Air-cooled Thermal Management System Research Articles

Development of Electro-Thermal Model for Air Cooling Study of Electric Vehicle Lithium-Ion Battery Module Operating in Indian Conditions and Drive Cycle

Lithium-ion cells have higher energy density at a specific power, making them a primary choice for battery packs in energy storage of modern technology, powering from smartphones to Electric vehicle (EV) and grid-scale energy storage systems. However, their performance, safety and lifespan are temperature sensitive and developing a fail-safe mechanism is considered as a pressing priority. In the present study, a 2D electro-thermal model is developed in MATLAB to characterize the thermal behaviour of cylindrical cells (individual and inline) during discharge. The thermal model solves the transient heat conduction equation with internal heat generation. The model is validated with the available experimental data for a single cell at a constant discharge rate and found to be in good agreement within 0.5°C. The analysis is extended to a battery module with 6 cell-inline configuration and validated. This validated model is used to study the impact of multiple cells (1-10) in inline configuration. For Indian drive cycle analysis, the current profile is estimated based on the drive cycle and its impacts on cell temperature rise in battery module is studied when subjected to variation in monthly average ambient temperature. Battery module maximum temperature rises to 60 °C and Δ T (Tmax - Tmin) across cells is 8.8 °C during summer conditions under natural convection due to multiple drive cycle loading. The battery module temperature can be kept under safe operating limits (Tmax≤ 45 °C, Δ T ≤ 4 °C) with forced convection of 2 m/s and 25 °C. The study aims to provide insights into the thermal behaviour of Lithium-ion cells that can be used to design safe and cost-effective air-cooled thermal management system for battery module.

Thermal Performance of a Novel Honeycomb Cooling System for Cylindrical Lithium-Ion Batteries

In this article, the effects of circular, cylindrical, square, and hexagonal crater shapes on cooling performance were analyzed by numerical simulation and experimental verification, and then a new honeycomb cooling structure for cylindrical batteries (18650 type for example) was proposed. The effects of honeycomb depth, side length and wall thickness on the cooling performance were investigated. A quadratic response regression model was numerically calculated based on the experimental scheme obtained from the Box-Behnken central combination test. The results showed that the hexagonal crater cooling structure can reduce the maximum battery temperature by 5.3% compared to the non-crater cooling structure. Therefore, the proposed honeycomb structure was reasonable. In addition, increasing the depth and the hedge length could effectively reduce the maximum battery temperature and temperature difference, and when a certain value was exceeded, a reverse temperature growth trend occurs. Within the range of variation, wall thickness had little effect on the cooling performance. The cooling performance was optimal when the depth is 0.475 mm, the side length is 1.250 mm, and the wall thickness is 0.125 mm. The novel cooling structure proposed in this study can provide a new idea for the structural design of air-cooled thermal management system for cylindrical batteries.

Multi-objective optimization of U-type air-cooled thermal management system for enhanced cooling behavior of lithium-ion battery pack

The forced air cooling of U-type BTMS (battery thermal management system) with 12 prismatic lithium-ion batteries is considerably improved by adjusting the distribution of battery spacing and/or the tapered inlet/outlet manifolds. The temperature and velocity distributions of BTMS with an inlet temperature of 25 °C and various inlet airflow rates are calculated by computational fluid dynamics (CFD). High inlet airflow rate reduces the average temperature of the hottest battery (Tave,max) but increases the maximum average temperature difference between batteries (ΔTave,max), and vice versa for low inlet airflow rate. Multi-objective optimization using Nelder-Mead algorithm combined with CFD is performed to minimize the objective functions including ΔTave,max, Tave,max, and power consumption of fan without changing the BTMS volume. Taking an inlet airflow rate and independent battery spacings as design variables (13 variables), the Tave,max and ΔTave,max of optimized module are reduced to 38.2 °C and 0.3 °C, respectively, with a power consumption of about 1.51 W. Taking a linearly dependent battery spacing, inlet airflow rate, and tapered inlet/outlet manifolds as design variables (3 variables), the multi-objective optimization is carried out in short time and the power requirement of fan is reduced to 1.05 W without sacrificing the cooling performance of U-type BTMS.

