# Effect of Nanofluids on Boiling Heat Transfer Performance
## 3 Effects of Nanofluid Physical Properties and Heated Surface on Boiling Heat Transfer
### Effect of Base Fluid Type on Boiling Heat Transfer
But under the same nanoparticle type and concentration, the thermal conductivity of the nanofluid is weakened with the ethylene glycol ratio. In addition, as the nanoparticles concentration and the proportion of ethylene glycol increases, the viscosity of the nanofluid increases. However, as the temperature increases, the viscosity of the nanofluid decreases. The different types of nanoparticles lead to the different thermal conductivity, but the effect on the boiling heat transfer performance depends largely on the deposition morphology of the nanoparticles on the heated surface. A small amount of deposition of nanoparticles increases the number of vaporization core points, and the boiling heat transfer performance is enhanced. Figure 11: Thermal conductivity and viscosity diagram of ethylene glycol water-based GNs nanofluids with temperature [115]. The deposition of the nanoparticles increases the roughness of the heated surface, which increases the wettability, resulting in an increase in critical heat flux. The formation of a closed porous deposit of the nanoparticles on the heated surface causes an increase in the heat transfer resistance and a decrease in the boiling heat transfer coefficient. In view of the divergence of nanofluids in boiling heat transfer, [PERSON] [123] found that the addition of Al\({}_{2}\)O\({}_{3}\) nanoparticles to isopropanol resulted in an increase in boiling heat transfer coefficient at low heat flux and a decrease at high heat flux. The effect of nanofluids on the boiling heat transfer coefficient depends on the concentration of the nanoparticles and the boiling temperature. [PERSON] [124] and [PERSON] [105] investigated the effect of refrigerant R141b-TiO\({}_{2}\) nanofluid on the boiling heat transfer performance. The addition of nanoparticles deteriorated the boiling heat transfer coefficient and deteriorated severely with the increase of nanoparticle concentration. It can be seen that the influence of nanoparticles on the boiling heat transfer performance still differs, but it is certain that the deposition of nanoparticles on the heated surface changes the wettability, resulting in an increase in the critical heat flux. At present, the effect of nanofluids on boiling heat transfer is mainly aimed at the increase of bubble activation points caused by the deposition of nanoparticles. Therefore, it is necessary to investigate the effect of the nanoparticle deposition surface on the boiling heat transfer performance. Nanoparticle deposition on a smooth surface increases the density of vaporized core points and increases the boiling heat transfer [110]. The deposited layer of nanoparticles on the heated surface will still have partial peeling during the boiling process. As the mass of the nanoparticles in the exfoliated layer increases, the boiling heat transfer coefficient decreases [125]. The difference in the base fluid makes a large difference in the physical properties of the nanofluid. The viscosity of the base fluid is greater, while the viscosity of the nanofluid is greater. The intense disturbance caused by the generation and detachment of bubbles is the main reason for the strong boiling heat transfer in the nucleus. Therefore, the difference in the nanofluid viscosity caused by the difference in the base fluid is crucial for the influence of boiling bubbles. It is easy to see from the above literature that the addition of nanoparticles to a base liquid having a relatively high viscosity greatly enhances the boiling heat transfer performance. Mainly reasons are that, first, the nanoparticles are dispersed in a solution with a high viscosity, and the stability is well guaranteed. Second, the addition of nanoparticles has little effect on the viscosity of the solution, resulting in a small change in bubble detachment and operation.