Latent Heat Of Fusion Research Articles

An experimental investigation on coalescing the potentiality of PCM, fins and water to achieve sturdy cooling effect on PV panels

Improving the efficiency of silicon photovoltaic (PV) panels is of utmost importance to achieve Sustainable Development Goal 7. The energy loss aided by the heat generation of PV panel is the leading cause of the degradation of PV panels' efficiency as well as its longevity. A novel cooling system with PCM, fins and still water is propounded in this research as a solution. The proposed configuration utilizes the latent heat of fusion of PCM and the latent heat of evaporation of water to achieve effective cooling in a passive approach. HS 29 PCM is chosen in context with the location and system thermal characteristics. The results highlight that the per day output of the proposed configuration is 8.12% and 9.39% higher than the PV panel without cooling for the observed two selected days respectively. The maximum power enhancement was 20.25% and on average 8.57% improvement is obtained relative to reference PV. The thermal characteristics revealed that the temperature of the cooled panel was below 50 °C while the PV panel without cooling reached about 73 °C. The average and maximum temperature drops are observed to be 10.14 °C and 16.7 °C respectively. The maximum enhancement in power conversion efficiency was 20.13% when compared to the uncooled PV panel. Furthermore, corrosion analysis and thermal stress assessment are performed to ensure the longevity of the system. The energy saving is scaled to a 1 MW large-scale PV system and the results show ∼367 MWh of annual energy savings and ∼ 2 ktoe of reduction in CO2 emissions. The inclusion of a cooling strategy significantly improves the performance of the PV panel and contributes further in attaining SDG 7.

Development of highly stable n-Heptadecane/water-based phase change emulsion with mixed surfactant for thermal management applications

Phase change material (PCM) emulsions have grown in popularity due to their versatility and various thermal management applications. Therefore, new PCM materials and emulsion compositions have been investigated to enhance their functionality and widen their range of applications. In the present work, PCM emulsion was formulated using n-heptadecane as a dispersed phase, DI-water as base fluid, and sodium dodecyl sulfate and Brij30 as surfactant. The effect of mixed surfactants on the stability and other thermophysical properties of the PCM emulsions were investigated. The emulsions with mixed surfactants show excellent stability when compared to single surfactants. The average droplet size of the PCM emulsion was 102.8 nm with a phase change temperature and latent heat of fusion of 18.9 °C and 14.17 Jg−1, respectively, for 10 wt% PCM concentration. The thermal conductivity was decreased by about 16.4 %, and the viscosity increased by nearly 128 % when compared with DI-water for the 10 wt% dispersed phase emulsion with mixed surfactants. The gravimetric and structural studies confirm the stability of dispersed phase and base fluid in the presence of surfactant. Overall, it can be concluded that the PCM emulsion with mixed surfactant can be a potential heat transfer medium with improved heat storage and transportation capacity.

The potential of arc-shaped fins for expedited solidification in triplex-tube latent heat storage: Parametric investigation

Phase change materials (PCMs) enable efficient thermal energy storage (TES) but suffer from poor thermal response. This study introduces and optimizes a novel arc-shaped fin configuration to improve heat recovery during PCM solidification in a horizontal triplex-tube TES unit. The effects of fin base length and inter-fin angle on solidification time, temperature distribution, and heat recovery rate are systematically analyzed. An asymmetric base length of 15 mm for internal fins and 10 mm for external fins substantially expedites solidification. This is attributed to enhanced heat conduction from the larger surface area of longer internal fins and increased natural convection from reduced external fin blockage. Furthermore, compact 0° inter-fin angles create extensive fin-free zones that encourage convection. The optimized arc-shaped fins reduce solidification time by about 75 % and elevate heat recovery rate by 284 % versus no fins. They also significantly outperform conventional longitudinal fins, which only achieved 47 % faster solidification and 80 % greater heat recovery over no fins. This highlights the profoundly favorable solidification enhancement and temperature uniformity offered by properly designed arc-shaped fins.