Numerical evaluation of the effect of air inlet and outlet cross-sections of a lithium-ion battery pack in an air-cooled thermal management system

In this paper, airflow around 16 cylindrical lithium-ion cells placed in a square battery pack (BTP) is numerically examined. Laminar airflow enters the BTP from the top of the battery cells (BTC) and exits from the bottom of the BTP. In this three-dimensional analysis, the effect of the air inlet and outlet cross-sections on the temperature of the battery (T-BT) cells and the maximum and average T-BT pack is evaluated. The finite element method is used to solve the equations of battery and airflow. The results show that the upper part of the BTCs is at a lower temperature than the lower parts. The BTCs located in the middle of the BTP have a higher temperature than the ones located around the BTP. An increment in the air inlet cross-section reduces the average and the maximum T-BT pack. Enhancing the air outlet cross-section has little effect on the T-BT cells. The T-BT cells is enhanced until 1500 s, after which it is reduced because the airflow is diminished due to that the battery charging stops.

Experimental and numerical analysis of holistic active and passive thermal management systems for electric vehicles: Fast charge and discharge applications

Lithium-ion capacitors (LiCs) are commonly used as power sources for electric vehicles (EVs) due to the combined advantages of electric double-layer capacitors (EDLCs) and lithium-ion batteries (LiBs) comprising high energy density, high power density, and long lifetime. However, the performance of the LiCs is susceptible to temperature. Therefore, a robust thermal management system (TMS) is crucial for EVs to operate efficiently and safely. In this work, holistic active and passive TMSs are designed to control the maximum temperature of the cell. In this regard, an air-cooled TMS (ACTMS) and a compact liquid-cooled TMS (LCTMS) are among the active cooling systems, where pure paraffin phase change material (PCM), PCM with added aluminum mesh grid foil (PCM-Al), PCM with an added heat sink (PCM-HS), and heat pipe cooling system (HPCS) are the investigated passive TMSs. Moreover, the experimental results are verified against numerical analysis using a computational fluid dynamics (CFD) software, COMSOL Multiphysics. The most efficient active and passive cooling systems are then selected in the CFD simulations to make a robust hybrid TMS for a module of LiC cells. The results exhibit that the LCTMS has the best performance where the maximum temperature of the cell is controlled at 32.5 °C, which shows the reduction of 41.2% compared to the natural convection (NC) case study. The PCM-HS has the best performance among the passive cooling systems, decreasing 38.3% compared to the NC. Moreover, the hybrid TMS decreases the maximum temperature by 50.1% while uniformizing the temperature along with the module by keeping the temperature difference below 4.5 °C between the coldest and hottest points on the cell.

Examination of Channel Angles Influence on the Cooling Performance of Air-cooled Thermal Management System of Li-Ion Battery

Air-cooled battery thermal management is the most frequent alternative for keeping the battery pack in hybrid electric vehicles and electric vehicles at the proper temperature. In the present study, the flow and thermal distribution in regular Z and U-type flow Battery Thermal Management Systems (BTMS) were optimized by modifying their inlet and outlet channel angles. The cooling performance of the systems was determined based on their flow and thermal fields using a Computational Fluid Dynamics (CFD) approach. The results show that the conventional Z-type flow cooling performance is improved by changing the input channel angle to 150° and the exit channel angle to 120°. The maximum temperature is reduced by 1.6 °C, and the maximum temperature difference is reduced by 3.7 °C, while the power usage is cut by 29%. By keeping the inlet channel angle perpendicular and changing the outlet channel angle to 135°, the cooling effectiveness of the conventional U-type flow BTMS is also increased. The maximum temperature drops by 0.4 °C, the maximum cell temperature difference drops by 1 °C, and its power consumption drops by 11%. The overall results suggest that inlet and outlet channel angles play a significant role in optimization and depend strongly on the flow type of BTMS.

