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Fluidized bed technology is widely used in chemical industries. The introduction of pulsating energy into a traditional fluidized bed can effectively reduce the generation of bubbles and improve th...

Fe7S8 has emerged as an attractive anode material for lithium-ion batteries (LIBs) due to its outstanding features such as low cost, high theoretical capacity, as well as environmental benignity. However, the rapid capacity fading derived from the tremendous volume change during the charging/discharging process hinders its practical application. Nanostructure engineering and the combination with carbonaceous material are essential to address this issue. In this work, Fe7S8 nanocrystals decorated on N, S-codoped carbon nanotubes (Fe7S8-NSC) were synthesized through a facile one-step pyrolysis of Fe-containing polypyrrole (PPy) nanotubes with sulphur powders under nitrogen atmosphere. When evaluated as anode of LIBs, Fe7S8-NSC demonstrates excellent cycling stability (718.8 mAh g-1 at 100 mA g-1 after 100 cycles) and superior rate ability (290.8 mAh g-1 at 2000 mA g-1). Moreover, Fe7S8-NSC shows a typical specific capacity recovery phenomenon, an extraordinary capacity of 744.4 mAh g-1 at 2000 mA g-1 after 1000 cycles can be achieved, which outperforms most of the Fe7S8-based anode materials reported before. The Fe7S8-NSC should be a promising anode material for high-performance LIBs.

Lithium ion batteries have been widely used in the power-driven system and energy storage system. While thermal safety for lithium ion battery has been constantly concerned all over the world due to the thermal runaway problems occurred in recent years. Lithium ion battery has high temperature sensitivity and the relatively narrow operating temperature range because of the complex electrochemical reactions at different temperatures. And the temperature change, including the global temperature change in different seasons and the local temperature rise that is induced by its self-heating etc., can trigger side reactions and then lead to thermal runaway, which should be further considered to ensure thermal safety of lithium ion battery. This review summarizes the inducements of thermal runaway and relevant solutions, spanning a wide temperature range. The low temperature induced issues, such as capacity fade and lithium plating and dendrite, can cause internal short circuit (ISC), while as the temperature is above the critical temperature, the speeding of side reactions and reduction of lifespan (T ​> ​40 ​°C) and thermal runaway (T ​> ​90 ​°C) will be triggered. In order to solve the thermal issues in batteries, extensive approaches have been investigated to prevent the occurrence, propagation and deterioration of thermal runaway, from the perspective of material to the battery system. The triggered mechanism at a wide temperature range, key factors for thermal safety and the effective heat dissipation strategies are concluded in this review. This review is expected to offer effective thermal safety strategies and promote the development of lithium ion battery with high-energy density.

Thermal energy storage (TES) is among the most powerful tools to alleviate the risk of fossil energy depletion. Latent heat density and thermal conductivity are the two most important parameters to evaluate the performance of TES materials. In this work, for the first time, we embed knitting aryl network polymers (KAPs) on the skeleton of copper foam (CF) in a biomimetic protocol, where the preparation process is inspired by the growing process of a natural coral and the obtained phase change material (PCM)-holding medium exhibits a bird nest-type morphology. Excellent energy storage performance was determined, where the thermal conductivity was up to 55.37 W m−1 K−1 and the encapsulation rate could reach 62.1% without the observation of any enthalpy attenuation even after a 300 energy charging and releasing cyclization, due to the relatively high surface area, i.e., 1079.1 m2 g−1 and high thermal conductivity of the copper skeleton inside. Further study revealed the good applicable properties in terms of shape adjustability, light-to-thermal and light-to-electric conversion.

The liquid range of nanofluids is a crucial parameter as it intensively determines their application temperature scope. Meanwhile, improved thermal conductivity and stability are of great significa...

Thermal energy storage with phase change materials (PCM) is of great significance for increasing energy efficiency and energy saving. In this paper, a novel capric acid-myristyl alcohol/expanded perlite composite PCM (CPCM) with two phase change peaks were prepared. The capric acid-myristyl alcohol (CM) were synthesized by capric acid (CA) and myristyl alcohol (MA) (WCA and WMA = 9:1). Three kinds of expanded perlites (EP) were employed as support materials in the prepared CPCM. The chemical structure, morphology, thermal properties, leakage and thermal energy storage performance of the CM/EPPCM were investigated. The results indicate that the CM/EPPCM has a good thermal stability and leakage-proof performance. In addition, the thermal characteristics of the CM/EPPCM were investigated using a building model. The experimental results shows that the application of the CM/EPPCM for building envelope can effectively reduce temperature fluctuation and improve the thermal comfort of the building.

Deep eutectic solvents (DESs) have gained much attention especially in the fields of catalysis, electrochemistry, material chemistry owing to their low cost, good stability, environmental friendly features. The low vapor, less volatile and wide liquid range properties of DESs inspired us to study their application in the field of heat transfer, especially adopted as a base solvent of nanofluids. In this work, glycerol/choline chloride (ChCl) deep eutectic solvent based nanofluids, by filling with nanoscale TiO2, Al2O3 and graphene oxide were demonstrated. Thermal conductivities of the developed nanofluids can be increased by 3–11.4%, and the working temperatures cover from −35 to 275 °C with keeping liquid state. The temperature-dependent viscosities were studied and a little dependence on nanofiller concentration was found in those three different nanofluids. Specific heat capacities of the developed nanofluids were found to be decreased compared with that of base solvent after dispersing nanoparticles. Interestingly, we found that the Al2O3-filled nanofluid exhibited a unique behavior of thermal conductivity by varying the volume fraction of Al2O3. 1H NMR and FT-IR were chosen to study the mechanism of thermal enhancement, which indicated that the hydrogen bond between glycerol and Al2O3 is responsible for this unique phenomenon of heat transfer enhancement.