Novel protic ionic liquids-based phase change materials for high performance thermal energy storage systems

Phase change materials (PCMs) are an important class of innovative materials that considerably contribute to the effective use and conservation of solar energy and wasted heat in thermal energy storage systems (TES). The performance of TES can be improved by using environmentally friendly PCMs called ionic liquids (ILs) based on ethanolamines and fatty acids. The 2-hydroxyethylammonium, bis(2-hydroxyethyl)ammonium, and tris(2-hydroxyethyl)ammonium palmitate ILs, which function is in the temperature range of 30–100 °C and provide a safe and affordable capacity, are introduced in this study for the first time as PCMs. PCMs' chemical composition and microstructure were examined using fourier transformation infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), respectively. DSC was used to evaluate the ILs' latent heat of fusion and specific heat capacity, while TGA was used to establish their thermal stability. Finally, a home-made device with a PCMs (synthesized ILs) container cell and a commercial thermoelectric generator device to record the real-time voltage (V) was used to convert thermal energy into electrical energy.

Reduction of heat load in an air-conditioned bus employing phase change material integrated glass window and roof: A coupled numerical and analytical approach

The study aims to analyze the heat load in an air-conditioned bus cabin by attaching a layer of phase change material to its roof and window glass. Enthalpy equation coupled with momentum and continuity equations has been solved in PCM layer, whereas only the diffusion equation is solved in roof and glass to obtain the spatiotemporal distribution of the temperature. A significant reduction in temperature on the inner and outer surfaces of the glass window and roof is noticed when PCM is attached. The inner surface of the glass shows a temperature reduction from 310 K to 301.5 K at 2.00 P.M, whereas the roof reveals a significant decrease of 14 K temperature when PCM is glued underneath. PCM helps keep the temperature at the inner surface under 302 K up to 12.00 pm However, the temperature rises to 308 K when PCM is not attached. The PCM thickness has a significant impact on temperature. An increase in thickness from 6 mm to 12 mm leads to a temperature reduction of 3 K to 4 K. Focusing on the performance of PCM, Na2SO4.10 H2O as a PCM is found to be beneficial since the phase change process (liquid fraction between 0 and 1) exists for a longer duration due to its high latent heat of fusion. The reduction in temperature using PCM is implicitly reflected in curtailing the total heat load in the cabin. Approximately 5 kW (45%) reduction in total heat load has been achieved using a 12 mm PCM layer on glass and roof during the peak time of solar radiation, substantially saving fuel and battery energy.

Enhancing Optimal Thermal Energy Storage in Solar Parabolic Concentrator System by Using Phase Change Material

Abstract: Solar Parabolic Trough Systems (PTS) are highly efficient solar thermal technologies for converting concentrated solar radiation into thermal energy. However, their intermittent energy production, primarily due to variations in solar availability, underscores the necessity for effective thermal energy storage (TES) solutions. Phase Change Materials (PCMs) have emerged as a promising means to store and release thermal energy efficiently. This study focuses on the critical task of optimizing PCM properties to enhance thermal energy storage within Solar Parabolic Trough Systems. The selection and fine-tuning of PCM properties are paramount to achieving superior TES performance. Parameters under scrutiny include the melting temperature, latent heat of fusion, thermal conductivity, and cost-effectiveness. Each of these factors plays a pivotal role in the overall efficiency and economic viability of PCM-based TES systems integrated with PTS. Through a thorough review of existing research and recent advancements in the field, this study sheds light on the profound impact of tailored PCM properties. It demonstrates how optimizing these properties can lead to substantial improvements in energy storage capacity, system efficiency, and overall cost-effectiveness. Such optimizations are crucial not only for enhancing the competitiveness of solar thermal technology but also for promoting sustainable energy utilization.

Optimization of PCM Properties for Thermal Energy Storage in Solar Parabolic Trough Systems: A Review

