Electric Vehicle Thermal Management Research Articles

Novel adjustable backflow structure in electric coolant pump for balancing hydraulic performance and reducing temperature rise

An electric coolant pump serves as the source for coolant circulation in the thermal management of electric vehicles. To address the thermal issues for the printed circuit board integrated within the electric coolant pump, a novel backflow structure with an adjustable orifice diameter is designed from the impeller outlet to the printed circuit board to promote convective heat dissipation. Eventually, this flow returns to the impeller inlet, thereby altering the hydraulic performance of pump. The balance between hydraulic performance and temperature rise is achieved by adjusting the orifice diameter. Considering the variations in coolant properties with respect to temperature, numerical simulations of the electric coolant pump are performed using the unsteady compressible Reynolds-Averaged Navier-Stokes Equations. There is good agreement between experimental and numerical simulations results in both cases with and without an orifice. On an average, by increasing the orifice diameter by 1.5 mm which results in a 1.11 % decrease in efficiency, a 0.008 decrease in pressure coefficient, and a reduction of temperature by 2.98 K on printed circuit board. As the orifice diameter increases, leakage losses in the rear side chamber increases with the improvement of heat dissipation. The clash between the backflow jet and the inflow from the suction pipe results in significant entropy generation, forming jet vortices and increasing in pressure fluctuation. However, when the orifice diameter exceeds 3 mm, the cooling advantages no longer justify the trade-off in hydraulic performance. Thus, 3 mm orifice diameter is an optimal compromise between hydraulic performance and temperature control.

Optimization of Energy Flow in Thermal Management of Electric Vehicles Based on Real Vehicle Testing and Digital Twin Simulation

Optimization of Energy Flow in Thermal Management of Electric Vehicles Based on Real Vehicle Testing and Digital Twin Simulation

Developing a flame-retardant flexible composite phase change material to realize both temperature control and thermal runaway prevention for lithium-ion battery pack

Exploring a facile solution to controlling the operating temperature within the range between −25 °C and 60 °C and the temperature difference between batteries less than 5 °C as well as preventing thermal runaway for battery packs, is significant, but remains challenging. Herein, a flame-retardant flexible composite phase change material was developed and applied for both the temperature control and thermal runaway prevention of battery packs. Specifically, a flame-retardant coating comprising 70 % polydimethylsiloxane as a binder was first investigated to determine the optimal mass ratio of 3:1 for the blend of expandable graphite and ammonium polyphosphate. The flame-retardant flexible composite phase change material was then produced by applying the optimal coating at a loading of 15 % on a flexible composite phase change material that was obtained from incorporating an ethylene propylene diene monomer with a mass fraction of 40 % into an 80 % paraffin/20 % expanded graphite composite. The flame-retardant flexible CPCM not only exhibited the highest flame-retardant rating of V-0, a significant latent heat capacity and good thermal reliability, but also demonstrated improved thermal conductivity and enhanced mechanical properties in tensile strength, bending, and compression as compared with the uncoated counterpart. The flame-retardant flexible composite phase change material achieves better temperature control performance for a battery pack compared to the material without a flame-retardant coating. Moreover, the flame-retardant flexible composite phase change material effectively prevents thermal runaway propagation within a battery pack. These favorable characteristics demonstrate the considerable potential of the flame-retardant flexible CPCM for battery thermal management in electric vehicles.

Heat transport characteristics of a flat-evaporator loop heat pipe for use in a thermal management system of electric vehicles

In this work, a flat-evaporator loop heat pipe (FELHP), with a 100 cm2 rectangular thermal interface and an overall length of approximately 2 m was devised for the thermal management of electric vehicles. A simple rectangular-cuboid evaporator was devised using a novel stepped-flat wick structure, and the heat transport characteristics were systematically investigated in terms of the heat load, relative height of the evaporator to the condenser (i.e., position), heat sink temperature, and working fluid. In particular, water-ethanol binary mixtures with different compositions were tested to find an optimum low-freezing-temperature working fluid for use in thermal management system of the electric vehicles driving outdoors. Over the tested heat load range, a significant position dependence of the operating temperature was observed with a thermal resistance change from 0.21 K/W ± 0.02 K/W to 0.14 K/W ± 0.01 K/W for a 0.4 m change in the position. In contrast, the operating temperature of the FELHP was insensitive to changes in the heat sink temperature. A binary mixture containing 20% water and 80% ethanol (by volume) resulted in comparable heat transport characteristics to those of pure water but had a much lower freezing temperature (e.g., a thermal resistance of 0.25 K/W ± 0.03 K/W at 450 W and a freezing temperature of approximately -59 °C), demonstrating that this was an optimum composition of the water-ethanol mixture working fluid of the FELHP.

