热管式均热平板的研究与应用

本文描述了热管技术在均热平析牟温度场控制中的应用，利用数值计算方法均热平析有效工作表面的温度进行了传热计算，得到了均热平板有效工作表面内的最大温差随平板工作温度、平板厚度方向上的圆孔直径和孔间距等影响因素的变化关系，为实际应用提供了可靠的理论依据。     

重力辅助平板型环路热管实验研究

研制了一套以不锈钢丝网为毛细芯的平板式蒸发器、风冷式冷凝器,以甲醇为工作工质的环路热管,并着重研究了其在不同热负荷条件下启动特性以及变工况条件下运行特征。实验结果表明,平板式LHP可以在1～10W/cm2热流密度范围内顺利启动,并有良好的适应变热负荷能力,在改变工况的时候系统一般能在3min内重新达到新平衡状态。系统在18～48W热负荷条件下出现波幅和周期不等的温度波动现象。实验系统的热阻在0.29～3.2℃/W之间,热阻与热负荷、系统倾角以及工质充灌量有关,并重点研究了倾角以及充灌量对系统启动及其变工况运行的影响。     

平板型环路热管温度波动现象研究

环路热管(loop heat pipe,LHP)是一种靠蒸发器内毛细芯产生毛细力驱动回路运行,利用工质相变来传递热量的高效传热装置.研制了一套小型平板式蒸发器、风冷式冷凝器的环路热管(mLHP),mLHP的毛细芯为500目不锈钢丝网,工质为丙酮和甲醇.蒸发器、冷凝器以及所有管路均由紫铜制成.着重研究了平板型mLHP在不同热负荷条件下的温度波动特性.实验结果表明,平板式mLHP在某些热流密度区间容易发生温度波动;同时,重点研究了工质对mLHP系统温度波动的影响,并给出相应的合理解释.     

新型平板型热管热回收装置传热性能实验研究

文中对采用了平板型热管技术的热回收装置的传热性能进行了实验研究。基于北京地区冬季室外气象条件,通过变化热回收装置的迎风风速、管排数、冷/热流侧风量比等参数,对该平板型热管热回收装置的换热效率、热回收量、系统能效比以及阻力特性等进行了比较分析。所得结果将对该热回收装置的优化设计与工程应用提供参考。     

锂离子电池热管理技术

电动汽车在应对气候变化和减少碳排放方面显示出了巨大潜力,电池作为电动汽车的动力来源,在性能和安全方面受温度影响很大。一套有效的热管理控制系统能使电池组温度保持在最佳工作范围内,提高整车的续驶里程。主要总结了目前对电池进行散热和保温的主流电池热管理技术——风冷、液冷、相变冷却、热管冷却以及电池加热技术。提出电池热管理技术应往智能化、集成化、与机器学习相结合、能够自适应调节电池生态温度的方向发展,将会有很大的研究空间。     

热管技术应用于太阳能平板集热器的研究

介绍了将热管技术应用于平板集热器,以克服其易冰冻、管内结垢、腐蚀等常见问题,论述了设计中需关注的影响因素,并针对热管及翅片的结构优化、加工工艺等进行了探讨.     

基于平板热管阵列的热激活主动保温墙体实验研究

针对太阳能等低温热源的被动传输与建筑利用问题,提出一种基于平板热管阵列的热激活主动保温墙体,测试热管倾角与热源温度对其能量传输性能影响,对比热激活主动保温墙体与普通节能墙体热工性能差异。结果表明：蒸发段施加低温模拟热源后,热管实测有效导热系数为4400～35400 W/(m·℃);主动保温情景下可降低热管倾角以提升有效导热系数,辅助功能情景下可提升倾角以达类似目的;低温热源注入可显著提升墙体热工性能,热源温度为25、35℃时,墙体实测U值由基准值0.50 W/(m²·℃)分别降至0.19和-0.08 W/(m²·℃)。     

