纳米流体作为柴油机冷却系传热介质的数值模拟

Numerical Simulation on Nanofluids as Heat Transfer Medium for Diesel Engine Cooling System

应用Cu-水纳米流体作为柴油机冷却系传热介质,利用CFD方法对质量浓度为0.5%,1%,3%和5%的Cu-水纳米流体在柴油机冷却水套内的流动和换热过程进行三维数值模拟.并采用湍流随机跟踪方法,对固液两相流离散项纳米粒子的运动进行轨迹追踪,得到了不同质量浓度纳米流体Cu粒子在柴油机水套内的浓度场分布、速度场分布、内能变化、停留时间、换热总量以及水套进、出口之间的压降变化计算结果表明,以Cu-水纳米流体作为传热介质可以显著提高柴油机的散热性能,随着纳米粒子浓度的增加,柴油机散热能力增强,水泵功率损失小范围增加,Cu粒子在水套内的平均停留时间与其浓度相关性不明显,换热效率与纳米流体的流速相关性不明显.

Cu-water nanofluids was utilized as heat transfer medium in the cooling system of the diesel engine. Based on the CFD method, 3-dimensional numerical simulation about flow and heat transfer process in the cooling system of engine was actualized for 0.5%, 1% ,3% and 5% mass concentration of nanofluids. According to stochastic particle tracking in turbulent flow, the moving track of nanoparticles was traced for solid-liquid two phase flow discrete phase. By this way, for Cu nanoparticles of different mass concentration nanofliuds in the cooling jacket of diesel engine, the results of the concentration distribution, velocity distribution, internal energy variation, resident time, total heat transfer and variation of total pressure reduction between inlet and outletwere ascertained. Simulation results prove that nanofluids as heat transfer medium can evidently enhance diesel engine heat transfer capability, when the concentration of nanoparticles increases. The enhancement of heat transfer capacity increases, power loss of water pump also increases in small scale. The relativity between the average resident time of Cu nanoparticles and Cu nanoparticles concentration is not clear in cooling jacket, and the relativity between heat transfer efficiency of Cu nanoparticles and nanofliuds flow velocity is not clear either.