Research and evaluation of the arrangement of heat exchangers in electric vehicle thermal management systems for CO2 refrigerant

The application of transcritical CO2 cycle in the thermal management system of electric vehicles has become increasingly prevalent, but the existing thermal management system architecture has not been optimized to specifically enhance the performance of CO2 refrigerant. This paper analyzes the impact of various heat exchanger arrangements on CO2 thermal management system and evaluates system configurations based on a new performance index, cycle coefficient of performance. The effects of air temperature, ambient temperature, and heat load on system performance are conducted with a high precision model. The chiller is connected in parallel-series with indoor heat exchangers, resulting in a maximum coefficient of performance improvement of 27.89% at an indoor air inlet temperature of 10 °C, and a maximum coefficient of performance improvement of 21.69% at an ambient temperature of 5 °C, under simultaneous heating conditions. The radiator is placed on the windward of gas cooler, leading to a maximum coefficient of performance increase of 4.85% in heating mode, but a maximum coefficient of performance decrease of 9.84% in cooling mode. The evaluation of these configurations across different operating cycles reveals that the parallel-series connection is well-suited for the new European driving cycle, showing an 18.4% improvement in cycle coefficient of performance compared to the series-parallel connection. The windward arrangement of radiator proves effective for highway fuel economy test cycle in winter and the new European driving cycle in summer. This study provides effective instruction for configuration design and evaluation of transcritical CO2 vehicle thermal management systems.

Evaporation performance of propane in offset strip-fin plate heat exchanger for refrigerant-based battery thermal management in electric vehicles

This study investigates the potential of refrigerant-based cooling (RC) using a natural refrigerant (propane) and lightweight energy-efficient brazed plate heat exchangers (PHXs) in the battery thermal management systems (BTMSs) of the electric vehicles (EVs). Experimental assessments were conducted to analyze the evaporative heat transfer characteristics of propane within an offset strip-fin flow-structured PHX under various operational conditions resembling the BTMS operation. The battery discharge rates, often represented by the C-rate, are determined by the discharging current relative to the battery's capacity. In this study, a heat generation model based on the C-rate was employed to evaluate the thermal performance of the battery. Parameters, such as mass flux (G) at 30–70 kg/m2s, discharge rates (C-rate) of 1, 1.25, and 1.5C, and saturation temperatures (Tsat) of 16–24 °C were explored, with the inlet vapor quality (xin) in the range of 0.1–0.8. The influence of G and Tsat on the heat transfer performance showed that higher G values (60 and 70 kg/m2s) achieved the maximum heat transfer coefficients (HTC), which resulted in impractical pressure drops (PD). While higher HTC and lower PD were observed at a Tsat of 24 °C, concerns about increased inner wall temperature (Tiw) and safety emerged at this temperature. Hence, the optimum conditions of G (30 and 50 kg/m2s) and Tsat (16 and 20 °C) were investigated. The average HTC increased by 29, 27, and 21 % at 50 kg/m2s compared to that at 30 kg/m2s with Tsat of 20 °C, resulting in an average of 0.7, 0.9, and 1.2 °C reduction in the Tiw for C-rates of 1.5, 1.25, and 1C respectively. Compared to the Tsat of 16 °C, higher HTC and lower PD were observed at 20 °C, however, the Tiw was in the range of 21.12–20.47 °C for Tsat of 20 °C, which is 3.5–4 °C higher than that at Tsat of 16 °C. The results from the critical heat transfer coefficient analysis showed that the peak heat dissipation with minimal wall temperature was attained with optimal xm of 0.45–0.5, which enhanced the cooling efficiency for both the G values of 30 and 50 kg/m2s, and both the Tsat values (16 and 20 °C).

