•A Li-ion battery cell is characterized during charging/discharging cycles.•The non-uniformly distributed temperature changes are mapped in time.•The capacity fade is measured under different ambient ...teperatures.•The response is measured under different discharge rates and ambient temperatures.
This paper documents the experimental characterization of a Li-ion battery cell during charging/discharging cyclic operations. The study of the battery cell is conducted in the absence of cooling aid system, and provides thermal and electrical insights. After describing the experimental set-up, the changes in temperature are presented and highlight the nonuniform distribution of the temperature on the battery cell surface. The findings indicate that the maximum temperature difference on the investigated battery cell surface may reach up to 11 C at 3C and 17 ⁰C at 5C, at the end of the discharge in the natural convection case. These changes in space come with temporal variations that are also documented. Voltage curves are provided during charging and discharging operations. The impact of the discharge rate, ambient temperature are then investigated together with the capacity fade after 500 cycles, and results showed that ventilation and low ambient temperatures allow to alleviate the battery capacity fade by 3%.
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•CHC is presented as a new method for the inactivation of pathogens in milk.•CHC treatment is more effective than HTST.•The effect of CHC on milk nutrition is similar to that of ...HTST.•The safety of CHC milk is similar to LTLT and lower than that of HTST.•CHC treatment costs $0.00268/L at a production rate of 4.2 L/min.
Hydrodynamic cavitation is a powerful tool for the enhancement of various processing applications. This study utilizes continuous hydrodynamic cavitation (CHC) for the inactivation of pathogens in milk for the first time. The thermal characteristics, inactivation performance, damage on the nutritional composition, product safety, and cost of the advanced rotational hydrodynamic cavitation reactor at pilot scale were comprehensively investigated. The inactivation results demonstrated that 5.89, 5.53, and 2.99 ± 0.08 log reductions of Escherichia coli, Staphylococcus aureus, and Bacillus cereus were achieved, respectively, at a final treatment temperature of 70 °C for 1–2 s. Moreover, the detrimental effect of CHC on the nutritional composition of milk, including mineral, fat, protein, and vitamin contents, was similar to that of high-temperature short-time method. The change in the concentrations of general bacteria and E. coli, as well as the pH value and acidity of the CHC treated milk stored at 5 °C for 14 days was found to be close to that of low-temperature long-time pasteurized milk. The cost of the present CHC treatment was $0.00268/L with a production rate of 4.2 L/min. CHC appears to be a remarkable method for the continuous processing of milk, as well as other liquid foods with high nutrition and “fresh-picked” flavor, due to its high efficacy, good scalability, high production capacity, and low operating and equipment costs.
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Composite materials have improved the fields of aerospace, marine and defence by supporting the manufacturing of several structures owing to their superior properties. The specific ...class of composite materials known as syntactic foams have come to the forefront for structural and functional applications. Therefore, the objective of this article was to present properties, material characterization, and applications of the new class of lightweight materials especially syntactic cellular foam made from the epoxy matrix and hollow glass microspheres (HGMs). The mechanical characterization of HGM filler–epoxy syntactic cellular foam for density, tensile properties, compressive properties, wear behaviour, fracture and impact toughness have been thoroughly reviewed along with dielectric properties. Finally, functional properties like buoyancy, acoustic, water-absorbing capability and the electromagnetic wave attenuation properties of epoxy/HGMs have been elucidated. Importantly, this succinct review stands to benefit both designers and developers/manufacturers of the aforementioned multi-functional materials for marine, electronics, aerospace and military/defence requisitions.
•Controlled experiments to explore the source of frequency-dependent heat have developed.•The heat generation mechanism of lithium-ion batteries under high-frequency AC excitation is different from ...those under low-frequency.•Frequency-dependent heat partly due to current harmonics, and partly from an unknown mechanism.
