脉动热管脉动流动以及传热理论和实验研究

发布时间：2019-05-16 05:42

【摘要】：脉动热管传热性能高效,能满足未来更高集成度设备的散热需求,且在振动、加速等恶劣条件下仍能较好的稳定工作,在船舶领域具有广泛的应用前景。但由于脉动热管传热机理极其复杂,需要对其传热以及外场强化进行理论和实验研究。因此,采用实验和理论研究相结合的方法,对影响脉动热管脉动流动和传热的细薄膜蒸发、超声波、电场、以及脉动对气液界面影响进行了研究。实验研究了无外场作用时脉动热管的传热规律,影响脉动热管脉动流动和传热的主要因素包括:热负荷、操作温度、充液率、倾斜角、工质物性;该实验验证了脉动热管的高效传热性能特点,其传热性能取决于内部工质的脉动频率、幅度以及细薄膜蒸发等。利用流体的动量守恒方程和蒸气宏观流动方程,建立了宏观流动影响下的细薄膜蒸发传热理论模型,研究了宏观流动对细薄膜蒸发传热的影响。宏观流动会极大地阻碍细薄膜蒸发,且热通量会随着过热度和调节系数的增加而增加。采用VOF(volumneof fluid)模型模拟研究了毛细管内气液两相流,分析了液塞的气液界面和内部涡流对传热的影响。接触角越小,涡流越容易产生,且涡流范围越广。建立了电场作用下细薄膜蒸发传热理论模型,利用该模型研究了电场对细薄膜区流体的分离压力、细薄膜厚度、气液界面温度、热通量等的影响。电场能减小细薄膜厚度,延长细薄膜区长度,能有效地强化细薄膜蒸发传热。基于脉动热管内工质脉动流动产生机理,即提高气泡产生能增强脉动和强化传热,实验研究了超声波对液体气化成核和脉动热管传热性能的影响。超声波能促进去离子水的气化成核,相比于单频超声波,双频超声波能更进一步促进其内部气化成核;超声波能有效地提高脉动热管的传热性能,双频超声波强化效果好于单频超声波,其强化效果与超声波频率、操作温度、倾斜角、工质物性有关。
[Abstract]:The heat transfer performance of pulsating heat pipe is efficient, which can meet the heat dissipation needs of higher integration equipment in the future, and can still work stably under bad conditions such as vibration and acceleration, so it has a wide range of application prospects in the field of ships. However, because the heat transfer mechanism of pulsating heat pipe is very complex, it is necessary to carry out theoretical and experimental research on its heat transfer and external field enhancement. Therefore, the effects of thin film evaporation, ultrasonic wave, electric field and pulsation on gas-liquid interface, which affect the fluctuating flow and heat transfer of pulsating heat pipe, are studied by means of experimental and theoretical research. The heat transfer law of pulsating heat pipe without external field is studied experimentally. the main factors affecting the fluctuating flow and heat transfer of pulsating heat pipe include heat load, operating temperature, liquid filling rate, inclination angle and physical properties of working fluid. The experimental results show that the high efficiency heat transfer performance of the pulsating heat pipe depends on the pulsating frequency, amplitude and thin film evaporation of the internal working fluid. Based on the momentum conservation equation and vapor macroscopic flow equation of fluid, the theoretical model of thin film evaporation heat transfer under the influence of macro flow is established, and the effect of macro flow on thin film evaporation heat transfer is studied. The macroscopic flow will greatly hinder the evaporation of thin films, and the heat flux will increase with the increase of superheat and adjustment coefficient. The gas-liquid two-phase flow in capillary was simulated by VOF (volumneof fluid) model, and the effects of gas-liquid interface and internal swirl of liquid plug on heat transfer were analyzed. The smaller the contact angle, the easier the vortex is, and the wider the range of vortex. The theoretical model of thin film evaporation heat transfer under the action of electric field is established. The effects of electric field on the separation pressure, thin film thickness, gas-liquid interface temperature and heat flux in thin film region are studied by using the model. The electric field can reduce the thickness of thin films and prolong the length of thin films, which can effectively enhance the evaporation and heat transfer of thin films. Based on the mechanism of fluctuating flow of working fluid in pulsating heat pipe, that is, increasing bubble generation can enhance pulsation and enhance heat transfer, the effect of ultrasonic wave on the heat transfer performance of liquid gasification nucleation and pulsating heat pipe is studied experimentally. Ultrasonic wave can promote the gasification and nucleation of deionized water. Compared with single-frequency ultrasound, dual-frequency ultrasonic can further promote the internal gasification and nucleation of deionized water. Ultrasonic wave can effectively improve the heat transfer performance of pulsating heat pipe. The strengthening effect of dual-frequency ultrasonic wave is better than that of single-frequency ultrasonic wave. The strengthening effect is related to ultrasonic frequency, operating temperature, inclination angle and working fluid physical properties.
【学位授予单位】：大连海事大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TK124;TK172.4

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