Supercapacitor, as a new energy storage system, has attracted increasing interests owing to its fast charge/discharge process, high-power density, and long-cycling life. However, exploring high-capacitance porous carbons as electrode materials has caused enormous attention around the world. Herein, we propose a nitrogen-doped porous carbon (NPC)-sandwiched 3D graphene (NPC-3DG) by direct freeze-drying of ZIF-8/graphene oxide mixed solution followed by a high-temperature thermal treatment. The characterizations of scanning electron microscopy, N2 adsorption/desorption isotherms, and X-ray photoelectron spectroscopy proves the sandwich structured frameworks of NPC-3DG with a high specific surface area of 726.9 m2 g−1 and a nitrogen content of 3.2 wt%. When used as capacitive electrode materials (in three-electrode system), the resultant NPC-3DG exhibited a high capacitance of 530.1 F g−1 at a current density of 1 A g−1. Moreover, the capacitance still maintains a high value of 337.2 F g−1 even at a high current density of 20 A g−1.

In this work, a one-step bimetallic activation method was developed combining the activation performance of metal activators (FeCl3/ZnCl2, FeCl3/MgCl2 and ZnCl2/MgCl2) and etching effect of CO2 to prepare biomass activated carbons from peanut shell for the application in supercapacitors. Results indicate that the loading of ZnCl2 and FeCl3 can produce amount of micropores during biomass pyrolysis, which can provide adsorbing sites for ions. The presence of MgCl2 can promote the formation of mesoporous structure, facilitating the transfer of electrolyte ions. Under suitable conditions, a high specific surface area of 1427.81 m2/g was obtained with a large proportion of micropores (73.91%). Graphitic structure was also formed using the bimetallic activation method and partially graphitic porous carbons were obtained, which can simultaneously provide electron pathway and energy storage capabilities. Abundant oxygen-containing functional groups were also obtained on the surface of the carbon samples to further improve their electrochemical performance. All the carbon samples activated at 800 °C from bimetallic activation exhibited good electrochemical performance as supercapacitor electrode. The FeCl3/MgCl2 activated sample at 800 °C (FE/MG-AC-800) exhibited the maximum discharge specific capacitance of 247.28 F/g at a current density of 1 A/g in the 1 M Na2SO4 electrolyte and good rate capability of 202.34 F/g at 10 A/g. Furthermore, high cyclic stability was also obtained with capacitance retention of 96.31% after 5000 cycles.

Four different trihydroxy crosslinkers were respectively used to construct molecular models of hypercrosslinked polyurethanes as shell materials of phase change nanocapsules for thermal energy storage so as to investigate the heat and mass transfer properties. The impacts of microscopic characteristics of crosslinkers on glass transition temperature, thermal expansion and diffusion, interaction energy, thermal conductivity, mechanical properties under tensile and shear stress as well as some of thermal properties after packing water molecules into the hypercrosslinked polyurethanes were simulated and analyzed based on equilibrium or non-equilibrium molecular dynamics methods. The results showed that the detailed molecular structure of crosslinkers, namely the positions of hydroxyl groups, the geometric features of skeleton and even involved element type, will determine the structural characteristics of the hypercrosslinked polyurethanes, such as the formed micro cavities, the dangling functional groups as well as stiffness of short chain, and then affect the heat and mass transfer as well as mechanical properties. Furthermore, the hypercrosslinked polyurethanes possess relatively high glass transition temperature, better heat transfer performance and excellent mechanical properties compared to the polyurethanes with low crosslink density.

The phase change process is of significant importance in the application of phase change material (PCM). In this paper, the modified enthalpy-transforming lattice Boltmznan (LB) model is developed to trace the location of solid-liquid interface, using the polynomial enthalpy function. The problems of two-region phase change and phase change by convection are solved to evaluate the presented LB model. The results show that by removing the non-differentiability of linear and hyperbolic-tangent enthalpy functions, the LB model with polynomial scheme can get the temperature distribution more accurately in the problem two-region phase change. Besides, in the problem of phase change by convection, resulted from the variable equivalent heat capacity during phase change, the melting rate of polynomial scheme is between linear scheme and hyperbolic-tangent scheme.

Aiming to combining the strength of flexibility and adaptation of oscillating heat pipe (OHP) with specific application in the field of waste heat recovery and storage, an OHP with external expansion structure was designed and fabricated. The start-up characteristic, working status, overall thermal resistance, local thermal resistance and dispersion ratio for the local thermal resistances under different filling ratios (FR), working fluids and heat loads were revealed and compared experimentally. The results showed that for the OHP with water, it exhibits well start-up performance under wide range of FRs and is able to work effectively under wide range of FR at proper heat load. Meanwhile, it also shows well adaptability to heat load under proper FR. The OHP has not obvious difference for each branch in the heat transfer performance under wide working conditions. When filled with self-rewetting fluid (SRWF), it has smaller overall thermal resistance than the water case at specific range of heat load. Comparing to the case with water, the OHP with SRWF can show better uniformity in the heat transfer capacity for each branch under appropriate condition. However, the uniformity of branch does not always contribute to increasing the heat transfer performance.

In this paper, in order to enhance the thermal performance of sodium acetate trihydrate (SAT) in thermal storage, novel composite phase change materials (CPCMs) that contains SAT (as PCM) and silicon carbide (SC), bentonite (as additives) were prepared. The microstructures, chemical structures, leakage performances, phase change properties, thermal stability and thermal energy storage performances of the CPCMs were investigated. The experimental results indicate that the bentonite is helpful to solve the leakage problem. The supercooling phenomenon and thermal conductivity of SAT are improved by adding SC. In addition, compared with those of pure SAT, the heat storage time and release time of SAT/bentonite/SC CPCMs are shorten by 25.44% and 78.5% respectively when the mass fractions of bentonite and SC of the CPCMs are 26 wt.% and 10 wt.%. The research results exhibit a reference value for improving the thermal performance of SAT in thermal energy storage process.

