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Flexible phase change materials (FPCM) with PA/SEBS/POE were prepared by melt blending method. The microstructure, thermal properties and cycle stability were characterized. The results show that a suitable SEBS and POE ratio can not only provide flexibility, prevent the leakage of paraffin, but also enhance the thermal conductivity. Then expanded graphite (EG) was added to prepare FPCM-EG and to further improve the performance. The experimental results show that the thermal conductivity and cycle stability increase with EG content increasing. When EG content is 15 %, the thermal conductivity is 3.572 W·m−1·K−1, which is 15.5 times of paraffin. And the leakage rate is less than 0.03 % after 20 cycles. After that, the FPCM-EG is used for thermal management of photovoltaic cell-thermoelectric (PV-TE) coupling system under simulated electric heating. The effects of EG content, heating flux and heat dissipation condition on temperature control and thermoelectric conversion performance were explored. The experimental results show that the FPCM-EG can significantly reduce heating surface temperature, improve power output and relieve the impact of heating flux variation. When EG content increases from 10 % to 15 %, the maximum heating surface temperature is reduced from 40.1 °C to 37.8 °C, and the power output is improved by 33.3 %. • Flexible PCMs with high thermal conductivity and latent heat were prepared. • The thermal conductivity is 3.572 W m−1·K−1, latent heat is 134.84 kJ/kg. • After 20 cycles, the leakage rate is less than 0.03 %. • The prepared FPCMs was used for thermal management of PV-TE system. • The surface temperature is reduced and power output is improved significantly. [ABSTRACT FROM AUTHOR]

Abstract A series of paraffin/expanded graphite (EG) composites with various mass fraction were prepared. The microscopic geometry configuration, thermal conductivity and saturation sorption capacity of EG were obtained. In this paper, a method based on the experiments of EG pores was proposed for constructing geometric models. The geometric model constructed by this method has obvious anisotropy and has been employed in the calculation. Furthermore, the numerical results of thermal conductivity indicate anisotropy of a single-pore. Moreover, it had been observed by experiment that the anisotropy is weakened and transformed to isotropy in the process of combining geometric models with a large number of single pores. The final numerical results agree well with the experiments, which validates the precision and reliability of the proposed model. The increasement of thermal conductivity is also calculated and discussed during the phase change process of paraffin/EG. Highlights • A method of EG pores was proposed for constructing geometric models which has obvious anisotropy. • The SEM micrograph and saturation sorption capacity are employed to build the geometric models of EG pores. • Effective thermal conductivity during non-phase change process and the phase change process was calculated. • The numerical results agree well with the experiments. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) which possess high thermal conductivity and excellent mechanical property have been prepared in this work according to a dual-level packaging technology. Porous graphite foam with bulk density of 0.25 g/cm 3 which is derived from worm-like expanded graphite is infiltrated by liquid paraffin. The as-infiltrated graphite foam is ball milled into small spheres with diameter of 1–3 mm. Then the spheres are sprayed with a pre-polymer composed of epoxy resin and its curing agent. These spheres are finally hot-pressing at 30 °C for 6 h under 1 MPa to obtain the PCMs. Correspondingly, porous graphite works as the first-level packaging (core) while epoxy resin film acts as the second-level packaging (shell) of paraffin. The thermal conductivity of PCM composites reach to 4.98 W/m K. Meanwhile, the compressive strength of PCM composites keeps a very stable value of 19.50 MPa when temperature increases from 25 to 90 °C. The excellent shape-stability of PCM is attributed to its dual-level packaging structure in which porous graphite prevents the leaking of liquid paraffin from the core and epoxy resin provides a strong polymer network at high temperature. [ABSTRACT FROM AUTHOR]

Sugar alcohols (SA) are attractive phase change materials (PCM) for thermal energy storage applications at low-to-medium temperatures (70–180 °C). Five pure sugar alcohols (xylitol, adonitol, L-arabitol, erythritol, D-mannitol) and three eutectic blends (eythritol/xylitol, L-arabitol/erythritol, L-arabitol/xylitol) are investigated in this paper. Experimental characterization of such materials as PCMs is provided. This encompasses the measurement of their melting point and latent heat of fusion, as well as the experimental determination of all key physical properties (specific heat, thermal conductivity, thermal diffusivity, density, viscosity) as a function of the temperature. The performances of the studied materials are compared to those of most currently used PCMs (paraffin waxes, salt hydrates etc.) in the field of thermal energy storage. The most significant applications, including solar seasonal energy storage, are also discussed. [ABSTRACT FROM AUTHOR]

