Experimental investigation on mini‐channel cooling–based thermal management for Li‐ion battery module under different cooling schemes

The performance of Li‐ion battery depends on the temperature. Active liquid cooling system can keep the battery temperature within an optimal range, but the system itself consumes energy. This paper reported the experimental work on the thermal performance of liquid cooling system for the battery module under different cooling schemes. It was hoped that energy consumption could be reduced as much as possible. Meanwhile, liquid cooling system could provide effective cooling for the battery module. Two identical real battery modules including 18 cylindrical cells (with and without cooling system) were manufactured for the validity of comparison. The 2 battery modules discharged at the discharge rates of 1C and 1.5C. Charge and discharge cycle test was also carried out. The results indicated that a simple hysteresis control cooling scheme could reduce the energy consumption effectively. The energy consumption was saved by 83.2% and 49% at the discharge rates of 1C and 1.5C, respectively. Meanwhile, the temperature of battery module was still kept within the optimal range. The maximum temperature appeared on different cells in the battery module during the process of charge and discharge. Thus, the temperature dynamic comparison mechanism was very necessary.     

Heat dissipation analysis of different flow path for parallel liquid cooling battery thermal management system

As the main form of energy storage for new energy automobile, the performance of lithium-ion battery directly restricts the power, economy, and safety of new energy automobile. The heat-related problem of the battery is a key factor in determining its performance, safety, longevity, and cost. In this paper, parallel liquid cooling battery thermal management system with different flow path is designed through changing the position of the coolant inlet and outlet, and the influence of flow path on heat dissipation performance of battery thermal management system is studied. The results and analysis show that when the inlet and the outlet are located in the middle of the first collecting main and the second collecting main, respectively; system can achieve best heat dissipation performance, the highest temperature decrease by 0.49°C, while the maximum temperature difference of system decreases by 0.52°C compared with typical Z-type BTMS under the discharge rate of 1 C. Then an optimization strategy is put forward to improve cooling efficiency compared with single-inlet and single-outlet symmetrical liquid cooling BTMS; the highest temperature of three-inlet and three-outlet is 27.98°C while the maximum temperature difference of three-inlet and three-outlet is 2.69°C, decrease by 0.7 and 0.67°C, respectively.     

Effects of reciprocating liquid flow battery thermal management system on thermal characteristics and uniformity of large lithium-ion battery pack

To investigate the thermal characteristics and uniformity of a lithium-ion battery (LIB) pack, a second-order Thevenin circuit model of single LIB was modeled and validated experimentally. A battery thermal management system (BTMS) with reciprocating liquid flow was established based on the validated equivalent circuit model. The effects of the reciprocation period, battery module coolant flow rate and ambient temperature on the temperature and the temperature imbalance of batteries were studied. The results illustrate that the temperature difference can be effectively reduced by 3°C when the reciprocating period is 590 seconds. The reciprocating coolant flow rate is 11.5% and 33.3% that of the unidirectional flow BTMS for cooling and heating when same thermal effects are to be achieved. Under the same ambient temperature condition, the maximum temperature and average temperature difference can be reduced by 1.67°C and 3.77°C, respectively, at best for the battery module investigated with a reciprocating liquid-flow cooling system. The average temperature difference and heating power consumption could be reduced by 1.2°C and 14 kJ for reciprocating liquid flow heating system with period of 295 seconds when compared with unidirectional flow. As a result, the thermal characteristics and temperature uniformity can be effectively improved, and the parasitic power consumption can be significantly reduced through adoption of a reciprocating liquid flow BTMS.     

