Conventional Thermal Management Systems Research Articles

Coupling optimization of protruding fin and PCM in hybrid cooling system and cycle strategy matching for lithium-ion battery thermal management

Based on liquid cooling and phase change material (PCM), a fin-enhanced composite thermal management system suitable for high power and extended cycle operations of lithium-ion battery module at high ambient temperature is proposed in this work. The coupling effect between the protruding fin structure and PCM thickness, as well as the addition of expanded graphite to the PCM, are investigated to optimize hybrid cooling arrangement. The results show that synergistic optimization of the protruding fin structure and PCM arrangement can enhance heat diffusion from the batteries to the cooling water, improve PCM utilization, and ensure sufficient latent heat. And then, the expanded graphite-modified PCM can make heat absorption and phase transition more uniform, and battery temperatures can be further decreased by up to 7.45 °C with 16 wt% expanded graphite. Clearly, the coupling optimization improves the cooling performance and applicability of conventional thermal management systems, while the temperature difference and maximum temperature in the optimized system have been regulated to within 4.30 °C and 46.78 °C under 40 °C environment and 5C discharge, respectively. Moreover, the cyclic charging and discharging strategies are designed and matched, and using the matching strategy with a fixed charge or discharge rate of 1C provides lower temperatures and better temperature uniformity, which can always control the temperatures below 47.22 °C and temperature difference below 4.69 °C. The optimized system with cycle strategy matching ensures the repeatability of battery operation and provides cooling solutions for different application scenarios.

Integrated Power and Thermal Management Systems for Civil Aircraft: Review, Challenges, and Future Opportunities

Projects related to green aviation designed to achieve fuel savings and emission reductions are increasingly being established in response to growing concerns over climate change. Within the aviation industry, there is a growing trend towards the electrification of aircraft, with more-electric aircraft (MEA) and all-electric aircraft (AEA) being proposed. However, increasing electrification causes challenges with conventional thermal management system (TMS) and power management system (PMS) designs in aircraft. As a result, the integrated power and thermal management system (IPTMS) has been developed for energy-optimised aircraft projects. This review paper aims to review recent IPTMS progress and explore potential design solutions for civil aircraft. Firstly, the paper reviews the IPTMS in electrified propulsion aircraft (EPA), presenting the architectures and challenges of the propulsion systems, the TMS cooling strategies, and the power management optimisation. Then, several research topics in IPTMS are reviewed in detail: architecture design, power management optimisation, modelling, and analysis method development. Through the review of state-of-the-art IPTMS research, the challenges and future opportunities and requirements of IPTMS design are discussed. Based on the discussions, two potential solutions for IPTMS to address the challenges of civil EPA are proposed, including the combination of architecture design and power management optimisation and the combination of modelling and analysis methods.

Stack cooling system coupled with secondary heat pump in fuel cell electric vehicles

Fuel cell electric vehicles (FCEVs) requires proper thermal management of a proton-exchange membrane fuel cell (PEMFC) stack, but conventional thermal management systems (TMSs) cannot manage the thermal requirements of PEMFCs under high-power density at high ambient temperatures. In this study, a stack cooling system coupled with a secondary heat pump in an FCEV is suggested. The enhanced thermal flexibility of the secondary heat pump system enabled extensive cooling with various TMS configurations. The cooling performance with different TMS configurations was evaluated, considering the thermal and electrical coupling of the heat pump system and the PEMFC stack. The results show that the stack temperature was lowered up to 2.6 °C when the excessive cooling load of the stack radiator was distributed to the cabin radiator under a relatively low-power output condition. To dissipate a large amount of waste heat from the stack, TMS requires a temporary shutdown of the cabin cooling system. In this case, utilizing the inactive outdoor heat exchanger as an additional radiator decreased the temperature up to 18.4 °C by extending the heat transfer area for stack cooling. This study proposes a cooling scheme for an FCEV and suggests appropriate cooling methods and configurations under various operating conditions.

