Analysis of Heat Dissipation Performance between a Horizontal and Longitudinal Battery Pack Based on Forced Air Cooling

A battery pack is the main energy storage element, and directly affects the performance of an electric vehicle. Battery thermal management system research and its development for a modern electric vehicle is required. This paper selects the forced air cooling of battery pack as the research object, and uses simulation methods to research the heat dissipation performance with different structures of battery packs. The results indicate that according to the four types of transient state conditions, the rising temperature of both battery packs are significantly higher than the temperature difference, the maximum temperature rise and temperature difference of a horizontal battery pack are lower than a longitudinal battery pack. When an electric vehicle begins to decrease speed, the curves of temperature rising and temperature difference increase. This shows the internal heat is continuously rising, so even in a electric vehicle beginning to decrease speed, the fan must work. The reference basis for choosing battery pack type and an analysis of heat flow field characteristics, including fan run‐time control, are offered.     

Research on the heat dissipation performance of lithium‐ion cell with different operating conditions

This paper aims to research the thermal power of lithium‐ion cell with different operating conditions. A 55‐Ah lithium‐ion cell is selected as the research object. Experiment and simulation are chosen as the methods to research the temperature distribution and thermal power of the cell under different conditions. Combining with the thermal power of cells, this paper also researches the heat dissipation performance of battery pack under different operation conditions. The results indicated that average thermal power of a 55‐Ah lithium‐ion cell decreases along with the increase of ambient temperature and the decrease of state of charge and charge and discharge rates. The results achieved through simulation and experiment are consistent, so simulation could be used to research the temperature distribution of cell during charge and discharge. As considering the longitudinal battery pack with steady analysis, high temperature area is in the centre, and the temperature of air inlet is relatively low. The airflow mostly passes the top of battery pack but not through both sides. As considering the longitudinal battery pack with transient analysis, the temperature rise of battery pack is evidently higher than the inner temperature difference by studying three operating conditions (sustained deceleration, sustained acceleration and pulsed discharge). The curves of temperature rise and inner temperature difference rise along with sustained acceleration of the electric vehicle; therefore, even if the electric vehicle begins to decelerate, the fan must still work until the temperature of battery pack decreases. Then, the references are given for researching thermal characteristic during charge and discharge of the cell and the heat dissipation analysis of battery pack. Copyright © 2017 John Wiley & Sons, Ltd.     

Heat dissipation analysis and optimization of the pure electric bus lithium-ion battery pack based on CFD

针对某纯电动客车电池箱散热效果不佳的问题,本文基于CFD技术以该车的电池箱散热系统为研究对象,建立了估算锂离子电池生热速率数学模型,采用三维软件UG建立电池箱的几何模型,并利用软件Star-ccm+对该模型的速度场和温度场进行仿真和分析。通过添加导流板等措施,对电池箱的结构进行了优化改进,并进行了正交仿真实验,确定了电池箱导流散热的最优方案,结果表明,导流板能够降低电池箱内单体电池的最高温度,使电池组温度分布更加均匀。     

新能源汽车动力电池冷却系统热仿真及优化

动力电池的温度控制是新能源汽车发展中的一个难题,而电池冷却系统在动力电池的温度控制过程中起着相当重要的作用。利用Solidworks软件对电池包进行建模,利用ICEM CFD软件对电池包模型进行网格划分等前处理。利用Fluent软件并采用控制变量法分别对冷却管道截面宽度、冷却液质量流量和冷却液进口温度等3个对电池包散热性能影响较大的参数进行仿真计算和对比分析。根据仿真结果选择可优化电池包散热性能的参数,并在原方案基础上提出了一种新的冷却管道分布方案。经过仿真计算发现,该方案可有效降低电池在使用过程中的最高温度和温差,提高了电池冷却系统的散热性能。     

增设通风孔的风冷式锂离子电池热管理系统数值研究

电池热管理系统的优化设计可以维持动力电池的高效性能,进而促进电动汽车产业的发展。本文采用CFD方法研究有通风孔的情况下,风冷式锂离子电池组在放电过程中的散热性能。研究结果发现,在电池组外壳增设通风孔可以明显提高整个电池组的冷却效果。风孔开设在主出风口的相反方向时,电池组的温升和温差最小。当风孔的面积与出口面积相等时,电池组的冷却效果最佳;继续增大风孔对电池组的冷却效果影响较小。最后探讨了空气进口温度和电池间冷却通道的变化对电池组散热效果的影响。采用在电池组外壳上开设多个通风孔的办法有助于电池热管理系统的冷却优化设计。     

