# Effect of Nanofluids on Boiling Heat Transfer Performance
## 2 Nanofluid Application in Engineering
### Nanofluid Application in Automobiles  
The car radiator consists of three parts which are including the inlet chamber, the outlet chamber and the radiator core. The coolant flows in the radiator core and the air passes outside the radiator. The hot coolant cools due to heat dissipation from the air and the cold air warms up by absorbing the heat dissipated by the coolant. Nanofluids can make the car radiators smaller and lighter, and develop in an efficient direction, which reduce the cost of the car [47; 48].  
[PERSON] [47] et al. used a mixed liquid whose volume ratio is 50:50 with ethylene glycol and deionized water (50 EG/50 DW) Al\({}_{2}\)O\({}_{3}\)-based nanofluid as a coolant for automotive radiators to investigate its heat transfer performance. The nanoparticle volume fraction is 0.2-0.8%, the coolant flow is 4-9 L/min, and the inlet temperature is 65-85 \({}^{\circ}\)C. Nanofluids can improve the heat transfer performance of heat sinks compared to conventional coolants. When the nanoparticle concentration is 0.2%, the heat transfer increased by 30%. [PERSON] [48] and others introduced the 50 EG/50 DW liquid-based graphene and silver nanofluids with the volume concentrations of 0.01%, 0.05%, and 0.1% in the automotive radiator. The coolant flow rate is between 0.08 kg/s and 0.11 kg/s, the coolant inlet temperature is between 55 \({}^{\circ}\)C and 85 \({}^{\circ}\)C, and the air flow rate is maintained at 2.1 m/s. The experiment found that the silver nanofluid increased the heat transfer rate by 4.4%, while the graphene nanofluid decreased compared with the base fluid. In the same ratio mixture of ethylene glycol and water, [PERSON] [49] evaluated the heat transfer characteristics of CuO and Al\({}_{2}\)O\({}_{3}\) nanofluids,  
Figure 3: Heat pipe schematic.  
which include the heat transfer coefficient, thermal conductivity, Nusselt number, and heat transfer rate. The CuO nanofluid exhibited the highest heat transfer performance, whose heat transfer coefficient was recorded as 36,384.41 W/(m\({}^{2}\)-K), the thermal conductivity was 1.241 W/(m\({}^{2}\)-K), the Nusselt number was 208.71, and the heat transfer rate was 28.45 W. The Al\({}_{2}\)O\({}_{3}\) nanofluid has a heat transfer coefficient of 31,005.9 W/(m\({}^{2}\)-K), a thermal conductivity of 1.287 W/(m\({}^{2}\)-K), a Nusselt number of 173.19, and a heat transfer rate of 28.25 W.  
[PERSON] [50] and [PERSON] [51] studied the heat transfer performance of automotive radiators using water-based Al\({}_{2}\)O\({}_{3}\) and water-based TiO\({}_{2}\) nanofluids, respectively. The fluid poisoning and the increase in the flow rate of the air improve the heat transfer performance. Adding the 0.2% volume of Al\({}_{2}\)O\({}_{3}\) nanoparticles, the heat transfer efficiency of the radiator is increased by up to 44.28%. While adding TiO\({}_{2}\) nanoparticles with concentration of 0.1% and 0.3% can improve the efficiency of the car radiator by 47%. The average heat transfer coefficient is directly affected by the increase in Reynolds number and volume concentration of the nanofluid.