High thermal conductivity metal materials such as metal foams, metal particles and even metal fins can effectively improve the thermal conduction of alkanes as phase change energy storage materials. For investigating the microscopic behaviors of alkanes interacted with nanoscale copper surface, the molecular system composed of copper surface and amorphous n-octadecane (denoted by system A) was initially constructed. Simultaneously, the single wall carbon nanotubes were added into the previous system (denoted by system B) to understand their effect on the alkane. By performing molecular dynamics simulations, the potential energy components, diffusion coefficient, structural evolution, spatial orientation correlation function, relative concentration and thermal conductivity were calculated, respectively. The results showed that the crystallization of alkane induced by copper contributing to the enhancement of thermal conductivity of alkane/copper compound phase change materials. And the additive of carbon nanotubes can significantly promote the ordered alignment of alkane molecules. The results also showed that the phase transition temperature of n-octadecane in system B was more than that in system A by about 10 K owing to the further crystallization of n-octadecane induced by single wall carbon nanotubes as illustrated from the diffusion coefficient trends and potential energy component analysis.

Phase change material (PCM) has been widely used in thermal management for its high latent heat and low price. However, further development of its application is limited by the low thermal conductivity. Oscillating heat pipe (OHP), an effective thermal transfer device, can be used to enhance the heat transfer of PCM and then improve the thermal performance. In this paper, both novel 3D-OHPs and regular OHPs were hired for PCM thermal performance enhancement. PCM coupled with two kinds of novel 3D-OHPs (4 layers 3D-OHP and 3 layers 3D-OHP) system and PCM coupled with multiple 2D-OHPs system were experimentally investigated. Results showed that the paraffin wax/3D-OHP system needed more time for completely melting of paraffin wax than paraffin wax/OHPs system. The temperature of wall and paraffin wax in the former system was lower during melting process. In the solidification process, both two systems performed better than paraffin wax only. The solidification time of the paraffin wax/4 OHPs system was about 0.48 times than that of pure paraffin wax and the paraffin wax/4-layers 3D-OHP only 0.29 times, which meant that paraffin wax/3D-OHP system had better performance.

The utilization of a Li metal anode is necessary in the development of next generation high energy density Li batteries, which is still hindered by problems of dendrite growth, volume change and electrolyte depletion. To overcome these difficulties, the employment of 3D porous current collectors has been demonstrated to be an effective strategy. However, the widely used porous metallic current collectors, such as commercial Cu foam, are always too heavy to meet the demand for high energy density. In this work, we develop a low-weight, flexible, hierarchically porous and textile-structured Cu current collector via a smart cotton T-shirt template method. By employing a variant of Schweizer's reagent as the Cu source, the T-shirt moulded Cu framework can inherit the textile morphology. The hierarchically porous structure and high surface area can lower the local current density, and the unique 3D structure can confine the growth of Li crystals, all of which can endow the novel textile-structured Cu with superior performance as a current collector for Li metal anodes. Furthermore, this strategy provides a convenient route for designing template-structured frameworks, which is useful not only for the development of a current collector, but also for the preparation of numerous structure-oriented materials.

Solving the mismatch between the supply and demand of energy in energy storage techniques is critical. Here, we report a novel Lewis acid catalysis induced in situ phase change material (PCM) shape-stabilization strategy to fabricate hyper-crosslinked polystyrene (HCPS) encapsulated PCMs towards the goal of highly efficient thermal energy storage. A simultaneous cross-linking and encapsulation process, enabled by a powerful FeCl3 catalyzed cross linking reaction, results in a highly efficient encapsulation rate. Thermal conductivity of the PCMs was enhanced by converting the cross-linking catalyst FeCl3 to Fe3O4 using a simple alkali treatment, by which 17% to 55% thermal conductivity enhancement was achieved compared with pure paraffin. Notably, waste polystyrene (PS) foam was demonstrated to be capable of being used as a starting material to support PCM, opening up a new avenue to utilize waste PS foam.

An experiment set for flow and heat transfer characteristics of nanofluids is established and the reliability of this experiment set is verified. Thermo-hydraulic performances of nanofluids flowing through a triangular tube with different structure twisted tapes are experimentally studied. The effects of nanoparticle mass fractions (ω = 0.1 wt%, 0.3 wt% and 0.5 wt%), Reynolds numbers (Re = 400–9000), different structure twisted tapes (P = 25 mm, 40 mm, 55 mm, 65 mm, 75 mm) on the Nusselt number and resistance coefficient enhancement ratios are experimentally investigated. It is found that the triangular tube with twisted tape can improve the Nusselt number by 52.5% and 34.7% at best in laminar and turbulent flow respectively compared with the corresponding smooth tube with the same fluid. The comprehensive performances of nanofluids in the triangular tube with twisted tape are also analyzed based on a comprehensive evaluation index. It is found that large nanoparticle mass fraction and small length of each twisted tape unit are more sensitive to the high comprehensive performance index. In addition, comprehensive performances between the triangular tube with twisted tape and the corrugated tube are compared. It is found that the triangular tube with twisted tape has an advantage over the corrugated tube in laminar flow.

Aimed to understand the thermal characteristic of closed loop oscillation heat pipe/phase change material (CLOHP/PCM) coupling module filled with different working media for thermal energy storage and thermal management application, experimental investigation on the heat charge and discharge process of the coupling module under different conditions was carried out. The main result shows that the CLOHP filled with self-rewetting fluid (SRWF) and not placed horizontally has better thermal transfer performance relative to the water case as the heat load is low. But, the CLOHP filled with water has better thermal transfer performance than the SRWF case in horizontal condition especially under low heat load. The rise speed of temperature in the heating section increases when the phase transition completes. The highest temperature of the PCM locates in the middle region. Standard deviation (STD) of PCM temperature keeps relative stable for a long time and then increases rapidly and the rise speed has a positive correlation with the heat load. The uniformity of PCM temperature has been greatly improved for those three cases compared to that without working medium. During the discharge process, the fluctuation occurs only when the temperature of evaporation exceeds about 60 °C.