Abstract: Solar Parabolic Trough Systems (PTS) are highly efficient solar thermal technologies for converting concentrated solar radiation into thermal energy. However, their intermittent energy production, primarily due to variations in solar availability, underscores the necessity for effective thermal energy storage (TES) solutions. Phase Change Materials (PCMs) have emerged as a promising means to store and release thermal energy efficiently. This study focuses on the critical task of optimizing PCM properties to enhance thermal energy storage within Solar Parabolic Trough Systems. The selection and fine-tuning of PCM properties are paramount to achieving superior TES performance. Parameters under scrutiny include the melting temperature, latent heat of fusion, thermal conductivity, and cost-effectiveness. Each of these factors plays a pivotal role in the overall efficiency and economic viability of PCM-based TES systems integrated with PTS. Through a thorough review of existing research and recent advancements in the field, this study sheds light on the profound impact of tailored PCM properties. It demonstrates how optimizing these properties can lead to substantial improvements in energy storage capacity, system efficiency, and overall cost-effectiveness. Such optimizations are crucial not only for enhancing the competitiveness of solar thermal technology but also for promoting sustainable energy utilization. The investigation presented herein underscores the significance of PCM property optimization as a strategic pathway toward advancing solar thermal technology. By maximizing energy storage capacity, minimizing thermal losses, and optimizing cost factors, we can unlock the full potential of PTS, making them more reliable and accessible for meeting the world's growing energy demands. This research serves as a valuable resource for engineers, researchers, and stakeholders working towards the integration of PCM-based TES with solar thermal systems. Ultimately, it contributes to the realization of a cleaner, more sustainable energy future, addressing the urgent need to reduce greenhouse gas emissions and our reliance on non-renewable energy sources

Study on Mushy Zone Coefficient in Solidification Heat Transfer Mathematical Model of Thin Slab with High Casting Speed

When the casting speed of the thin slab continuous caster is increased, the ratios of the solid and liquid phases in the solidification front of the molten steel in the mold change, which affects the thickness of the solidified shell. In order to accurately calculate the thickness of the solidified shell and determine the value range of the mushy zone coefficient suitable for the mathematical model of solidification heat transfer at high casting speed, this paper established the solidification heat transfer mathematical model in thin slab funnel mold, and the influence of different mushy zone coefficients on the accuracy of solidification heat transfer mathematical model was analyzed and compared with the actual solidified shell thickness. The results showed that, when the casting speed was increased to 4~6 m/min and the coefficient of the mush zone coefficient was 3 × 108~9 × 108 kg/(m3⋅s), the thickness of solidified shell calculated by the solidification heat transfer model was in good agreement with that measured in practice. The research in this paper provides an important reference for the establishment of the solidification heat transfer mathematical model at high casting speed in the future.

Analysis of soil behavior under freezing and thawing conditions

Understanding of the thermal, hydraulic and mechanical behavior of soils under freezing and thawing is important in solving problems of permafrost engineering and artificial ground freezing. Accurate mathematical descriptions of heat and moisture transport and the associated mechanical deformations is critical for developing such understanding. Phase change and transition during freezing and thawing are characterized by a strong non-linearity due to the rapid variations of thermo-physical properties of the material and the release of the latent heat of solidification. Such processes cannot be easily and accurately modelled via the use of local (differential) formulations [1,2]. A non-local formulation, developed within the framework of peridynamics [3–5] is proposed here for ground freezing and thawing. It expands the domain of applicability of the first work on non-local modelling of heat transfer with water flow in saturated porous media [6] into modelling the thermo-hydro-mechanical behavior of unsaturated soils.
 The mathematical description of unsaturated soil behavior is based on three governing equations of conservations of water mass, energy and linear momentum, which are complemented by constitutive relationships that represent the change of soil properties.
 Using the local mathematical model of unsaturated soils [7,8], a peridynamics mathematical framework is formulated. Following [6], the bond-based peridynamics considers a soil body as a collection of particles, see Fig. 1 for the 1D case. The term `bond' refers to the interactions between two points, located at depths and . The point interacts with all other points within a certain finite region , called the horizon of z.
 The peridynamic form of the water mass conservation is:
 where is the water pressure head; is time; is the volumetric content of a soil component; is the density of a soil component; and is the vertical coordinate. The micro-diffusivity function can be defined following [9]. Here, the subscripts i, l, a and s refer to ice, liquid water, air and soil particles respectively.
 The peridynamic form of the energy conservation is:
 where is temperature; is the latent heat of water solidification; is the average thermal conductivity of soil; is the vector of water flux; is the average heat capacity of unsaturated soils and is the specific heat capacity of liquid water. Here, is a micro-conductivity function and is a micro-velocity function, for more details see [6,10].
 The peridynamic form of the linear momentum conservation is:
 where is the acceleration of the peridynamics particle ; is a pairwise force density vector between particles and that depends on its initial and deformed positions Z and Z’; is the horizon volume associated with the particle ; is the body force on the particle . The elastic stress-strain relation for unsaturated soils can be stated as:
 where is the stress increment tensor; is soil compressive modulus for unsaturated conditions, and is the strain increment tensor due to the elastic deformation of the soil matrix, that can be find from the relation for the total strain increment tensor of unsaturated soils . Here is the strain increment tensor corresponding to the change of soil volume due to the frost heave; and is the strain increment tensor corresponding to the plastic deformations of soils.
 The numerical implementation of the peridynamic formulation is verified by comparing the results of simulations with analytical solutions and the formulation is validated by comparing these results with experimental data under the condition of one-dimensional heat and water transfer obtained by laboratory experiments. In the experiments, soil cylinders were cooled from one surface by a source of negative temperature. As a result, the freezing front propagated along the cylinder. The temperature profile in the column was changing, and water migration was observed. The developed model is shown to predict the results of these experiments well.
 The proposed peridynamic model is the first to combine the flow of liquid water with heat transfer and mechanical deformations in the presence of a change of the water phase state in unsaturated soils. It is demonstrated that for the soils with relatively high initial water content, the developed approach describes effectively the change of liquid water content and predict soil deformation. The set of integral-differential equations are solved by a simple numerical scheme.