Dispersion of highly conductive nanoparticles in Phase Change Materials (PCMs) tends to improve the thermophysical properties of nanocomposites. The current research condenses the synthesis, chemical, physical, and thermal characterization of novel nano-enhanced eutectic phase change materials (NeUPCMs) dispersed with TiO 2 nanofillers for thermal management applications. The base matrix primarily comprises of a eutectic of paraffin wax and palmitic acid. Detailed analysis of the uncertainty of each thermophysical property measured was performed. The synthesized nanocomposite logged a maximal thermal conductivity of 0.59 W/mK (2.3-fold as compared with the base-0.25 W/mK) with 0.5% nanofillers. The composites displayed excellent solar transmissivity (82%) as they were doped with nanofillers having a high refractive index. The latent heat of the NeUPCMs got enhanced by 17% whereas the melting point showed a slight decrement in nanocomposites. Further, zero phase segregation, no subcooling, stable phase transition temperature, and good chemical, and thermal stability were noted from digital scanning calorimetry results with NeUPCMs. The composites exhibited good thermal reliability beyond 500 thermal cycles. It could be potentially deployed in the thermal management of medium-temperature systems like PVT and LCPVT systems. [Display omitted] • Novel nanocomposites were synthesized using paraffin wax, palmitic acid, and TiO 2. • Nanocomposite had a maximal enhancement of 131.5% in thermal conductivity. • 38% rise in solar transmittance when compared with the eutectic base. • Thermophysical properties remained stable even after 500 thermal cycles. [ABSTRACT FROM AUTHOR]

Highly paraffin/butyl stearate-loaded phase change microcapsules were synthesized by cosolvent-free interfacial polymerization using low-toxicity dicyclohexylmethane-4, 4′-diisocyanate as the shell material. The formation of the microcapsules and their distribution in the epoxy were studied by means of optical microscope and scanning electron microscopy, respectively. The chemical composition of microcapsules was confirmed through Fourier transform infrared spectrometer. And the phase change properties, thermal stability and cyclic thermal stability of microcapsules and their thermal insulation properties and thermal response behavior in the epoxy were investigated through differential scanning calorimetry, thermogravimetric analysis, leakage prevention test, thermal conductivity test and temperature response experiment, respectively. The synthesized spherical microcapsules have distinct core-shell structure with an average diameter of 220.6 μm. The microcapsules achieve an encapsulation rate of 78.5%, with the melting enthalpy and the crystallization enthalpy being 148.5 J/g and 159.2 J/g, respectively. They not only exhibit good thermal stability and cyclic thermal stability, but also can disperse in the epoxy uniformly and combine with the epoxy tightly. In addition, compared with the pure epoxy, the epoxy containing 15 wt% microcapsules experiences a 10.1% decreases in thermal conductivity and a 55.4% increase in delayed time of temperature rise/fall, showing an excellent temperature regulation ability. [Display omitted] • HMDI was employed as the shell material due to low toxicity. • The microcapsules with core-shell structure achieve an encapsulation rate of 78.5%. • High enthalpy microcapsules exhibit 99.2% of heat-storage efficiency. • The microcapsules have high thermal stability, reliability and applicability. • 15 wt% microcapsules increase the time delay by 55.4% for temperature rise/fall. [ABSTRACT FROM AUTHOR]

The objective of this study is to overcome the leakage and low thermal conductivity problems of paraffin as PCMs (phase change materials) for thermal energy storage by impregnating SEBS/paraffin/HDPE FSPCMs (form-stable phase change materials) into metal foam. The form-stable composites were prepared by absorbing paraffin into the network of powder-like styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymer and covering high-density polyethylene (HDPE) on pre-prepared SEBS/paraffin mixture. The composites were characterized by using differential scanning calorimetry (DSC), Scanning electron microscope (SEM), Fourier Transform Infrared Spectrometer (FT-IR), X-Ray Diffraction (XRD) and Hot disk. Paraffin leakage was investigated by accelerated degradation test at 80 °C. The melting temperature and latent heat of the composites were determined as 50.56 °C and 151.6 J/g, respectively. FT-IR results revealed good chemical compatibility among paraffin, SEBS and HDPE. SEM images and XRD test results demonstrated that the paraffin had uniformly dispersed into SEBS. This composite was testified able to keep paraffin from seepage with only 2.39 wt% of paraffin loss after 50 thermal cycles test (150 h). In addition, the thermal conductivity of SEBS/paraffin/HDPE was 0.272 W/m K, which was increased up to 2.142 W/m K when copper foam was embedded in the composite. [ABSTRACT FROM AUTHOR]