In order to further understand the operational characteristic of long heat transport distance oscillation heat pipe (OHP) for solar energy application, an experimental investigation on the thermal performance of OHP with higher initial vacuum and pressure fluctuation behavior inside under two kinds of inner diameters, two kinds of working media, and different inclination angles and filling ratios (FR) were carried out. The main result shows that the OHPs exhibit excellent heat transfer performance. The effective thermal conductivity is about two orders of magnitude larger than that in the previous work and some other researchers’ work. The start-up temperature of the OHP with 3 mm inner diameter increases from 45 °C to 58 °C with the growing of FR from 30% to 70% when injected with SRWF and placed vertically. The start-up temperature is inversely related to the inclination angle under the same condition. The working status of the OHP with 3 mm inner diameter and SRWF is hardly effected by the inner pressure. However, the effect is contrary for OHP with critical inner diameter. It can be inferred that the movement law of the liquid medium in the OHP is random and chaotic through the pressure frequency spectrum analysis.

The development of electric vehicles (EVs) is beneficial to a cleaner environment. As the powertrain of EVs, power battery is limited obviously by its fast operating temperature rise and large temperature variation among different parts, so an efficient battery thermal management (BTM) system is desirable. In this paper, a battery thermal management system using kaolin/expanded graphite (EG)/paraffin composite was designed. By contrasting different thermal properties of ternary composites with various proportions, the most suitable composite with 10 wt% EG and 10 wt% kaolin was selected for the thermal management testing, which has a conductivity of larger than 6 W/(m·K) and did not shows any visible leakage after 30 min at 60 °C. In the thermal management test, the temperature of a single battery was effectively controlled under 45 °C even at the discharge rate of 4C, and the temperature difference of the single battery was restrained within 5 °C. Besides, the composite had reduced the temperature of the battery pack by 25.77% at 4C rate, and the temperature difference of the battery pack or each battery in the pack could be greatly controlled once the phase change occurred. In conclusion, the excellent temperature controlling performance of the new phase change material (PCM) was verified in this paper, and the importance of reasonable dosage distribution of PCM in battery pack was put forward.

Catalytic performance of Cu and Zn catalysts was investigated during rice husk (RH) high-temperature pyrolysis under isothermal conditions in a micro-fluidized bed reactor. The results showed that the presence of Cu and Zn evidently influenced the release characteristics and conversion of the gas components. The impregnated Cu promoted the conversion of H2, CH4, CO and CO2, while Zn showed positive catalytic effect on the conversion of H2, CH4 and CO2 and negative effect on the conversion of CO. The X-ray diffraction patterns of the residue chars revealed that metallic copper nanoparticles (Cu0) were formed during Cu impregnated biomass pyrolysis. Textural characterization and SEM images showed that the impregnation of Cu and Zn, particularly Zn, promoted the generation of micropores and mesopores, with the pore sizes predominantly at around 1.3 nm and 3.9 nm. Reaction kinetics for generating these gases was studied based on model fitting method, and the most probable reaction mechanism was obtained based on the relative error between experimental and calculated conversion data. The resulting apparent activation energies were 85.08, 12.56, 49.72 and 38.37 kJ/mol for the formation of H2, CO, CH4 and CO2 from pure RH pyrolysis. The presence of Cu decreased the forming activation energies of the four gases, and Zn decrease the forming activation energies of H2, CH4 and CO2 while increased the value for the formation of CO.

Solar steam generation systems have drawn widely interest for water purification to solve the fresh water shortage recently. In this work, a typical bi-layer system was prepared by daubing carbon particles on the air-laid paper (C-paper). The effects of the thickness of the air-laid paper film and the carbon particle concentration on the evaporation rate were investigated. Results turn out that: with the increase of the layers of papers, the evaporation rate increases initially until the paper film reaches a thickness of nine layers, and then saturates to a constant value. The thickness of nine layers of air-laid papers is optimum for enhancing the evaporation rate when more layers of papers could not further increase the evaporation rate. With the increase of the concentration of the carbon particles, the evaporation rate also initially increases rapidly and then gradually tends to a constant value, due to both of the limited ability of vapor passing through the top layer and the reduced light absorption capability of carbon particles induced by the stack of carbon particles. Applying the optimum thickness of the paper film and the optimum concentration of carbon particles in our C-paper system, the evaporation rate and the evaporation efficiency under a solar power illumination of 1 kW·m−2 can be respectively 0.964 kg·m−2·h−1 and 70%, which are close to the ones of the home-made CNT-paper and GO-paper systems. The C-paper is an excellent candidate for solar steam generation applications, thanks to its easy preparation, high efficiency and low cost.

The work aims to investigate an effective method of catalytic reforming of tar during biomass high-temperature pyrolysis using rice husk char (RHC) and metal impregnated (Fe, Cu and K) char in a dual-stage reactor. The char and char-supported catalysts exhibited high catalytic performance, in terms of the high tar conversion efficiencies of 77.1% for RHC, 82.7% for K-RHC, 92.6% for Fe-RHC and 90.6% for Cu-RHC at 800 °C. Moreover, K-RHC and Cu-RHC catalysts after three cycles still exhibited high activity for tar removal. The catalytic tar conversion by char or char-supported catalysts contributes to improving the yield of syngas, particularly the combustible gases of H2, CO and CH4, corresponding to the syngas yield increasing from 196.6 mL/g for thermal reforming to 269.6 mL/g for K-RHC, 274.9 mL/g for Cu-RHC and 342.7 mL/g for Fe-RHC at 800 °C, respectively. The results from GC–MS analysis illustrated that the addition of char and char-supported catalysts promoted the transformation of larger polycyclic aromatic hydrocarbons into lighter tar compounds, leading to an increase in the proportion of single-ring tars. XRD results indicated that the most active phases of the fresh K-RHC, Cu-RHC and Fe-RHC for tar cracking and reforming were KCl, Cu and Fe, respectively. Textural characterization showed the addition of Fe and Cu was in favor of producing highly porous carbon materials and led to the increase in specific surface area and total pore volume.

