# Effect of Nanofluids on Boiling Heat Transfer Performance
## 3 Effects of Nanofluid Physical Properties and Heated Surface on Boiling Heat Transfer
### Effect of Nanoparticles on Boiling Heat Transfer  
#### 3.1.1 Effect of Nanoparticle Types on Boiling Heat Transfer  
The nanoparticles have a large specific surface area and the thermal conductivity is larger than that of the base liquid. However, the thermal conductivity, specific surface area of the different nanoparticles [106; 107], the difference in density between the nanoparticles and the base [85], and the affinity for the base liquid are different [107; 108]. At present, the study of boiling heat transfer of nanoparticles includes metal oxides Al\({}_{2}\)O\({}_{3}\)[70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86], Fe\({}_{2}\)O\({}_{3}\)[76; 81], Fe\({}_{3}\)O\({}_{4}\)[67; 92], CuO [71; 87; 88; 89; 90; 87; 80; 87; 88; 89; 100; 101], ZnO [79; 89; 103; 104; 105], nonmetal oxide SiO\({}_{2}\)[79; 81; 98; 99], carbon nanotubes [71; 76; 80; 95; 96; 97], graphene [93; 94] etc. [PERSON] et al. [71] studied the flow boiling heat transfer performance of water-based Al\({}_{2}\)O\({}_{3}\), CuO and functionalized multiwalled carbon nanotube (MWCNT) nanofluids in annulus heat transfer. In terms of boiling heat transfer, the functionalized multiwalled carbon nanotube nanofluid has better and lower deposition resistance than Al\({}_{2}\)O\({}_{3}\) and CuO nanofluids. The density of Al\({}_{2}\)O\({}_{3}\) is much lower than that of CuO, so the difference in density between Al\({}_{2}\)O\({}_{3}\) nanoparticles and water is much smaller than the difference in density between CuO nanoparticles and water. The stability of the water-based Al\({}_{2}\)O\({}_{3}\) nanofluid is better, thereby reducing the scaling thermal resistance of the heated surface, and the thermal conductivity is better than that of the water-based CuO nanofluid. Since the deposition of the nanoparticles on the boiling surface reduces the surface roughness and the number of nucleation sites, so that the bubble transport phenomenon is weakened and the heat transferred by the surface transfer is reduced, which make the heat transfer deteriorated. The boiling heat transfer coefficient curves of water-based Al\({}_{2}\)O\({}_{3}\), CuO, and CNT nanofluids are shown in Figure 5. It can be seen from the figure that adding the nanoparticles to deionized water can enhances the boiling heat transfer performance. CNT nanofluids have the best boiling heat transfer performance, followed by CuO nanofluids, and finally Al\({}_{2}\)O\({}_{3}\) nanofluids. In short, the starting point temperature of the nucleate boiling, the average bubble diameter, the heat transfer coefficient and the heat flux at the nucleate boiling start point depend on the rate of mass flow of the nanofluid. [PERSON] et al. [80] studied the effect of adding ZnO, Al\({}_{2}\)O\({}_{3}\), and CNT nanoparticles with mass concentration of 0.01% and 0.05% to deionized water on boiling heat transfer performance. The results show that ZnO and Al\({}_{2}\)O\({}_{3}\) nanoparticles deteriorated the boiling heat transfer performance and the CNT enhanced boiling heat transfer performance compared with the deionized water. The reason is  
Figure 5: Influence of heat flux on HTC of different nanofluids in forced convection and nucleate boiling regions [71]. that the ZnO and Al\({}_{2}\)O\({}_{3}\) nanoparticles reduce the roughness of the heated surface, while CNT improves the roughness of the heated surface, but at low concentrations the surface deteriorates. Figure 6 shows the different kinds of nanometers deposition surface after the experiment. [PERSON] [76] et al. studied the boiling heat transfer performance of water-based Fe\({}_{2}\)O\({}_{3}\), Al\({}_{2}\)O\({}_{3}\), and CNTs nanofluids on the copper surface at a volume concentration of 0.02% and 0.1%, and the deposition surface of Fe\({}_{2}\)O\({}_{3}\), Al\({}_{2}\)O\({}_{3}\), and CNTs after experiment on the deionized water. The CHF and Zuber correlation curves [109] and Kindlikar correlation curves [110] of different nanoparticle types were compared.