The utilization of aerogel with the 3D network structure is regarded as an important method to construct phase change materials (PCMs). In this work, a series of novel paraffin-based composite PCMs were fabricated with boron nitrid@chitosan aerogel (BNCA) as skeleton materials by a freeze-drying and impregnation method. XRD, SEM, TGA, Hot Disk, DSC and FT-IR were used to character the samples and thermal cycles were employed to measure the shape stability. The results revealed that paraffin wax (PW) had been successful and effectively embedded into the prepared BNCA with a porous structure. Moreover, the morphologies of BNCA/PW composite remained stable after 100 times thermal cycles. In addition, the thermal conductivity of BNCA/PW composite was notably high as 1.14 W/(m·K), which was 4.07 times higher than PW (0.28 W/(m·K)). Simultaneously, the phase temperatures of BNCA/PW composite containing 41 wt% skeleton were 50.5 and 52.9 °C, and its latent heats were 118.4 and 114.9 J/g, respectively. The BNCA/PW composite showed an excellent chemical compatibility between PW and BNCA, and presented broad application prospects in energy storage of electronic systems. [Display omitted] • Synthesis of porous boron nitride@chitosan aerogel by freeze-drying method. • Synthesis of BNCA/PW composite PCMs by vacuum impregnation. • The mass fraction of paraffin can be controlled, without leakage. • Good thermal conductivity and thermal reliability of BNCA/PW composite PCMs. • After 100 thermal cycles, the thermal properties and shape stability of the composite remain good. [ABSTRACT FROM AUTHOR]

Paraffin is a common organic phase change material (PCM) that finds many applications in thermal energy storage (TES) systems. One common characteristic of organic PCMs is their low thermal conductivities. This – in turn – causes a slow thermal response when paraffin is used in high power applications. In this study, paraffin–nanomagnetite (Fe 3 O 4 ) composites (PNMC) were prepared by a dispersion technique to enhance their thermal properties. Nano magnetite prepared using the cost-effective sol–gel method was mixed into paraffin at two different mass fractions: 10% and 20%. Scanning electron microscope (SEM) was used to observe the morphologies of nanomagnetite and PNMCs during different stages of the composite production process. SEM analysis results showed that nanomagnetite particles of 40–75 nm in size were homogeneously distributed in the paraffin structure. The latent heat storage capacity of PNMC, measured by differential scanning calorimetry (DSC) at 1 °C/min, was found to be 8% higher than paraffin alone. Thermal conductivities and diffusivities of paraffin and PNMCs were determined by the “DICO” method. For 10% and 20% by weight PNMCs, the thermal conductivities were increased by 48% and 60%, respectively. These results clearly indicate that the addition of Fe 3 O 4 nanoparticles is an efficient and cost effective method to enhance the heat transfer properties of paraffin, when they are incorporated into latent heat storage systems. [ABSTRACT FROM AUTHOR]

Expanded graphite (EG) powder as a typical porous material has high thermal conductivity and large surface area that are often used to enhance the thermal conductivity of phase change materials (PCMs). Ten composites of paraffin/EG powder with various weight fractions were elaborated by high pressure compression. Their microstructure configuration and thermal properties were characterized with Scanning Electron Microscopy (SEM), Thermal Constant Analyzer. The saturation sorption capacity of EG under compression was experimentally determined. The thermal conductivity of the paraffin/EG composite is greatly enhanced by 41 times in maximum as compared to pure paraffin. Based on the experimental quantification, we propose a novel two-level scale model from micro-scale to macro-scale to compute the thermal conductivity of the composite. The numerical results agree well with the experimental data that validate the precision and reliability of the proposed model. Furthermore, the results reveal that both keeping porous EG structure at original morphology and increasing the saturated sorption capacity of paraffin in EG could eventually improve the heat transfer capacity of the composites. In addition, the proposed model would require more experimental validation based on the composites with different materials in future work. [ABSTRACT FROM AUTHOR]

