中文摘要：

探究纳米粒子浓度对纳米流体在微细通道内流动沸腾传热和压降特性的综合影响,运用超声波振动法制备质量分数为0.05%、0.1%、0.2%、0.3%、0.4%均匀、稳定的Al2O3/R141b纳米流体制冷剂,在直接激光烧结（DMLS）微型换热器内,设计系统压力为176k Pa,纳米流体制冷剂入口温度为40℃、热流密度24-42k W/m^2和质量流率183.13-457.83kg/（m^2·s）工况下,进行单因素实验及正交实验,运用方差齐性检验法及多指标综合评价法研究粒子浓度对纳米流体在微细通道内流动沸腾传热和压降特性的综合影响。研究得出：纳米粒子浓度对纳米流体沸腾传热有显著性影响,对总压降没有显著性影响;纳米流体流动沸腾总压降随浓度的增加而减少,传热性能随纳米颗粒浓度增加成非线性变化,质量分数为0.05%-0.1%之间,传热系数随颗粒浓度的增加而增加,当质量分数大于0.1%时,传热系数随颗粒浓度的增加而减少;综合考虑纳米颗粒浓度对传热及压降的影响,运用熵值法得出纳米颗粒对传热及压降影响的权重分别为0.285、0.715,基于多指标综合评价法得出纳米流体颗粒质量分数为0.2%时,纳米流体的传热系数最佳,总压降最小。

英文摘要：

Uniform and stable Al2O3/R141 b for 0.05% to 0.4% was prepared by ultrasonic vibration in order to comprehensively investigate the influence of nanoparticles concentrations on heat transfer and pressure drop of nanofluid. Single-factor test and orthogonal test experiment were investigated in micro heat exchanger by direct metal laser sintering（DMLS） under the conditions of different heat flux from 24—42k W/m^2,mass flow rate from 183.13kg/（m^2·s） to 457.83kg/（m^2·s）,system pressure 176kPa and inlet temperature 40 ℃, respectively. Meanwhile, comprehensive evaluation of nanoparticles concentration on influence of heat transfer and pressure drop of nanofluid flow boiling by homogeneity of variance test and multi-index comprehensive evaluation method. Results showed that nanoparticles concentrations has significant impact on heat transfer of Al2O3/R141b. The performance is nonlinear with the increase of nanoparticles concentration,heat transfer coefficient increases with the increase of particle concentration between 0.05% and 0.1%,and the heat transfer coefficients decrease with increased concentration while the concentration is greater than 0.1%. Considering the influence ofnanoparticles concentration on heat transfer and pressure drop,and the impact of nanoparticles on heat transfer and pressure drop weight were 0.285,0.715 using entropy value method. Based on the multi-index comprehensive evaluation method for nano fluid particle concentration was 0.2%,in which the heat transfer coefficient of nanofluids is the best,and pressure drop is the minimum.