Nanofluid Based on New Generation Transformer Oil: Synthesis and Flow Properties

Mineral and Ester Nanofluids as Dielectric Cooling Liquid for Power Transformers

“…Starting with metal oxides, ferrous and ferric oxides arise from the co-precipitation of their cations from respective chloride, nitrate, or sulphate salts in a watery solution following the addition of bases such as ammonia or sodium hydroxide under shaking [ 137 ]. This procedure, based on pH changes, was followed in many works [ 107 , 145 , 149 , 150 , 151 , 152 , 153 , 154 , 155 ], including those specific to thermal-dielectric nanofluids with transformer oils [ 8 , 20 , 34 , 58 , 96 , 123 , 124 , 156 ]. Alternative methods used the reaction of iron precursors in alcoholic-organic solutions [ 23 , 55 , 139 , 146 , 157 ], and again there were examples in thermal-dielectric research [ 7 , 19 , 21 , 55 , 66 , 108 , 109 ].…”

“…These can be included either as reagents during the synthesis of particles [ 8 , 21 , 25 , 55 , 59 , 65 , 66 , 107 , 108 , 109 , 133 , 139 , 156 , 157 ], added to nanoparticles [ 7 , 19 , 34 , 51 , 57 , 58 , 61 , 66 , 70 , 73 , 85 , 91 , 96 , 113 , 124 , 137 , 148 , 149 , 151 , 152 , 153 , 158 ], or at both times [ 107 ]; they can be in a aqueous solution [ 20 , 25 , 67 , 107 , 123 , 124 ], organic solvent [ 7 , 19 , 21 , 51 , 59 , 61 , <...…”

“…Treatment is often carried out above the rated temperature in order to assure the adsorption of these reagents [ 7 , 8 , 19 , 58 , 66 , 73 , 96 , 108 , 109 , 123 , 124 , 129 , 156 ]. In the cases that we reviewed related to dielectric nanofluids, the temperatures during surfactantion were approximately 80–90 °C [ 8 , 34 , 73 , 129 ].…”

“…In addition, when considering surfacted particles, it has been noticed that the surfactants themselves can increase the thermal conductivity of the base fluid; the higher the concentration, the bigger the increase [ 61 , 73 ]. However, this effect is small compared to the nanoparticle effect on the base fluid [ 58 , 73 ].…”

“…Characteristics that could condition the convection performance of a coolant oil, such as viscosity, especially with natural flux, were not generally harmed by the presence of nanoparticles. Although slight increases were found [ 49 , 51 , 56 , 58 , 61 , 81 , 86 , 91 , 94 , 111 , 115 , 127 , 180 ], they were just as frequent as those with no effects [ 12 , 25 , 26 , 51 , 59 , 60 , 62 , 64 , 98 , 119 , 121 , 123 , 130 ]. Indeed, reductions in the viscosity were also noticed [ 22 , 51 , 84 , 91 , 95 ].…”