Performance assessment of thermal management systems for electric and hybrid electric vehicles

Thermal management systems (TMS) are one of the key components of electric and hybrid electric vehicles to achieve high vehicle efficiency and performance under all operating conditions. Current improvements in electric battery technology allow vehicles to have relatively long ranges, fast acceleration, and long life while keeping low‐maintenance costs and considerably lower emissions. However, the vehicle performance is significantly affected by the battery operating conditions. Moreover, the cell life cycle, safety, and possibility of thermal runaway significantly depend on peak temperature rise and temperature uniformity of the battery. Therefore, various TMSs are created to keep batteries within ideal operating ranges. In this article, three different TMS systems—passive cabin cooling (via air), active moderate liquid circulation (via refrigerant), and active liquid circulation (via refrigerant and coolant)—are analyzed and compared with electric and hybrid electric vehicles. A second law analysis is used to examine the areas of low exergy efficiency in each system and minimize the entropy generation based on the system configuration. Moreover, TMS systems are compared on the basis of battery temperature increase and temperature uniformity. Various parametric studies are conducted to compare the TMS in different ambient and operating conditions. On the basis of the analysis, the active liquid circulation (via refrigerant and coolant) is determined to have the lowest battery temperature increase (3.9 °C in 30 min) and most cell temperature uniformity (2.5 °C median) as well as the lowest entropy generation rate (0.0121 W/K) among the compared systems. Copyright © 2012 John Wiley & Sons, Ltd.     

车用锂离子电池液冷式热管理系统实验研究

锂离子电池组的热管理对电动汽车的性能和安全性具有重要意义。基于多通道蛇形波纹管液冷式热管理系统,以200个18650型锂离子电池组为热管理对象,对电池在各种充放电倍率下所需的冷却液流量、泵功消耗以及热管理收益进行了实验研究。结果表明,热管理系统对动力电池在各种充放电应用条件下都具有较好的热管理效果,电池最大温度和最大温差基本可控制在40℃以下和5℃以内。提高冷却水流速对系统热管理能力的提升具有一定的效果,但是随着流速增大,热管理能力提升的边际效益也更趋明显;而系统运行所消耗的泵功增加导致了热管理收益随冷却水流速增加而大幅降低。从电池的性能安全以及热管理有效性的角度综合考虑,各充放电倍率下热管理系统的冷却水流速都是以保证电池安全和性能指标的最低流速为优。     

Experimental examination of large capacity liFePO4 battery pack at high temperature and rapid discharge using novel liquid cooling strategy

To overcome the significant amounts of heat generated by large‐capacity battery modules under high‐temperature and rapid‐discharge conditions, a new liquid cooling strategy based on thermal silica plates was designed and developed. The superior thermal conductivity of the thermal silica plate combined with the excellent cooling effect of water led to a feasible and effective composite liquid cooling system during long cycle testing. The experimental results showed that the addition of thermal silica plates can greatly improve the cooling capacity that can allow the maximum temperature difference to be controlled at 6.1°C and reduce the maximum temperature of the battery module by 11.3°C, but still outside the optimum operating temperature range. The water flow significantly enhanced the cooling performance/stability, and slight temperature fluctuations were observed during cycling. The cooling performance obviously improved as the flow rate rose. When the velocity reached a critical value, further increase in water flow rate induced a slight influence on the cooling capacity due to the limitation of the materials. The maximum temperature (T_max ) could be reduced to 48.7°C, and temperature difference (?T ) could be maintained within 5°C when the water flow velocity increased to 4 mL/s, which was determined as the best value. The energy consumed by the water pump is only 1.37% of the total energy of the battery module. Overall, these findings should provide novel strategies for the design and optimization 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.     

A comprehensive thermal analysis for the fast discharging process of a Li-ion battery module with liquid cooling

Appropriate temperature range and distribution is necessary for Li-ion battery module, especially in real application of electric vehicles and other energy storage devices. In this study, a comprehensive design of liquid cooling–based thermal management system for a Li-ion battery module's fast discharging process is investigated, and thermal analysis and numerical computation are conducted. The effects of different flow directions, different shapes of the liquid channels, different widths of channels, different thicknesses of cold plate, and the comparison between uniform and nonuniform channels' distribution are analyzed. Simulation results indicate that the liquid cooling system provides acceptable cooling performance in preventing heat runaway of the battery module under 5C discharging current rate. A five-channel cooling plate can reduce the maximum temperature with appropriate design. Additionally, specific flow direction mini-channels, different shapes of the liquid-channels, and nonuniform channels are designed to compare the maximum temperature and uniformity of temperature distribution in the module. Maximum temperature can be improved through the increase of channel width and thickness of the cooling plate. The original design is proved to be the best design considering the maximum temperature, maximum temperature deviation, and final temperature standard deviation of the fast discharging process.     

