Thermal Conductivity Of Composite Phase Change Materials Research Articles

Thermophysical Investigation of Multiform NiO Nanowalls@carbon Foam/1-Octadecanol Composite Phase Change Materials for Thermal Management.

Multiform NiO nanowalls with a high specific surface area were constructed in situ on carbon foam (CF) to construct NiO@CF/OD composite phase change materials (CPCMs). The synthesis mechanism, microstructures, thermal management capability, and photothermal conversion of NiO@CF/OD CPCMs were systematically studied. Additionally, the collaborative enhancement effects of CF and multiform NiO nanowalls on the thermal properties of OD PCMs were also investigated. NiO@CF not only maintains the porous 3D network structure of CF, but also effectively prevents the aggregation of NiO nanosheets. The chemical structures of NiO@CF/OD CPCMs were analyzed using XRD and FTIR spectroscopy. When combined with CF and NiO nanosheets, OD has high compatibility with NiO@CF. The thermal conductivity of NiO@CF/OD-L CPCMs was 1.12 W/m·K, which is 366.7% higher than that of OD. The improvement in thermal conductivity of CPCMs was theoretically analyzed according to the Debye model. NiO@CF/OD-L CPCMs have a photothermal conversion efficiency up to 77.6%. This article provided a theoretical basis for the optimal design and performance prediction of thermal storage materials and systems.

A novel battery thermal management based on composite phase change material with liquid-assisted cooling for different ambient temperatures

In this work, a thermal management system (TMS) employing the combination of composite phase change material (CPCM) and liquid cooling was developed for a lithium battery module. To enhance the temperature uniformity of the battery module, a new strategy was proposed creatively, which varied the thermal conductivity of the CPCM wrapping the battery depending on the position of the battery. Firstly, the thermal conductivity of CPCM was optimized for a single battery thermal management. Then, the temperature control effects of the proposed TMS were investigated numerically on the battery module. Results indicate the thermal conductivity of CPCM should not be more than 3 W/m·K. At 40 °C of ambient temperature, the only CPCM cooling can maintain the surface temperature of battery with 5C discharging within 44 °C, presenting excellent uniformity. At 45 °C, CPCM fails and liquid cooling can inhibit the temperature rise of the batteries, but increases the temperature inconsistency. Compared to the CPCM with constant thermal conductivity (3 W/m·K), the surface temperature difference of the battery module decreases from 5.30 to 2.95 °C employing CPCM with varying thermal conductivity (0.6–3 W/m·K). Decreasing coolant temperature can reduce the battery module temperature, but increase its temperature difference. The effectiveness of the varying λCPCM on the temperature uniformity of a battery module has also been verified by the designed experiment. This study can potentially provide significant guidance to the design of a lithium battery module based on the coupling CPCM and liquid cooling.

High thermal conductivity composite phase change material with Zn2+ metal organic gel and expanded graphite for battery thermal management

Phase change materials (PCMs) with promising potential thermal energy is stored and released much thermal energy during phase change process, which has greatly prospect in building energy conservation, waste heat recovery, energy storage, electrical vehicles (EVs) and other fields. Nevertheless, the low thermal conductivity and easy leakage of PCM is still a challenge to restrict its fasting development. Traditional supporting material is hard to reconcile antileakage and thermal conductivity of composite PCM (CPCM). Herein, the polyethylene glycol (PEG) with three-dimensional Zn2+ metal–organic gel (ZnHGL) as high-thermal conductivity support framework, styrene–butadiene–styrene block copolymer (SBS) and expanded graphite (EG) has been designed and prepared PZSE with high thermal conductivity, accompany with double transferring heat and supporting network structure. In contrast with pure PEG, the thermal conductivity of PZSE2 is increased by obvious 8.7 times when Zn2+ metal–organic gel and SBS with the proportion of 1:1, the mass maintenance rate and latent heat storage capacity are increased to 99.5 % and 103.64 J/g, respectively. Further, the thermal imaging camera indicate that PZSE2 exhibit a stable temperature-regulation property, which is benefited to extend the time to adjust the temperature. Additionally, the maximum temperature and temperature differential of the battery module with PZSE2 can be maintained within 60 °C and 6 °C, respectively, even at 1.5C discharge rate after ten cycling process. It indicates that the battery module with PZSE2 has optimum thermal management effect. Therefore, PZSE with metal–organic gel and EG can provide a promising candidate utilization in thermal regulation of EVs and energy storage.