The chemical bonding is usually not avoidable at a welding or fusion interface and sometimes is desirable to enhance the mechanical strength, while it might strongly affect the thermal contact resistance which plays a critical role in hindering heat dissipation of electronic devices. In this paper, we employ a non-equilibrium molecular dynamics method to study the effect of chemical bonding on the thermal contact resistance. Results show that the chemical bonding can greatly affect the thermal contact resistance. With the increase of the chemical bonding ratios, the thermal contact resistance firstly drops dramatically until arrives at a bonding ratio of about 20% where the thermal contact resistance is only about 15% that with a bonding ratio of 0%, and then gradually decreases to 0. Analyzing the spectral energy density of phonons at the interface, we conclude that the increase of the phonon velocity should be responsible for the decrease of the thermal contact resistance. By simulating the thermal contact resistance of silica with different morphologies (crystalline or amorphous silica), we found that different morphologies could lead to different thermal contact resistances, although this difference is less than 6%. This study is expected to provide references for managing thermal transport at a welding or fusion interface.

The solid-liquid phase change process is important to phase change material (PCM). In this paper, in order to investigate the solid-liquid phase change process in a spherical capsule, the axisymmetric lattice Boltzmann (LB) for phase change is proposed firstly. The problems of one-region phase change in cylindrical coordinate system and solid-liquid phase change by convection in cylindrical enclosure have been solved to verify the present LB model. The distributions of outer wall temperature of spherical capsule are linear. The results show that more heat transferred through the upper region of outer wall may enhance the natural convection and accelerate the process of heat transfer. However, the ratio of energy consumed by latent heat decreases with the slope, leading to more non-uniform temperature distribution. Furthermore, when the slope is larger than 0.2547, more heat is applied to rise the temperature of PCM, resulting in the slower melting rate.

The performance and life span of the power battery are limited by its operating temperature, hence the battery thermal management (BTM) is a key technology for electric vehicle. In this study, a novel BTM system based on composite phase change materials (C-PCM) with aluminum boxes is developed. The temperature control performance of the system is tested at different discharge rates (1C, 2C) at different ambient temperature (0 °C, 10 °C, 20 °C and 30 °C). The results show that the C-PCM can significantly reduce the average temperature and improve the temperature uniformity of the lithium ion battery pack. Furthermore, the performance of the C-PCM for the thermal control starts to deteriorate after completely melting, therefore an accurate dosage estimation of the C-PCM is a key problem for its application.

The phase change material (PCM) receives more and more attention on account of the large amount of heat absorption and release during the process of phase change. In order to further investigate the heat transfer behavior of phase change, a discrete unified gas kinetic scheme (DUGKS) derived from Boltzmann equation for solid-liquid phase change has been developed in this paper. The phase change problems, including the phase change by conduction and by convection, are solved to verify the present DUGKS. The results of DUGKS agree well with that of analytical solution or benchmark solution. In the simulations of natural convection with phase change, the non-uniform mesh has been considered to evaluate the performance of DUGKS. Besides, no phase interface effect, with which the temperature is lower than the initial one in lattice Boltzmann (LB) method, is obtained in present DUGKS.

Fuel cell polymer membrane as the core of the proton exchange membrane fuel cell (PEMFC) plays an important role in maintaining high intrinsic proton conductivity and insulating electrode. To investigate the effect of crosslinking formation on proton conduction, the proton mobility and ion conduction were calculated and analyzed by using molecular dynamics (MD) simulation. As the crosslinking number increased, the proton diffusion coefficients increased at first and then decreased. The results indicated that the formation of crosslinked bonds was beneficial for opening new channels to enhance the proton conductivity. But too many crosslinking also can decrease proton diffusivity due to the blocking along the chain backbone. Besides, the proton conduction was better at 350 K than at 300 K. It can be concluded that temperature also had a significant impact on diffusivity and conductivity.

Stable TiO2-water nanofluids are prepared by a two-step method, and the morphologies of nanoparticles and the stability of nanofluids are investigated. The heat transfer and flow characteristics of nanofluids flowing through a horizontal circular tube and a horizontal elliptical tube are experimentally investigated. The effects of nanoparticle mass fractions (φ = 0.1 wt%, φ = 0.3 wt%, φ = 0.5 wt%) and Reynolds numbers ( Re = 5000 - 15 , 275 ) on the Nusselt number and flow frictional resistance coefficient are discussed. In addition, computational formulas for heat transfer and flow performances are put forward based on the experimental data using the polynomial fit technique. Also, thermo-hydraulic comprehensive performances of nanofluids in the horizontal circular tube and the horizontal elliptical tube are studied.

Latent functional thermal fluid (LFTF) has a higher heat capacity compared with traditional fluid. In this paper, microencapsulated phase change material (MicroPCM) slurry as LFTF, which was composed of water/ethanol as base fluid and parafin/melaine resin MicroPCM as additive, was prepared. The physical and thermal properties of the slurry with different MicroPCM mass fractions had been studied. In addition, the heat transfer performance of base fluid and MicroPCM slurry in a horizontal circular tube had been experimentally investigated. The results showed that the convective heat transfer coefficients of MicroPCM slurry were about 2 times and 3 times higher than that of base fluid when the mass fractions of MicroPCM were 5% and 10%, respectively. This indicated that the MicroPCM had great potential applications in heat transport and thermal energy storage.

