Effective battery thermal management (BTM) is critical to ensure fast charging/discharging, safe, and efficient operation of batteries by regulating their working temperatures within an optimal ...range. However, the existing BTM methods not only are limited by a large space, weight, and energy consumption but also hardly overcome the contradiction of battery cooling at high temperatures and battery heating at low temperatures. Here we propose a near-zero-energy smart battery thermal management (SBTM) strategy for both passive heating and cooling based on sorption energy harvesting from air. The sorption-induced reversible thermal effects due to metal–organic framework water vapor desorption/sorption automatically enable battery cooling and heating depending on the local battery temperature. We demonstrate that a self-adaptive SBTM device with MIL-101(Cr)@carbon foam can control the battery temperature below 45 °C, even at high charge/discharge rates in hot environments, and realize self-preheating to ∼15 °C in cold environments, with an increase in the battery capacity of 9.2%. Our approach offers a promising route to achieving compact, liquid-free, high-energy/power-density, low-energy consumption, and self-adaptive smart thermal management for thermo-related devices.
Thermal energy storage is highlighted as a crucial strategy for energy saving and utilization, in which domain, latent heat storage using phase change materials has gained great potential for ...efficient heat storage and thermal management applications. A strategy for developing high energy-storage-density and power-density latent heat storage units, through the compression-induced assembly of expanded graphite based stearic acid composites and the macro encapsulation method by using polyethylene shells, is demonstrated. The fabricated composite shows a satisfactory phase change enthalpy of 161.24 ± 0.5 J g−1, and enhances thermal conductivity to 13.4 ± 0.8 W m−1 K−1. The resulting heat storage unit also exhibits form-stable, leakage-proof, good homogeneity, and high-power-density behaviors. A 0.462 kWh proof-of-concept prototype of the packed-bed latent-heat-storage system by using 492 heat storage units has demonstrated its feasibility in fast heat charging/discharging operations. The outlet air temperature in the discharging process can maintain above 30 °C for over 1.74 h with a heat storage utilization efficiency of 90.3 ± 6.1% and an effective discharging efficiency of 93.5 ± 9.4%, under a volumetric flow rate of 30 m3 h−1 and heat storage temperature of 27–86 °C. The maximum and average power density, and effective energy density are obtained as 20.7 ± 1.6 kW m−3, 14.2 ± 0.9 kW m−3, 24.8 ± 2.5 kWh m−3, respectively, with a discharging threshold temperature of 30 °C. This high-power-density apparatus using form-stable heat storage units has realized hourly rapid heat charging-discharging processes, showing its prospective potential of low-temperature heat storage and thermal management.
•A compression-induced assembly and macro encapsulation method is developed to prepare phase-change heat storage units.•The fabricated EG-SA composite exhibits a satisfactory phase change enthalpy and enhanced thermal conductivity.•The resulting heat storage units show form-stable, leakage-proof, good homogeneity, and high-power-density behaviors.•A packed-bed latent-heat-storage prototype is demonstrated to realize hourly rapid heat charging and discharging processes.
The effect of recycled coarse aggregate (RCA) on the fresh and hardened properties of C40 self-compacting concrete (SCC) was investigated in this paper. The slump, T
500 (the time needed for SCC to ...spread into a round configuration with a nominal diameter of 500 mm), the slump flow and the flow time of fresh C40 SCC as well as the compressive strength and modulus of elasticity of hardened C40 SCC were studied. The modulus of elasticity of C40 SCC was calculated by theoretical formula, and the calculated values were compared with the experimental values. Mechanisms that effect on the C40 SCC properties at fresh and hardened states were also explored. The experimental results showed that the slump values of the C40 SCC are beyond 250 mm. The C40 SCC with RCA replacement content of 50% showed the highest slump value of 275 mm. All T
500 values of the C40 SCC are within 5 s. The slump flow of the C40 SCC slightly increases with the increase of replacement content of the RCA. In contrast, the compressive strength and modulus of elasticity of the C40 SCC slightly decrease with the increase of replacement content. The experimental values of modulus of elasticity are lower than that of the calculated values. Submerged in water before mixing of RCA leading to the slump flow of the C40 SCC increases with the increasing replacement content of the RCA. The old cement mortar attached to the RCA surface is the main reason that weakens the mechanical properties. The lower amount of coarse aggregate and the higher amount of cement paste attribute to the lower values of modulus of elasticity. This study implied that RCA can be effectively used in the production of C40 SCC without any significant sacrifice on workability and mechanical properties.