Preparation and thermal conductivity enhancement of binary non-eutectic phase change materials based on alum-urea for solar heat storage system

Heat accumulators using latent heat storage are commonly used in solar energy storage systems. Potassium aluminum sulfate dodecahydrate (Alum) is an inexpensive phase change material, but the high phase change temperature limits its application in heat accumulator. To address this limitation is controlling the melting temperature of Alum. In this study, Alum-urea mixtures were first developed by adding 10 wt% urea. Modified phase change materials (MPCM) without phase separation and supercooling were developed by adding NiSO4·6H2O and xanthan gum to the Alum-urea mixture. Composite phase change materials (CPCM) with high thermal conductivity were developed by loading MPCM in expanded graphite. The melting temperature of the Alum-urea mixture was 72.52 °C with 10 wt% urea content, which was 21.4% lower compared to the Alum. The MPCM still has a high phase change enthalpy (157.7 J·g−1) and ignorable subcooling degree (0.8 °C). The thermal conductivity of CPCM is increased by 16 times, and it has good photothermal conversion ability. The CPCM holds significant promise for applications in latent heat energy storage.

Effect of composite cooling strategy including phase change material and liquid cooling on the thermal safety performance of a lithium-ion battery pack under thermal runaway propagation

In this work, a composite cooling system including composite phase change material(CPCM) and liquid cooling is designed for battery pack, and the effects of coolant flow rate, battery spacing, thermal conductivity of CPCM, channel number of cooling plate on the safety performance of battery pack under thermal runaway propagation are studied. The results reveal that: (1)Coolant flow rate increase mainly delays the thermal runaway propagation on both sides of cooling plate. When the coolant flow rate is 0.029 m/s, the thermal runaway propagation time through the cooling plate is 32.9s, which is extended by 1.84 times than that at 0.009 m/s (2)Battery spacing increase delays thermal runaway propagation and changes the propagation path. (3)Thermal conductivity reduction of CPCM can significantly delay thermal runaway propagation, because the heat is concentrated in the periphery of the battery and is hard to transfer though CPCM and cooling plate. (4)Compared with other influence factors, channel number of cooling plate has less influence on the overall thermal runaway propagation time. When the channel number is between 5 and 1, the total thermal runaway time changes within 25.5s–27s. The conclusions in this work are helpful to design a safer thermal management system for lithium-ion battery packs.

Nano-silver@polydopamine carbonized melamine foam supported polyethylene glycol phase change materials: With simultaneous improved photo-thermal conversion ability

Ag nanoparticles are commonly used for phase change material (PCM) modification to improve the photo-thermal convertibility in composite phase change materials (CPCM) owing to enhance carrier's ability to absorb photons by virtue of its unique localized Surface Plasmon Resonance effect (LSPR). Currently, redox method is considered to be the most effective method for the preparation of Ag nano-coating. However, it is still challenging to obtain a dense and uniform Ag nano-coating on the carrier surface due to the difference in the binding force between Ag nanoparticles and different carriers. Herein, a new preparation strategy is demonstrated, in which the carrier is pre-modified by adding a polydopamine (PDA) coating to enhance the bonding between the carrier and the silver nanoparticles, and then a stable three-dimensional silver nano-conducting network is obtained by redox. Consequential stable architecture contributes to polyethylene glycol (PEG) loadings reach 98%, simultaneously with an ultra-high photo-thermal conversion efficiency of 97.9%. Furthermore, this paper demonstrates the effect of carbonization temperature on the flexibility of melamine carbon foam (CMF), and different nano-Ag concentrations on the thermal conductivity of CPCM. This finding provides valuable guidance for the engineering of high photo-thermal conversion performance CPCM and strengthens their practical implementation in solar energy storage and thermal management.