Stable Al2O3-water and TiO2-water nanofluids are prepared, and the morphology of nanoparticles and the stability of nanofluids are analyzed. An experimental set for heat transfer characteristics of CPU cooled by nanofluids is established in this paper. The heat transfer and flow characteristics of nanofluids in the CPU heat sink are experimentally studied. The effects of nanoparticle mass fractions (Al2O3-water: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5% and 2%; TiO2-water: 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 1%) and Reynolds numbers (Re: 146, 275, 406, 479, 541, 593, 707 and 812) on the heat transfer and flow characteristics are discussed. In addition, the comprehensive evaluation for thermo-hydraulic performance of nanofluids is investigated. It is found that the nanofluids with the highest nanoparticle mass fraction have not the best heat transfer performance, and Nusselt number firstly increases and then decreases with nanoparticle mass fraction, and the critical nanoparticle mass fractions for the best heat transfer performance of Al2O3-water and TiO2-water nanofluids are ω = 1.0% and ω = 0.4% respectively. It is also found that Al2O3-water and TiO2-water nanofluids can reduce the temperature of CPU by 23.2% and 14.9% at best compared with water respectively.

The phase change material (PCM) can be used in thermal energy storage (TES) with large latent heat. However, due to the heat accumulation in the upper region, the solid-liquid phase change process will be slowed down. In this paper, in order to enhance the heat transfer of nanoparticle-enhanced PCM (NEPCM) in TES, a separate plate is applied to weaken the heat accumulation. The phase change multiple-relaxation-times lattice Boltzmann (MRT-LB) model is employed to solve the numerical problem and the effects of separate plate location, nanoparticle volume fraction and Rayleigh number are investigated. The results show that for all the Rayleigh numbers and volume fractions, the NEPCM of the case that separate plate is located in the middle of cavity melts fastest. Furthermore, the separate plate can reduce the temperature standard deviation. However, when the location of separate plate is less than 0.3, the melting process is slowed down, resulted from the heat accumulation near the separate plate.

Flow resistance and enhanced heat transfer characteristics of TiO2-water nanofluids in a stainless-steel corrugated tube and a circular tube are investigated by experimental and numerical methods respectively. The flow and heat transfer characteristics of TiO2-water nanofluids and deionized water in test tubes are compared in this paper. In addition, effects of Reynolds number (Re) and nanoparticle mass fraction (ω) on flow and heat transfer performances are discussed respectively, and Nusselt number (Nu) and resistance coefficient (f) are studied respectively. Finally, comprehensive performance of flow resistance and heat transfer enhancement is evaluated. It can be obtained that adding nanoparticle into deionized water doesn’t cause a large additional resistance loss in some degree, while the combination of corrugated tube and TiO2-water nanofluids shows an excellent heat transfer enhancement, which can enhance the heat transfer by 53.95% at maximum extent. In addition, the corrugated tube has a strong sustainability in enhancing heat transfer. The enhanced heat transfer rising part (6000 ≤ Re ≤ 10,000) has a large rising slope (about 7.90E−5), and the descending slope (about 7.16E−6) of enhanced heat transfer part (10,000 ≤ Re ≤ 12,000) is small.

An experimentally investigation on the effect of heating powers, layer number, operating orientations and filling ratios on three-dimensional oscillating heat pipe (3D-OHP) was studied in detail. Each layer of 3D-OHPs had the similar shape of single layer OHP with 90 mm wide, 150 mm high and 2turns. The distance between adjacent tubes and adjacent layers were both 26 mm. The thermal performance was studied by testing the start-up power, temperature and thermal resistance. Another 2D-OHP with same turns and similar geometry size as 3D-OHP was also tested to compare the difference between two OHPs. The results showed that the 4 layers 3D-OHP had the smallest start-up power and temperature among single layer to 5 layers 3D-OHPs under the similar heating powers both vertically and horizontally placed. It also had the smallest thermal resistance after start-up, which indicated that 4 layers 3D-OHP had the best thermal performance under the similar working conditions among 3D-OHPs. The 4 layers 3D-OHP with 50% filling ratio had the lowest start-up power and temperature and good heat transfer ability both vertically and horizontally placed. Compared with 2D-OHP, the thermal resistance of 3D-OHP was lower under high heating power in horizontal orientation. In general, the 3D-OHP had its unique advantages because of its multi-layer structure.

Latent heat storage using metals as solid-liquid phase change materials (PCMs) have been concerned for medium-temperature thermal energy storage. However, due to the leakage and corrosion problems during phase transformation, the use of metallic PCMs are greatly limited. Encapsulation of PCM microparticles to form microencapsulated PCMs (MEPCMs) is an effective strategy, which is unfortunately technologically difficult for metallic PCMs. In this study, we develop metallic Sn MEPCMs coated by a stable SnO2 shell through a facile self-oxidation method. Sn@SnO2 core-shell MEPCMs are fabricated by two steps: firstly, Sn microspheres are pre-treated by vapor or water to form an oxide precursor shell on Sn microspheres; secondly, heat oxidation treatment under O2 atmosphere is conducted to form a stable SnO2 shell. The Sn@SnO2 microcapsules exhibit a melting point of ~232 °C and latent heat of ~53 J/g. Importantly, the capsules present an excellent thermal cycling stability, in which after 100 cycles of melting-freezing the phase change properties and core-shell structure could be well retained. These results reinforce the promising application of microencapsulated Sn in medium-temperature thermal storage.

In this paper, the thiol-modified paraffin/silica microencapsulated phase change materials (MEPCM) was synthesized using tetraethoxysilane (TEOS) and (3-mercaptopropyl)-trimethoxysilane (MPTMS) by interfacial co-hydrolysis and co-polycondensation as the aim of improving the thermal stability and suspension stability. The effect of MPTMS was analyzed by SEM, TEM, FT-IR, DSC, TGA, the leakage test and gravity sedimentation test. The most satisfied sample (S3) showed a high thermal storage density of 125.82 J/g, along with an encapsulation efficiency of 65.74%. It also appeared excellent thermal stability after 1000 cycles with 94.11% latent enthalpy remained and kept 99.48% mass after heating at 80 °C more than 150 min. Beneficial from the hydrophobicity regulation by the thiol functional group, the MEPCM exhibited the good suspension stability for 14 days without any surfactant. The modified MEPCM was used to prepare latent functionally thermal fluids (LFTF), which presented 41% improvement of the heat transfer performance when 2wt% MEPCM was added. In addition, a layer of copper nanoparticles was successfully synthesized on the surface of MEPCM for the thermal conductivity enhancement. Therefore, the modified MEPCM provided a new sight on the interfacial modification of MEPCM and has a significant potential for new type thermal fluids.

