纳米流体重力热管.doc
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纳米流体重力热管,摘 要随着热管在生产和生活的各个领域被广泛应用，人们对于热管的研究也越来越深入并提出了很多方法来提高热管的传热效率；近年来，纳米技术快速发展并在强化传热领域得到应用。因此，将纳米流体与热管技术相结合，研究新型热管，在理论上存在可行性。本文将纳米流体作为热管的工质，实验研究纳米流体对重力热管传热性能的影响。本课题以小型重...
内容介绍
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摘 要
随着热管在生产和生活的各个领域被广泛应用，人们对于热管的研究也越来越深入并提出了很多方法来提高热管的传热效率；近年来，纳米技术快速发展并在强化传热领域得到应用。因此，将纳米流体与热管技术相结合，研究新型热管，在理论上存在可行性。
本文将纳米流体作为热管的工质，实验研究纳米流体对重力热管传热性能的影响。本课题以小型重力热管作为研究对象，设计制作了多根热管，考察纳米流体浓度、充液率、热管倾角，冷凝段的换热条件对重力热管传热效率的影响，通过分析计算对比了不同热管之间的传热性能差异。
本实验中，热管工质有两种：去离子水、TiO2纳米流体。实验相关参数为：加热功率从20W到180W，以热流量每递增20W作为一个工况；TiO2纳米流体的浓度为0.2%wt、0.5%wt、1%wt、2%wt；重力热管的充液率为50%、60%、70%；热管倾角为竖直和水平；冷凝段换热条件为自然空冷和强迫风冷，风速控制在6m/s。
实验结果表明，在采用纳米流体作为工质时，重力热管的换热性能有了较大幅度的提高，换热系数比去离子水热管最大增加了2.3倍。重力热管换热性能先随纳米流体浓度的增加而增加，而后随浓度的增大而下降，这说明对于重力热管的换热性能，纳米流体存在一个最佳浓度。在本实验条件下，工质为TiO2纳米流体时，此最佳浓度在0.5％wt左右。当充液率大于50%以后，纳米流体重力热管的换热系数随充液率的增大而快速下降，当充液率达到70%，换热系数仅为50%充液率的27.3%～40%，换热性能恶化。在热管的冷凝端加强制对流循环可以明显降低冷凝段的温度和热管的工作温度。
实验研究表明，以纳米流体作为工质，能够显著提高重力热管的换热系数，强化热管的换热性能。纳米流体很有希望成为一种强化热管换热性能的新型工质。
关键词 纳米流体；重力热管；强化换热；充液率
Abstract
With heat pipe being widely used in production and living areas, it’s more and more in-depth research. Many methods have been adopted to improve thermal performance of heat pipe. In recent years, nanotechnology are developed rapidly and applied in heat transfer enhancement. Therefore, it’s practical in theory that research new types of heat pipe combining nanofluid with heat pipe technology.
The author employed nanofluid as the working fluid in the gravity heat pipe. The experiments were carried out to explore the heat transfer enhancement of gravity heat pipe with nanofluid in it. In this study, a variety of heat pipes are produced. Effects of the TiO2 nanofluid concentration, filling ratio, inclination angle, thermal performance of condensation section on the efficiency of heat pipe were researched experimentally. The thermal performance of different gravity heat pipes was compared through the analysis and calculation after experiment.
The working fluids used in this experiment were DI water, TiO2 nanofluid. Parameters in this experiment were as follows: heating power increased from 40W to 80W, each increment of 20W as one working condition; the concentrations of TiO2 nanofluid were 0.2%wt, 0.5%wt, 1.0%wt, 2.0%wt; the filling ratios of heat pipe were 50%, 60%, 70%; inclination angles were vertical and horizontal; condensation section was forced air cooling with wind speed of 6m/s approximately.
The experimental results showed that the thermal performance of gravity heat pipe was greatly improved after nanofluid was used. Heat transfer coefficient increased by 2.3 times than heat pipe using DI water. The thermal performance of gravity heat pipe increased with increase of the particle concentration firstly and then decreased apparently which indicated that an optimal particle concentration existed. The optimal concentration of TiO2 nanofluid was about 0.5%wt in this experimental condition. After filling ratio is more than 50%, the heat transfer coefficient of gravity heat pipe dropped quickly along with the increase of filling ratio. Compared to 50% filling ratio, the heat transfer coefficient is only 27.3%～40% when filling ratio reached 70%. The thermal performance of nanofluid heat pipe got worse. Forced convectional circulation in condensation section can reduce the operating temperature of heat pipe as well as the temperature of condensation section apparently.
Experiment showed that the nanofluid could increase the heat transfer coefficient and improve the thermal performance of gravity heat pipe significantly. Nanofluid was expected to be a new type of working fluid to enhance the thermal performance of heat pipe.
Keywords nanofluid; gravity heat pipe; heat transfer enhancement; filling ratio
目 录
摘 要 I
Abstract III
第1章 绪 论 1
1.1 研究目的和意义 1
1.2 国内外研究历史及进展 1
1.2.1 热管的发展 1
1.2.2 热管的应用 3
1.3 本文的研究对象和方法 3
1.4 本论文所作的工作 4
第2章 重力热管理论 5
2.1 重力热管简介 5
2.2 重力热管的传热机理 6
2.3 重力热管的传热极限 8
2.3.1 携带极限 8
2.3.2 沸腾极限 8
2.3.3 干涸极限 9
2.4 充液量与倾角对重力热管传热的影响 10
2.4.1 充液量的影响 10
2.4.2 倾角的影响 11
2.5 本章小结 11
第3章 纳米流体及在传热学中的应用 12
3.1 纳米流体简介 12
3.2 纳米流体的制备 12
3.3 纳米技术在传热学中的应用 14
3.3.1 纳米流体强化传热机理 14
3.3.2 纳米流体在沸腾换热中的应用 14
3.3.3 纳米流..