Thermohydraulic performance comparison of 3D printed circuit heatsinks with conventional integral fin heatsinks

Additive manufacturing has enabled the fabrication of intricate geometries and structures of numerous sizes at high accuracy, which has attracted researchers towards its application as 3D-printed heatsinks. In this context, current work is focused on exploring the potential of periodic lattices of cellular materials as heat sinks and their comparison with conventional thermal management systems. Thermohydraulic characteristics of the heatsinks with channel designs of cellular structures, namely, simple cubic and body-centered cubic, are evaluated and compared with the performance of conventional heatsinks with integral fins. The heatsinks' conjugate heat transfer and flow are solved numerically, employing a validated model built on 3D Reynolds averaged Navier Stokes with the Shear Stress Turbulence model. Water and critical CO2 are used as coolants in this study. Results show that the SC design performs best compared to the classic finned design with an overall performance evaluation criterion of around 4.45 times higher at a flow rate of 1.5 L/min using water as a coolant. In addition, body-centered cubic lattice performs with a PEC of 4.33 at the same flow rate and working fluid. The computed results demonstrate that the performance of 3D-printed heatsinks geometries is significantly superior to the classic designs making them an ideal candidate for designing further compact and efficient heat removal systems for electronic devices.

Universal Electric Vehicle Thermal Management System

<div class="section abstract"><div class="htmlview paragraph">As the demand for Electric Vehicles (EVs) is increasing to limit global warming, observation shows that the significant application of EV is in cold and mild climate regions. Heat pump and CO2 system are two major Thermal Management Systems (TMS) used in these EVs. These TMS are constrained to cold climate applications securing better COP for heating function but sacrificing cooling COP when the same TMS applied to hot climate regions. This study presents a new Electric Vehicle Thermal Management System (EVTMS) limited to active liquid battery cooling for the application of Electric Vehicles in hot climate regions. The proposed system has integrated Battery Thermal Management System and Cabin HVAC using a shared electric compressor. This integrated solution also utilizes waste heat recovery to contribute for better system COP when compared to conventional TMS used for EV's. The decrease in the number of pipes and switching valves due to integrated solution also results in low refrigerant pressure drop preventing penalty on compressor duty. Battery cells target temperature of 27°C and, temperature delta of 4°C across battery cells is also considered as a prime motive during this study. Different strategies to control battery cells target temperature; the cabin HVAC system is studied. System simulation for typical thermal load in an EV is the first objective. The benefits of the proposed system are validated using an experimental test at a typical load condition. COP comparison for an existing system with proposed EVTMS proves the proposed system to be 50% energy efficient under typical thermal load from battery and cabin.</div></div>

Distributed thermal management system for downhole electronics at high temperature

The logging tools, which are widely utilized to detect the underground petroleum resources, are usually exposed to the high-temperature environment. Conventional thermal management system (CTMS) generally utilizes the vacuum flask for high-temperature insulation and phase change materials (PCMs) for centralized heat storage. As the heat sources increase and the skeleton becomes longer, the thermal performance of CTMS declines due to the increasing thermal resistance between heat sources and PCMs. To tackle this issue, a distributed thermal management system (DTMS) is proposed for the long-skeleton and multi-heat-source logging tools by arranging PCMs dispersedly in the skeleton. Numerical simulations are conducted to compare the performance of DTMS and CTMS. It is showed that the maximum temperature of DTMS decreases by 68 °C compared with CTMS, and the heat storage of PCMs in DTMS is 3.5 times higher than that in CTMS. Furthermore, the simulation results are validated by experimentally investigating the thermal performance of the logging tool with DTMS, and good agreement between the simulation and experiment is reached with the maximum relative error lower than 10%. DTMS is more practical for the realistic logging tools than CTMS, which may contribute to the development of the oil and gas detection in deeper and hotter wells.

Recent Developments in Thermal Management of Electrified Powertrains

Thermal management is becoming ever more important in passenger vehicles in the trend of vehicle electrification. Even though most of the passenger vehicles still have relatively conventional thermal management systems, advanced technologies have been increasingly developed. The internal combustion engine have had the central role in thermal management but due to the powertrain hybridization and electrification, the engines are nowadays more efficient, smaller in size, and running less frequently. Especially for plug-in hybrid and electric vehicles, engines are not always used or not even available, and, thus, there is no excess heat readily available. This paper reviews the present technology for the thermal management of electrified powertrains in passenger vehicles. In this context, thermal management takes into account the cooling and heating systems for the powertrain components, and different methods to develop and improve thermal systems efficiency. This paper investigates the recent technology advances for improving energy efficiency of thermal systems. The research focus is on the hybrid and electric vehicles and especially on the challenges of improving thermal energy efficiency and performance.