This work conducts a thermal performance investigation on an industrial-scale low-temperature latent heat storage unit based on thermal behavior identification and parametric analysis of the storage ...unit. The thermal performance of thermal power-driven and heat transfer fluid temperature-driven charges and discharges are investigated. Two groups of parametric analyses are conducted to reveal the effects of different operating conditions and heat transfer structures on the power rate and thermal efficiency of the storage unit. Two practical application scenarios including a space heating system and a domestic hot water supply system using the storage unit are designed and simulated. The results show that the charging/discharging thermal power and charging/discharging efficiency are always inversely correlated. Using densified fin structures can effectively improve the charging rate and discharging efficiency of the storage unit at specific operating conditions. In addition, a single storage unit with a storage capacity around 100 kWh can meet a 16-h heating demand of space heating with a base heating load of 30 W m−2 and a minimum heating temperature of 40 °C for an area of 195.7 m2,and can provide 2500 L of domestic hot water above 45 °C for the daily use of 25 residents within 6 h.
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•Investigates the 3-D transient thermal behavior of a 100-kWh latent heat storage unit•Evaluates the thermal performance of two modes of charge and discharge of the storage unit•Explores the effects of operating conditions and fin interval on power rate and thermal efficiency•Designs the application scenario of the storage unit for spacing heating and domestic hot water supply
The current research focus on Content-Based Video Retrieval requires higher-level video representation describing the long-range semantic dependencies of relevant incidents, events, etc. However, ...existing methods commonly process the frames of a video as individual images or short clips, making the modeling of long-range semantic dependencies difficult. In this paper, we propose TCA (Temporal Context Aggregation for Video Retrieval), a video representation learning framework that incorporates longrange temporal information between frame-level features using the self-attention mechanism. To train it on video retrieval datasets, we propose a supervised contrastive learning method that performs automatic hard negative mining and utilizes the memory bank mechanism to increase the capacity of negative samples. Extensive experiments are conducted on multiple video retrieval tasks, such as CC WEB VIDEO, FIVR-200K, and EVVE. The proposed method shows a significant performance advantage (∼ 17% mAP on FIVR-200K) over state-of-the-art methods with video-level features, and deliver competitive results with 22x faster inference time comparing with frame-level features.
High-performance electromagnetic interference (EMI) shielding materials with ultralow density, excellent flexibility, and good mechanical properties are highly desirable for aerospace and wearable ...electronics. Herein, honeycomb porous graphene (HPG) fabricated by laser scribing technology is reported for EMI shielding and wearable applications. Due to the honeycomb structure, the HPG exhibits an EMI shielding effectiveness (SE) up to 45 dB at a thickness of 48.3 μm. The single-piece HPG exhibits an ultrahigh absolute shielding effectiveness (SSE/t) of 240 123 dB cm2/g with an ultralow density of 0.0388 g/cm3, which is significantly superior to the reported materials such as carbon-based, MXene, and metal materials. Furthermore, MXene and AgNWs are employed to cover the honeycomb holes of the HPG to enhance surface reflection; thus, the SSE/t of the HPG/AgNWs composite membrane can reach up to 292 754 dB cm2/g. More importantly, the HPG exhibits excellent mechanical stability and durability in cyclic stretching and bending, which can be used to monitor weak physiological signals such as pulse, respiration, and laryngeal movement of humans. Therefore, the lightweight and flexible HPG exhibits excellent EMI shielding performance and mechanical properties, along with its low cost and ease of mass production, which is promising for practical applications in EMI shielding and wearable electronics.
A quasi-isostatic pressing technique for encapsulating spherical high-temperature inorganic phase change materials (PCMs) was presented in this work. To enhance the thermal conductivity of PCMs, ...graphite powder was dispersed into the PCM pellets. Meanwhile, cellulose particles, as sacrificial particles, were mixed with the PCM pellets to relieve the volumetric expansion of the PCMs during the phase change process. The effects of the latent heat, thermal conductivity, and thermal expansion behavior of the PCM/graphite capsule were investigated. The PCM capsules were able to work at temperatures up to 900 °C, including undergoing a solid-liquid phase change at 803 °C with a latent heat of 159.6 J g−1, and survived more than 300 thermal cycles as thermal energy storage devices. The thermal performance of the PCM capsules between 500 and 900 °C was numerically investigated using a modified one-dimensional (1-D) enthalpy-based model. The results indicated that the average heat transfer of the PCM capsules with graphite-dispersed core was significantly elevated during both the charging (by 92.5% for 99% charge) and discharging (by 168.4% for 99% discharge) processes, compared to the pure core PCMs.