Numerical investigation of air cooling system for a densely packed battery to enhance the cooling performance through cell arrangement strategy

Recent studies have revealed that the operating temperature and temperature uniformity within the battery pack significantly affected its performance. In this study, the air-cooled thermal management system of a densely packed battery pack was numerically investigated under different cell arrangements such as inline, offset, and staggered configurations to evaluate their cooling characteristics. The effects of inlet ambient air velocity and discharge rate were also evaluated to guarantee the temperature of the battery pack operated within an optimal range. The results revealed that increased airflow enhanced the cooling performance of the system but also increased the flow resistance, resulting in large power consumption. A battery pack operating at the low discharge rate of 0.5C might not require forced air-cooling. For fast discharge rates, especially over 2C-rate, forced air-cooling would not be economical for battery thermal management. A narrow cell-to-cell distance can decrease the cell temperature and also improve space utilization; however, it increased the power consumption for circulating air and the risk of a thermal runaway propagation. A trade-off between thermal dissipation and energy consumption was investigated. After comparing several circumstances, the offset layout was the appropriate choice for the air-cooled thermal management system, followed by the inline layout. It satisfied the requirements of low power consumption, high space utilization, and efficient cooling performance; in particular, the offset layout consumed about 43.1% less power than the inline layout, while losing space utilization of only 6.3%.

RETRACTED: Study of the effect of the aspect ratio of a cylindrical lithium-ion battery enclosure in an air-cooled thermal management system

Batteries are utilized to store electrical energy in various devices due to their industrial importance, So in this paper, airflow is simulated in a channel to cool a two-dimensional, transient lithium-ion battery cylindrical cell. There is a circular PCM chamber around the battery. Battery cooling is evaluated by changing the aspect ratio of the PCM chamber and air velocity in the range of 0.2 to 0.4 and 0.001 to 0.005 m/s. COMSOL software is used for the simulations. The values of Tbattery, PCM chamber, the volume fraction (VFR) of molten PCM, and ambient air temperature are examined during the PCM charging and discharging process when the battery is working. The results of this study demonstrated that an enhancement in the air velocity causes the battery temperature (Tbattery), i.e., the maximum temperature and average temperature of the battery and the average temperature of PCM inside the chamber, to decrease. Also, the VFR of molten PCM is reduced with the air velocity. Over time, the values of air outlet temperature, Tbattery, and VFR of molten PCM decrease. Enhancing the aspect ratio intensifies the amount of temperature at the outlet. The aspect ratio of 0.2 corresponds to the lowest average temperature of the PCM chamber and the minimum VFR of molten PCM, while the aspect ratio of 0.35 corresponds to the highest average temperature of the PCM chamber and the maximum VFR of molten PCM.

A Novel Air-Cooled Thermal Management Approach towards High-Power Lithium-Ion Capacitor Module for Electric Vehicles

This work presents an active thermal management system (TMS) for building a safer module of lithium-ion capacitor (LiC) technology, in which 10 LiCs are connected in series. The proposed TMS is a forced air-cooled TMS (ACTMS) that uses four axial DC 12 V fans: two fans are responsible for blowing the air from the environment into the container while two other fans suck the air from the container to the environment. An experimental investigation is conducted to study the thermal behavior of the module, and numerical simulations are carried out to be validated against the experiments. The main aim of the model development is the optimization of the proposed design. Therefore, the ACTMS has been optimized by investigating the impact of inlet air velocity, inlet and outlet positions, module rotation by 90° towards the airflow direction, gap spacing between neighboring cells, and uneven gap spacing between neighboring cells. The 3D thermal model is accurate, so the validation error between the simulation and experimental results is less than 1%. It is proven that the ACTMS is an excellent solution to keep the temperature of the LiC module in the desired range by air inlet velocity of 3 m/s when all the fans are blowing the air from both sides, the outlet is designed on top of the module, the module is rotated, and uneven gap space between neighboring cells is set to 2 mm for the first distance between the cells (d1) and 3 mm for the second distance (d2).

