A Numerical Study on Heat Transfer Characteristics of a Novel Rectangular Grooved Microchannel with Al2O3/Water Nanofluids
A Numerical Study on Heat Transfer Characteristics of a Novel Rectangular Grooved Microchannel with Al2O3/Water Nanofluids
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DOI：
10.3390/en15197187
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发表时间：
2022-09
期刊：
影响因子：
3.2
通讯作者：
Xiaoxing Zeng;Hao Yu;T. He;N. Mao
中科院分区：
文献类型：
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作者：
Xiaoxing Zeng;Hao Yu;T. He;N. Mao
微通道换热器是建筑空调制冷设备中最紧凑、最有效的换热器之一，纳米流体在微通道中的应用使其具有更高的导热性，进一步提高了其热性能。考虑到建筑领域，特别是空调系统能耗的持续快速增长，需要进一步提高纳米流体微通道的传热性能以实现节能。本研究分析了纳米流体与流动扰动结构结合对微通道传热增强的影响，这也是值得注意的新颖之处。提出了一种矩形沟槽微通道（RGMC），并利用CFD方法研究了其在Al2O3/水纳米流体中的热性能，采用混合模型模拟Al2O3/水纳米流体，考虑基液与纳米颗粒之间的滑移速度。结果表明，在1.5 m/s时，纳米流体体积为2 %的RGMC的Nu比相同纳米流体的光滑微通道（SMC）的Nu大38.5%，比纯水的RGMC的Nu大36.7%，表明新型RGMC结构具有更好的传热性能。在进口速度为1.5 m/s时，当Al2O3含量为2 vol%时，RGMC的最高温度比SMC低5 K。进一步分析流体流动与换热的综合效应表明，RGMC在中心线附近的协同角β远低于SMC，表明沟槽诱导的流动结构导致了更好的热性能。在1.5 m/s时，含2 vol%纳米流体的SMC的βα值为89.4℃，比RGMC的βα值高1.66℃；在0.25 m/s时，两种微通道的βα值接近。这表明在较高的进口速度下，凹槽结构表现出更大的增强。结果表明，纳米流体与沟槽结构相结合可以显著增强微通道的换热性能。纳米流体在低进口速度下增强换热，而凹槽结构在高进口速度下增强换热。本文的研究将有助于高效微通道换热器的设计，促进建筑节能。
The microchannel heat exchanger is one of the most compact and effective heat exchangers used for cooling devices in building air conditioning system, while application of nanofluids in microchannel further enhance its thermal performance due to its much higher thermal conductivity. Considering the continuous rapid increase in energy consumption in the building sector, especially in air conditioning systems, the heat transfer performance of a microchannel with nanofluids should be further enhanced to realize energy savings. This study analyzes the influence of combining nanofluid and flow disturbance structure on the heat transfer enhancement of a microchannel, which is also the noted novelty. A rectangular grooved microchannel (RGMC) is proposed, and its thermal performance using Al2O3/water nanofluids is investigated using the CFD method, with the mixture model to simulate the Al2O3/water nanofluids considering the slip velocity between the base fluid and nanoparticles. The results show that at 1.5 m/s, Nu of RGMC with 2 vol% nanofluids is 38.5% larger than that of smooth microchannel (SMC) with the same nanofluids, and 36.7% larger than that of RGMC with pure water, indicating the much better heat transfer performance of the novel designed RGMC structure. The maximum temperature for RGMC is 5 K lower than SMC with 2 vol% Al2O3/water nanofluid at inlet velocity of 1.5 m/s. Further analysis on the integrated effect between fluid flow and heat transfer shows that the synergy angle β near the center line of RGMC is much lower than that of SMC, representing that the better thermal performance is caused by the flow structured induced by the grooves. Moreover, at 1.5 m/s, βα of SMC with 2 vol% nanofluid is 89.4 Deg, which is 1.66 Deg higher than the βα value of RGMC, while at 0.25 m/s, the βα of two types of microchannel are close to each other. This indicates that the groove structure shows greater enhancement at higher inlet velocity. It is concluded that combining nanofluid and groove structure can significantly enhance heat transfer of the microchannel. The nanofluid enhances heat transfer at lower inlet velocity, while the groove structure enhances it at higher inlet velocity. This study will be helpful for the design of a high-efficiency microchannel heat exchanger that promotes building energy savings.