Intelligent Thermal Management Research Articles

Bioinspired Passive Cooling Hydrogel for Visualizing Hygroscopicity and Desorption Process

AbstractSelf‐hygroscopic hydrogels, characterized by high evaporation enthalpy, cooling efficiency, and self‐regulating properties, have garnered significant attention. However, most current research focuses on enhancing the hygroscopic and desorption performance, often overlooking the importance of monitoring the self‐regulation process, which limits its further application. Advanced visualization technologies, such as in situ electrical impedance tomography, low‐field nuclear magnetic resonance, and hyperspectral imaging, offer potential insights into this behavior, yet they often require additional devices, incur high costs, and involve complex sample preparation processes. Therefore, drawing inspiration from nature, humidity‐color‐sensitive hydrogels (HCSHs) strategy is proposed for visualized cooling. Benefiting from the strong polar responsiveness of the aggregation‐induced emission (AIE) molecules, the hydrogel's fluorescence significantly changes with varying interior water content, thereby its self‐regulation process is monitored easily. Further, the obtained hydrogel could be applied in the electronic device cooling owing to the polymer skeletons’ high swelling ratio, strong adhesion, and excellent self‐hygroscopic properties. This strategy overcomes current limitations in the visual technology of self‐hygroscopic materials and provides new insights into intelligent thermal management for electronic devices.

Highly hygroscopic needle-punched carbon fiber felt with high evaporative cooling efficiency and fire resistance for safe operation of ultrahigh-rate lithium-ion batteries

The effective thermal management of lithium-ion batteries is the key to ensuring their fast charging-discharging, safe and efficient operation. Herein, inspired by transpiration-driven water transport in plants, we report a highly hygroscopic needle-punched carbon fiber felt (HS/CFF) with high evaporative cooling efficiency and fire resistance for the safe operation of lithium-ion batteries working at ultrahigh-rate conditions. The three-dimensional fiber skeleton structure constructed by needle punching in the carbon fiber felt enables effective water transport and storage in HS/CFF, without any water leakage. At an ultra-high discharge rate of 10 C, HS/CFF can reduce the maximum temperature of commercial lithium-ion batteries by 18 °C, and can keep the battery temperature below 60 °C. During 500 cycles of charge-discharge, HS/CFF maintains stable evaporative heat dissipation performance, which helps to improve the safety of lithium-ion batteries and extend their service life. Moreover, HS/CFF remains non-combustible even under exposure to a flame (600-700 °C) for 10 min, and the HS/CFF can be reused after the burning test, with the original excellent heat dissipation effect unchanged. This flexible, fire-resistant cooling material offers a promising avenue for low-energy intelligent thermal management of lithium-ion batteries and other heat-generating electronic devices.

Subdiffusive and superdiffusive phonon transport induced significant thermal rectification across a one-dimensional Kapitza interface

Anomalous heat conduction in low dimensional materials shows divergent thermal conductivity with increasing characteristic length, which brings many opportunities in thermal management applications and unexplored phonon transport mechanisms. The molecular heterojunctions, consisting of an interface that is formed by different lattices, exhibit unique physical properties especially thermal rectification phenomenon. In this work, we investigate the heat conduction across a one-dimensional heterojunction bridging a carbon nanotube (CNT) and a boron nitride nanotube (BNNT). The molecular dynamic (MD) simulation shows that the rectification ratio is as high as 8.9 in a 300-nm system at/above the room temperature, which is due to the asymmetric interfacial thermal conductance in the opposite directions of heat flow. The interfacial thermal conductance (G) obeys the length dependence of G ∝ Lβ, presenting a divergent and convergent behaviors of anomalous heat conduction that was only reported for homogeneous materials. By analyzing the length-dependent and temperature-dependent phonon density of state, this anomalous interfacial heat conduction can be explained by the Kapitza resistance model and the population of frequency-dependent phonons. Further calculation of mean square displacement of atoms validates the superdiffusion and subdiffusion behavior of the interfacial conductance. This result demonstrates the superb capability of the one-dimensional heterojunction to control phonon transport, which could be used as the basic element of high-efficient and intelligent thermal management devices.

Dynamic Spectral Metafabric with Unidirectional Moisture Transport Property for Personal Thermal Management.