Development of Energy-Efficient Thermal Management System for Proton Exchange Membrane Fuel Cell and Reformer

The rising energy cost and limited supply of fossil fuel make it important for an alternative renewable energy source. Of all the alternatives, proton exchange membrane (PEM) fuel cell is very promising due to its high efficiency and zero emission characteristics. A fuel cell converts chemical energy to electricity by combining hydrogen with air. However, hydrogen storage poses a lot of practical challenges. Hence, alcohol based steam reforming systems are widely used for on-site hydrogen generation instead. During operation, a fuel reformer needs heating to maintain its temperature. At the same time, the fuel cell stack needs cooling to maintain its temperature. Currently, separate heating and cooling systems are used, resulting in an inefficient thermal management system. In this study, a more efficient thermal management system is proposed. It incorporates a vapor compression refrigeration (VCR) system to a reformer - PEM fuel cell unit. A VCR system can be seen as a device that transports heat from one place to another with a very high efficiency. In this application, heat is removed from the stack and is transferred to the reformer. This method will save around 38% of energy as compared to the conventional thermal management system.

Passive, internal thermal management system for batteries using microscale liquid–vapor phase change

Conventional thermal management systems for lithium-ion batteries remove heat from the exterior surface of the battery, causing undesirable temperature increase and thermal gradients inside the battery. Internally cooling batteries can reduce both of these effects, improving safety and durability. In the present study, a novel internal cooling system that utilizes passive, liquid–vapor phase change processes is investigated using representative geometry and a surrogate heat source. Frictional and heat transfer characteristics of the representative cooling system with buoyancy driven flow are reported over a range of net heat inputs (94–6230 W L−1) and saturation temperatures (24 °C–33 °C). The results show that the mass flow rate increased to a maximum near a heat input of 1350 W L−1, and there was a slight influence of saturation temperature on the performance of the system. In addition, the calculated two-phase frictional pressure drops in the microchannel evaporator (3.175 mm × 160 μm channels) are compared to the representative correlation database (Dh < 1 mm) and used to develop a new frictional pressure drop model with improved accuracy over the tested mass flux range (45 < G < 112 kg m−2 s−1). The results presented here are utilized in a subsequent investigation to determine the performance improvement in large lithium-ion battery packs intended for electric and hybrid electric vehicular applications through internal cooling.

Design and Characterization of High-Voltage Silicon Carbide Emitter Turn-off Thyristor

A novel MOS-controlled silicon carbide (SiC) thyristor device, the SiC emitter turn-off thyristor (ETO), as a promising technology for future high-voltage and high-frequency switching applications has been developed. The world's first 4.5-kV SiC p-type ETO prototype based on a 0.36 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> SiC p-type gate turn-off (GTO) shows a forward voltage drop of 4.6 V at a current density of 25 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a turn-off energy loss of 9.88 mJ. The low loss shows that the SiC ETO could operate at a 4-kHz frequency with a conventional thermal management system. This frequency capability is about four times higher than the 4.5-kV-class silicon power devices. The numerical simulations and theoretical analysis have been carried out to show the potentially improved performance of the high-voltage SiC ETOs. The results show that the high-voltage (10-kV) SiC n-type ETO has much better tradeoff performance than that of the p-type ETO due to a smaller current gain of the lower bipolar transistor in the SiC n-type GTO. Further improvement of the 10-kV SiC n-type ETO can be made with the optimum design of the drift layer carrier lifetime and buffer layer doping concentration of the 10-kV SiC GTO. The theoretical analysis and numerical simulation shows the SiC ETO also has the excellent reverse bias safe operating area. The experimental and theoretical studies show that the SiC ETO is a promising candidate for high-voltage (> 5 kV) power conversion applications.

Integrated thermal management of a hybrid electric vehicle

A thermal management methodology, based on the Vehicle Integrated Thermal Management Analysis Code (VITMAC), has been developed for a notional vehicle employing the all-electric combat vehicle (AECV) concept. AECV uses a prime power source, such as a diesel, to provide mechanical energy which is converted to electrical energy and stored in a central energy storage system consisting of flywheels, batteries and/or capacitors. The combination of prime power and stored energy powers the vehicle drive system and also advanced weapons subsystems such as an ETC or EM gun, electrically driven lasers, an EM armor system and an active suspension. Every major system is electrically driven with reclamation when possible from braking and gun recoil. Thermal management of such a complicated energy transfer and utilization system is a major design consideration due to the substantial heat rejection requirements. In the present paper, an overall integrated thermal management system (TMS) is described which accounts for energy losses from each subsystem component, accepts the heat using multiple coolant loops and expels the heat from the vehicle. VITMAC simulations are used to design the TMS and to demonstrate that a conventional TMS approach is capable of successfully handling vehicle heat rejection requirements under stressing operational conditions.