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Hybrid and ramjet engines became now effective propulsion systems with great development potential in different fields. They require using proper high-energy components. At high-speed blowing conditions conventional polymer fuels exhibit relatively low regression rate. As an alternative, it is proposed to use paraffin and based on it compositions. Paraffin is high-energy hydrocarbon with a low melting point leading to a high regression rate in high-speed blowing conditions. The results of experimental study of regression behavior of paraffin mixtures with various additives under intensive hot air blowing at 1 MPa pressure are presented. Stearic acid, nanoaluminum Alex, aluminum hydride AlH 3 , B and mechanoactivated aluminum boride AlB 2 were used as 10 % by mass additives. Experiments were conducted on cylindrical perforated samples. Using original design microwave gauge the current diameter of a sample bore was measured during experiment with subsequent calculation of regression rate. Based on experimental data and the results of heat balance calculation, the temperature on the gasified surface of paraffin fuel was estimated. • Paraffin based mixtures regression rate was studied under hot air blowing at 1 MPa. • Original microwave gauge was used to record permanently paraffin regression rate. • Additives of B, AlH 3 and AlB 2 essentially increased the paraffin regression rate. • Additive of Alex practically did not change the paraffin regression rate level. • Need to refine heat transfer coefficient for a liquid collapsing layer is formulated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tetrahedrally coordinated framework-associated Fe3+ species form strong Lewis acid sites. • Paraffin cracking is initiated by strong Lewis acid sites of Fe-ZSM-5. • Fe-ZSM-5 increases propene, butenes and aromatics selectivity compared with Al-ZSM-5. • Fe 2 O 3 particles does not catalyze paraffin cracking. Iron-modified Al-ZSM-5 increases selectivity to propene, a key petrochemical resulting from fluid catalytic cracking (FCC). However, the type and role of active iron species remain unclear, hindering efforts to streamline the design of selective FCC additives. Here, we investigated Al-free Fe-ZSM-5 catalysts containing iron species in the form of framework Fe3+, extra-framework Fe3+, oxidic clusters, and oxide micro aggregates in n-octane cracking (FCC model) to assess their effect on catalytic cracking. DR-UV–Vis spectroscopy, 57Fe Mössbauer Spectroscopy, FTIR studies of pyridine adsorption, and n-octane cracking tests at 500 °C revealed that framework-associated coordinatively unsaturated Fe3+ species, which induce strong Lewis acidity, are responsible for paraffin cracking initiation, whereas bulk iron oxides on the zeolite surface are inactive. In comparison with Al-ZSM-5, Fe-ZSM-5 increases the olefinicity of the valuable C 3 -C 4 fractions (selectivity to propene and butenes) and promotes aromatization reactions due to the lower relative strength of Fe-induced Brønsted acid sites and dehydrogenation properties. As shown by our 57Fe Mössbauer study (performed at −269 °C) of the catalyst in calcined, spent, and regenerated states, Fe-ZSM-5 deactivation is associated with the loss of tetrahedrally coordinated Fe3+ species. Therefore, tuning Fe-ZSM-5 C 3 -C 4 selective FCC additives requires stabilizing framework Brønsted and framework-associated Lewis acid sites while decreasing the concentration of iron oxide species. Ultimately, these findings may enable us to meet the demand for propene derived from FCC cracking, which is expected to grow in the foreseeable future. [ABSTRACT FROM AUTHOR]

