基于泡沫铜/石蜡的动力电池散热性能研究

石蜡作为一种相变材料具有稳定性好、成本低廉等优点,但是其缺点是导热系数较低。利用泡沫铜的多孔结构,将石蜡压入泡沫铜的孔隙中作为相变材料的本体,在此结构中,泡沫铜不仅发挥了多孔连续框架的优势,而且作为强化传热骨架,结合了石蜡相变吸热的性质,在一定程度上弥补了石蜡导热系数较低的不足。实验对电池和电池模块进行不同工况、不同放电倍率的测试,比较各工况下单体电池及电池模块温度分布情况,可以得出泡沫铜/石蜡相变材料冷却系统中动力电池的散热效果非常明显。     

服役工况下车用锂离子动力电池散热方法综述

随着电动汽车的广泛使用,锂离子动力电池俨然成为纯电动汽车首选的动力来源,然而其热安全性问题也日益突出.基于此,本文针对车用锂离子动力电池在服役工况下尤其高温时存在的安全性差、工作不可靠及循环寿命短等热问题,根据电池的动态散热特性着重介绍了车用锂离子动力电池常用的冷却方法,包括空冷散热、液冷散热、相变材料冷却、热管冷却和耦合散热,说明了集多种冷却方式耦合的热管理系统与单一散热方法相比不仅能提高散热效率,还可以改善电池的均温性.并结合上述散热方法的研究进展及关键技术,主要在空冷通道优化、液冷结构设计及冷却液介质分析、相变材料应用特性、热管的冷却特性及热特性等方面进行了具体综述.最后,针对目前常用的动力电池散热方法中存在的问题提出了合理化建议,展望了电池热管理系统与汽车乘员热舒适性、电动机舱热管理及车辆热环境相耦合,形成整车热管理系统的开发,以期为电池热管理系统设计开发等相关领域的研究提供一定参考.     

电池排布对锂电池组相变热管理性能的影响

为了探究电池单体排布对锂电池组热管理性能的影响,采用COMSOL Multiphysics软件建立相变冷却耦合空气冷却锂电池组散热模型,模拟不同单体电池间距以及相变材料用量下电池组温度场变化情况.研究发现,当单体电池均匀排布时,随着电池间距的增大,相变冷却系统内温差先降低后升高,在10 mm时温度均匀性最优.维持相变材...     

相变材料与水套式液冷结构耦合的圆柱型锂离子电池组热管理仿真分析

针对圆柱型锂离子电池组散热问题,设计了一种新型的相变材料(PCM)-水套式液冷耦合散热结构模型.首先研究了电池组在PCM模型的散热下,不同电池间距对电池组表面温度的影响,并得出PCM模型的最佳电池布局.然后根据PCM模型的最佳电池布局,优化PCM-水套式液冷耦合散热结构模型,即找出PCM散热模型的最佳流道结构.通过仿真分析结果表明,在6流道结构模型下,电池之间的最佳间距为8 mm;PCM-水套式液冷耦合散热模型的效果最佳,在3 C和5 C高倍率放电时,电池组的表面最高温度分别为33.78、41.11℃,相比于同尺寸PCM散热模型的最高温度,分别降低了7.23、1.06℃.采用PCM-水套式液冷耦合散热模型,电池之间的最大温差均维持在5℃以内.结果表明:该新型的PCM-水套式液冷耦合散热结构能在一定程度上保证电池组的正常工作,并提高电池组的安全性和耐用性.     

