基于热舒适性纳米喷泉的流动与传热特性

目前关于纳米喷泉流动与传热特性及微区域热舒适度方面的研究较少，为了研究其流动与传热机理，本文基于气-液两相流模型和金刚石-乙二醇/水纳米流体高沸点、低冰点等优良特性，在有限柱体空间内建立了一种基于热舒适性的新型高效换热喷泉-“纳米喷泉”，对比研究了金刚石-乙二醇/水纳米流体、水射流工质分别对喷泉流动与传热的影响，同时讨论了纳米颗粒体积分数v和表征流体流动情况的雷诺数（Reynolds，Re）对喷泉流动与传热的影响，分析了局部温度分布、流线分布、平均温度和流体换热量在空间内的变化，并依据ASHRAE 55-1992标准和ISO7730标准对微区域的热舒适度进行了评价。结果表明：随着Re数和v增大，换热强度均得以不同程度地提升，热舒适程度也逐渐增加。Re=1.0×10⁵和Re=1.2×10⁵时，纳米颗粒体积分数从0增加至1%的换热强度提升较为明显，前后两种Re数可分别强化1.5%和2.8%；Re=1.4×10⁵时，体积分数从3%增至5%的换热强度可提升11.5%，强化效果最为明显。故较小Re数下，较低组分的纳米流体强化换热效果较好；而在较大Re数下，较高组分纳米流体的强化换热效果更好。

Study on flow and heat transfer characteristics of nano-fountain based on thermal comfort

There were few researches about the flow and heat transfer characteristics of fountain based on thermal comfort of micro-regional,so a new kind of fountain model named "nano-fountain" was established in a limited cylinder space to investigate the associated characteristics,which has high thermal conductivity and two phases(H₂O-air and diamond-ethylene glycolEG]/H₂O nanofluid-air). Then the flow and heat transfer characteristics of H₂O-air and diamond-EG/H₂O nanofluid-air were studied respectively with different nanoparticle volume fractions and Re numbers. The effects of local temperature,streamlines distribution,average temperature as well as the flow and heat transfer characteristics were discussed. In addition,thermal comfort was evaluated according to the ASHRAE standard 55-1992 and standard ISO7730. The results showed that heat transfer enhancement increases with the increase of Re numbers and volume fractions in different degrees,and thermal comfort also increases. Diamond-EG/H₂O nanofluid showed larger enhancement than H₂O,and could enhance the heat transfer by 1.5% and 2.8% respectively at Re=1.0×10⁵ and Re=1.2×10⁵;In addition,it could enhance the heat transfer by 11.5% when nanoparticle volume fraction increases from v=3% to 5% at Re=1.4×10⁵. Thus it showed larger enhancement in lower volume fraction at lower Re number,and heat transfer enhancement showed more obvious in large volume fraction at larger Re number.