Numerical simulation and optimization of compact latent heat exchanger with micro-channel plate in shape-stabilized composite phase change material

To enable the rapid provision of domestic hot water, this study presents the independent design of a plate heat exchanger featuring a large heat exchange area and a compact structure. Utilizing a sandwich structure, the thermal storage unit integrates two shaped composite phase change materials (CPCM), namely sodium acetate trihydrate (SAT)/expanded graphite (EG) blocks of identical thickness — in conjunction with a micro-channel heat exchange plate. Multiple thermal storage units are stacked to create the heat exchanger. Experimental validation of the heat transfer performance of this thermal energy storage heat exchanger is conducted, accompanied by the establishment of a heat transfer model elucidating the interaction between the phase change material (PCM) and the fluid. The investigation explores the impact of varying thicknesses of shape-stabilized CPCM, thermo-physical parameters of CPCM, and flow rates on enhancing the thermal efficiency of the thermal energy storage heat exchanger. Results indicate a competitive relationship between the phase change enthalpy and thermal conductivity of CPCM under constant density. Increasing the mass fraction of SAT effectively boosts its heat storage density. However, this improvement is counterbalanced by a reduction in CPCM's thermal conductivity, resulting in diminished heat transfer rates within the material and reduced efficiency in transferring heat between the material and the fluid. Optimal performance is achieved when the mass fraction of sodium acetate trihydrate is 80 wt% and the CPCM thickness is 20 mm. At these parameters, the thermal energy storage heat exchanger exhibits the highest heat transfer efficiency. Furthermore, the heat exchanger is capable of producing 197.86 kg of hot water in 1365 s at an inlet flow rate of 300 L/h, achieving an impressive discharging efficiency of 82.73 %. These findings underscore the feasibility of employing the mini-channel plate thermal energy storage heat exchanger for the rapid preparation of domestic hot water.

Research on modified expanded graphite/eutectic salt composite phase change material in cold chain transportation

Attention to the use of phase change materials (PCMs) in cold chain transportation has increased in recent years. In this work, a form-stable composite phase change material (CPCM) prepared by a novel eutectic salt (Na2SO4·10H2O-MgSO4·7H2OH2O) PCM composite with modified expanded graphite (MEG) was investigated. The hydrophilicity of expanded graphite (EG) and its compatibility with the eutectic salts were improved by coating SiO2. The results showed that microstructure of the EG was maintained after modification, and adsorption of the PCM by the MEG was 55.23 wt% higher than that of the EG. The CPCM with 20 wt% MEG exhibit a high enthalpy of 180.8 J/g, the phase transition temperature of −5.6 °C and a high thermal conductivity of 5.183 W/(m·K). The thermal conductivity of CPCM was 8 times as large as that of the PCM. Moreover, the thermal performance of the CPCM was small change after 200 thermal cycling, exhibiting good thermal cyclic reliability. Besides, a potential application test of the form-stable CPCM was performed through a low temperature insulation box. It showed that form-stable CPCM can control sudden temperature fluctuation and maintain stable temperature for longer time inside the insulation box.

Polyethylene glycol with dual three-dimensional porous carbon nanotube/diamond: a high thermal conductivity of composite PCM

Polyethylene glycol (PEG) is widely used as a phase change material (PCM) in thermal energy storage systems due to its high latent heat and chemical stability. However, practical application has been hindered by its low thermal conductivity and leakage issues. Therefore, developing shape-stable high thermal conductivity PCM is of great importance. In this study, new shape-stable composite PCM with high thermal conductivity and leak-prevention capabilities were designed. The porous carbon skeleton of diamond foam (DF) and dual-3D carbon nanotube-diamond foam (CDF) were prepared using the microwave plasma chemical vapor deposition method. The composite materials (DF/PEG and CDF/PEG) were produced by vacuum impregnation with PEG and skeletons. The results showed that CDF/PEG had the highest thermal conductivity, measuring 2.30 W·m−1·K−1, which is 707% higher than that of pure PEG. The employing of 3D networks of CNTs, which can improve the phonon mean free path in DF/PEG (1.79 W·m−1·K−1) while reducing phonon dispersion.The phonon vibration of dual-3D CDF plays an important role in heat transfer. PEG was physically absorbed and well-distributed in CDF, alleviating leakage of liquid PEG. The weight loss of CDF/PEG was only 25% at 70 °C for 120 s. Using CDF is an attractive and efficient strategy to increase the heat transfer of PEG and improve heat storage efficiency, alleviate the problem of poor shape-stability.