Lithium-ion batteries suffer severe energy loss, significant pulse power decline, and reduced life cycle under cold weather. It is imperative to preheat the lithium-ion batteries for electric vehicles (EVs) at low temperatures. At present, various internal alternative current (AC) heating methods have been proposed to achieve fast and high-efficiency battery preheating. However, there is still confusion in the selection of the AC frequency. Researchers have found that the simplified Bernardi heat generation model is not always suitable for AC preheating, especially at high AC frequencies. Under these scenarios, a frequency-dependent heat is generated, making the traditional thermal model inapplicable. In this paper, the source of frequency-dependent heat is analyzed experimentally. Based on the electrochemical impedance spectrum (EIS) data and entropy thermal coefficient of the cell in the experiment, controlled experiments in different frequencies are developed to compare the cell heat generation rate. The experiments showed that the heat generation rate is highly correlated to its frequency. Further analysis show that the frequency-dependent heat is not due to electrochemical reaction, partly due to Joule effect by current harmonics, and partly from unknown mechanism (nominate “extra-heat”).
The external partitions of a building (walls, roof, etc.) in addition to their supporting functions must also ensure an internal microclimate suitable for comfortable human work, recreation and other ...activities. This article analyzes the thermal characteristics of the external walls of a residential house and thermographically examines the joints of the different structures of the building. Thermographical examination may be performed either passively or actively. In the former case, the object of the examination ir heated up to a given temperature, after which thermographical images of the object are taken and analyzed. In the latter case, thermographical analysis is made of the object in its naturally established thermal conditions. This article examines the thermal characteristics of the partition structures of a residential building. The values of the thermal properties of the materials are taken from the documentation provided by their manufacturers, and in their absence, the data of the technical building regulations is used. Calculated analytically: the wall of the western annex only meets the C energy class requirements, the insulation of the old part of the building raised the heat transfer coefficient of the partition to class A, the thermal characteristic of the eastern annex wall corresponds to the A + energy class. This thermographic examination showed that the facade covered by the fibrous cement siding absorbed less heat compared to the masonry facades. Based on theoretical calculations and the thermographic analysis, it is recommended to additionally insulate the western annex from the inside. If possible, it is also recommended to additionally insulate both facade joints with polyurethane foam and to seal them with waterproofing mastic to prevent the sunrays from reaching the foam.
•A system-level thermal-electrochemical model of thermal batteries during activation stage is built.•Fuse strip has important effects on the activation process of thermal batteries.•The difference of ...internal resistance between the unactivated and activated state can reach 12 orders of magnitude.
As the primary reserve batteries widely used in military domain, the intricate thermal-electrochemical behaviors and tiny time scale of the activation process make the development of thermal batteries a pain-stacking work, as lacking of the precise model to guide the design process. In this study, a system-level thermal-electrochemical model for evaluating the main technical indexes of LiSi/FeS2 thermal batteries during activation stage is built, which comprehensively considers the main physical and chemical processes such as combustion, heat transfer, phase change, ion transport, voltage variation and so on. The activation characteristics of two types of 5-cell thermal batteries are predicted by this model, and the activation voltages of the two batteries are tested to validate the model. The model possesses the high precision with error less than 5 % by comparing the simulation results of activation voltage with that of experiment results. Specifically, the model reveals that the instantaneous temperature of pyrotechnic pellet after combustion is around 1570 K, and the electrolyte becomes molten and its internal resistance sharply decreases to mΩ level when the temperature reaches its melting point. The variation process of activation voltage is mainly dominated by the geometry size of cell stack and the thickness ratio of pyrotechnic pellet to single cell, besides, the activation time can be considered to be the peak value time of activation voltage. Fuse strip has important effects on the activation process of thermal batteries, especially in the rapid increase period of activation voltage, and the heat transfer is the time-limited step of the activation process. The difference of internal resistance between the unactivated state and activated state of thermal batteries can reach 12 orders of magnitude. These results indicate that our model can perform well in evaluating the activation process of thermal batteries and guiding the optimal design.
Flow control using surface Dielectric Barrier Discharge (DBD) plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry. ...The induced flow field of the plasma actuator, with the starting vortex in the wall jet, plays an important role in flow control. However, the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator, and most of the total energy is used in gas heating and dielectric heating. Therefore, an in-depth analysis of the thermal characteristics of the plasma actuator is the key to develop its potential capability further. In addition, compared with the investigation on the aerodynamic characteristics of the plasma actuator, there is a relative lack of detail in the study of its thermal characteristics. Understanding the thermal characteristics of the plasma actuator is of great interest for providing a deeper insight into the underlying working principles, advancing its numerical simulation model, prolonging its life, and achieving several potential engineering applications, such as anti-icing and deicing. The present paper reviews the thermal characteristics of the plasma actuator, summarizes the influence of the dielectric film and actuation parameters on heating, and discusses the formation and transfer mechanism of the induced heating based on the discharge regimes of the plasma actuator in one cycle.
