Heat Transfer Characteristics of 1-D Ferromagnetic Nanofluid

Improving the efficiency of the cooling medium to increase productivity and decrease energy consumption is one of the biggest challenges in the current world. Industries, including transportation, manufacturing, and electronic devices, etc. usually have to spend millions of dollars for cooling and temperature control which can be saved upon the use of efficient cooling media. Especially, high power engines, microelectronic devices operated at high speed, bright optical devices among many others require more cooling efficiency. Industrial coolants i.e. water, ethylene glycol (EG) or mineral oils have long been used for heat transport. However, low thermal conductivity of these coolants has made them inefficient options for high performance operations. As an example, at room temperature, the thermal conductivity of water is 0.606 kW/mK whereas for Ethylene Glycol it is only 0.25 kW/mK. These conventional coolants cannot match the ever-growing demand and new types of coolants with higher thermal conductivity are required.

Metal nanofluids can be potential candidates to replace these inefficient coolants because of their superior thermal properties such as high thermal conductivity, diffusivity, and heat transfer coefficient compared to the base fluids. Large surface to volume ratio of nanoparticles where a large number of surface atoms can take part in the heat transfer process is postulated to be one of the main reasons. Nanofluids are a stable suspension of nanoparticles in base fluid media which can offer better thermal conductivity and efficiency. However, preparing stable suspension is one of the major challenges during nanofluid preparation as particles sediment over time which can decrease the thermal properties. This is especially true for nanoparticles because of their high surface energy as they tend to form aggregates that can adversely affect the stability of prepared nanofluid. So far, most research investigations have been done on 0-D nanoparticle based nanofluids and the study of their thermal conductivity. Research investigations on 1-D nanostructure based nanofluids is still scarce. In this work, we have developed a suitable route to prepare novel water-based Cobalt nanowire nanofluids and studied their thermal conductivities. The nanowires were surface treated prior to nanofluid preparation to aid the stability process. Results show that the prepared nanofluid is stable and the thermal conductivity was studied using the transient plane source method employing a special liquid cell. We also found that the thermal conductivity increases by up to 8.5% compared to water with only 0.01 vol% of nanowire loading. The effect of pH on nanofluid thermal conductivity increase is also studied.