动力汽车用锂电池热管理系统仿真分析

为了研究动力汽车用锂电池温度场分布,建立了单体电池及电池组仿真模型,通过实验与FLUENT软件模拟验证的方式分析单体电池温度场。通过仿真分析讨论电池组温度场,采用三种不同的进出风方式进行空气强制冷却电池组,分析了进出风口有倾角与无倾角的不同温度控制效果,结果表明带有倾角的进出风方式有利于降低电池组最高温度。采用电池组壳体侧面开孔方式进行电池组热管理,可有效改善电池组放电过程的温度分布均匀性。     

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。     

Thermal management of lithium‐ion batteries for electric vehicles

Thermal issues associated with electric vehicle battery packs can significantly affect performance and life cycle. Fundamental heat transfer principles and performance characteristics of commercial lithium‐ion battery are used to predict the temperature distributions in a typical battery pack under a range of discharge conditions. Various cooling strategies are implemented to examine the relationship between battery thermal behavior and design parameters. By studying the effect of cooling conditions and pack configuration on battery temperature, information is obtained as to how to maintain operating temperature by designing proper battery configuration and choosing proper cooling systems. It was found that a cooling strategy based on distributed forced convection is an efficient, cost‐effective method which can provide uniform temperature and voltage distributions within the battery pack at various discharge rates. Copyright © 2012 John Wiley & Sons, Ltd.     

Lithium battery thermal management system for hybrid vehicles

为研究动力电池组的温度特性以及维持其工作在最佳的温度范围内,以锂离子电池为研究对象,设计了一种新型混合动力汽车的电池热管理系统,利用空调系统和发动机排气系统来调控电池组的温度。建立了锂电池组的三维瞬态产热数值模型,以电池组的三维尺寸和进风口流速为输入参数,以降低电池组的最大温升和提高电池组的温度均匀性为输出参数,利用FLUENT仿真软件和DesignXplorer模块进行联合优化设计了电池组的结构。优化后的电池组的温升比优化前降低了5.39 K,电池组温差降低了6.41 K。分析了恒倍率放电以及对流换热系数对单体电池温升的影响,研究表明：放电倍率越大电池温升越快,放电结束后电池的温度越高,在对流换热系数小于30 W/（m²·K）时,散热效果明显。对电池组在不同条件下加热或者冷却进行了仿真分析,验证了该电池热管理系统的可行性。     

Experimental study of a direct evaporative cooling approach for Li-ion battery thermal management

A desirable operating temperature range and small temperature gradient is beneficial to the safety and longevity of lithium-ion (Li-ion) batteries, and battery thermal management systems (BTMSs) play a critical role in achieving the temperature control. Having the advantages of direct access and low viscosity, air is widely used as a cooling medium in BTMSs. In this paper, an air-based BTMS is modified by integrating a direct evaporative cooling (DEC) system, which helps reduce the inlet air temperature for enhanced heat dissipation. Experiments are carried out on 18650-type batteries and a 9-cell battery pack to study how relative humidity and air flow rate affect the DEC system. The maximum temperatures, temperature differences, and capacity fading of batteries are compared between three cooling conditions, which include the proposed DEC, air cooling, and natural convection cooling. In addition, a DEC tunnel that can produce reciprocating air flow is assembled to further reduce the maximum temperature and temperature difference inside the battery pack. It is demonstrated that the proposed DEC system can expand the usage of Li-ion batteries in more adverse and intensive operating conditions.     

Exergy Analysis of Electric Vehicle Heat Pump Air Conditioning System with Battery Thermal Management System

The exergy analysis of an electric vehicle heat pump air conditioning system(HPACS) with battery thermal management system was carried out by studying the exergy loss of each component. The results indicate that the compressor is the main source of system exergy loss in all operation conditions. The exergy loss distribution of HPACS is almost the same when the battery thermal management system integrated into the HPACS in cabin and battery mixed cooling mode and the system exergy loss was linearly related to the compressor speed in cooling modes. The performance of the HPACS is better than that of the positive temperature coefficient(PTC) heater in cabin heating mode. The degree of exergy efficiency improvement of the alternative mode was discussed at all operation conditions in cabin heating mode. The results indicate that the optimization effect using the electric vehicle HPACS to replace the PTC heater is obvious at lower compressor speed, surrounding temperature and internal condenser air flow rate.     