In this study, expanded graphite (EG)/paraffin (PA)/silica (SiO 2) composite phase change materials (PCM), with good thermal conductivity and impermeability, were fabricated for potential applications in solar energy. The EG-PA was first prepared by vacuum adsorption and then encapsulated by SiO 2 through solid-phase wet grinding in the presence of sodium silicate. Our results show that the EG-PA-SiO 2 composite have optimal properties when the mass ratio of raw material is PA: sodium silicate: H 2 O = 1:9:2:8. The latent heat of melting of the EG-PA-SiO 2 composite prepared at this mass ratio is 106.2 J/g. The core material loss ratio, after washing with petroleum ether, is 4.79%. The thermal conductivity is 2.053 W/m·K, which is 8.5 times higher than that of pure paraffin wax, and the melt permeability is 9.35% after 120 min at 60 °C. Under simulated sunlight, the time required for the composite material to change from 30 °C to 65 °C is reduced by 70.78% compared to PA and the heat absorption and release times are nearly unchanged under multiple cycles. These results indicate that the material has a stable photothermal conversion efficiency. [Display omitted] • Expanded graphite, paraffin and silica composites were made by solid-phase wet grinding method. • Silica encapsulated the composite, reducing leakage. • Composites showed improved thermal conductivity and impermeability. • The composite has stable photothermal conversion, and there is no obvious leaking sign. [ABSTRACT FROM AUTHOR]

Abstract: Composite phase change materials (PCM) for latent heat thermal energy storage were made by mixing two different kinds of exfoliated graphite nanoplatelets (xGnP-1 and xGnP-15) into paraffin wax. Direct casting and two roll milling were used to prepare samples. The investigation on the thermal and electrical conductivity of nanocomposites with these two nanoplatelets was performed. Higher thermal conductivity of composite PCM can be achieved with nanofillers of larger aspect ratio, better orientation and lower interface density. The thermal physical properties of the nanocomposites were investigated by differential scanning calorimetry and thermal gravimetric analysis. It was found that the latent heat of the nanocomposites was not adversely affected by the presence of xGnP nanoplatelets and the thermal stability improved. [Copyright &y& Elsevier]

Abstract: A series of polyol acetal derivatives were synthesized through condensation reactions of aromatic aldehyde with polyols, including sorbitol, mannitol, xylitol, and pentaerythritol. They were examined as gelators in the formation of paraffin-based shape-stabilized phase change materials (PCMs), in which 1,3:2,4-di-(4-methyl) benzylidene sorbitol (MDBS) exhibited excellent thermal stability. Three-dimensional netted structural phase change materials were obtained by paraffin doped with different gelators, which were thermally stable so that no leakage of paraffin occurs even under higher temperature than the melting point of paraffin. It was found that PCMs doped with 3wt% expanded and exfoliated graphite (EG) exhibited better thermal conductivity, similar phase change temperature and heat storage density. [Copyright &y& Elsevier]

Abstract: The shape-stabilized phase change material (PCM) based on paraffin and high-density polyethylene (HDPE) is used as a storage media in thermal energy storage. This storage media can retain the shape even when paraffin is in the liquid state, and no paraffin is observed, but it has a low thermal conductivity and is easily flammable, which limits the utility area in thermal energy storage. The motivation of this study was to improve thermal conductivity and flame retardant property of shape-stabilized PCM. A flame retardant shape-stabilized PCM made of paraffin, HDPE, expanded graphite (EG) and intumescent flame retardant (IFR) was presented. To characterize the resulting product, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), hot disk thermal constants analyzer, attenuated total reflectance fourier transform infrared (ATR-FTIR) and cone calorimeter measurements were employed to investigate their microcosmic shapes, crystalline behaviors and thermal properties. The SEM results indicated that paraffin and EG were well dispersed in the network formed by HDPE. The thermal conductivity and the flame retardant efficiency of IFR could be improved by adding EG. The possible flame retardant mechanism for paraffin/HDPE/IFR/EG as a shape-stabilized PCM was proposed. [Copyright &y& Elsevier]