随着热管在生产和生活的各个领域被广泛应用，人们对于热管的研究也越来越深入并提出了很多方法来提高热管的传热效率；近年来，纳米技术快速发展并在强化传热领域得到应用。因此，将纳米流体与热管技术相结合，研究新型热管，在理论上存在可行性。
本文将纳米流体作为热管的工质，实验研究纳米流体对重力热管传热性能的影响。本课题以小型重力热管作为研究对象，设计制作了多根热管，考察纳米流体浓度、充液率、热管倾角，冷凝段的换热条件对重力热管传热效率的影响，通过分析计算对比了不同热管之间的传热性能差异。
本实验中，热管工质有两种：去离子水、TiO2纳米流体。实验相关参数为：加热功率从20W到180W，以热流量每递增20W作为一个工况；TiO2纳米流体的浓度为0.2%wt、0.5%wt、1%wt、2%wt；重力热管的充液率为50%、60%、70%；热管倾角为竖直和水平；冷凝段换热条件为自然空冷和强迫风冷，风速控制在6m/s。
实验结果表明，在采用纳米流体作为工质时，重力热管的换热性能有了较大幅度的提高，换热系数比去离子水热管最大增加了2.3倍。重力热管换热性能先随纳米流体浓度的增加而增加，而后随浓度的增大而下降，这说明对于重力热管的换热性能，纳米流体存在一个最佳浓度。在本实验条件下，工质为TiO2纳米流体时，此最佳浓度在0.5％wt左右。当充液率大于50%以后，纳米流体重力热管的换热系数随充液率的增大而快速下降，当充液率达到70%，换热系数仅为50%充液率的27.3%～40%，换热性能恶化。在热管的冷凝端加强制对流循环可以明显降低冷凝段的温度和热管的工作温度。
实验研究表明，以纳米流体作为工质，能够显著提高重力热管的换热系数，强化热管的换热性能。纳米流体很有希望成为一种强化热管换热性能的新型工质。
关键词 纳米流体；重力热管；强化换热；充液率
Abstract
With heat pipe being widely used in production and living areas, it’s more and more in-depth research. Many methods have been adopted to improve thermal performance of heat pipe. In recent years, nanotechnology are developed rapidly and applied in heat transfer enhancement. Therefore, it’s practical in theory that research new types of heat pipe combining nanofluid with heat pipe technology.
The author employed nanofluid as the working fluid in the gravity heat pipe. The experiments were carried out to explore the heat transfer enhancement of gravity heat pipe with nanofluid in it. In this study, a variety of heat pipes are produced. Effects of the TiO2 nanofluid concentration, filling ratio, inclination angle, thermal performance of condensation section on the efficiency of heat pipe were researched experimentally. The thermal performance of different gravity heat pipes was compared through the analysis and calculation after experiment.
The working fluids used in this experiment were DI water, TiO2 nanofluid. Parameters in this experiment were as follows: heating power increased from 40W to 80W, each increment of 20W as one working condition; the concentrations of TiO2 nanofluid were 0.2%wt, 0.5%wt, 1.0%wt, 2.0%wt; the filling ratios of heat pipe were 50%, 60%, 70%; inclination angles were vertical and horizontal; condensation section was forced air cooling with wind speed of 6m/s approximately.
The experimental results showed that the thermal performance of gravity heat pipe was greatly improved after nanofluid was used. Heat transfer coefficient increased by 2.3 times than heat pipe using DI water. The thermal performance of gravity heat pipe increased with increase of the particle concentration firstly and then decreased apparently which indicated that an optimal particle concentration existed. The optimal concentration of TiO2 nanofluid was about 0.5%wt in this experimental condition. After filling ratio is more than 50%, the heat transfer coefficient of gravity heat pipe dropped quickly along with the increase of filling ratio. Compared to 50% filling ratio, the heat transfer coefficient is only 27.3%～40% when filling ratio reached 70%. The thermal performance of nanofluid heat pipe got worse. Forced convectional circulation in condensation section can reduce the operating temperature of heat pipe as well as the temperature of condensation section apparently.
Experiment showed that the nanofluid could increase the heat transfer coefficient and improve the thermal performance of gravity heat pipe significantly. Nanofluid was expected to be a new type of working fluid to enhance the thermal performance of heat pipe.
Keywords nanofluid; gravity heat pipe; heat transfer enhancement; filling ratio
目 录
摘 要 I
Abstract III
第1章 绪 论 1
1.1 研究目的和意义 1
1.2 国内外研究历史及进展 1
1.2.1 热管的发展 1
1.2.2 热管的应用 3
1.3 本文的研究对象和方法 3
1.4 本论文所作的工作 4
第2章 重力热管理论 5
2.1 重力热管简介 5
2.2 重力热管的传热机理 6
2.3 重力热管的传热极限 8
2.3.1 携带极限 8
2.3.2 沸腾极限 8
2.3.3 干涸极限 9
2.4 充液量与倾角对重力热管传热的影响 10
2.4.1 充液量的影响 10
2.4.2 倾角的影响 11
2.5 本章小结 11
第3章 纳米流体及在传热学中的应用 12
3.1 纳米流体简介 12
3.2 纳米流体的制备 12
3.3 纳米技术在传热学中的应用 14
3.3.1 纳米流体强化传热机理 14
3.3.2 纳米流体在沸腾换热中的应用 14
3.3.3 纳米流..
