The study of Nanofluids is an emerging field of research in the past decade. Nanofluid is a mixture of liquid and solid phase nanosized particles which have shown high thermal properties compared to the base fluid. Many researches have shown that nanofluids have improved thermal properties such as thermal conductivity compared with the base fluid, and these findings have led many researchers to look for the potential of applying Nanofluids in existing thermal systems. With microgrooves being a good method to increase the surface area for heat transfer, nanofluids and microgrooves may be used together to improve the performance of a cooling system. This thesis aims to study the stability of nanofluids and the effect of a microgrooved surface on evaporation of nanofluids.

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The study of Nanofluids is an emerging field of research in the past decade. Nanofluid is a mixture of liquid and solid phase nanosized particles which have shown high thermal properties compared to the base fluid. Many researches have shown that nanofluids have improved thermal properties such as thermal conductivity compared with the base fluid, and these findings have led many researchers to look for the potential of applying Nanofluids in existing thermal systems. With microgrooves being a good method to increase the surface area for heat transfer, nanofluids and microgrooves may be used together to improve the performance of a cooling system. This thesis aims to study the stability of nanofluids and the effect of a microgrooved surface on evaporation of nanofluids.

The most common way to prepare nanofluid is by two-step method which disperses dry nanoparticles in a base fluid. However, ultrasonication is needed to break down large clusters in order to produce a stable nanofluid. Experiments have been conducted to investigate the effect of ultrasonic time on the stability of nanofluids. An optimal duration of 1 hour ultrasonication has been identified and the pH value of a nanofluid without a surfactant can remain at a stable level for 5 hours.

Microgroove is an opened channel with a dimension in micrometers. Liquid will be drawn into microgroove due to the presence of capillary pressure when immersed in liquid. The extended meniscus formed in a microgroove offers an increased surface area for evaporation. Experiment has been conducted to investigate the effect of a microgrooved surface on the evaporation rate of water and nanofluids under different environmental conditions. Results show that a microgrooved evaporator using water as the coolant offers an enhancement in the evaporation rate as large as 21.4% compared with the evaporator without microgrooves. By using 0.5 vol% Al₂O₃ nanofluid as a coolant, a further 44.6% improvement has been found. Microgroove evaporator and nanofluid could be used in different cooling system such as cooling tower.