Thermal behaviour of Paraffin-MWCNT stabilized by Sodium dodecylbenzene sulphonate nano-enhanced phase change material for energy storage applications

The Phase change materials (PCMs) possess the great potential to store renewable and sustainable thermal energy that can mitigate the issue of energy to a great extent. However, the low thermal conductivity hinders the extensive use of PCM in various applications. To alleviate this deficiency, the PCMs are often incorporated with highly conductive nanoparticles. The carbon-based nanoparticles are highly regarded to be a promising option because of their elevated thermal conductivity like Multiwall carbon-nanotube (MWCNT). However, these highly conductive nanoparticles sometimes exhibit the issue of non-uniform dispersion with PCM. In this paper, we report the use of surface-modified MWCNT by using stabilized Sodium dodecylbenzene sulphonate surfactant (SDBS) with Paraffin wax (PW) RT47 at wt% 0.1 and 0.3 of MWCNT. The sample is created by using two-step method. Further, for characterization; chemical composition by Fourier transform infrared spectroscopy (FTIR), thermal conductivity by thermal property analyzer (TEMPOs) and for thermal stability, thermal gravimetric analyzer (TGA) is used. The results showed a significant enhancement in the thermal conductivity of composite PCM, the inclusion of 0.1 and 0.3 wt% of surface-modified MWCNT increased the thermal conductivity up to 51.29% and 76.5% respectively. The FT-IR confirms that the components are physically mixed in NePCM composite, no chemical reaction appeared as no displacement of characteristic peaks or a new peaks appeared. TGA results showed the prepared nano-enhanced phase change material (NePCM) is stable. Thus, surface modification of MWCNT by using SDBS for PW can be the effective method to boost the overall performance of NePCM without losing its basic characteristics. Therefore, based on results, it can be concluded that the surface modified Paraffin/MWCNT NePCM is well suited for applications like energy storage, photovoltaic thermal system, and battery thermal management. PCM showed enhanced thermo-physical properties. Therefore, it might be the candidate for energy storage and other thermal practical applications in future.

Research of the thermal storage properties of thermally conductive carbon fiber-reinforced paraffin/olefin block copolymer composite phase change materials with thermotropic flexibility

This study focuses on the fabrication and evaluation of paraffin (PA)/olefin block copolymer (OBC)/carbon fiber (CF) composite phase change materials (CPCMs) prepared using the melt impregnation process. The resultant PA/OBC/CF CPCMs exhibit superior thermal stability below 200 °C and maintain excellent shape stability at 60 °C. These characteristics are attributed to the alternating soft and hard segments of OBC, wherein the hard segments prevent liquid leakage from PA. The distinct structure of OBC further lends flexibility and recyclability to the PA/OBC/CF CPCMs. The latent heat of these CPCMs ranges from 169.1 to 197.6 J/g. Notably, the CPCMs variant (PA/OBC/CF-1) with 2 wt% CF addition retains 95 % of its initial latent heat even after 100 thermal cycles, thereby demonstrating superior cycling stability. The thermal conductivity of CPCMs with 10 wt% CF is 1.3 times that of pure PA. This significant improvement in thermal conductivity is attributed to the heat conduction pathways provided by the fibrous CF. These results indicate that the fabricated CPCMs offer substantial promise for utilization in low-temperature waste heat recovery applications.