Terahertz waves exhibit excellent performance in molecular information detection of substances. Since natural materials exhibit weak absorption of terahertz waves, it's conventional to involve mixing analyte with polymer diluents and pressing them into pellets, or enhance the light-material interaction through coupling systems of natural materials with metamaterials. However, both pressure-induced metastable crystal structure transformations and spatial overlap between the analyte and metasurfaces can impact the absorption of terahertz waves by organic crystals. This paper proposes a novel analytical approach using paraffin as a dilution matrix for qualitatively and quantitatively characterizing organic crystals with THz spectroscopy. The featureless refractive index spectra and negligible absorption demonstrated the feasibility of paraffin as a diluting analyte. The analytical process was further demonstrated with well-studied lactose by being diluted in molten paraffin at different mass-ratios and solidified as pellets under room temperature and ambient pressure. A continuous wave terahertz frequency domain spectroscopy system (THz-FDS) is used for spectral acquisition over 0.4–1.3 THz. The experimental results reveal a significant linear correlation between the absorption coefficient peak areas and molar concentration of lactose, with a correlation coefficient R2 of 0.9678. Our method provides an additional optional dilution matrix for terahertz spectroscopy characterization of organic crystals, enabling non-destructive, rapid, and direct measurement of metastable crystals. Furthermore, this study on paraffin as a binder material holds potential for enhancing spatial overlap between natural materials and metamaterials in the field of metasurface-enhanced sensing. • A novel THz spectroscopy analytical approach using paraffin as a dilution matrix. • A pressure-free sample preparation method for THz spectral characterization. • Non-destructive, rapid, and direct measurement for metastable crystals. • Qualitative and quantitative analysis of metastable organic crystals. • Potential to enhance the spatial overlap between natural materials and metamaterials. [ABSTRACT FROM AUTHOR]

Investigating the nanostructure's atomic and thermal properties (TP) might help enhance energy conversion and storage technologies. This is particularly important when considering phase change materials (PCM) and their use in thermal energy storage systems. However, understanding the behavior of nanostructure's atomic and thermal components in response to temperature (Temp) changes is critical, as is improving its heat transfer capacities for a wide range of applications by examining the effect of external heat flux (EHF). As a result, the major goal of this research was to determine the effect of EHF on the atomic and TP of silica aerogel (SA)/paraffin/CuO nanostructures. This investigation was done using molecular dynamics (MD) simulation and LAMMPS software. To achieve this, a study was undertaken into the effect of EHF of different magnitudes (0.01, 0.02, 0.03, and 0.05 W/m2) on the maximum (Max) density (Dens), velocity (Vel), and Temp, as well as HF, thermal conductivity (TC), and charging and discharging time. The results show that when the EHF increased to 0.05 W/m2, the Max Dens value decreased to 0.0754 atoms per square centimeter. Furthermore, the Max Temp and Vel increased to 1018.82 K and 0.0139/fs, respectively. Increased external heat discharge improved the thermal effectiveness of simulated construction. Increasing the EHF raised the TC and HF to 95.93 W/m2 and 1.93 W/mK, respectively. Finally, the results of this simulation are expected to improve understanding of nanostructure TP and their potential applications in improved energy conversion and storage technologies. [ABSTRACT FROM AUTHOR]

This experimental measurement examines Photovoltaic/Thermal (PVT) systems with semicircle absorber tubes, focusing on the impact of nanoparticle-enhanced phase change material (NPCM). Four PVT systems are analyzed, all using a standard PV module: a. PVT1: cooled by water; b. PVT2: cooled by water and NPCM; c. PVT3: cooled by nanofluid; d. PVT4: cooled by nanofluid and NPCM.The research evaluates their thermal, electrical, and overall performance and efficiencies at volumetric flow rates of 1–5 LPM under harsh outdoor conditions. The results reveal that the PVT4 system demonstrates the highest efficiency. At a volumetric flow rate of 5 LPM and a surrounding temperature of 47.94 °C, it achieves electrical, thermal, and total efficiencies of 12.70 %, 78.99 %, and 91.83 %, respectively. By enhancing the heat transfer between nanofluids and NPCMs, system cooling is enhanced and thermal efficiency is greatly increased. Additionally, the use of such systems notably reduced the surface temperature, exhibiting a decrease of about 35.09 % compared to the standard PV module while the use of nanofluid cooling only without NPCM caused a reduction of 29.93 % compared to the PV module. Importantly, the PVT4 setup outperforms the unenhanced PV module (PVT3) in overall efficiency by 14.04 %. In this study, PV modules are cooled by a heat exchanger made up of semicircular tubes attached to their backs. The study confirms that a PCM enhanced with nanoparticles performs well in the PVT system when semicircular absorption tubes are used. A significant reduction in surface temperatures is achieved with the use of this heat exchanger, resulting in remarkable thermal efficiency. As a result of this cooling effect, the PV module is more efficient than a traditional solar module in terms of electrical output. This type of system is likely to influence the development of more convenient and efficient solar energy systems. It is possible to use the heat absorbed by PV modules in other ways as well. [ABSTRACT FROM AUTHOR]