Abstract: Using exfoliated graphite nanoplatelets (xGnP), paraffin/xGnP composite phase change materials (PCMs) were prepared by the stirring of xGnP in liquid paraffin for high electric conductivity, thermal conductivity and latent heat storage. xGnP of 1, 2, 3, 5 and 7wt% was added to pure paraffin at 75°C. Scanning electron microscopy (SEM) morphology showed uniform dispersion of xGnP in the paraffin wax. Good dispersion of xGnP in paraffin/xGnP composite PCMs led to high electric conductivity. The percolation threshold of paraffin/xGnP composite PCMs was between 1 and 2wt% in resistivity measurement. The thermal conductivity of paraffin/xGnP composite PCMs was increased as xGnP loading contents. Also, reproducibility of paraffin/xGnP composite PCMs as continuous PCMs was manifested in results of electric and thermal conductivity. Paraffin/xGnP composite PCMs showed two peaks in the heating curve by differential scanning calorimeter (DSC) measurement. The first phase change peak at around 35°C is lower and corresponds to the solid–solid phase transition of the paraffin, and the second peak is high at around 55°C, corresponding to the solid–liquid phase change. The latent heat of paraffin/xGnP composite PCMs did not decrease as loading xGnP contents to paraffin. xGnP can be considered as an effective heat-diffusion promoter to improve thermal conductivity of PCMs without reducing its latent heat storage capacity in paraffin wax. [Copyright &y& Elsevier]

Xylitol with high latent heat of 243.28 kJ/kg and a significant supercooling degree has been considered to be a potential phase change material (PCM) for long-term thermal energy storage (TES). Xylitol can be kept in a supercooled or supersaturated metastable for a long time. In our study, it took 23 days and 30 min respectively that xylitol liquid and xylitol liquid adding 5 wt% ethanol crystallized completely at room temperature of 15 ± 5 °C. Unfortunately, the low thermal conductivity and leakage of xylitol restrict its thermal performance. In this paper, xylitol/expanded graphite (EG) composite PCMs with 5, 8, 10, 12 and 15 wt% EG content were prepared by an "impregnation and compression" two-step method. The results of SEM, XRD and FT-IR show that xylitol is well impregnated into the micropores of EG and has good chemical compatibility. The thermal performance test shows that the thermal conductivity of composite PCMs increases dramatically and the latent heat decreases with the increase of EG. The experimental results show that the latent heat of 10 wt% EG is 209.73 kJ/kg and 192.18 kJ/kg, respectively, during the charging and discharging process. The thermal conductivity of 10 wt% EG is 3.91 W/(m·K), as 9.29 times as xylitol. Besides, the crystallization of xylitol in EG and the mass loss of the composites have also been studied. The results show that 10 wt% EG composites crystallized completely after 16 days. These results prove that xylitol/EG composite PCMs have broad application prospects in long-term TES. ∙ A shape-stable xylitol/expanded graphite composite phase change material was prepared. ∙ The crystallization process of xylitol liquid and xylitol liquid adding 5 wt% ethanol at ambient temperature was studied. ∙ The thermal properties of shape-stable xylitol/expanded graphite composite phase change material were studied. ∙ The composite was characterized and the feasibility of its application in long-term thermal energy storage was preliminarily proved. [ABSTRACT FROM AUTHOR]