Personal thermal management technology, which adjusts the heat exchange between the human body and the environment, can passively heat or cool the body to maintain a comfortable core temperature, thereby enhancing comfort and reducing energy consumption. However, most existing personal thermal management materials have static properties, such as fixed solar reflectance and infrared emissivity, which do not support real-time dynamic temperature regulation. Moreover, sweat accumulation on the skin surface, while contributing to temperature regulation, can significantly reduce comfort. This study constructs a unidirectional moisture-permeable intelligent thermal management fabric system to achieve superior thermal and moisture comfort in complex environments. The fabric incorporates thermochromic microcapsules into PAN nanofibers by using electrospinning technology for intelligent thermal management. Subsequent hydrophobic treatment of the fiber film surface imparts the fabric with unidirectional wetting properties. The nanofibrous structure provides intrinsic elasticity and breathability. In heating mode, the fabric's average sunlight reflectance is 42.1%, which increases to 82.2% in cooling mode, resulting in a reflectance difference of approximately 40%. The hydrophobic treatment endows the fabric with excellent moisture absorption and perspiration properties, demonstrated by a unidirectional moisture transport index of 696.63 and a perspiration evaporation rate of 5.88 mg/min. When the fabric temperature matches the ambient temperature, the photothermal conversion power difference of the Janus metafabric in two modes reaches 248.37 W m-2. Additionally, Janus metafabrics show the potential for temperature-responsive design and repeated writing applications. The outstanding wearability and dynamic spectral properties of these metafabrics open new pathways for sustainable energy, smart textiles, and thermal-moisture comfort applications.

Construction of wear-resistant visible-infrared-compatible camouflage film and its spectral control mechanisms

The ceaseless advancement of modern surveillance technologies has underscored an urgent need for the development of stealth materials with multi-spectral camouflage capabilities. Spectral selectivity, achieved through the design of micro-nano structures, can effectively manage conflicting requirements across various light regimes. Nonetheless, creating visible-Infrared (IR)-compatible devices that are both structurally simple and suitable for use as optic windows or coatings remains a formidable challenge. Here, we report a MgF2/Ag/MgF2 visible-IR-compatible film based on Monte Carlo optimization which has high visible transparency, low IR emissivity, ideal wear-resistance, and dynamic tunability. The designed film can maintain high transparency (∼80%) to ensure replication of background without sacrificing low IR emissivity (∼0.3). Notably, the film maintains its spectral selectivity across a wide range of angles and is endowed with the capability for dynamic modality switching between “heating” and “cooling” states under electrical actuation with good stability under long-term service and harsh environment. This film has a maximum temperature characteristic modulation range of 3.5 °C, demonstrating excellent performance in intelligent thermal management. It is also compatible with electrochromic camouflage devices enabling it to cover a broader spectrum of reconnaissance without contradictions. It is an effective way to fulfill the camouflage requirements and smart thermal management across diverse environments, and possesses great potential for scalability and flexibility.

Realization of an Adaptive Radiative Cooler with a Multilayer-Filter VO2-Based Fabry–Pérot Cavity

A high-performance adaptive radiative cooler comprising a multilayer-filter VO2-based Fabry–Pérot (FP) cavity is proposed. The bottom FP cavity has four layers, VO2/NaCl/PVC/Ag. Based on the phase transition of VO2, the average emissivity in the transparent window can be switched from 3.7% to 96.3%. Additionally, the average emissivity can also be adjusted with external strain to the PVC layer, providing another way to attain the desired cooling effect. An upper filter is included to block most of the solar radiation and provide a transmittance of 96.7% in the atmospheric window. At high temperature, the adaptive emitter automatically activates radiative cooling. The net cooling power is up to 156.4 W⋅m−2 at an ambient temperature of 303 K. Our adaptive emitter still exhibits stable selective emissivity at different incident angles and heat transfer coefficients. At low temperature, the radiative cooling automatically deactivates, and the average emissivity decreases to only 3.8%. Therefore, our work not only provides new insights into the design of high-performance adaptive radiative coolers but also advances the development of intelligent thermal management.

Pressure induced thermal conduction paths in liquid metal-boron nitride fillered thermal interface materials with high thermal conductivity

With the continuous evolution of wearable and mobile devices, flexible electronics, and intelligent thermal management, there is a growing interest in thermal interface materials (TIMs) that combine high thermal conductivity with low modulus for stretchability. However, materials with high thermal conductivity often come with elevated Young's modulus. Here, we have developed a TIMs by combining liquid metal and BN with polydimethylsiloxane (PDMS), achieving a blend of low modulus and high thermal conductivity. To enhance thermal conductivity, we introduced boron nitride sheets as “scalpel”, puncturing the oxide layer of the liquid metal under pressure to establish a continuous thermal path. After pressure induction, the LM-BN/PDMS composite exhibits a thermal conductivity of 4.3 W/(m K), with a Young's modulus of only 193 kPa and a fracture strain of 483%. Furthermore, it demonstrates outstanding thermal stability under multiple thermal shock cycles, indicating significant potential for applications in future thermal management for flexible electronic devices, wearable devices, and beyond.