Although PV panels are widely used to generate electricity from solar energy, their most important defect is the reduction of electrical efficiency with the increase of their temperature. The aims of this research is thermal management of a PV panel using phase change materials (PCM) and hierarchical ZnO/expanded graphite (EG) nanofillers to increase its production capacity. Two types of ZnO nanoparticles (rod- and flower-shaped) are synthesized using sonochemical method, and doped on EG particles to improve the thermal conductivity of the PCMs. A new bio-PCM consisting of oleic acid and beeswax is prepared and its performance is compared with paraffin and beeswax. The effect of PCM thickness (h=10- 30 mm) and weight fraction of nanoparticles (ϕ = 1–5%wt) on temperature (T s,ave), open-circuit voltage, current, and electrical performance of the PV panel is investigated. Results show that T s,ave for pure paraffin, beeswax and bio-PCM has decreased from 64.23 o C (without cooling) to 54.11 o C , 57.15 o C and 51.41 o C , respectively. For all PCMs, adding flower-shaped ZnO/EG particles shows better results compared to rod-shaped one. The composite of bio-PCM with ZnO/EG has a higher positive effect on T s,ave reduction and in generating voltage compared to paraffin and beeswax. PCMs composed of ZnO/EG particles with ϕ=5 wt% exhibited the minimum values of electrical efficiency. In addition, T s,ave decreased intensively from h= 10 mm to h= 25 mm, but no significant difference is observed between h = 25 mm and h= 30 mm. The bio-PCM has proper melting point and heat storage capacity to cool down PV panel, which led to high power production. The maximum electrical efficiency is achieved using composite of bio-PCM and flower-shaped ZnO/EG particles at h= 25 mm, which is circa 12.88 %. • Thermal management of PV panel by composite of bio-PCMs with ZnO/EG particles. • Rod- and flower-shaped ZnO particles are synthesized and doped on EG particles. • Effect of PCM thickness on the thermal performance of PV panel is investigated. • Adding flower-shaped ZnO/EG particles have better thermal and electrical performance. • Maximum electrical efficiency of PV panel is 12.88 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant volume change during solidification of phase change materials (PCMs) • Examined phase change heat transfer analytically and experimentally. • Developed shrinkage profiles of paraffin materials during solidification. • Reported effects of container surface wettability and chemical additives. Phase change materials (PCMs) are widely used for thermal energy storage and other applications. During the solidification of a PCM, a volume change occurs due to thermal expansion and structural change of the molecules. A concave shape may be created during the solidification shrinkage. This paper investigates the shrinkage profile formed during the solidification of paraffin wax and its relationship with the surface wettability (contact angle), considering the effect of density changes. The contact angle of a paraffin droplet on a surface indicates the extent of adhesion between the solid surface and paraffin. The experimental study examines a mixture of wax with nanoparticles, wax with surfactants, different coatings on the container surface, and different solidification temperatures. Enhanced adhesion and increased shrinkage height are observed due to the non-polar interaction between coated surfaces and paraffin, facilitated by induced dipole-induced dipole forces. The addition of 3% octadecylamine enhances adhesion between paraffin and the container, as driven by dipole–dipole forces between the hydroxyl group on epoxy resin-container surfaces and the hydrophilic amine group of octadecylamine. The shrinkage height increases with a decrease in the contact angle of paraffin on the surface. The shrinkage profile also changes with the solidification temperature. The highest shrinkage profile is achieved for the highest solidification temperature. [ABSTRACT FROM AUTHOR]