Investigation of hydrodynamic lubricant film breakdown between the journal and bearing in a high-speed coolant pump of electric vehicles

The high-speed coolant pump is essential for electric vehicle thermal management, ensuring optimal module temperatures. The pump impeller and bearing are combined into a rotor and then fit on a fixed shaft with a clearance, aiming to generate a complete lubricant film between the stationary journal and rotating bearing during pump operations. However, during the pump durability test under off-design conditions, severe wear occurred on both the journal and bearing. A novel simulation method based on computational fluid dynamics and dynamic mesh is developed to investigate the lubrication failure. User-defined functions are programmed to articulate the simultaneous rotation and whirl of the bearing, and the effects of temperature and cavitation are considered. Both the pump and bearing simulations closely align with experimental results. When the radial force of the pump rotor is steady, the bearing only rotates without whirling, and the bearing load capacity can counteract the maximum radial force of the rotor. However, the rotor experiences fluctuating radial forces over time, primarily attributed to elevated pressure levels at the volute tongue caused by the rotor–stator interaction. This phenomenon results in the bearing to rotate and whirl simultaneously. The load capacity generated by the backward whirl of the bearing is greater than that of the forward whirl. Nevertheless, the bearing whirl initiates a decline in the extremum values of lubricant film pressure. Subsequently, both load capacity and minimum film thickness exhibit a continuous decrease, eventually culminating in the breakdown of the complete lubricant film and resulting in contact wear failure. These new findings contribute to proposing measures to reduce wear under unsteady excitations.

Thermal management improvement in electric vehicles through design optimization of coolant distributor valves

On battery electric vehicles a precise control of heat flows is required for passenger comfort and for both performance and safety of battery packs. This is typically achieved with a thermal management system which employs some type of liquid coolant to transfer heat. Coolant distributor valves are used to regulate coolant flows through the exchangers, for example to recover heat from hot sources, thus to increase vehicle energy efficiency. The development of this type of component is high-priced and the design is generally complex since several operating functions and manufacturing constraints should be satisfied. Despite this complexity and the positive impact such valves have on the thermal management of electric vehicles, a few works are currently available in the literature on design procedures for this component, where only a partial overview of the topic is provided and a comprehensive design methodology considering the effective operating conditions is still missing. In this work we construct a physical model of the valve for torque, internal leakage and pressure drop, and we build an optimization procedure to improve the global performance of the valve. We compare the obtained designs with a simpler approach that optimizes performance parameters independently and we show that designs which severely under-perform with respect to the uncontrolled performance parameters can be produced if an over-simplified design approach is followed. We then show with a global vehicle thermal model that the impact of valve design on global vehicle performance crucially depends on the thermal exchanges at vehicle level and, thus, on its operating conditions. In particular, the impact is considerable when mixing of cold and hot flows through the valve occurs. For a specific example vehicle evaluated in a type-3a cycle of the Worldwide Harmonized Light Vehicle Test Procedure, a valve determined with the proposed optimization procedure allows us to obtain in this condition an increase of about 1 km in the vehicle driving range with respect to a valve defined with the simpler approach.

Innovative Thermal Management System for Electric Vehicle Batteries: Phase Change Material, Heat Pipe and Heat Sink Box Integration

The adoption of electric vehicles has significantly contributed to the reduction of greenhouse gas and pollutant emissions. However, the high heat release generated by the vehicle batteries poses a challenge. To tackle this issue, a passive cooling thermal management system was developed for the batteries, utilizing a combination of a heat sink box, phase change material, and heat pipe. Phase change material of soy wax was employed as the cooling medium, alongside an L-shaped heat pipe equipped with fins. Temperature measurements were conducted using a type-K thermocouple connected to the NI DAQ 9214 module, while the electric current power varied between 1.2 and 52.5 W. The results demonstrate that the implementation of heat pipes in the battery thermal management system led to temperature reductions of approximately 31%, while the utilization of box heat sinks resulted in temperature decreases of up to about 40% compared to cases without passive cooling. Moreover, when combining the heat sink box with soy wax phase change material and heat pipe, the temperature dropped by about 66% under maximum heat load conditions. This integrated approach showcases the effectiveness of a passive cooling method for battery thermal management in electric vehicles, particularly as soy wax’s melting temperature aligns with the recommended working temperature range of the batteries.