Magnetically triggered heat release from hydrate salt composite microchannels for low-temperature battery thermal management

While active thermal managements for Li-ion battery (LIB) consume a large amount of energy, passive one based on phase change material (PCM) fails to release thermal energy for heating as required. Thus, intelligent heat storage and release is urgently needed for utilizing PCM as passive thermal management. Herein, porous boron nitride/polyvinyl alcohol (BN/PVA) skeleton with highly ordered microchannels was fabricated to impregnate hydrate salt sodium acetate trihydrate (SAT) solution forming shape-stable SAT@BN/PVA composite with efficient thermal energy storage performance. Disturbance from magnetic trigger in the hydrate salt composite microchannels promotes nucleation and solidification, thus initiates heat release as required and remotely. Meanwhile, anisotropic heat transfer from the highly ordered microchannels can effectively enhance heat release velocity and efficiency. The magnetic triggered process is studied theoretically and experimentally, and optimized to release heat in 25 s with efficiency up to 99%. Consequently, heat release can improve temperature by 10 °C when battery pack stops working at −20 °C and enhance discharge capacity by 75% during cold-start. This research provides a new method for intelligent thermal management of LIB working in cold environment.

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.

Bio‐inspired Thermal Diode with Anti‐Gravity Unidirectional Heat Transfer and Switchable Functionality for Intelligent Thermal Management

AbstractPhase‐change thermal diodes with asymmetric and adjustable heat transfer capacity exhibit great application prospects in spacecraft heat management and solar energy storage. Current heat modulation strategies mainly depend on the anisotropic assistance from gravity and the rectification ratio can hardly be adjusted due to the immobilized inner structures. Here, a novel bioinspired thermal diode vapor chamber has been carried out with magnetic microgroove cones array sealed between two copper plates, where the evaporating plate with porous copper foam can reserve water and the condensing plate with patterned wettability can coagulate vapor into droplets at designated spot. With microgroove cones rooting from the evaporating plate and their tips contacting the condensing plate, these cones can directionally and rapidly transport condensed liquid from the condensing plate to evaporating plate under the unbalanced strong capillarity while prohibiting water flowing backward. This eventually leads to unidirectional liquid‐vapor circulation and anti‐gravitational directional heat transferring with a rectification ratio as high as 7.4. Such flowing of liquid can also be regulated by magnetically controlling the bending of cones to realize switched ON–OFF of thermal diode and achieve further modulation of heat management. This bioinspired thermal diode vapor chamber provides new ideas for intelligent thermal management systems.

Fast and scalable production of crosslinked polyimide aerogel fibers for ultrathin thermoregulating clothes

Polyimide aerogel fibers hold promise for intelligent thermal management fabrics, but their scalable production faces challenges due to the sluggish gelation kinetics and the weak backbone strength. Herein, a strategy is developed for fast and scalable fabrication of crosslinked polyimide (CPI) aerogel fibers by wet-spinning and ambient pressure drying via UV-enhanced dynamic gelation strategy. This strategy enables fast sol-gel transition of photosensitive polyimide, resulting in a strongly-crosslinked gel skeleton that effectively maintains the fiber shape and porous nanostructure. Continuous production of CPI aerogel fibers (length of hundreds of meters) with high specific modulus (390.9 kN m kg−1) can be achieved within 7 h, more efficiently than previous methods (>48 h). Moreover, the CPI aerogel fabric demonstrates almost the same thermal insulating performance as down, but is about 1/8 the thickness of down. The strategy opens a promisingly wide-space for fast and scalable fabrication of ultrathin fabrics for personal thermal management.

Preparation of V2O5 thin films on AA6061 alloy using thermal evaporation

Spacecrafts often operate in severe environments with large exterior temperature fluctuations varying from −150 °C to +150 °C. Spacecraft internal parts work at their optimal efficiency between a range of temperatures, most likely between −10° C to 40 °C, beyond which they suffer damage. Consequently, good thermal management of spacecraft is required. The current technologies may become inadequate in the future owing to stringent requirements of micro- and nanosatellites, which entail the necessity of smaller and smarter thermal control subsystems. Traditional thermal technologies such as heaters, thermostats, heat pipes, coolers, and louvers will almost probably not be adequate to satisfy the requirements, since they are typically heavy and consume more electricity. Hence, Variable emittance coatings, which may modify the effective infrared emissivity and hence the radiative heat transfer rate, will be the inevitable potential choice for flexible or intelligent thermal management of spacecraft. Among all vanadium oxides, VO2 has been shown to exhibit a reversible phase shift at positive temperatures at 68 °C. This phase shift modifies its thermo-optical properties. Thermal evaporation was used to create V2O5 thin films on an AA6061 substrate, and subsequent reduction with N2 gas resulted in the creation of VO2. SEM, EDAX, and XRD were used to characterize the materials.