微槽群平板热管散热器传热性能的研究

分别选择不同的翅片间距和高度,对一种新型微槽群平板热管散热器的翅片结构进行优化,得到了热管散热器的最佳整体结构。结果表明:翅片的间距为14mm、高度为60mm时,平板热管散热器的传热性能最好。将热管、管脚以及翅片的温度与实验结果进行对比,结果吻合良好。     

基于热管技术的锂电池箱热管理系统设计与实验验证

动力电池热管理不仅影响系统效率、充放电能力,而且事关系统安全性和可靠性,尤其"热失控"危害更甚。为此,针对大功率动力电池箱,提出一种基于热管-翅片-集热板组合,并结合加热器件、低功耗电控风扇及其智能控制算法的热管理系统。通过有限元计算模拟和实际充放电试验,验证了该热管理系统性能。以磷酸铁锂动力电池为例,计算与测试结果表明,1C高强度连续充放电情况能将电池组温升控制在15℃以内、风扇调速温差控制在2℃以内,严重故障时仍能将电池温度降至安全温度。此外,采用预热片对电池组预热,实现了电池组冷启动功能。该系统能有效解决过热、过冷情况下的电池组热管理问题。     

Experimental investigation of a flat plate heat pipe performance using IR thermal imaging camera

This paper presents results and analysis of an experimental investigation into determining the thermal performance of a flat plate heat pipe using infra red (IR) thermal imaging camera. Steady state and transient temperature distribution of the evaporator surface of the flat plate heat pipe were measured using a single heat source with varied heat flux inputs. For performance comparison, the experimental measurements were also carried out on an identical flat plate heat pipe with a defect and on a solid copper block of similar dimensions. It was shown that temperature excursion on the surface of the fully functioning flat plate heat pipe is less than 3 °C for operating temperatures up to 90 °C and heat flux inputs ranging from 4 to 40 W/cm². Furthermore, the thermal spreading resistance of the flat plate heat pipe was found to be about 40 times smaller than that of the solid copper block and flat plate heat pipe with a defect.     

Experimental study on thermal performance of a pumped two-phase battery thermal management system

Battery thermal management system (BTMS) is of great significance to keep battery of new energy vehicle (NEV) within favorable thermal state, which attracts extensively attention from researchers and automobile manufacturers. As one BTMS scheme, pumped two-phase system displays excellent cooling capacity owing to large amount of latent heat usage, while there is limited research efforts focusing on the feasibility of the BTMS scheme. This paper experimentally investigates thermal performance of a pumped two-phase BTMS heated by a dummy battery with relative high heat fluxes. The effects of heat fluxes, flow rates and cold source temperatures on thermal performance have been studied and conclusions have been drawn accordingly. The results show that the thermal performance of the system is generally enhanced with the increase of the refrigerant flow rates. When the heat flux and cold source temperature are 0.11 W/cm² and 10°C, respectively, t_avg and △t_max are decreased by 3.4°C and 0.5°C, respectively, when the refrigerant flow rate is increased from 0.20 to 1.67 L/min. Meanwhile, heat transfer coefficient is also improved with an increase of the flow rates, while the enhancements become less obvious under high heat flux. In addition, the t_avg and △t_max of cold plate surface are increased when the heat flux is elevated, while the t_avg at the low flow rate is increased slightly. However, the increase of △t_max is more obvious at the low flow rate, compared to that at high flow rate. When the heat flux is increased from 0.11 to 0.60 W/cm², t_avg is increased by 3.8°C under the flow rate of 0.2 L/min, while that at the flow rate of 1.67 L/min is almost doubled. Meanwhile, the heat transfer coefficient is increased monotonously at the low flow rate, while that at the high flow rate is first decreased and then increased. Besides, lower surface temperatures can be obtained with low cold source temperatures. However, cold source temperatures affect temperature uniformity less.     

Experimental study on the operating characteristics of a flat bifacial evaporator loop heat pipe

There is growing demand for highly efficient heat transfer devices having excellent performance, operational stability and low power consumption. Although loop heat pipes satisfy these requirements, conventional loop heat pips have limited application to flat heat sources due to their mostly cylindrical evaporator shape. To overcome this limitation, various types of flat evaporator loop heat pipes have been developed, though their operational reliability is still uncertain. In this work, we focused on the development of a flat bifacial evaporator loop heat pipe, and its operating characteristics at transient and steady states are discussed in detail.     