Owing to their high theoretical capacity, energy density, good environmental protection, and low cost, lithium-sulfur batteries are regarded as extremely promising next-generation energy storage equipment for electrical and portable devices. However, their practical application is mainly hindered by the polysulfide shuttle and the slow redox kinetic in the electrochemical process. In this study, we prepared FeWO4 nanorods by a simple hydrothermal method to enhance the electrochemical performance of lithium-sulfur batteries. The FeWO4 nanorods act as catchers and electrocatalyst for polysulfide in lithium sulfur batteries. These FeWO4 nanorods could efficiently adsorb polysulfide and enhance the conduction of Li ions, leading to inhibition of the polysulfide shuttle effect and enhancement of the electrochemical reaction kinetic for cycling stability and rate performance. Density functional theory calculation shows the existence of the high binding energy between FeWO4 nanorods and polysulfide, which can limit polysulfide to the surface of FeWO4 nanorods. Therefore, the Li-S batteries with FeWO4 nanorods not only provide an initial discharge capacity of 1318 mAh g−1 at the current of 0.8 mA with high coulombic efficiency of 97%, but also shows a capacity decay rate of 0.07% during 600 cycles at a current of 3.2 mA. With the above-mentioned dates, this work offers a promising new strategy to regulate the kinetic behaviors of polysulfide for high-performance Li-S batteries.

Fluidized bed technology plays a vital role in petrochemistry and coal separation. To enhance fluidization stability, the flow is periodically introduced into the gas–solid fluidized bed to form a pulsed gas–solid fluidized bed (PGFD). As the main fluidization parameter, the minimum fluidization velocity (umf) can reflect the change of the critical state of particles in the PGFD, directly affecting the study of two-phase distribution in the bed. Due to lack of theoretical study on umf in PGFD, the work proposed a novel method to predict umf combined with soft sphere model. Meanwhile, the spring-damping model (SDM) and the resonance force model (RFM) were developed under the action of pulsating airflow. A theoretical model of umf was then derived for PGFD based on experimental stress analysis of particles. The error of the new model is small, which is in good agreement with the data in the existing literature and present work.

Regardless of the high latent heat of organic phase change materials (PCMs) for thermal energy storage, their intrinsically low thermal conductivity has constrained their wide application. In order to improve the thermal conductivity of paraffin PCM, porous copper foams as supporting frameworks are fabricated by a simple solution combustion synthesis (SCS), using copper nitrate as oxidizer and starch as fuel. The SCS is conducted under inert atmosphere and the efficient exothermic reaction occurs at around 100 °C. At an optimal oxidant-fuel condition of 4.43 g copper nitrate to 2 g starch, a good porous copper scaffold is prepared, which is further shaped and sintered to form robust copper foams. Paraffin is infiltrated into the copper foams to form PCM composites and the thermophysical properties are analyzed. Due to the continuous copper skeleton as heat transfer path, the thermal conductivity of the composite is improved to 3.29 W m−1 K−1 from 0.25 W m−1 K−1 of pure paraffin. The enhanced heat transfer properties of PCM composites as-supported by the facilely SCS-derived copper foams can reinforce the application in solar thermal harvesting and thermal management.

With the development of applications in the sub-zero temperature region, the high performance heat transfer element, heat pipe is expected to play an important role in this field. However, suitable working fluid for low temperature heat pipe is limited, the two commonly used substances, Freon and ammonia are environmentally harmful. In contrast, carbon dioxide (CO2) is an environmentally friendly gas and can be a promising candidate working fluid for low temperature heat pipe because of its suitable thermal properties. At present, CO2 heat pipes are seldom investigated and used in the sub-zero temperature region. So, the heat transfer performance of CO2 heat pipe is experimentally investigated, and influences of heat loads, filling ratios, condenser conditions (temperature, length, and position) are investigated. The results show that the performance of CO2 heat pipe is satisfactory, its thermal resistance can be 0.2–0.4K/W and its equivalent thermal conductivity can be 3.7 × 104 W/(m•K). Besides, the performance of R134a heat pipe is investigated as a control group, it is found that its thermal resistance is 2–5 times that of CO2 heat pipe in sub-zero temperature region. The results illustrate that the CO2 heat pipe has a good application prospect in the field of low temperature range from -50 °C to 0 °C.

The hybrids of hexagonal boron nitride and graphene have drawn great attentions recently, owing to their many desirable electronic properties, such as a layer-dependent direct bandgap and high carrier mobility. However, the thermal transport properties of them are less investigated and almost unknown. Herein, we implement molecular dynamics simulation to study the thermal transport in one of these hybrids, BC 2 N at the first time, including size, temperature and strain effects on the thermal conductivity of BC 2 N monolayer. We found that BC 2 N owns a strong anisotropy of in-plane thermal transport and the in-plane phonon modes dominate the heat transport, contributing more than 80% in the unstrained BC 2 N monolayer at room temperature. Furthermore, for some two-dimensional materials like silicene, the buckled structure is considered as the main reason for the enhanced thermal conductivity resulted from the tensile strain; however, as a planar two-dimensional material without the buckled structure, the enhancement of thermal conductivity of BC 2 N is also observed when applying a small tensile strain, which is very interesting and suggests that the buckled structure is not the only mechanism for the tensile strain induced thermal conductivity enhancement. Our findings supplement the influence of strain on phonon transport at nanoscale, and show the BC 2 N as a competent candidate for energy devices and electronic thermal management.