Model of Fusion of Pure Metals

Abstract—There are model for calculating the latent heat of fusion of pure metals, included the contribution of the phonon “analogue of the Casimir force” to the melting of metals. The model makes it possible to explain the mismatch between the experimental value of the latent heat of melting and the theoretically calculated sum of the jump in the configuration and vibrational entropy during the phase transition from solid to liquid. The described approach also makes it possible to estimate the magnitude of the volume change during melting using the values of the crystallogeometric and thermodynamic parameters of the material.

Numerical Analysis of The Multilayer Structures Melting with Different Hole Network with Phase Change Material

Phase change materials (PCM) are used with different geometries to increase thermal performance. The thermal performance of the geometries on phase change materials have been investigated. For thermal energy storage systems (TES), porous structures are widely used to increase the thermal performance of the PCM. In addition, geometric parameters affect heat transfer, flow and melting solidification. In this work, the thermal performance of multilayer structures with different surface geometries and the control of the melt fraction of the PCM was investigated in terms of energy efficiency. The results were obtained by modeling the studies in the Computational Fluid Dynamics (CFD) program. The physical model was obtained by creating a multi-layer porous structure with different surface geometries in each layer thanks to the additive system. Modeling was carried out for natural convection depending on time. Paraffin was used as the PCM. The melting temperature of the paraffin used is 41 °C and the latent heat of fusion is 165 kJ/kg. In the present work, the distribution of melting isotherms gives more homogeneous results for the selected geometry. The results of PCM multilayer structure and other geometries were compared under the same conditions and it was seen that the multilayer structure improved the thermal performance. All melting graphs range from 0-1 (0: solid, 1: liquid). The results obtained for the selected geometry show that the melting value is between 0.8-0.9. In addition, the proposed physical model is a subject that can be encountered in engineering applications, thermal design engineering. In this respect, it is thought that the results obtained from the study, especially in the field of energy storage, will fill an important gap.

Enhancing the performance of composite phase change materials using novel triply periodic minimal surface structures

