of magneto-viscoelasticity of magnetic fluids and development of its applications in thermal and mechanical systems
Creators: name: PATHAK, Saurabh
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400202
subject: Automotive engineering materials
classificationCode: 401807
subject: Nanomaterials

description: Magnetic fluid (MF) has shown tremendous potential applications in various fields due to its sensation and actuation properties. Still it has not come to its full potential even after four decades of significant research work. Although in the last decades, MF has gained lots of momentum with novel application developments in the thermal and biomedical fields. This work is focused on understanding the properties of MF in detail and develop novel application of MF which has potential to provide effective solution to different areas. For the preparation of MF, we have utilized three methods, chemical co-precipitation, sol-gel and hydrothermal techniques to optimize the synthesis process of MF for the desired application. The prepared fluids were well characterized for their structural, magnetic and rheological properties. The fluid prepared by the co-precipitation method is most stable in our synthesis and thus we have used them for all the devices. <br><br>

Working in the direction of device fabrication, we have developed three novel applications of the MFs; MF-based temperature sensor, energy harvester and shell-and-tube thermal energy storage unit of the latent heat with annular fins-magnetic ring systems. We have developed a high precision temperature sensor using MF with sensitivity in mK range sensitivity. Low frictional and sealing properties of MF has been used to measure the temperature. Permanent magnet immersed in MF forms a liquid bearing around the magnet. These bearings have very low coefficient of friction (μf = 0.002). Frictional losses reduce significantly with the use of these bearing in the device, thus efficiency and effectiveness of the system increases. MF bearing works as a perfect air tight seal and does not allows air to pass. Utilizing low frictional and sealing properties of MF, we have designed a very precise temperature sensor which responds to the minute change in temperature. MF based thermometers can be very simple and cost effective method for precision temperature sensing. Sensitivity and range can be tuned according to the required application. Further, we have proposed a shell-and-tube thermal energy storage unit of latent heat with annular fins-magnetic ring systems which shows higher thermal efficiency compared to the natural convection systems used currently in various systems. This is a novel method for improvement of energy storing capabilities of thermal energy storage unit and achieving higher efficiency of the mobilized thermal energy storage unit. We have observed approximately 60% increase in heat transfer which ultimately resulting in 20% increase in fin efficiency for the annular fins-magnetic ring systems compared to without annular fin geometry. Natural convection thermal energy system is limited due to its lower efficiency which can be improved significantly using MF rings. Moreover, another novel development utilizing the similar property of magnetic bearing formation, we have developed an efficient wind energy harvester. MF contains nanomagnetic particles which sticks to the magnets forming bearing around the edges and provide magnets a passive levitation which eventually results in ultra-low frictional surface between the permanent magnet and bottom glass substrate. The motion of the magnets attached to the rotating fan-shaft assembly by input wind relative to the fixed coils induces current in the coil. The phenomena have been effectively utilized to develop a highly efficient prototype wind energy harvester which can even run at very low wind speed of 2m/s. The prototype wind energy harvester generates 2.59Watt power with an efficiency of 26% at a wind speed of 4.5m/s. Also, simulations are used to validate the experimental results of the prototype and simulation model can be further extended to upscale the harvested power. The invention has a tremendous potential to produce highly efficient wind energy conversion at large scale as it solves the major problem encountered in the current wind energy conversion systems.