Simulation analysis of the influence of internal surface morphology of mini-channel on battery thermal management

Lithium-ion batteries, as the only source of driving force for electric vehicles (EV), directly determine the vehicle's power performance, driving mileage, and working stability. The performance, safety, and longevity of lithium-ion batteries are related to battery temperature. In this article, surface topography has been added in mini-channel liquid cooling plate, the influence of different shapes, different heights, different diameters, and different numbers of surface topography on the cooling effect of mini-channel liquid cooling plate were researched by using CFD method. This article revealed that the addition of surface topography in mini-channel can affect the flow trajectory of coolant and improve the cooling capacity of the cold plate. When five cylindrical surface topography with a diameter of 10 mm and a height of 1.5 mm were added in each channel, the highest temperature of the battery can be suppressed to 42.01°C and the maximum temperature difference can reach 15.78°C under 3C discharge rate, compared with the smooth mini-channel, decreased by 1.02°C and 0.85°C, respectively.     

Liquid cooling based on thermal silica plate for battery thermal management system

To achieve safe, long lifetime, and high‐performance lithium‐ion batteries, a battery thermal management system (BTMS) is indispensable. This is especially required for enabling fast charging‐discharging and in aggressive operating conditions. In this research, a new type of battery cooling system based on thermal silica plates has been designed for prismatic lithium‐ion batteries. Experimental and simulations are combined to investigate the cooling capability of the BTMS associated to different number of cooling channels, flow rates, and flow directions while at different discharge C‐rates. Results show that the maximum temperature reached within the battery decreases as the amount of thermal silica plates and liquid channels increases. The flow direction had no significant influence on the cooling capability. While the performance obviously improves with the increase in inlet flow rate, after a certain threshold, the gain reduces strongly so that it does not anymore justify the higher energy cost. Discharged at 3 C‐rate, an inlet flow rate of 0.1 m/s was sufficient to efficiently cool down the system; discharged at 5 C‐rate, the optimum inlet flow rate was 0.25 m/s. Simulations could accurately reproduce experimental results, allowing for an efficient design of the liquid‐cooled BTMS.     

Effect of dynamic load on the temperature profiles and cooling response time of a proton exchange membrane fuel cell

Polymer Electrolyte Membrane Fuel Cells (PEMFC) is an electrochemical device that generates electrical energy from the reactions between hydrogen and oxygen. An effective thermal management is needed to preserve the fuel cell performance and durability. Cooling by water is a conventional approach for PEMFC. Balance between optimal operating temperature, temperature uniformity and fast cooling response is a continuous issue in the thermal management of PEMFC. Various cooling strategies have been proposed for water-cooled PEMFC and an approach to obtain a fast cooling response was tested by feeding the coolant at a high temperature. In this paper, the operating behaviour was characterized from the perspectives of temperature profiles, mean temperature difference, and cooling response time. A 2.4 kW water-cooled PEMFC was used and the electrical load ranged from 40 A–90 A. The operating coolant temperature was set to 50 °C where the maximum stack operating temperature is 60 °C. The stack temperature profiles, cooling response time, mean temperature difference and cooling rates to the load variation was analysed. The analysis showed that the strategy allowed a fast cooling response especially at high current densities, but it also promotes a large temperature gradient across the stack.     