Organic phase change materials (PCMs) are widely used in thermal management applications owing to their high latent heats of fusion and low cost. Unfortunately, their poor thermal conductivities severely hamper the thermal transport process. Hence, PCMs are often hybridized with high thermal conductivity materials that promote phase change for time-sensitive applications and potentially increase the power density of thermal energy storage (TES) devices. Optimized thermally conductive networks with high-latent-heat PCM matrices are critical in the thermal management of high heat flux applications. With advancements in additive manufacturing, it has become easier to create complex topologies, such as triply periodic minimal surfaces (TPMS), that can further augment the performance of composite PCMs. TPMS surfaces have shown great promise in improving thermal transport performance but investigations into their thermal properties remain limited. In this study, the thermal performances of PCM infused TPMS structures of wall thicknesses varying from 0.4 mm to 0.8 mm were systematically investigated. The TPMS structures were designed using level-set equations, and each system of structures was fabricated by selective laser melting, a metal additive manufacturing technique. Numerical investigations were performed to understand the phase change dynamics of PCM in TPMS cells and experiments were performed to determine their thermal properties and phase change performance for thermal energy storage applications. Our simulations revealed that for structures with uniform wall thickness of 0.4 mm, the novel Neovius structure resulted in the highest effective thermal conductivity enhancement. For a given thickness, it is thus hypothesized that more complex TPMS topologies have higher surface areas and volumes which enhance their thermal conductivities. However, the complex shape of the Neovius structure could not be further uniformly thickened without self-intersecting geometries. Ultimately, a balance of both the surface area and thickness of the TPMS cell determines the thermal conductivity enhancement. Overall, the 0.6 mm thick IWP cells had the highest thermal conductivity of 13.84 W/m K, which was consistently verified in experiments. This is likely due to the fact that it has a larger surface area than the P structure but is also thicker than the 0.4 mm Neovius structure. To further demonstrate the potential application of our PCM-based TPMS design, low temperature thermal cycling tests were performed. Our results showed the IWP cell structure promoted a more uniform temperature distribution as compared to the P cell. Phase change in the 0.6 mm thick IWP cell structure was completed 1.4 times faster than the 0.8 mm thick P cell and 1.8 times faster than the 0.6 mm thick P cell. The purpose of this study is to provide useful guidelines for the selection of TPMS structures for various applications such as battery packs and spacecraft and to open doors for the co-optimization of materials and device geometry for enhanced energy and power density.

Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension

Abstract. Heterogeneous ice nucleation is thought to be the primary pathway for the formation of ice in mixed-phase clouds, with the number of active ice-nucleating particles (INPs) increasing rapidly with decreasing temperature. Here, molecular-dynamics simulations of heterogeneous ice nucleation demonstrate that the ice nucleation rate is also sensitive to pressure and that negative pressure within supercooled water shifts freezing temperatures to higher temperatures. Negative pressure, or tension, occurs naturally in water capillary bridges and pores and can also result from water agitation. Capillary bridge simulations presented in this study confirm that negative Laplace pressure within the water increases heterogeneous-freezing temperatures. The increase in freezing temperatures with negative pressure is approximately linear within the atmospherically relevant range of 1 to −1000 atm. An equation describing the slope depends on the latent heat of freezing and the molar volume difference between liquid water and ice. Results indicate that negative pressures of −500 atm, which correspond to nanometer-scale water surface curvatures, lead to a roughly 4 K increase in heterogeneous-freezing temperatures. In mixed-phase clouds, this would result in an increase of approximately 1 order of magnitude in active INP concentrations. The findings presented here indicate that any process leading to negative pressure in supercooled water may play a role in ice formation, consistent with experimental evidence of enhanced ice nucleation due to surface geometry or mechanical agitation of water droplets. This points towards the potential for dynamic processes such as contact nucleation and droplet collision or breakup to increase ice nucleation rates through pressure perturbations.

Cryo-powered desalination: Experimental investigations on brine droplets freezing in a natural convection environment

Freeze desalination (FD) is an energy-efficient desalination method that shows promise over traditional thermal-based approaches. FD requires minimal energy by utilizing latent heat of fusion during the phase transition of saltwater from liquid to solid state. However, the stochastic nature of nucleation and salt trapping in the formed ice has hindered industrial implementation. This study focuses on experimental investigations of ice nucleation during the freezing of brine droplets. The effects of droplet size (3–9 μL), salinity (0–70 g/L), and freezing temperature (−15 °C to −40 °C) on nucleation behavior are examined. Results showed that smaller droplets exhibit faster cooling rates, reduced supercooling degrees (SD) (12.00 to 9.81 °C), and quicker nucleation onset (117.95 to 72.7 s). Higher droplet salinity leads to decreased nucleation temperatures (from −13.89 to −15.32 °C) while lower freezing temperatures enhance cooling rates and reduce nucleation times (from 123.6 to 48.2 s). The analytical model has accurately predicted nucleation times and temperature evolution. Simulation results suggest that freezing at extremely low temperatures, i.e., −40 °C, yields to shorter nucleation time, i.e., 50 s for 5μL brine droplet. Varying initial temperatures (20–50 °C) showed faster precooling but delayed nucleation, while nucleation temperatures remain consistent. These insights contribute to optimizing FD for energy-efficient desalination.