动力电池支撑架结构设计及散热性能分析

可再生能源的发展势必带动动力电池的发展,在促进退役动力电池循环利用方面也将取得较大成效,在动力电池发展过程中,其安全性是值得广泛关注的重点问题,为提高动力锂电池组放电时散热效率,设计电池组支撑架,采用计算机仿真的方法研究不同支撑架结构、不同工质、不同流速下18650型锂电池构成的动力电池组的热性能。通过对空气和水2种工质流体、工质流速大小、工质入口位置等参数进行组合仿真分析,结果表明,随着工质流速的增加,电池组及支撑架表面的最高温度逐渐降低,当工质流速大于10 m/s时趋于稳定;适当的工质流入口的位置可增强降温效果,在低流速状态下,空气和水分别作为冷却工质时,纵向包裹型电池支撑架比横向包裹型电池支撑架电池组中表面温度分别降低了2.64%和1.86%;在高流速状态下,空气和水分别作为冷却工质时,纵向包裹型电池支撑架比横向包裹型电池支撑架电池组中表面温度分别降低了3.15%和1.83%。动力电池支撑架结构设计可为后续电池热控制提供理论参考。     

Air cooling strategy of power battery based on minimum energy consumption

针对目前电动汽车动力电池风冷散热能耗高、散热滞后的问题,提出一种基于最小能耗的动力电池风冷控制策略,根据车载导航系统预报的工况信息预测动力电池的未来温升,在满足动力电池散热需求的前提下以风机能耗最少为目标,运用分段式动态规划算法确定风机在未来路段的开启时机与最优风速。以添加了坡度信息的ARB02、HWFET和UDDSHDV的组合工况为测试工况,对动力电池未来温升的精度进行了硬件在环试验,得出实际路况试验温度与预报工况试验温度的最大差值为0.3℃,最大偏差率为0.7%。与其他两种控制策略进行了Fluent仿真对比,结果表明基于最小能耗控制策略下动力电池的最高温度为39.87℃,最大温差为1.1℃;风机能耗是全程开启型控制策略的77.2%,是温度开关型控制策略的53.7%。该策略能有效控制动力电池的温度且风机能耗最小。     

Performance of serpentine channel based Li-ion battery thermal management system: An experimental investigation

Thermal management of large-scale Li-ion battery packs is of great significance to their safety and life cycle, which would impact their applicability in electric vehicles. Of the many strategies developed for this purpose, indirect liquid cooling has already demonstrated quite high potentials in thermal regulation of such battery systems. In this study, a compact lightweight serpentine wavy channel configuration was chosen to construct an indirect liquid cooling system for a battery module of cylindrical Li-ion cells. The serpentine channel has a number of six internal minichannels. Experimental test data were used to conduct a comprehensive thermal analysis to examine the highest temperature, the maximum temperature difference, and the heat accumulation percentages, and so forth within the battery pack. Results have revealed the ability of the cooling system to maintain the module temperature within appropriate working conditions for electric vehicle applications for most cycling tests including two driving cycles. Furthermore, the analysis insights raised by this study could be useful in understanding the cooling performance of the liquid-based thermal management systems for electric vehicles.     

A review on lithium-ion power battery thermal management technologies and thermal safety

Lithium-ion power battery has become one of the main power sources for electric vehicles and hybrid electric vehicles because of superior performance compared with other power sources.In order to ensure the safety and improve the performance,the maximum operating temperature and local temperature difference of batteries must be maintained in an appropriate range.The effect of temperature on the capacity fade and aging are simply investigated.The electrode structure,including electrode thickness,particle size and porosity,are analyzed.It is found that all of them have significant influences on the heat generation of battery.Details of various thermal management technologies,namely air based,phase change material based,heat pipe based and liquid based,are discussed and compared from the perspective of improving the external heat dissipation.The selection of different battery thermal management (BTM) technologies should be based on the cooling demand and applications,and liquid cooling is suggested being the most suitable method for large-scale battery pack charged/discharged at higher C-rate and in high-temperature environment.The thermal safety in the respect of propagation and suppression of thermal runaway is analyzed.     