In this paper, a novel liquid cooling based thermal management system for the cylindrical lithium-ion battery module with variable contact surface is designed. Contact surface size is determined by aluminum block length. The cooling system relies on aluminum block which can effectively transfer heat from battery to cooling water. A battery module with six cells along flow channel is chosen to study the effects of aluminum block length and velocity on the thermal performance in the way of simulation. Three change types of contact surface are studied and their performance are compared with the system with constant contact surface at different inlet velocities. The results indicated that the system with variable contact surface is superior to the system with constant contact surface. It can significantly improve temperature uniformity. When inlet velocity is 0.05 m/s, the maximum temperature can decrease to the same value and temperature difference decreases by 6%, 14% and 28%. Finally, an optimal design is presented with system weight, pump power consumption and cooling performance taken into consideration.

An experimental investigation on the effect of cooling air velocities, operating orientations and heat inputs on a three-dimensional oscillating heat pipe (3D-OHP) was studied seriously. The 3D-OHP had dimensions of 90 mm × 61 mm × 150 mm, 6 total turns, 3 layers along width direction and 4 layers along length direction. Unlike traditional OHP designs, this new three-dimensional multi-layer design allows for different working conditions in thermal management such as multi-heat source cooling and higher heating fluxes cooling. The thermal performance of the 3D-OHP was studied by testing temperature variation measured at various heat inputs under different cooling air velocities and operating orientations. The results indicated both the cooling air velocities and operating orientation significantly affect the start-up, oscillation and dry-out of the 3D-OHP. The start-up temperature decreased and the dry-out limit increased with the increase of cooling air velocities and the decrease of the operating angle. Difference of thermal resistance in each layer along different directions was also calculated. It was found that only operating orientation had remarkable influence on thermal resistance of different layers along length direction. The difference between the thermal resistance of the skin layer and the inner layer increased with the decrease of operating angle.

Enhancement of the thermal conductivity of composite materials has become more and more common in heat exchangers by applying artificially designed fillers. In this paper, the effective thermal conductivity of composite materials is investigated based on an extensive numerical study. The effective thermal conductivity of composite materials packing with different shapes of fillers are compared under the same volume fraction, thermal conductivity ratio and the thermal conduct resistance. The results indicate that the effective thermal conductivity of composite materials decreases as the thermal conduct resistance increases and the decline ratio will gradually slow down. Different shapes of fillers have different sensitivity degree on the thermal conduct resistance. Composite materials packing with the fillers which provide a longer path for the heat flow have a higher effective thermal conductivity than other types of fillers. A series of new generalized correlations is proposed by using the method of nonlinear regression. These new generalized correlations can be used at a wide range of thermal conductivity ratio ( 1 ⩽ κ ⩽ 1000 ) , thermal conductivity resistance ( 0 R c ∗ ⩽ 1 ) and volume fraction ( 0 φ ⩽ 0.2 ) .

The maximization of oscillating heat pipe (OHP) has important significance on OHP based large-scale thermal energy storage (TES) system. In order to understand the thermal performance of OHP with long heat-transport distance for thermal energy storage (TES) application, a large-OHP testing platform was constructed. The influence of working medium type, heating load, cooling condition on the thermal efficiency, thermal resistance and effective thermal conductivity of OHP were investigated and analyzed. The results mainly showed that the OHP with self-rewetting fluid (SRWF) has greater heat transfer limit and can work normally under larger heating load compared to that with water or ethanol as working medium. The OHP with filling ratio (FR) of 40–80% can endure higher heating load compared to the case of FR = 30%. It can be concluded that the best FR is about 40% under large heat load (the effective thermal conductivity reaches 5676 W m−1 °C−1 at 700 W). The SRWF based OHP with long heat-transport distance in this paper has lower thermal resistance and larger heat density compared to those of some other research groups.

Fuel cell polymer membranes such as the Dow, Nafion and Aciplex membranes as the core of the proton exchange membrane fuel cell (PEMFC) play an important role in maintaining high intrinsic proton conductivity. For investigating the dynamic properties and thermal properties of fuel cell polymer membranes, the proton mobility and thermal conductivities of the Dow, Nafion and Aciplex membranes were calculated by using molecular dynamics (MD) simulations. Compared with the Dow and the Nafion membranes, the Aciplex membrane presented a better mobility of water molecules and hydronium ions at 350 K and it showed a better thermal property due to its side chain is long enough to form a “highway” of heat conduction. The results indicated that both the structure of side chain and temperature have effect on the dynamic properties and thermal properties of fuel cell polymer membranes.

The battery thermal management technology is vital for the development of new energy vehicles. In order to understand the performance of the phase change material/heat pipes (PCM/HP) coupled thermal management system for cylindrical power battery, an PCM/HP coupled BTM module was designed and tested experimentally in detail. The results showed that the effect of temperature control based on PCM is improved comparing to air-based BTM under natural convection. The maximum temperature of PCM/HP coupled BTM can be controlled below 50 °C for longer time than those of the air-based case and PCM-based case under the same conditions. The temperature difference can be reduced about 33.6% through filling PCM and it can progress a decline of 28.9% further through embedding HP into the PCM. The maximum temperature difference of PCM/HP coupled BTM can be controlled below 5 °C for longer time than those of the two other cases, air-based BTM and PCM-based BTM. It is almost the same in the first 620 s under different velocities, which are all less than 5 °C.

With the development of electric vehicles (EV), battery thermal management (BTM) has become more and more significant to maintain the temperature of batteries. For the purpose of improving cooling performance of BTM, a lattice Boltzmann (LB) model for Cu-water nanofluid based BTM is applied to simulate the natural convection. In order to ensure the accuracy of the numerical model, a validation has been implemented by solving a problem of a hollow cylinder with a uniformly distributed heat boundary. The investigations for nanofluid volume fraction of 0–6% and Rayleigh number of 10 3 –10 6 have been conducted. The results showed that adding Cu nanoparticles can enhance the cooling performance and decrease the temperature difference of BTM. When Rayleigh number is 3 × 10 5 , the maximum temperature can be reduced by 6.5% with 6 vol.% nanofluid. Moreover, the intensity of heat transfer was increased prominently by enhanced natural convection when Rayleigh number varies from 10 4 to 10 6 .