Alloying Reversed Anisotropy of Thermal Transport in Bulk Al0.5Ga0.5N.

Anisotropic heat transfer is crucial for advanced thermal management in nanoelectronics, optoelectronics, thermoelectrics, etc. Traditional approaches modifying thermal conductivity (κ) mostly adjust the magnitude but disregard anisotropy. Herein, by solving the Boltzmann transport equation from first principles, we report κ anisotropy modulation by alloying gallium nitride (GaN) and aluminum nitride (AlN). The alloyed Al0.5Ga0.5N demonstrates reversed κ anisotropy compared to the parent materials, where the preferred thermal transport direction shifts from cross-plane to in-plane. Moreover, the κ anisotropy (κin-plane/κcross-plane) in the Al0.5Ga0.5N alloy is enhanced to 1.63 and 1.51 times that in bulk GaN and AlN, respectively, which can be further enhanced by increased temperature. Deep analysis attributes the alloying reversed κ anisotropy of Al0.5Ga0.5N to the structure distortion-driven phonon group velocity, as well as phonon anharmonicity. The alloying reversed κ anisotropy as reported in this study sheds light on future studies in advanced heat dissipation and intelligent thermal management.

Analytical and experimental study of hybrid photovoltaic–thermal–thermoelectric systems in sustainable energy generation

A new hybrid system, known as photovoltaic–thermal–thermoelectric (PVT-TE), has been proposed to enhance the conversion efficiency of PV cells by incorporating an intelligent thermal management system, which leverages the dual functions of thermoelectric (TE). This study aims to explore the potential for creating a hybrid system that is more efficient and offers improved performance than standalone photovoltaic thermal (PVT) systems. The key parameters for the creation of a hybrid system were analysed, and the theoretical and experimental results were compared to validate the model. The performance of the PVT-TE collector was evaluated through a steady-state analysis using a one dimensional (1D) mathematical model. Energy balance equations were solved using Microsoft Excel and inverse matrix method. Experiments on PVT and PVT-TE collectors were examined at a solar radiation intensity of 593.16 W/m2. The air mass flow rate was set at 0.009, 0.021, 0.039, 0.069 and 0.095 kg/s for specific radiation intensity. The thermal and electrical performance of the hybrid system was higher than that of the conventional PVT system. The PVT-TE system combines photovoltaic and thermoelectric components, including a thermoelectric module and an air collector. The integration improves system efficiency and performance, surpassing previous research efforts. The PVT-TE system with an air collector has innovative features including efficient thermal-electric conversion, integrated component utilisation, and air collector integration. The overall efficiency of the hybrid system was 7.05%–31.13% higher than the theoretical values and 9.64%–34.83% higher than the experimental values. The increase in the output power of the hybrid system was also higher by 32.59%–55.93%. The findings indicate that the integration thermoelectric (TE) with PV cells has the potential to enhance solar thermal systems' performance. This study provides the basis for further analysis and optimisation of PVT-TE hybrid systems.

Thermal management with fast temperature convergence based on optimized fuzzy PID algorithm for electric vehicle battery

In this study, we propose an optimized fuzzy proportional-integral-differential (Fuzzy PID) algorithm used in a rapid temperature control system for automotive batteries. Based on the proposed algorithm, an intelligent thermal management system with temperature feedback mechanism is built by switchable thermoelectric (TE) devices in working mode, simultaneously offering both heating and cooling capabilities. Assisted by liquid cooling optimization, the battery pack temperature is rapidly converged by the regulation of TE devices. Experimental results demonstrate that the temperature of a thermal runaway battery pack can be lowered from 63.5 °C to 25 °C in just 280 s, while the temperature of a frozen battery pack can be raised from −10 °C to 25 °C within 185 s. Compared to multi-channel liquid cooling method, our temperature control time is reduced by approximately 76%. The innovative structure and optimized temperature control algorithm can obviously enhance the efficiency of the battery temperature control system in new energy electric vehicle field.