•Thermal characteristics of coal under different stress unloading at 30–300 °C.•Oxidation promotes the maximum heat release acceleration d (HF).•The thermal properties of coal are related to stress ...nonlinearity.•When the pre-oxidized coal sample is oxidized again, it is easier to oxidize.
The oxidation heat characteristics of coal are key factors affecting the spontaneous combustion of coal. To study the thermal characteristics of the secondary oxidation of unloaded coal, a C600 microcalorimeter was used to test the unloaded coal under different stress conditions (0 MPa, 3 MPa, 6 MPa, 9 MPa, 12 MPa, 15 MPa) at 30–300 °C. The initial heat release temperature, heat release, and activation energy of coal were analyzed. The results shows that the initial heat release temperature of unloaded coal shows a trend of first increasing and then decreasing with increasing stress, and as the degree of oxidation increases, the maximum value of the initial heat release temperature point moves to a lower value. As the stress increases, the amount of heat release shows a fluctuation that first decreases and then increases, and as the degree of oxidation increases, the minimum heat release moves forward from 12 MPa for primary oxidation to 6 MPa for secondary oxidation. Similarly, the activation energy first increases and then decreases with increasing stress, and the maximum activation energy increases with increasing degree of oxidation, which is consistent with the trends of heat release. As the degree of oxidation increases, the overall performance of unloaded coal with increasing stress shows that the preoxidized coal sample is more susceptible to oxidation when it is reoxidized.
•A simplified CFD model of micro-channel separate heat pipe with louvered fins was established.•The two-phase flow pattern inside the evaporator was investigated.•The thermal characteristics under ...different filling ratios were analyzed and compared with experiment.
This paper established a CFD model of the evaporator of a microchannel separate heat pipe (MCSHP) used for special indoor environment cooling (e.g., telecommunication station) to study its heat transfer characteristics and flow mechanisms under different filling ratios. The louvered fin model outside the pipe was simplified to shorten the computation time without ignoring the thermal enhancement. The CFD simulation results were validated by experimental data. The optimal refrigerant filling ratio was from 68% to 100%. The bubble flow existed inside the whole pipe during the early stage of evaporation, and converted to slug flow under continuously heating. It was found that the cooling capacity increased with the filling ratio, and was high to 4087 W at the filling ratio 78%. Due to the formation and movement of refrigerant bubbles, the liquid fraction distribution inside the evaporator varied with the filling ratio and dimensionless time. The distribution of wall temperature and the liquid fraction both indicated that the effective heat transfer area of two-phase region was a key parameter affecting the cooling capacity. This study can be used to simplify experiment procedure and to optimize the system design and operation of MCSHP.
•Effect of initial temperature of a lithium battery during charging is studied.•Distributions of local current density and heat generation rate are analyzed.•Non-uniformity of local current density ...increases at lower initial temperature.•Charging energy efficiency varies at different initial temperatures and C-rates.
Due to the discharging or long-term placing, the initial temperature of a lithium-ion battery during charging is different, which may lead to various electrochemical and thermal characteristics. An electrochemical-thermal coupled model is developed for a lithium-ion battery and experimentally validated. The local current density, heat generation rate and charging energy efficiency of the battery during charging at different initial temperatures are numerically investigated. The spatial distribution of local current density of the battery cell is non-uniform at different initial temperatures. And the non-uniformity increases with the decreasing of initial temperature, especially in the negative electrode. Initial temperature influences the spatial and temporal distributions of heat generation rate in the battery cell. Most of the heat (over 95%) is generated in the electrodes. And the part of irreversible heat contributes to over 60% of the total heat generation in the negative electrode. The charging energy efficiency changes with the difference of the total irreversible heat and the input charging energy. The charging energy efficiency of the battery increases with the increasing of initial temperature at 0.5 C charging rate, while it will decrease after the initial temperature exceeds 40 °C and 25 °C at 1 C and 2 C charging rate, respectively. So it should use reasonable charging rates at different initial temperatures. These findings give help for the battery management systems design to achieve higher charging energy efficiency.
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