缸盖鼻梁区氧化铝纳米流体沸腾换热数值模拟

Numerical simulation of Al_2O_3 nano-fluid boiling heat transfer in bridge zone of cylinder head

利用数值模拟软件CFX建立氧化铝纳米流体沸腾换热模拟简化模型,研究氧化铝纳米流体作为冷却液以改善缸盖鼻梁区换热效果问题;选取粒径为20、40、60 nm流体,每种流体设置质量分数为3%、5%、10%和20%等4组实验,外加纯基液进行对比,共13种纳米流体,研究其在简化模型中的冷却效果,分析火力面侧的气泡分布和热流密度,同时探讨传热强化的原因以及粒径和质量分数对传热的影响。模拟结果表明,氧化铝纳米流体均能够强化该区域的沸腾换热,纳米颗粒与基液的对流换热以及纳米颗粒与壁面的接触换热均使传热得到强化,且粒径和质量分数越大,强化传热效果越好。

To explore the cooling effect in the bridge zone of cylinder head with Al2O3 nano-fluid applied as the coolant, a simpli- fied boiling heat transfer model was built by CFX. The cooling performances of 13-group coolants in which the grain size was 20, 40, 50 nm, while the mass fraction was 3% , 5% , 10% , 20% were studied by using the simplified model. Bubble distribution and wall heat flux on fire-wall boundary were analyzed. It is concluded that all the 13-group nano-fluids can enhance the boiling heat transfer. The reason for the enhancement of heat transfer and the influence of particle size and mass fraction are analyzed. It is obtained that con- vective heat transfer between particle and base fluid, and contact heat transfer between particle and heated wall can both enhance heat transfer. In addition, larger particle size and larger mass fraction lead to better cooling performance.