Experimental studies on a high performance compact loop heat pipe with a square flat evaporator

A thorough experimental investigation was carried out on a copper–water compact loop heat pipe (LHP) with a unique flat, square evaporator with dimension of 30 mm (L)×30 mm (W)×15 mm (H) and a connecting tube having an inner diameter of 5 mm. Using a carefully designed experimental system, the startup process of the LHP when subjected to different heat loads was studied and the possible mechanisms behind the observed phenomena were explored. Two main modes, boiling trigger startup and evaporation trigger startup, were proposed to explain the varying startup behavior for different heat loads. In addition, an expression was developed to describe the radius of the receding meniscus inside the wick, to balance the increased pressure drop along the LHP with increasing heat loads. Finally, insight into how the compact LHP can transfer heat loads of more than 600 W (with a heat flux in excess of 100 W/cm²) with no occurrence of evaporator dry-out was provided.     

A quasi-3D analysis of the thermal performance of a flat heat pipe

The thermal performance of a flat heat pipe thermal spreader has been described by a quasi-3D mathematical model and numerically modeled. An explicit finite volume method with under-relaxation was used for computations in the vapor phase. This was combined with a relatively small time step for the analysis. The physical problem consisted of an evaporator surface that was transiently heated non-uniformly for a short period of time and the heat source then removed. Then the system was cooled by natural convection and radiative heat transfer at the condenser region. The transient temperature distributions at the front and back of the heat spreader were obtained for different times during the transient period. The velocity distribution in the vapor core was also obtained. Due to the effect of phase change at the evaporator and condenser sides, a significant amount of energy is found to be absorbed and partially released during the transient heating and cooling processes. The numerical results indicate that advection and the high thermal diffusivity of the vapor phase accelerate the propagation of the temperature distribution in the vapor core, making it uniform during this process. The condenser temperature distribution was almost uniform at the end of the transient heating process. The transient temperature distribution on a solid aluminum plate was compared with the flat heat pipe results and indicated that the flat heat pipe successfully spread the heat uniformly at the condenser side of the structure.     

Thermal management system of lithium‐ion battery module based on micro heat pipe array

Temperature affects the performance of electric vehicle battery. To solve this problem, micro heat pipe arrays are utilized in a thermal management system that cools and heats battery modules. In the present study, the heat generation of a battery module during a charge‐discharge cycle under a constant current of 36 A (2C) was computed. Then, the cooling area of the condenser was calculated and experimentally validated. At rates of 1C and 2C, the thermal management system effectively reduced the temperature of the module to less than 40°C, and the temperature difference was controlled less than 5°C between battery surfaces of the module. A heating plate with 30‐W power effectively improved charge performance at low temperature within a short heating time and with uniform temperature distribution. Charge capacity obviously increased after heating when battery temperature was below 0°C. This study presents a new way to enhance the stability and safety of a battery module during the continuous charge‐discharge cycle at high temperatures and low temperatures accordingly.     

Experimental investigation of silver nano-fluid on heat pipe thermal performance

Nano-fluid is employed as the working medium for a conventional 211 μm wide × 217 μm deep grooved circular heat pipe. The nano-fluid used in this study is an aqueous solution of 35 nm diameter silver nano-particles. The experiment was performed to measure the temperature distribution and to compare the heat pipe thermal resistance using nano-fluid and DI-water. The tested nano-particle concentrations ranged from 1 mg/l to 100 mg/l. The condenser section of the heat pipe was attached to a heat sink that was cooled by water supplied from a constant-temperature bath maintained at 40 °C.At a same charge volume, the measured nano-fluid filled heat pipe temperature distribution demonstrated that the thermal resistance decreased 10–80% compared to DI-water at an input power of 30–60 W. The measured results also show that the thermal resistances of the heat pipe decrease as the silver nano-particle size and concentration increase.