Numerical investigation on integrated thermal management for lithiumion battery pack with phase change material and liquid cooling

为满足3 C放电倍率下电池组散热要求,提出了PCM\液冷复合式散热方案,利用有限元分析了液体流速、流道排列方式、铝制框架鳍宽和环境温度对电池组温度的影响。结果表明,增加流速可优化电池组散热性能,但当流速大于0.08 m/s时,流速的增加对散热系统无明显优化;各流速下Type I散热方式效果均为最优且电池组满足散热要求;鳍宽为2 mm时可将电池组最高温度进一步降低1.6℃;当环境温度从38℃增至42℃时,复合式散热系统体现了良好的热稳定性能。     

The forced air cooling heat dissipation performance of different battery pack bottom duct

Due to the requirement of the battery for the thermal management system, based on the coupling relationship between the velocity field and the thermal flow field of the field synergy principle, the flow paths of the forced air cooling system for different battery packs were analyzed. First, the thermodynamic parameters of the battery were collected through experiments and verified by simulation. Secondly, based on the collected thermodynamic parameters of the battery, the heat generation model of the battery, the heat conduction model of the gas, and the coupled heat dissipation model of the battery and air were established. Determine the boundary conditions, calculation methods and evaluation indicators required for simulation; Finally, based on four different driving conditions, the forced air cooling performance of the double “U” shape duct and double “1” type duct is simulated. Through the analysis of the results, the dual “U” air ducts have a more heat dissipation effect on the battery pack than the double “1” shape duct. The results conform to the definition of the field synergy principle for the coupling relationship between the velocity field and the heat flow field. Then research provide references for the design of battery packs and matching of cooling systems.     

汽车空调制冷剂直冷动力电池热管理系统的PID控制研究

电池热管理对电动汽车的安全和寿命至关重要。本文采用铝翅片铜管作为基础结构,设计一种结构紧凑、轻量型的18650型锂离子电池模组,采用基于PID原理的算法作为电动汽车空调系统电子膨胀阀的控制方案,实验研究R134a制冷剂直接气液两相流冷却电池模组的换热性能。结果表明：所提出的电池热管理系统能够快速响应温度的变化,并降低电池模组的温度。此外,当控制方案为动态温度PID算法时,电池模组以1 C倍率放电过程中电池之间的最大温差小于4℃,并且电池模组的最高温度低于36℃。     

Numerical study on thermal behavior and a liquid cooling strategy for lithium-ion battery

Investigation on the thermal behavior of the lithium-ion battery which includes the temperature response, heat contribution and generation, is of vital importance for their performance and safety. In this study, an electrochemical-thermal cycling model is presented for a 4 Ah 21700 type cylindrical single cell and 3× 3 battery pack and the model is validated by experiment on a single cell. Thermal behavior on a single cell is first analyzed, the results show that the heat generated in the charge is smaller than the discharge, and the polarization heat contributes the most to total heat, especially under higher rate. It can also be concluded from the battery pack that the temperature of the cell inside the battery pack is significantly greater than the external battery, while the temperature difference exists the opposite regular due to the worst heat dissipation of the central cell. Finally, after taking the enhanced liquid cooling strategy, the maximum temperature is 320.6 K that is reduced by 9.38%, and the maximum temperature difference is 4.9 K which is reduced by 69.6% at 2C, meeting the requirements of battery thermal management system.     

Experimental investigation on thermal performance of silica cooling plate‐aluminate thermal plate‐coupled forced convection‐based pouch battery thermal management system

The power battery as an indispensable part of electric vehicle has attracted much attention in recent years. Among these, the lithium‐ion battery is the most important option due to the high energy density, good stability, and low discharge rate. However, the thermal safety problem of lithium‐ion battery cannot be ignored. Therefore, it is very necessary to explore an effective thermal management system for battery module. Here, a thermal silica cooling plate‐aluminate thermal plate (SCP‐ATP) coupling with forced convection air cooling system as a thermal management system is proposed for improving the cooling performance of pouch battery module. The results reveal that the heat dissipating performance and temperature uniformity of pouch battery module with SCP‐ATP are greatly improved compared with other thermal management systems. Moreover, the highest temperature can be controlled below 50°C, and the temperature differences can be maintained with 3°C when the SCP‐ATP coupling forced convection is utilized to enhance the heat transfer coefficient. Furthermore, considering the cooling effectiveness and consumption cost comprehensively, the optimal air velocity of the SCP‐ATP coupling forced convection cooling system is 9 m/s. In addition, the SCP‐ATP filling with different proportions of acetone has also been investigated for pouch battery module, indicating that 50% acetone exhibited a better heat transfer effect than the 30% one. Therefore, this research would provide a significant value in the design and optimization of thermal management systems for battery module.