Numerical investigation of cooling performance of a novel air-cooled thermal management system for cylindrical Li-ion battery module

Batteries strongly influence the performance of electric vehicles. Therefore it is crucial to develop a battery thermal system that is highly efficient in removing the battery pack's heat during its operation. In this paper, a numerical analysis of a lumped thermal model coupled with fluid flow equations is employed to investigate the novel air-cooled battery thermal management system (BTMS). The cooling efficiency of the proposed battery thermal system with commercial thermal interface material (3M™) is investigated by comparing it with a standard battery pack at different discharge rates. The proposed solution offers a 25% reduction in peak temperature when compared to the standard one. The thickness of the thermal interface material is found to have an insignificant impact on the battery pack's thermal performance. Introducing forced air-cooling in the battery pack reduced the maximum temperature considerably but increased the temperature difference compared to the battery pack without forced convection. Then the effect of various structural and operational parameters on the performance of the BTMS is investigated. Moving the air inlet-outlet boundaries to a central location increased the uniformity of temperature distribution in the battery pack. Although the increase in the inlet airflow velocity reduces the maximum temperature, it comes at the cost of an increase in temperature difference and power consumption. It is further observed that a reduction in ambient temperature reduces the peak temperature and makes the temperature distribution in the battery pack more homogeneous. The discharge voltage curves indicate a slight reduction in cell potential as a reducing function of temperature.

Heat pipe air-cooled thermal management system for lithium-ion batteries: High power applications

Thermal management of lithium-ion (Li-ion) batteries in Electrical Vehicles (EVs) is important due to extreme heat generation during fast charging/discharging. In the current study, a sandwiched configuration of the heat pipes cooling system (SHCS) is suggested for the high current discharging of lithium-titanate (LTO) battery cell. The temperature of the LTO cell is experimentally evaluated in the 8C discharging rate by different cooling strategies. Results indicate that the maximum cell temperature in natural convection reaches 56.8 °C. In addition, maximum cell temperature embedded with SCHS for the cooling strategy using natural convection, forced convection for SHCS, and forced convection for cell and SHCS reach 49 °C, 38.8 °C, and 37.8 °C which can reduce the cell temperature by up to 13.7%, 31.6%, and 33.4% respectively. A computational fluid dynamic (CFD) model using COMSOL Multiphysics® is developed and comprehensively validated with experimental results. This model is then employed to investigate the thermal performance of the SHCS under different transient boundary conditions.

Three dimensional thermal model development and validation for lithium-ion capacitor module including air-cooling system

Lithium-ion capacitor (LiC) has emerged as a promising technology for high power applications due to the solution offered by its power density, higher-voltage operation than super-capacitor (SC), and their excellent durability (more than 2 million cycles). However, for this kind of applications, a thermal management system is crucial to ensure thermal stability and a long lifespan. Nonetheless, in order to design a proper thermal management system, dedicated thermal modelling development is an essential task. In this study, a detailed three-dimensional thermal model is developed in COMSOL Multiphysics software at cell and module level. Pertaining to the versatility of the detailed model, an air-cooled thermal management system is designed considering different topologies. Then, different operating and design parameters including inlet air speed, inter-cell spacing, and the airflow direction are studied comprehensively. The simulation results are validated with experimental results showing an acceptable error of less than 2 °C. It is proved and validated that the side cooling topology with a 5 m/s air velocity and a 5 mm spacing between cells is the optimum design.

Experimental study of an air-cooled thermal management system for high capacity lithium–titanate batteries

Lithium–titanate batteries have become an attractive option for battery electric vehicles and hybrid electric vehicles. In order to maintain safe operating temperatures, these batteries must be actively cooled during operation. Liquid-cooled systems typically employed for this purpose are inefficient due to the parasitic power consumed by the on-board chiller unit and the coolant pump. A more efficient option would be to circulate ambient air through the battery bank and directly reject the heat to the ambient. We designed and fabricated such an air-cooled thermal management system employing metal-foam based heat exchanger plates for sufficient heat removal capacity. Experiments were conducted with Altairnano's 50 Ah cells over a range of charge-discharge cycle currents at two air flow rates. It was found that an airflow of 1100 mls−1 per cell restricts the temperature rise of the coolant air to less than 10 °C over ambient even for 200 A charge-discharge cycles. Furthermore, it was shown that the power required to drive the air through the heat exchanger was less than a conventional liquid-cooled thermal management system. The results indicate that air-cooled systems can be an effective and efficient method for the thermal management of automotive battery packs.