Abstract:

Modified graphene/deionized water (DW) based amphiphilic nanofluid (A-nanofluid) without surfactant was prepared through chemical method. The thermal performance of solar gravity heat pipe (SGHP) with A-nanofluid was investigated under different heating powers, incline angles and concentrations. It was found that A-nanofluid can reduce the start-up temperature of the SGHP compared with DW. Within the measured range of heating power, the thermal resistance of the SGHP filled with A-nanofluid is obviously lower than that with DW when the heating power is relatively small. However, the difference of thermal resistance of the SGHP filled with A-nanofluid and DW is almost negligible with the increase of heating power. The incline angle has great influence on the heat transfer capacity of the evaporation section when the incline angle is relatively small. When the heating power is 20 W and the nanofluid concentration (mass ratio) increases from 0.1% to 0.6%, the heat transfer coefficient of the evaporation section decreases by 54.7%; when the heating power is 40 W, the nanofluid concentration (mass ratio) increases from 0.1% to 0.6%, the heat transfer coefficient of the evaporation section decreases by 48.9%.

Key words: solar gravity heat pipe, amphiphilic nanofluid, stability, heat transfer, evaporation

摘要：

针对石墨烯/水纳米流体的分散不稳定问题，采用化学方法制备了不含表面活性剂的改性石墨烯/水两亲性纳米流体，研究了以改性石墨烯/水两亲性纳米流体为工质的太阳重力热管在不同加热功率、安装角度和浓度下的热性能。结果表明，与去离子水相比，两亲性纳米流体可以降低热管的启动温度。在实验加热功率范围内，当加热功率相对较小时，两亲性纳米流体热管的热阻明显低于去离子水；随着加热功率的增加，热阻差异可以忽略。当安装角度相对较小时，其对蒸发段传热能力影响较大。当加热功率为20 W，纳米流体质量分数从0.1%增加到0.6%时，蒸发段传热系数下降了54.7%；当加热功率为40 W，纳米流体质量分数从0.1%增加到0.6%时，蒸发段传热系数下降了48.9%。

关键词: 太阳能重力热管, 两亲性纳米流体, 稳定性, 传热, 蒸发