Thermal behavior and morphology evolution of polyamide 12 in laser powder bed fusion process: Experimental characterization and numerical simulation

A particle scale numerical model of laser powder bed fusion (L-PBF) for semi-crystalline polymer PA12 is presented in this work. The model is developed by the finite element method under the framework of the level-set method. The asymmetrical and kinetical thermal behavior of semi-crystalline polymer is implemented in the thermal model, enabling better considering the latent heats during different phase transformation processes. Particle consolidation under laser irradiation is simulated by hydrodynamics. The physical properties of PA12 powder are identified by experiments regarding the inputs of the numerical model. Before performing L-PBF processing simulations, the numerical powder bed model, the implementation of crystallization kinetics, and the related hydrodynamic parameters are verified by comparing simple simulations with the experiments. The influence of phase transformation latent heat on the temperature calculation and the consequent melt pool profile is discussed in the single-track simulation: the peak temperature on the top surface of the substrate is significantly lower when properly considering the re-melting fusion latent heat with the modified crystallization kinetics. As a result, a shallower melt pool is obtained. The effect of processing parameters on the temperature field and shape of the melt pool is also modeled. This parametric study indicates that decreasing the scanning velocity can eliminate the inter-layer lack of fusion phenomenon. Additionally, the thermal interaction between adjacent scanning tracks can improve the fusion continuity in the gap area of neighbor tracks. Finally, optical observations are conducted to validate the simulated morphology of the melt pool. A good agreement between numerical results and experimental observations is obtained, indicating the ability of the numerical model to simulate the PA12 L-PBF process.

Improving thermal performance of a passive ventilation and cooling system by integrating a phase-change material: Dynamic characteristics and parametric examinations

The coupling of a solar chimney (SC) with an earth–air heat exchanger (EAHE) is a passive ventilation and cooling system that provides fresh air and cooling to buildings. However, inherent disadvantages of the coupled system include the mismatch of the induced airflow rate and internal cooling load and the low nighttime ventilation rate, which limit the full utilization of the coupled system. These issues can be mitigated by integrating a phase-change material (PCM) in the system of SC combined with EAHE (SCEAHE). Parametric investigations were conducted to examine the thermal performance improvement of the PCM-based SCEAHE system using a dynamic model. The numerical data revealed that solar energy was effectively extracted and reallocated by the PCM, thereby increasing the nighttime airflow rate and reducing the indoor air temperature. The phase-change temperature of the PCM not only affected the airflow rate but also the thermal environment at night and in the early morning. Therefore, a PCM with a higher phase-change temperature is recommended in this study. The latent heat of fusion had a larger impact on the induced ventilation rate than the outlet air temperature of the EAHE when the latent heat of fusion exceeded 175 kJ/kg. In addition, a PCM with a thermal conductivity <1 W/(m·K) is suggested. In practical application, a thickness range of 0.04–0.05 m is the most suitable. The specific heat of the PCM had slight influence on the thermal performance of the proposed system.

Thermal properties investigation of paraffin wax/titania nanocomposites as phase change materials

The use of phase change materials (PCMs) for thermal storage, thermal management, and thermal insulation has been widespread for many years. Thermal storage systems (TES) based on PCMs can be improved and optimized by adding nanoparticles (NPs) to them. Throughout this study, PCM nanocomposites (NCs) based on paraffin wax (PW) loaded by anatase titania (TiO2) NPs were fabricated and characterized to examine their thermal performance as phase change materials. The as-synthesized TiO2 NPs were obtained by hydrolysis technique and showed a well-defined spherical shape with a diameter in the nanoscale range and a crystallite size ~ 22.75 nm. Throughout the used concentrations of TiO2 NPs, 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.5%, the morphological feature for the PW/TiO2 NCs revealed a good dispersion of NPs in PW. The non-isothermal differential scanning calorimetry (DSC) measurements at a constant heating rate of 10 °C min−1 were used in order to get the melting point (Tm), latent heat of fusion (LH), and latent heat rate (LHR) as a function of TiO2 NP concentrations for the investigated PW/TiO2 NCs. Both LH and LHR values for PW/TiO2 NCs are higher than those obtained for a pure PW sample. The significant enhancement in LH and LHR values for PW/TiO2 NCs was found to be 21.2% and 134.3% in comparison with the pure PW sample, respectively. The thermal stability of the investigated PW/TiO2 NCs was examined using thermal gravimetric (TG) scans. It is found that the thermal stability varies with TiO2 NP concentrations with a non-monotonic trend. At concentrations up to 0.25 mass%, the thermal stability improved. For concentrations over 0.25 mass%, the degradation process became rapid.