Performance investigation of electric vehicle thermal management system with thermal energy storage and waste heat recovery systems

This study investigates the electric vehicle thermal management system performance, utilizing thermal energy storage and waste heat recovery, in response to the imperative shift toward carbon-free electric vehicles to overcome the challenge of low energy efficiency in the thermal management system. The heat generation according to the electrical load on the battery was calculated based on experimental data. The thermal performances of the cabin, power electronic thermal management, and battery thermal management system were explored under various operating conditions at different ambient temperatures. A fully charged thermal energy storage system, including low- and high-temperature phase change materials and waste heat recovery systems, was applied in summer and winter. The total energy consumption for cooling and heating saved to a maximum of 65.9 % in summer and 26.2 % in winter. The mileage extension rate was calculated by distributing the power demand according to the vehicle exterior and motor performance of the battery. Thus, by directly saving the thermal parasitic electrical energy and using it to extend the driving mileage, the electric vehicle achieved a mileage extension of 24.2 % in summer and 18.6 % in winter.

A bio-inspired shape memory alloy-based smart fin system for adaptive thermal management

Thermal management systems utilizing fixed-area extended surfaces for thermal enhancement have been extensively investigated. Unlike these systems, in nature, few creatures display the ability to control heat dissipation in adaptation to changes in environmental conditions by controlling their exposed surface area of the body. Motivated by this, the primary objective of this research is the design, development, numerical and experimental evaluation of an adaptive variable area smart fin system for intelligent thermal management using a high-strain SMA spring actuator. Unlike most thermal management devices and techniques that involve a fixed surface area, a smart fin controlled by Pennate structure-based SMA (PeSMA) actuator is proposed for large actuation and compact arrangement. The capabilities of the smart fin to adaptively enhance heat transfer are experimentally demonstrated and numerically modeled. The proposed fin design can deliver improved thermal performance in terms of reduced operating temperature and pressure drop, which is an indicator of operational cost when the application involves variable and uncertain thermal load conditions. We envisage one of the future applications of this technology in the battery thermal management of Electric Vehicles (EVs) where deployable compact heat transfer system is highly desirable.

Influences of suction pipe structures on hydraulic performance and internal flow of electric coolant pumps

An electric coolant pump (ECP) serves as a critical component in the thermal management of electric vehicles. To fulfill the requirements of pressurizing and circulating coolant for various components, a complex structure with multiple pipes is integrated into the pump inlet. This study focuses on the design and analysis of three suction pipe structures: a straight pipe (Case A), a bend (Case B), and a combination of a bend with manifolds (Case C). The objective of this study is to explore the impacts of suction pipe structures on the hydraulic performance, flow pattern, temperature distribution, and vorticity of ECP. Taking into account the variability of coolant physical parameters with temperature, ECP is numerically simulated using the unsteady Reynolds-averaged Navier–Stokes (RANS) equation and the shear stress transport k–ω turbulence model. The experimental and numerical results exhibit good agreement. Case A demonstrates the highest efficiency, Case B follows as the second most efficient, and Case C displays the lowest efficiency. However, the pressure rise remains essentially consistent in all cases. The average efficiencies of Cases B and C are 1.18% and 2.13% lower than that of Case A. The temperature of ECP increases with an increase in the coolant temperature. The temperature of the printed circuit board (PCB) surpasses that of the motor. Case A exhibits the most favorable flow pattern, while Case C demonstrates the least favorable. The bend introduces secondary flow, further intensified by the manifold, leading to an increase in vorticity. The high-vorticity zones expand as the flow rate increases. This study offers valuable insights into the optimization of the ECP suction pipe structure.