Multifunctional flexible composite phase change material with high anti-leakage and thermal conductivity performances for battery thermal management

Composite phase change material (CPCM) as passive battery thermal management system (BTMS) still confronted many challenges such as easy leakage, high rigid and low thermal conductivity. In this study, a multifunction flexible CPCM with high anti-leakage and thermal conductivity performances has been proposed which is utilized the polymerizing and crosslinking reaction with polyethylene glycol and hexamethylene diisocyanate to address the leakage of CPCM in essence. The results revealed that the CPCM exhibited excellent antileakage and elastic performance. Especially, the thermal conductivity of CPCM is obviously improved by 2.8 times owing to the synergistic effect of 3 wt% aluminum nitride and 2 wt% carbon nanotubes. Besides, the maximum temperature of the battery module with multifunction flexible CPCM can be controlled below 45 °C even at 1.5C discharge rate, and the corresponding temperature difference is maintained within 4.3 °C. With these outstanding properties, the multifunctional flexible PEAC can provide an efficient solution to improve the thermal safety of battery packs in applications, which will significantly promote the development of EVs.

Nickel foam/Covalent-Organic Frameworks for composite phase change materials with enhanced solar-thermal energy conversion and storage capacity

Shape-stabled composite phase change materials (CPCMs) with outstanding thermal properties and solar-thermal conversion capabilities are of great importance in the efficient usage of renewable solar energy. In this work, Covalent-Organic Frameworks (i.e., COF TpPa) with excellent solar energy absorption capability were successfully loaded within nickel foam (NF) to form NF/TpPa support by a solvothermal method. Subsequently, polyethylene glycol (PEG2000) was adsorbed into the three-dimensional backbone of NF/TpPa to prepare novel CPCMs. With the introduction of TpPa, the PEG can be stably anchored and prevented from leaking because of the capillary forces and hydrogen bonding. The effects of TpPa content and pore size of NF on the thermal characteristics of CPCMs were explored. The obtained PEG/NF/TpPa composites have high thermal storage capacity (118.26 J·g−1), excellent thermal reliability and 1.9 times thermal conductivity of pure PEG. The pore size of NF has a positive correlation with the thermal conductivity of CPCMs. Remarkably, the solar-thermal conversion and storage capacity of CPCMs are greatly improved by TpPa, with its outstanding capacity for light absorption and high surface areas. The solar-thermal conversion efficiency of CPCMs ranges from 89.58% to 96.80%, which is higher than many of the currently reported solar-responsive CPCMs.

Study on Thermal Runaway Risk Prevention of Lithium-Ion Battery with Composite Phase Change Materials

To reduce the thermal runaway risk of lithium-ion batteries, a good thermal management system is critically required. As phase change materials can absorb a lot of heat without the need for extra equipment, they are employed in the thermal management of batteries. The thermal management of a Sanyo 26,650 battery was studied in this work by using different composite phase change materials (CPCMs) at different charge–discharge rates. The thorough analysis on the thermal conductivity of CPCMs and the effect of CPCMs was conducted on the maximum surface temperature while charging and discharging. The findings demonstrate the ability of the composite thermal conductivity filler to increase thermal conductivity. It is increased to 1.307 W/(m K) as the ratio of silica and graphene is 1:1 (CPCM-3). The CPCMs can reduce the surface temperature of the cell, and the cooling effect of CPCM-3 is the most obvious, which can reduce the maximum temperature of the cell surface by 13.7 °C and 19 °C under 2 C and 3 C conditions. It is also found that the risk of thermal runaway of batteries under CPCMs thermal management is effectively reduced, ensuring the safe operation of the battery. This research can assist in the safe application of batteries and the development of new energy sources.