Thermal management of lithium-ion battery module using the phase change material

One of the significant challenges in the fast adoption of electric vehicles in the market is the thermal management of the battery pack. The current advancement in active and passive cooling techniques is helping resolve this issue in electric vehicles. The present work focuses on the use of passive cooling techniques, such as phase change material (PCM) and the heat sink, to maintain the battery module temperature within the thermal safety limit. The cartridge heaters were used as the mock-up cells. A 3 × 3 array of mock-up cells was formed with a cell-to-cell spacing of 6 mm. OM42 was used as a PCM with a melting point temperature of 44°C and latent heat of fusion, 199 kJ/kg. The experiments were conducted at different power settings of 10–40 W with an interval of 10 W. A heat sink was integrated into the bottom of the battery module. It was observed that increased power input reduces the time required to reach the operating temperature limit of 60°C. After incorporating the PCM, this time was extended by 100.8%, 35.5%, 24.7%, and 21.2% for the power input of 10, 20, 30, and 40 W, respectively. Cell-5 was found to be the most heat-affected cell in the battery module. At higher power inputs of 30 and 40 W, the temperature variation along the height of cell-5 was more than 5°C with and without the PCM. The present findings provide more insights into the heat dissipation at lower and higher power inputs, which may help designers to modify the existing battery thermal management system design efficiently.

Microencapsulated phase change material through cellulose nanofibrils stabilized Pickering emulsion templating

Phase change materials (PCMs) possess remarkable capability to store and release substantial amounts of energy during the processes of melting and crystallization across a wide temperature range, thus holding great promise in applications related to temperature regulation and thermal energy storage. Herein, to effectively address PCM leakage and enhance thermal conduction, PCM microcapsules with melamine–formaldehyde resin (MF) shell were prepared using in situ polymerization of Pickering emulsions stabilized by cellulose nanofibrils (CNFs). CNFs were selected as the stabilizers for the Pickering emulsions and as reinforcing nanofillers for the MF shell, owing to their excellent emulsifying capability, high mechanical strength, and sustainable nature. Paraffin wax (PW) was utilized as the PCM material. The resulting PCM microcapsules with MF resin shells and PW core had a diameter ranging from 2 to 4 µm. Results showed that microcapsule with the core–shell ratio of 2 (Micro-2.0) exhibited the highest latent heat of crystallization and latent heat of fusion, measuring approximately 128.40 J/g and 120.23 J/g, respectively. The encapsulation efficiency of Micro-2.0 was determined to be approximately 79.84%.

Investigation on nonequilibrium crystallization of highly undercooled Cu–Ni–Co alloys

Deep undercooling rapid solidification experiments of Cu–Ni–Co alloys were carried out using the molten glass purification cycle superheat method. 130 K, 177 K and 277 K undercooling degrees were obtained and analysed for Cu55Ni43Co2 alloy. The crystallographic information obtained by EBSD and the dynamics of the solidification front taken by high speed photography were analysed and it was concluded that both the formation of relatively rounded equiaxed grains during the first refinement and the subsequent formation of finer subcrystals were due to the release of a large amount of solidification energy during the solidification process. The re-glow stage releases a large amount of latent heat of solidification resulting in the remelting of the dendrites. TEM tests were carried out on Cu55Ni43Co2 alloy with a maximum undercooling of 277 K. It was found that part of the substructure showed a high density dislocation network. By analysing the effect of increasing undercooling on the microstructure evolution, combined with the EBSD and TEM characterisation data, it was found that the stress-induced recrystallization mechanism was the dominant factor in the grain refinement mechanism at large undercooling.