Temperature control characteristics of intelligent cooling system for high-speed marine diesel engine

ABSTRACT To improve energy conservation and reduce emissions of an engine, this study applies intelligent thermal management to a cooling system. With a marine high-speed diesel engine as the research object, an intelligent cooling system based on controllable cooling components was developed. A variable-universe fuzzy control algorithm is designed to control an electronic thermostat, and a ‘T–S fuzzy control + BP-PID’ control algorithm is proposed to control standard electric drive pumps. The experimental results indicate that the intelligent cooling system considerably reduces the warm-up time, achieves accurate cooling, and effectively inhibits the hot immersion phenomenon. The intelligent control algorithm has control characteristics such as rapid response, strong adaptive ability, small overshoot, smooth transition, and high precision. The intelligent cooling system reduced the cooling-system power consumption by 5.52%–57.93%, fuel consumption rate by 1.43%–5.15%, smoke emission by 1.40%–4.69%, CO emission by 2.14%–6.03%, and HC emission by 7.41%–12.26%.

Bandwidth-Aware High-Efficiency Video Coding Design Scheme on a Multiprocessor System on Chip

H.265/high-efficiency video coding (HEVC) provides a multitude of video data compression to minimize data storage and data transmission while preserving video coding quality and ameliorating coding bit rates. However, HEVC encoder chips are frequently integrated into mobile multiprocessor system-on-chip (MPSoC) systems that adopt intelligent thermal and power management techniques for heat- and power-dissipation reductions. Consequently, the accessible coding bandwidth (CB) for HEVC encoder chip use is not fixed, and the compressed video data for data transmission within MPSoCs are restricted to time-altering wireless transmission bandwidths (TBs). Therefore, the proposed bandwidth-aware H.265/HEVC controller design solves the video coding problems of limited CB and TB by jointly using a machine-learning method and convex optimization. The ancillary experimental and implementation results demonstrate that the proposed CB-TB rate-coding distortion (CB-TB-R-D) algorithm modeling and the very large-scale integration (VLSI) hardware architecture are applicable for CB- and TB-constrained HEVC encoder design within MPSoC.

Research Progress and Prospect of Thermal Management of Automotive Lithium-ion Batteries

As an important energy storage device, lithium-ion batteries are widely used in mobile electronic devices, electric vehicles and other fields. However, lithium-ion batteries generate a lot of heat during the charging and discharging process, and if effective thermal management is not carried out, it will lead to problems such as battery performance, reduced safety and even thermal runaway. Therefore, it is of great significance to study the thermal management strategy of lithium-ion batteries to improve battery performance and safety. This paper reviews the progress of thermal management research on lithium-ion batteries in recent years, analyzes the working principles of active cooling and passive cooling in detail, proposes the application methods of composite cooling, and looks forward to the future research should focus on the research and development of Multiphysics coupling simulation, intelligent thermal management system and new thermal management materials to achieve efficient thermal management of lithium-ion batteries and improve battery performance and safety.

Advanced Phase Change Materials from Natural Perspectives: Structural Design and Functional Applications.

Phase change materials have garnered extensive interest in heat harvesting and utilization owing to their high energy storage density and isothermal phase transition. Nevertheless, inherent leakage problems and low heat storage efficiencies hinder their widespread utilization. Nature has served as a great source of inspiration for addressing these challenges. Natural strategies are proposed to achieve advanced thermal energy management systems, and breakthroughs are made in recent years. This review focuses on recent advances in the structural design and functions of phase change materials from a natural perspective. By highlighting the structure-function relationship, advanced applications including human motion, medicine, and intelligent thermal management devices are discussed in detail. Finally, the views on the remaining challenges and future prospects are also provided, that is, phase change materials are advancing around the biomimicry design spiral.

Rapid-actuating high-Tg shape memory polyimide composites with synergistic “micro-nano” thermal conduction networks

Shape memory polyimide (SMPI) is one of the most promising intelligent materials and has a high potential for deformable flexible electrodes, intelligent thermal management devices, and high temperature active deployable structures, etc. In this paper, silane-modified AlN nanoparticles (M-AlN) are composited with SMPI matrix resin to prepare fast-response high-Tg shape memory composites. Besides, nano-sized AlN and micron-sized Al2O3 are used to construct “micro-nano” synergistic thermal conduction networks, in which the AlN acted as the “thermal conduction island”, and the Al2O3 acted as the “thermal conduction bridge”. The results show that the in-plane thermal conductivity of Al2O3/M-AlN/M-SMPI-2 is 5.99 W m−1K−1, compared with SMPI, its thermal conductivity increases by 91%. In addition, the shape transition temperature of Al2O3/M-AlN/M-SMPI-2 was higher than that of pure SMPI, which was at 426 °C, and the thermal response shape recovery speed is also greatly improved by 433%, which can be used in rapid-actuating and high temperature active deformation structure.