Investigation of multifactorial effects on the thermal performance of battery pack inserted with multi-layer phase change materials

The safe and efficient power battery thermal management system (BTMS) is a prerequisite for the effectiveness and long service life of electric vehicles. So, a BTMS with inserted multi-layer phase change materials (PCMs) is proposed to enhance the safety and working performance of battery pack. Effects of PCM settings and operating conditions on the thermal performance of battery pack are discussed and analyzed. The results reveal that PCM cooling plays a significant role in the thermal management of battery pack, where the maximum temperature value and temperature difference of BTMS with multi-layer PCM #C are respectively reduced by 13.61 °C and 2.54 °C compared to battery pack without PCM. Besides, the coupling effects of multiple factors, that is, PCM permutation, the thickness and height of PCMs, and ambient temperature, on the heat dissipation of battery pack are discussed via orthogonal results analysis. The optimized multi-layer PCMs are obtained for the BTMS, i.e., Ps = 121, h1 = 5 mm and L = 6 mm, which achieves the lowest values of Tmax = 43.02 °C and ΔT = 3.37 °C at Tamb = 20 °C. It provides insights for optimizing thermal control strategies for the advancement of thermal management in electric vehicles, ultimately enhancing safety, performance, and longevity.

Integrated Thermal Management of Electric Vehicles Based on Model Predictive Control With Approximated Value Function

Integrated Thermal Management of Electric Vehicles Based on Model Predictive Control With Approximated Value Function

Thermal management of Li-ion batteries in electric vehicles by nanofluid-filled loop heat pipes

An analytical model is developed to determine the thermal performance of a Loop Heat Pipe filled (LHP) with copper oxide–water and alumina–water nanofluids for battery thermal management in electric vehicles. The thermal performances of the LHP are predicted for different heat loads and nanoparticle concentrations. It is demonstrated that for fast charging operation corresponding to a heat load of 150 W, the LHP ensures evaporator temperatures of less than 60 °C for a heat sink temperature of 40 °C. The heat transport capacity of the LHP is enhanced and the evaporator temperature is deceased by augmenting the nanoparticle concentration. The water–CuO nanofluid-filled LHP performs better than the water–Al2O3 nanofluid-filled one. The addition of the nanoparticles increases the LHP total pressure drop and the driving capillary pressure. The capillary limit of the water–CuO nanofluid-filled LHP is hardly affected by CuO nanoparticle concentration until 6% beyond which the capillary limit starts decreasing. For the water–Al2O3 nanofluid-filled LHP, the capillary limit decreases when Al2O3 nanoparticle concentration increases. Beyond 6% Al2O3 nanoparticle concentration, the capillary limit of the Al2O3-filled LHP becomes lower than the water-filled one.

Integrated testing of electric vehicle thermal management and optimization of flow field uniformity in air supply system

To meet the requirements of integrated testing and performance calibration for the early development of electric vehicle thermal management, this paper conducted research on the configuration scheme design of the electric vehicle thermal management integrated testing platform and simulation and optimization of the air supply system flow field. Firstly, a requirement analysis of the testing environment and the overall design of the testing platform was performed. Secondly, simulation techniques were applied to optimize the uniformity of the intake airflow field in the test section, which was then validated through real testing. Finally, a comparative study of the tested system was conducted through CFD simulations in two different environments, the testing platform and the actual vehicle underhood. The results indicate that the intake airflow field uniformity in the test section falls within ?3%. The intake flow rate errors for the radiator and condenser, compared to those in the actual vehicle, were found to be 0.039% and 2.116%, respectively. These findings confirm that the testing platform offers good consistency with the flow field in real vehicle testing scenarios.