Parameter optimization and sensitivity analysis of a Lithium-ion battery thermal management system integrated with composite phase change material

In order to ensure the performance and to extend the life cycle of power battery module within electric vehicle, a battery thermal management system (BTMS) integrated with composite phase change materials (PCM) was proposed. The heat dissipation performance of BTMS using paraffin/expanded graphite (EG) composite PCM with different mass fraction was investigated. The results showed the optimal heat dissipation performance was observed using composite PCM with 20 wt% EG. The combined effect of liquid volume fraction and thermophysical parameters of composite PCM on heat dissipation performance of battery module was revealed. The phase transition temperature of composite PCM was found to have the largest impact on the maximum temperature and temperature uniformity of battery module, followed by latent heat and thermal conductivity of composite PCM. A 10 % decrease in the phase transition temperature led to a 7.9 % in the maximum temperature of battery module. Both the thermal conductivity and latent heat growth contributed to the reduction in the maximum temperature of battery module. Composite PCM with the thermal conductivity of 3 W m−1 K−1, phase change temperature of 38 °C, and latent heat of 220 J g−1, was found to achieve the optimal heat dissipation performance of BTMS and a high utilization rate of 97.3 % for composite PCM. The findings of this work could be beneficial for future development of highly-efficient and economical composite PCM for BTMS.

Evaluation and optimization on heat transfer performance of a composite phase change material embedded in porous ceramic skeleton: A lattice Boltzmann study

The thermal performances of phase change materials (PCMs) are of great importance to latent heat thermal energy storage applications. In order to improve the thermal properties, the composite PCM of inorganic salt embedded in porous ceramic skeleton was proposed and investigated in this study. The numerical model for the phase change process of PCM was developed by applying the lattice Boltzmann method. Simulation results indicate that the existence of porous ceramic materials could not only enhance the heat conduction of PCM but also hinder the convective heat transfer. In addition, the results show that Rayleigh number has a significant effect on the melting process of PCM. At low Rayleigh number, the existence of ceramic skeleton can significantly improve the thermal conductivity of composite PCM. However, at high Rayleigh number and porosity, the reduction of convective heat transfer might be greater than the heat conduction enhancement due to the addition of porous skeleton materials. By designing an appropriate non-uniform pore network of porous skeleton materials, further enhancement of heat conduction without obvious loss of convective heat transfer has been achieved. The research results obtained in this study could provide useful guidance for designing high-performance phase change energy storage materials.

Metal Nanoparticles Decorated on Carbon Nanotube Surfaces as Fillers to Improve Thermal Conductivity of Stable Phase Change Composite Materials

The composite phase change materials (CPCM) are prepared by using porous silicon carbide foam as the carrier, N-octadecane (C18) as the phase change material, and metal nanoparticles decorated on carbon nanotube surfaces (M-NPs@CNTs) as fillers. It is a new type of shape and performance stable C18/M-NPs@CNTs/SF CPCM with better performance. The thermal conductivity of the C18/M-NPs/CNT/silicon carbide foam (SF) composite is higher than that of pure C18. When the thermal filler is AgNPs@CNTs, the thermal conductivity of CPCM is improved by 666% compared with C18. The results of thermogravimetric and differential thermal analysis indicate good structural stability and chemical stability. C18/1wt%AgNPs/CNT/SF has the highest thermal conductivity and heat storage capacity, and the best overall performance in the process of thermal energy storage and release. The silver nanoparticles The well-dispersed thermal fillers (M-NPs@CNTs) form excellent heat conduction path and improve the thermal performance of the system. The SF is an excellent thermal conductive carrier materials and its porous structures are attributed to the adsorption of phase change materials and structural stability of CPCM. The application of SF both improves the thermal conductivity and electrical resistivity of CPCM and decreases its leakage during phase change. The application of solid-liquid CPCM can be enlarged in thermal management field.

Thermal Properties and Characterization of n-Decyl-Lauryl Alcohol/Expanded Graphite/Silicon Carbide Composite Phase Change Materials for Refrigerator Cold Energy Storage