Review on phase change materials based battery thermal management technology

因环保和节能的需要,电动汽车必将成为未来汽车发展的重要方向。影响电池性能、寿命的热管理技术近年来发展迅速。电池热管理根据其传热介质分为空气冷却技术、液体冷却技术和相变材料冷却技术。本文根据近年来国内外对基于相变材料的动力电池热管理研究状况,综述了电池热管理相变材料的研究进展,重点总结了用于电池热管理的相变材料、PCM/高导热粒子、PCM/泡沫金属以及PCM用于电池热管理的形式。     

电池热管理用相变储能材料的研究进展

因环保和节能的需要,电动汽车必将成为未来汽车发展的重要方向。影响电池性能、寿命的热管理技术近年来发展迅速。电池热管理根据其传热介质分为空气冷却技术、液体冷却技术和相变材料冷却技术。本文根据近年来国内外对基于相变材料的动力电池热管理研究状况,综述了电池热管理相变材料的研究进展,重点总结了用于电池热管理的相变材料、PCM/高导热粒子、PCM/泡沫金属以及PCM用于电池热管理的形式。     

泡沫金属内石蜡相变凝固的数值模拟

研究了泡沫金属中相变材料的相变熔化过程,由于金属骨架和相变材料传热性能的巨大差异,建立了骨架和相变材料的双温度模型,采用显热容法进行了数值模拟。模拟结果显示,相变材料中填充泡沫金属,能有效改善相变材料的温度分布;在相变时,骨架与相变材料的温差较大,局部热不平衡明显;泡沫金属孔隙率越小,石蜡熔化越快。     

光伏组件相变材料控温性能的实验研究

随着光伏电池的温度上升,其光电转化效率将会下降。为了控制光伏电池的温度,本文提出采用相变材料来调节光伏电池工作温度。分别以复合石蜡、聚乙二醇和十水硫酸钠作为光伏组件背板散热相变材料,并搭建实验平台进行实验研究。实验结果表明:光伏相变组件(PV/PCM)的热均匀性较普通光伏组件好,能降低热斑现象的发生,同时能有效降低温升从而提高光伏组件电输出性能。在三种相变材料中,十水硫酸钠具有更好的控温效果;此外,通过增加相变材料的用量能够延长组件的控温时间,通过对比发现40 mm厚度的相变材料具有最好的实验效果。最后,本文发现在相变材料中加入一定量的石墨烯有助于进一步强化组件的散热。     

基于肋片强化散热的相变光伏电池性能研究

光伏电池的光电转化效率随着自身温度的升高而降低。采用相变材料冷却光伏电池是一种提高光电转化效率的有效手段。文章设计了一种基于肋片的相变光伏电池模型,并通过数值模拟分析了相变材料、肋片对光伏电池的冷却效果,肋片对相变光伏电池发电性能的影响,相变材料的用量对光伏电池温度的影响,以及当相变材料用量一定时,肋片的间距、厚度以及基板的厚度对光伏电池温度的影响。研究结果表明,相变材料和肋片的使用,均能够降低光伏电池的温度并提高光伏电池的发电性能。     

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。     

基于相变材料的动力电池热管理研究进展

相变材料（PCM）由于具有相变潜热大、相变时体积变化小的优点,成为电池热管理研究的主要方向之一。本文介绍了相变材料的蓄热原理,综述了主要相变材料石蜡以及针对其导热系数不高而进行的强化换热研究成果,介绍了相变材料耦合其他多种冷却方式在动力电池热管理上的应用,并展望了未来PCM的研究方向。     

Heat transfer enhancement for thermal energy storage using metal foams embedded within phase change materials (PCMs)

In this paper the experimental investigation on the solid/liquid phase change (melting and solidification) processes have been carried out. Paraffin wax RT58 is used as phase change material (PCM), in which metal foams are embedded to enhance the heat transfer. During the melting process, the test samples are electrically heated on the bottom surface with a constant heat flux. The PCM with metal foams has been heated from the solid state to the pure liquid phase. The temperature differences between the heated wall and PCM have been analysed to examine the effects of heat flux and metal foam structure (pore size and relative density). Compared to the results of the pure PCM sample, the effect of metal foam on solid/liquid phase change heat transfer is very significant, particularly at the solid zone of PCMs. When the PCM starts melting, natural convection can improve the heat transfer performance, thereby reducing the temperature difference between the wall and PCM. The addition of metal foam can increase the overall heat transfer rate by 3-10 times (depending on the metal foam structures and materials) during the melting process (two-phase zone) and the pure liquid zone. The tests for investigating the solidification process under different cooling conditions (e.g. natural convection and forced convection) have been carried out. The results show that the use of metal foams can make the sample solidified much faster than pure PCM samples, evidenced by the solidification time being reduced by more than half. In addition, a two-dimensional numerical analysis has been carried out for heat transfer enhancement in PCMs by using metal foams, and the prediction results agree reasonably well with the experimental data.     