Using Latent Heat Storage for Improving Battery Electric Vehicle Thermal Management System Efficiency

<div>One of the key problems of battery electric vehicles is the risk of severe range reduction in winter conditions. Technologies such as heat pump systems can help to mitigate such effects, but finding adequate heat sources for the heat pump sometimes can be a problem, too. In cold ambient conditions below −10°C and for a cold-soaked vehicle this can become a limiting factor. Storing waste heat or excess cold when it is generated and releasing it to the vehicle thermal management system later can reduce peak thermal requirements to more manageable average levels. In related architectures it is not always necessary to replace existing electric heaters or conventional air-conditioning systems. Sometimes it is more efficient to keep them and support them, instead. Accordingly, we show, how latent heat storage can be used to increase the efficiency of existing, well-established heating and cooling technologies without replacing them. We investigate different possibilities for the integration of phase change materials into a baseline battery electric vehicle thermal management system and compare the resulting benefits.</div>

Application of Neural Network Feedforward in Fuzzy PI Controller for Electric Vehicle Thermal Management System: Modeling and Simulation Studies

The electric vehicle thermal management system (EVTMS) plays a crucial role in ensuring battery efficiency, driving range, and passenger comfort. However, EVTMSs still face unresolved challenges, such as accurate modeling, compensating for temperature variations, and achieving efficient control strategies. Addressing these issues is crucial for enhancing the performance, reliability, and energy efficiency of electric vehicles. Therefore, this study presents a cooling EVTMS model, considering both the battery pack temperature and the cabin comfort, and utilizes the prediction of neural network as a feedforward in a fuzzy PI controller to compensate for the model temperature variations. The simulation results reveal that, compared with PI controller and MPC, the neural network fuzzy PI (NN-Fuzzy PI) controller can well predict and compensate for the system’s nonlinear characteristics as well as the time-delay caused by heat transfer, achieving superior control performance and reducing energy consumption. The battery pack temperature and PMV fluctuations are effectively constrained within [−0.5, 0.5] and [−0.1, 0.1], reducing up to 150% and 164%, and the energy consumption of the pump and compressor are reduced by up to 0.23 and 100.1 KJ, with ranges of 18% and 2.68%. Meanwhile, the neural network feedforward also works effectively in different controllers. The findings of this research can provide valuable insights for TMS engineers to select advanced control strategies.

Research on prediction model of electric vehicle thermal management system based on particle swarm optimization- Back propagation neural network

The variation of temperature in various components of the Electric Vehicle Thermal Management (EVTM) system is the main factor affecting energy consumption. A good temperature prediction method is a prerequisite for optimizing energy strategies. The temperature variation of each component in the thermal management system is influenced by various factors, such as ambient temperature, vehicle speed, and air conditioning compressor speed. Therefore, this paper proposes a temperature prediction method based on Particle Swarm Optimization (PSO) and Back propagation Neural Network (BP). The PSO-BP method is used to update the weights and thresholds of the neural network. Real-time data collected from road experiments are used to ensure the accuracy of the influencing factors. Simulation results show that compared to the BP neural network, the proposed PSO-BP prediction method reduces the prediction errors by 66%, 75%, and 25% respectively.

Surrogate-based optimization of the attack and inclination angles of a delta winglet pair vortex generator in turbulent channel flow

Vortex generators (VGs) have been extensively studied and utilized in multifunctional heat exchangers/reactors due to their remarkable ability to create coherent flow structures and streamwise vortices. These characteristics significantly enhance the mixing and heat transfer performance in laminar and turbulent flow regimes. With the advancement of computational power, VG shape optimization has become feasible, leading to the discovery of various optimized shapes in the literature for different Reynolds numbers. In this paper, the response surface polynomial method is employed as a surrogate model to optimize the angle of attack and inclination angle of a delta winglet VG at a Reynolds number of 4,600. The potential applications of these optimized designs are diverse, particularly in scenarios that require cooling or heating. Some examples include photovoltaic (PV) panel cooling, waste heat recovery in hybrid PV/solar water heating systems, energy-efficient HVAC systems, and thermal management in electric vehicles. To achieve this objective, Computational Fluid Dynamics (CFD) simulations are conducted to compute the thermal performance factor of each VG design at various values of attack and inclination angles. By enhancing mixing and heat transfer capabilities, this design can have a substantial impact on various renewable energy applications, contributing to a greener and more sustainable future. The highest thermal enhancement factor of 1.15 is found to be achieved for an inclination angle of −45° and an angle of attack of 35°. This means that optimized VG enhances heat transfer by 15% compared to empty channel flow, while maintaining the same pumping power.