The current challenge for the application of organic phase change materials is to compromise the conflicting influence of high thermal conductivity matrix content on the heat storage performance and thermal conductivity of phase change composites. Herein, we prepared graphene aerogel (GA) and GA-based paraffin phase change composite (GAP) by the widely reported hydrothermal method and studied the application potential of GA in GAP. The underlying mechanism of paraffin latent heat enhancement caused by GA was discussed from the perspective of the crystallization and phase change process of paraffin. X-ray diffraction and differential scanning calorimetry results showed that as the GA content increased, the paraffin in GAP had an increased crystallinity and exhibited increased latent heat. Activation energy of paraffin's phase change process calculated according to Kissinger model was effectively reduced when GA content was greater than 7.3 wt%, implying a considerable increase in the thermal response rate of GAP. In addition, in order to improve the thermal conductivity enhancement efficiency of GA, thermal conductivity of GAP was predicted by finite element numerical simulation. A good agreement was observed between the experimental and numerical results and some practical suggestions were made for the experimental preparation process. Image 1 • Improvement of PCMs' latent heat caused by graphene aerogel (GA) is explained. • A numerical model is built to predict the thermal conductivity of GA based PCC. • Practical suggestions were made for the preparation process of GA based PCC. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene-reinforced structural materials with excellent solar-thermal conversion, mechanical and thermal transfer properties present attractive prospects for the fabrication of high-performance composite phase change materials (PCMs). Herein, multifunctional 3D continuous sponge frameworks wrapping with reduced graphene oxide (rGO) are facilely prepared via simply circular impregnation and in-suit reduction process. Further, the stable combination of 3D support material and phase change matrix through vacuum melting infiltration can successfully obtain the rGO@sponge framework/paraffin wax (rGO@SF/PW) composite shape-stabilized PCMs. As an advanced energy conversion and storage PCMs, the rGO@SF/PW achieves efficient solar-thermal conversion effciency of 85%, excellent energy storage properties (phase-change enthalpy of 170.4 J/g for the loading amount of 90 wt%), high thermal transfer performance and good cycling thermal stability. Based on the comprehensive performances of the rGO@SF/PW, domestic storage systems for solar-thermal water are designed to broaden the application of PCMs in the solar-thermal energy area. • Multifunctional three-dimensional continuous sponge frameworks wrapping with reduced graphene oxide are facilely prepared via circular impregnation and in-suit reduction process. • The composite phase change materials exhibit excellent energy storage properties and high thermal conductivity. • The obtained shape-stabilized composite phase change materials achieves efficient solar-thermal conversion effciency of 85%. • Domestic storage systems for solar-thermal water are designed. [ABSTRACT FROM AUTHOR]

The latent heat thermal storage using Phase Change Materials (PCMs) is one of the essential aspects to be addressed for rapid expansion of utilisation of Renewable Energy sources and waste heat. The major disadvantage of PCMs, deployed in such thermal storage systems, is their low thermal conductivity and, in some cases, low latent heat. Paraffin wax/expanded graphite (PW/EG) composite PCMs with the EG mass fraction of 2%, 4%, and 6% were prepared by absorption of molten organic material into the EG structure. FireCarb TEG-315 and FireCarb TEG-160 were used as EG of A- and B-type, respectively, and PW 53–57 °C was deployed as the PCM in this study. Polarizing optical microscope, scanning electron microscopes and Fourier transform infrared spectroscopy were used to characterize the structure of composite PCMs. Thermal properties of pure Paraffin and produced composite materials were determined using a differential scanning calorimeter and thermal conductivity analyser. One of originalities of this work is that the statistical method of assessment of heterogeneity in composite PCMs was proposed for the first time with the use of Matlab software. This method was deployed for the quantitative assessment of uniformity of the EG distribution in composite PCMs structure. The novelty of obtained results is in detection of intermolecular interaction between B-type EG and PW. This interaction further enhances thermo-physical properties of the PW/EG composites. In contrast to pure PW and PW/A-type EG composite PCMs, in which the solid-solid transition and solid-liquid phase change are observed, PW/B-type EG compositions exhibit only the solid-liquid phase change. The heat storage capacity in both types of compositions was found to be almost identical. Despite of prolonged sample's ultrasonic treatment, the structure of PCM compositions was found to be far from being homogeneous. However, the thermal conductivity of compositions with 6 wt % of EG was determined to be 0.977 W/m°C for the PCM with A-type EG and 1.263 W/m°C for the PCM with B-type EG in comparison with the value of 0.258 W/m°C for pure PW. These values of the thermal conductivity correspond to the enhancement ratios of 3.79 and 4.9, respectively. If uniformity in the EG distribution in PW can be improved, then the thermal conductivity of composite PCMs would also considerably increase. Findings of this work are being used for designing a cost efficient solar thermal storage system with the reduced charging/discharging times as a part of an international project funded by EC. Image 1 • Paraffin wax/expanded graphite (EG) compositions with EG mass fractions of 2%, 4%, and 6% were analysed. • FTIR analysis indicates that B-type of two (A- and B-) types of tested expanded graphite interacts with paraffin. • The compositions with A-type EG exhibit solid-solid transition and solid-liquid phase change. • The compositions with B-type EG exhibit the solid-liquid only phase change. • Thermal conductivity enhancement ratio is 3.79 and 4.9 for PCM compositions with A- and B-type 6wt% EG, respectively. [ABSTRACT FROM AUTHOR]