Active (air-cooled) vs. passive (phase change material) thermal management of high power lithium-ion packs: Limitation of temperature rise and uniformity of temperature distribution

The effectiveness of passive cooling by phase change materials (PCM) is compared with that of active (forced air) cooling. Numerical simulations were performed at different discharge rates, operating temperatures and ambient temperatures of a compact Li-ion battery pack suitable for plug-in hybrid electric vehicle (PHEV) propulsion. The results were also compared with experimental results. The PCM cooling mode uses a micro-composite graphite–PCM matrix surrounding the array of cells, while the active cooling mode uses air blown through the gaps between the cells in the same array. The results show that at stressful conditions, i.e. at high discharge rates and at high operating or ambient temperatures (for example 40–45 °C), air-cooling is not a proper thermal management system to keep the temperature of the cell in the desirable operating range without expending significant fan power. On the other hand, the passive cooling system is able to meet the operating range requirements under these same stressful conditions without the need for additional fan power.     

Phase change materials for smart textiles – An overview

Phase change materials (PCM) take advantage of latent heat that can be stored or released from a material over a narrow temperature range. PCM possesses the ability to change their state with a certain temperature range. These materials absorb energy during the heating process as phase change takes place and release energy to the environment in the phase change range during a reverse cooling process. Insulation effect reached by the PCM depends on temperature and time. Recently, the incorporation of PCM in textiles by coating or encapsulation to make thermo-regulated smart textiles has grown interest to the researcher. Therefore, an attempt has been taken to review the working principle of PCM and their applications for smart temperature regulated textiles. Different types of phase change materials are introduced. This is followed by an account of incorporation of PCM in the textile structure are summarized. Concept of thermal comfort, clothing for cold environment, phase change materials and clothing comfort are discussed in this review paper. Some recent applications of PCM incorporated textiles are stated. Finally, the market of PCM in textiles field and some challenges are mentioned in this review paper.     

Thermal energy storage properties of the capric acid–stearic acid binary system and 48# paraffin–liquid paraffin binary system

In this paper, the phase change temperature, latent heat and thermal stability of the capric acid–stearic acid binary system and 48# paraffin–liquid paraffin binary system were experimentally studied. The experimental results showed that the phase change temperature and phase change latent heat change with the content of the component. The phase change temperature of binary mixtures changes in a wide range, so they can be used in different fields by adjusting mixing ratio. The phase change latent heat of fatty acid mixtures is higher than that of paraffin mixtures. The thermal stability of fatty acid mixtures is better than that of paraffin mixtures. The mixtures used in the phase change material (PCM) wall or the PCM floor as energy storage materials are given in the paper.     

Characterising PCM thermal storage systems using the effectiveness-NTU approach

Thermal performance characterisation of thermal storage systems employing phase change materials (PCMs) has been carried out predominantly through numerical modelling. These models do not provide a direct representation of the storage system, and cannot readily be used to design a thermal storage unit (TSU) for a particular application to meet the performance specification. Furthermore, limited consideration is given to exergy efficiency of the PCM system being studied. The phase change profiles identified in detailed simulation of PCM encapsulated in flat containers, have been employed to analytically formulate the TSU effectiveness using the familiar effective-NTU (ε-NTU) approach. A one and two dimension formulation were developed with respect to the phase change fraction. This single parameter function can be used for sizing a TSU, by determining the redundant amount of PCM defined by the minimum effectiveness during discharging. Furthermore by optimising design parameters, exergy losses can be minimised by maximising the effectiveness over the full charging – discharging cycle. The study demonstrated that for air based systems phase change can be represented in one-dimension, however for liquid based systems two-dimensional phase change needs to be considered.     