•Encapsulation of high-temperature inorganic phase change materials using graphite as heat transfer enhancer was presented.•The PCM capsules had a solid-liquid phase change at 803 °C (159.6 J g−1) and could survive more than 300 thermal cycles.•The numerical results showed that the PCM/graphite performed a significantly enhanced average heat transfer.
•A 1-D enthalpy-based D-C model is developed and validated for the packed-bed TES.•An efficient tank size estimation strategy is proposed to design the scale of system.•Systems with four typical ...packed-bed are sized under practical operating conditions.•The strategy is self-convergent, computing cost saving and generally applicable.
Thermocline storage in a packed-bed is considered as a promising thermal energy storage (TES) method that achieves cost reduction with respect to current concentrated solar power (CSP) plants. Several parametric studies investigated thermal performances of different types of packed-bed thermocline TES systems, and cost analyses and dimension design studies were conducted based on this. However, parametric studies typically involve high computing costs for a dimension design, and results obtained by correlation fitting suffer from a relative lack of accuracy. The main objective of the present study involves directly determining the tank size of a packed-bed thermocline TES system to satisfy certain design requirements of a CSP plant without requiring parametric studies. In order to achieve this goal, a one-dimensional enthalpy-based dispersion-concentric (D-C) model is developed and validated to investigate the periodic thermal behavior of the system. An efficient tank size estimation strategy is proposed based on the periodic thermal performance of the system. The strategy is used to size four different packed-bed thermocline TES types under two exemplary operating conditions. The results reveal that tank size estimation strategyisindependent ofinitial conditions, and that it is self-convergent, involves cost saving in terms of computing costs, is generally applicable, and can provide guidelines for the design of a TES system for CSP plants.
Water-based adsorption thermal battery (ATB) could provide huge possibility in widespread applications; especially for space heating, leading to appreciable energy saving and low-grade heat energy ...utilization. A proof-of-concept prototype based on composite adsorbents has been constructed to investigate the thermal performances of a packed-bed ATB. A possible strategy of tunning airflow rate for performance regulation is proposed and studied to realize stable thermal output. Additional experimental results indicated that the output temperature and heating power can be synchronously stabilized through progressive tunability of loop airflow rate in the loop-cycle ATB system. The output RH spans 40–60% along the effective discharging process, enabling a controllable humidity management in the application of direct space heating considering human thermal comfort. A three-dimensional computational model for predicting the overall thermal output performances of a packed-bed adsorption thermal battery is further developed and established. The simulation results reveal that an effective heating time of 8.6 h with a discharging threshold temperature of 24 °C, and an average power density of 19.3 kW m−3 can be achieved with a maximum heat discharging efficiency of 63.4%. It is, therefore, apparent that the ATB is capable of achieving stable thermal outputs for space heating applications.
•An experimental and numerical parametric study analysis for the packed-bed adsorption thermal battery is conducted.•A strategy of tunning airflow rate for stable output performance is proposed and developed for adsorption thermal battery.•The proposed modelling and optimization method can be employed to analyze and predict overall thermal output performances.•Different combinations of open-cycle and loop-cycle modes in adsorption thermal battery can meet various heating demands.
Moisture-based adsorption thermal battery (ATB) holds great potential for addressing energy storage and utilization challenges. In this work, a proof-of-concept solar harvesting building envelope ...using the Trombe-wall (T-wall) based ATB design is proposed and investigated, featuring a developed composite sorbent as the porous wall for effective heat storage and utilization. To demonstrate the feasibility of employing the ATB-based building envelope for day-and-night space heating, a 3-dimensional simulation model of the ATB wall is meticulously designed and comprehensively studied. Parametric analyses of various working conditions, including examining the effects of solar radiation intensity, air temperature, air humidity, and airflow velocity on the heat charging and discharging performances of the ATB wall, are conducted using the numerical model. Simulation results indicate that, under a solar irradiance level of 700 W m−2 during the daytime, an average output air temperature of 42.4 °C and an average heating power density of 2.5 kW m−3 are achieved. Extending the heat charging time to 8 h and 12 h significantly improves the desorption efficiency, which is able to reach 47.2% and 75.0%, respectively. In terms of heat discharging performances, various working conditions investigated in the ATB wall model will lead to different thermal output performances.
•A building envelope concept of solar ATB wall is proposed to realize continuous space heating and low energy consumption.•A 3-dimensional simulation model of the solar ATB wall is investigated for parametric analysis and performance prediction.•The effects of solar radiation, air temperature, humidity and flow rate on the heating performance of the model are examined.
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