Comparative study of high concentrating photovoltaics integrated with phase‐change liquid film cooling system

In high concentrating photovoltaic systems, thermal regulation is of great importance to the conversion efficiency and the safety of solar cells. Direct‐contact liquid film cooling technique is an effective way of thermal regulation with low initial investment. Tilt of solar cells is common in concentrating solar systems. An evaluation of direct‐contact liquid film cooling technique behind tilted high concentration photovoltaics was performed using both experimental and computational approaches. In the experiment, deionized water was used as the coolant at the back of simulated solar cells. Solar cell inclination of 0° to 75° with inlet water flow rate of 100–300 L/hour and inlet temperature of 30°C to 75°C were experimentally investigated. A two‐dimensional model was developed using computational fluid dynamics technique and validated by experimental results. The effects of inclination on average temperature, temperature uniformity, and heat transfer coefficient were discovered in this paper. The results indicated that 20° is the optimum angle for liquid film cooling. In addition, optimum inlet width, temperature, and velocity for inclination over 30° are 0.75 mm, 75°C, and 0.855 m/s, respectively.     

Multiwalled Carbon Nanotube Nanofluid for Thermal Management of High Heat Generating Computer Processor

Minichannel heat sink geometries with varying fin spacing were tested with de‐ionized water and MWCNT (1 wt %) nanofluid to evaluate their performance with flow components of a liquid cooling kit. Four heat sinks with fin spacing of 0.2 mm, 0.5 mm, 1.0 mm, and 1.5 mm were used in this investigation. Heat sink base temperature was analogous to processor operating temperature which was the prime parameter of interest in this investigation. The base temperature decreased by reducing the fin spacing and using multiwalled carbon nanotube (MWCNT) nanofluid. The lowest value of heat sink base temperature recorded was 49.7 ^°C at a heater power of 255 W by using a heat sink of 0.2 mm fin spacing and MWCNT nanofluid as a coolant. Moreover, as a result of reduced fin spacing and using MWCNT nanofluid as a coolant the value of overall heat transfer coefficient increased from 1200 W/m²K to 1498 W/m²K, translating to about a 15% increase. The value of thermal resistance also dropped by reducing the fin spacing and using MWCNT nanofluid. The most important aspect of the study is that the heat sinks and MWCNT nanofluid proved to be compatible with the pump and radiator of the commercial CPU liquid cooling kit. The pump was capable to handle the pressure drop which resulted by reducing the heat sink fin spacing and by using MWCNT nanofluid. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(7): 653–666, 2014; Published online 11 November 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21107     

Cooling of lithium-ion battery pack using different configurations of flexible baffled channels

The rated temperature and its uniformity of lithium-ion (Li-ion) battery (LIB) pack are the main demands for safe and efficient operation. This paper investigates an air cooling system of a pack of five prismatic LIB's generating considerable heat through discharging energy. The cooling system is a three-dimensional channel with flexible baffles of different arrangements installed on the walls of the channel to lower and regulate the temperature of the batteries. Three arrangements of these baffles are studied, transverse; L-shaped and staggered. The study is formulated as turbulent fluid–structure interaction and solved numerically using the finite elements method. The study was conducted for five spaces between batteries, S = 0, 1, 2, 3 and 4 mm and three different inlet air velocities, U_in = 0.5, 1 and 2 m/s. It was found that the flexible baffles guide the coolant towards the batteries smoothly with less pressure drop and this significantly improves the performance of the battery thermal management system due to the reduction of the maximum temperature and temperature variation as well. The staggered arrangement of the baffles shows the most effective configuration, where the maximum temperature difference between batteries is only 1.85°C for S = 1 mm and U_in = 2 m/s.     

Investigation on thermal management performance of wedge‐shaped microchannels for rectangular Li‐ion batteries

The performance of power battery is a significant factor affecting the overall quality of electric vehicles. To optimize the thermal management effect of battery pack, cold plate with wedge‐shaped microchannels was proposed in this paper. On the basis of the models of the independent cold plate and the battery‐cooling module, the effects of outlet aspect ratio, flow rate, and branching structure on the heat dissipation performance of the cold plate were studied at first. Afterwards, the effects of cooling surface, flow rate, and branching structure on the temperature distribution of the battery module were simulated. The results showed that the wedge‐shaped channels provided a good cooling efficiency and surface temperature uniformity. When the wedge‐shaped channel was used in thermal management of the battery module, the side‐cooling method reduced the temperature difference of batteries by more than 35.71% compared with front cooling under the mass flow rate of 2 × 10^?5 kg/s. At a discharge rate of 3.5 C, the flow rate of 1 × 10^?4 kg/s controlled the battery temperature to within 45°C, and the branching structure designed for the module successfully decreased the maximum temperature difference from 7.27°C to 4.67°C, which has been reduced by approximately 35.78%.     