Investigations on thermal and optical performances of a glazing roof with PCM layer

The thermal and optical performances of a roof in a building containing phase change material (PCM) were investigated in this paper. The glazing roof model consists of two layers of glass and one layer of PCM. The purpose of filling the roof structure with PCM is to utilize the solar energy efficiently. The effectiveness of thermal and optical performances of the roof PCM system was determined by analyzing the heat flux and temperature at the indoor surface with different absorption coefficients and refractive index of PCM in solid and liquid states. The results show that the absorption coefficients and refractive index of solid and liquid PCMs have both effects on thermal performance in the roof PCM system. Of all the thermal performances, the effect on internal temperature, temperature lag, and total transmitted energy is smaller and the effect on solar transmittance and transmitted solar energy is bigger. The absorption coefficients have the opposite effect with the refractive index on interior temperature lag. Considering the indoor daylight, increasing the refractive index and absorption coefficient of liquid PCM is a better method to better the thermal performance of a roof PCM system. Copyright © 2017 John Wiley & Sons, Ltd.     

Performance assessment of a passive core cooling design for cylindrical lithium‐ion batteries

Battery thermal management (BTM) system is an indispensable component for large‐sized lithium‐ion battery packs used in aerospace and automotive applications. Besides providing a proper temperature range for batteries to operate, thus improving their efficiency, lifespan, and safety, the BTM system also needs to be well designed with considering the cost, weight, and practicability. In this paper, an internal passive BTM system is proposed for the cylindrical Li‐ion batteries. The design embeds a phase change material (PCM) filled mandrel inside the battery to achieve the cooling effect. A thermal test cell is first fabricated and tested in a wind tunnel under different cooling scenarios, and it is also used to verify a numerical thermal model. The proposed BTM system is further examined through the model and found to be able to create a preferable environment for batteries to operate. Specifically, the core BTM system consumes less PCM and achieves lower temperature rises and more uniform temperature distributions than an external BTM system. The proposed design can also exert its full latent heat to manage the heat generated from the battery without having a thermally conductive matrix, which is usually composite with PCM in external BTM systems. In addition, experiments show that the battery equipped with the proposed BTM system is ready for intensive cycling tests.     

Thermal properties of paraffin/graphite composite phase change materials in battery thermal management system

Abstract

The thermal properties of paraffin/graphite composite phase change materials for power nickel metal hydride batteries were experimentally investigated. Two different modes for heat dissipation were designed in this experimental study: air cooling and cooling with phase change materials. Paraffin/graphite composite phase change thermal energy storage materials were prepared and tested by differential scanning calorimetry. It appeared that the battery thermal management system with phase change materials had better performance than air cooling, especially when the scale of paraffin/graphite composite material approximates 4:1.     

低温下电池系统台架试验液冷控制方法的优化研究

随着电动汽车快速发展,对动力电池性能的要求日益严苛,电池热管理技术的升级优化变得十分迫切。由于国内缺乏电池系统试验水冷控制策略规范,台架试验与整车试验中的电池系统性能表现差异较大,导致试验结果严重脱节,系统级试验失去了原有的测试验证意义。本文对液冷台架试验方法的实际应用开展研究,通过功率、冷却液比热容、进出水口温差、流量等因素的关联计算,优化了电池系统台架液冷控制方法,使台架试验能够更好地模拟实际整车水冷情况。通过对电池系统进行 -20℃低温快充、-10℃低温快充和 -20℃低温慢充三项试验,验证了该电池系统台架液冷控制方法在低温下的改善效果。相较于传统台架液冷试验方法,采用该液冷控制方法能够使电池系统的温度及电性能更符合实际整车变化,保证了电池系统在系统级试验阶段与整车级试验结果保持一致,实现了电池系统在台架液冷试验的真实性能考核。