In this study, a kind of phase change materials (PCMs) with a low melting point (around 0 ℃) was prepared using n-decyl alcohol (DA) and lauryl alcohol (LA) as PCM, expanded graphite (EG) as supporting matrix. Nano silicon carbide (SiC) as a thermal conductivity promoter was added to modify the composite PCM. Expanded graphite with strong adsorption performance was used to not only prevent the leakage, but enhance the thermal conductivity. Leakage experiments showed that the maximum adsorption rate of DA-LA in composite PCM was 92 wt.%. The physical properties and chemical compatibility of composite PCM were studied, and the results showed that the raw materials were well absorbed and dispersed homogeneously into the porous structure of the EG, and they were only a physical bond with each other without chemical reaction. The melting and solidification temperature of composite PCM with the SiC mass ratio 3 wt.% was -0.85 ℃ and 1.08 ℃, and the latent heat of melting and solidification was 85.62 J/g and 74.94 J/g, respectively. the thermal conductivity of composite PCM with 9 wt.% SiC addition was 1.61, which was more than 4.19 times that of pure DA-LA. Thermogravimetric Analysis (TGA) experiment showed that composite PCM had outstanding thermal stability and durability. The present study confirms that this composite PCM is a potential candidate for cold energy storage in refrigerator applications.

Ni@rGO into nickel foam for composite polyethylene glycol and erythritol phase change materials

The exploitation of shape-stabilized composite phase change materials (CPCMs) with high solar-thermal conversion efficiency, thermal storage capacity and thermal conductivity has attractive prospects for solar energy utilization. In this work, reduced graphene oxide (rGO) nanosheets decorated with Ni nanoparticles (Ni@rGO) are successfully filled into the nickel foam (NF) skeletons by acidic graphene oxide solution impregnation and subsequent thermal reduction methods. The obtained NF/Ni@rGO supports with controllable Ni@rGO content are used as the carrier for loading polyethylene glycol (PEG) and erythritol (ET) to prepare CPCMs. The Ni@rGO hybridization enhances the interaction of the carrier framework with the PCM, which can effectively increase the PCM loading and prevent its leakage. As compared with bare NF supported CPCMs, the NF/Ni@rGO supported CPCMs have better shape stability, far higher thermal storage density, and better recyclability. The optimized CPCMs with PEG and ET show high latent enthalpies of 125.30 J·g−1 and 280.66 J·g−1, respectively. It is also found that the thermal conductivity of CPCMs is significantly improved to 0.9199 W·m−1K−1 for NF/Ni@rGO-10/PEG and 0.9146 W·m−1K−1 for NF/Ni@rGO-10/ET, which is 344 % and 35 % higher than that of PEG and ET, respectively. In addition, the decoration of Ni nanoparticles on the rGO support (i.e., NF/Ni@rGO-10) could further improve the thermal conductivity, solar-thermal conversion efficiency (95.74 %) and electro-thermal conversion efficiency (71.39 %) of CPCMs. This research furnishes the basis for the development of high performance CPCMs. Moreover, it has great potential and broad application prospects in the efficient utilization of solar energy and thermal management of electronic devices.

Pore scale simulation for melting of composite phase change materials considering interfacial thermal resistance

• Implicit-enthalpy-based LBM with interfacial thermal resistance is proposed. • Porous structure is reconstructed by randomly generation-growth method. • The effective thermal conductivity of composite PCMs is evaluated. • The effect of natural convection, porosity and interface on melting are analyzed. The convective melting process and thermal performance of phase change materials (PCMs) incorporating porous skeleton in the one-side-heated rectangular cavity are investigated numerically in this work. A pore-scale lattice Boltzmann method (LBM) with implicit scheme is developed to explore the solid–liquid phase change process. The interfacial thermal resistance between the skeleton and PCMs is considered by interfacial conditions treatment. The random porous microstructure is generated by quartet structure generation set (QSGS) which is used to compute effective thermal conductivity in LBM. The validations of the current model are employed by the two-phase series conduction model and previous numerical results. The effects of porous structure, skeleton material, and thermal interfacial conditions on heat transfer characteristics are systematically investigated. The computational results show that the melting rate and effective thermal conductivity increase with the reducing porosity and the high thermal conductivity of the skeleton material accelerate the melting process. In addition, the consideration of interactions in the LBM leads to a significant difference. When the thermal interfacial resistance is set to be 1 × 10 −4 m 2 W/K, the temperature drop is very large in two-phase conduction, the melting rate decreases remarkably in the phase change process. The present simulation is also suitable for optimizing the porous structure to prepare various composite PCM in the thermal energy storage field.