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。     

An improved electrothermal-coupled model for the temperature estimation of an air-cooled battery pack

This work establishes an improved electrothermal-coupled model for the estimation of the temperature evolution in an air-cooled pack with three parallel branches and four serial cells in each branch. This model includes the influences of the cells' state of charge (SOC) and temperature on the ohmic and polarization resistances and polarization capacitance. The current distribution in the pack is considered in the model and applied to predicting the inconsistent effect of cell temperature. Moreover, the pipe network theory is used to model the airflow in the pack and the heat convection between the air and the batteries. An experiment is implemented to verify prediction precision in the electrical and thermal parameters of the pack. The results show that the electrothermal model accurately estimates the electrical and thermal performance of the air-cooled pack. The relative error of the pack terminal voltage between the prediction and the experiment is 3.22% under the conditions of a discharging rate is 1.5 C (C denotes the ratio of charging/discharging current to battery capacity), environment temperature of 37°C, and air inlet velocity of 6 m/s. Regarding the prediction error in the temperature, the root mean square errors of most batteries are no more than 0.6°C under the conditions of discharge rates of 1 C and 1.5 C and ambient temperatures of 17°C, 27°C, and 37°C.     

Performance of a liquid cooling-based battery thermal management system with a composite phase change material

This article reports a recent study on a liquid cooling-based battery thermal management system (BTMS) with a composite phase change material (CPCM). Both copper foam and expanded graphite were considered as the structural materials for the CPCM. The thermal behaviour of a lithium-ion battery was experimental investigated first under different charge/discharge rates. A two-dimensional model was then developed to examine the performance of the BTMS. For the copper foam-based CPCM modelling, an enthalpy-porosity approach was applied. The numerical modelling aimed to study the impacts of CPCM types and inlet velocity of heat transfer fluid on both the maximum battery temperature and temperature distribution under different current rates. Dimensional analyses of the results were performed, leading to the establishment of relationships of the Nusselt numbers and dimensionless temperature against the Fourier and Stefan numbers.     

NCR18650A电池的充放电温度特性与管理

采用实验测试与数值仿真的方法对NCR18650A三元锂电池组在1 ~ 3 C放电和1.6 C充电过程的温升特性进行测试,同时验证所建立电池产热模型的准确性。结果显示,实验测试结果与电池产热模型仿真结果之间的相对误差在合理范围内,满足工程应用需求。电池组在自然冷却的情况下,仅在1 C放电状态下符合其最佳工作区间42.5 ~ 45.0℃的要求,3 C放电倍率下最高温度为89.4℃。提出并建立基于热电致冷主动热管理模型,将热电致冷组件设置在电池组上方,致冷功率为50 W时可有效控制电池组3 C放电过程的温度,在最佳工作区间实现电池单体温差小于5℃,抑制电池组的热失效并实现良好的均温性。     

A review of novel thermal management systems for batteries

In the recent years, significant developments in the electric batteries have made them one of the most promising storage technologies for electrical energy. Among the various rechargeable batteries that are developed, lithium ion batteries stand out due to their capability of storing more energy per unit mass, low discharge rate, low weight, and lack of a memory effect. The advantages that batteries offer have promoted the development of the electric and hybrid electric vehicles. However, during charging and discharging processes, batteries generate heat. If this heat is not removed quickly, the battery temperature will rise, resulting in safety concerns and performance degradation. Thermal management systems are developed to maintain the temperature of the battery within the optimum operation range. This review paper focuses on novel battery thermal management systems (BTMSs). Air, liquid, phase change material, and pool‐based BTMSs are considered. Air‐based thermal management systems are discussed first. Liquid cooling systems and phase change‐based systems are discussed subsequently, and then the recently proposed evaporating pool‐based thermal management system is considered.