• Nano Ti 2 O 3 was investigated as nano additives for the first time to synthesize composite PCM with paraffin wax. • The best mass fraction of nano Ti 2 O 3 (9 wt%) is given in this research. • The photothermal conversion rate is 76.96% for composite PCM. • The thermal conductivity of composite PCM has an enhancement of 37.8% compared to pure paraffin wax. • The latent heat shows a decrease of only 5.3% compared to pure paraffin wax. Organic phase change material (PCM) has gathered considerable interest in various fields, especially in solar photothermal conversion. Nanoparticles were often utilized to improve the photothermal and thermal performances of PCM. In this work, the nano-scaled particles are obtained by grinding coarse Ti 2 O 3 powder, then they have been successfully dispersed into paraffin wax with various mass fractions. The thermal and photothermal performances get an experimental evaluation. The results indicate that the latent heat is decreased with the mass fraction, while the photothermal conversion efficiency gets improvement with the mass fraction. The 9 % mass fraction gives the highest thermal conductivity with an improvement of 37.8 % and the photothermal conversion efficiency is about 80 %. Besides, these improvements are accompanied by a mere 5.3 % drop in latent heat, much lower than the mass fraction of nanoparticles. Nano Ti 2 O 3 is first reported as an ideal particle for photothermal conversion of PCM, and it is suggested that the mass fraction should be less than 30 %. [ABSTRACT FROM AUTHOR]

• Solar dryer with liquid thermal storage infused in copper tubes to form a composite heat exchanger is investigate. • Used C 15 -C 50 crankcase oil formed part of the liquid thermal storage materials investigated. • Paraffin and C 15 – C 50 crankcase oil exhibited a maximum thermal storage temperature difference of about 10.8 °C above ambient temperature. • The average exergy efficiency of 45–49.9% were achieved for using thermal storage material. • Used C 15 -C 50 crankcase oil showed a prospect as a suitable heat storage medium in solar drying design. The study presents a comparative thermodynamic analysis of degraded C 15 -C 50 grade crankcase oil (DCO) and paraffin thermal storage (PTS) as heat storage materials in solar drying. The goal is to convert DCO from waste to a useful product in solar drying. The assessment was based on drying efficiency, energy and exergy analysis, sustainability assessment and CO 2 mitigation of each solar dryer. The difference in drying efficiency between the dryer with DCO and that with PTS is less than 1.5 % while the difference between the specific energy consumption is less than 9 %. In contrast, the difference between the dryer with DCO and that without thermal storage is 24.2 %. The mean exergy efficiency ranged between 41.6 and 49.9 %. The values of the waste exergy ratio (WER), sustainability index (SI) and improvement potential (IP) for the three dryers ranged from 0.00 ≤ WER ≤ 1.00, 0.00 ≤ SI ≤ 34.56, 0.00 ≤ IP ≤ 2.68 kW. Using these dryers instead of diesel, grid-based electricity or coal-powered dryer will limit a maximum of 5,792,826 tons of CO 2 from the atmosphere. [ABSTRACT FROM AUTHOR]

• This experimental study presents the effect of paraffin volume on the hot water output in a mantled hot water tank. • Paraffin capsules have not affected temperature distribution inside the tank. • Each four paraffin capsules have decreased the temperature inside the tank by about 1°C. • There is no significant change in Richardson and MIX numbers with the increasing paraffin volume. • While hot water output increases with the increasing number of capsules, up to 13 capsules, it drops dramatically after 13. • The hot water output has been increased by 20% with 13 paraffin capsules. This experimental study aims to determine the effect of the amount of encapsulated phase change material (PCM) on the hot water output in a vertical mantled hot water tank. Paraffin which has a 58–60 °C melting point has been used as PCM, and it has been placed inside the tank with 5-liter cylindrical capsules. First, 4, 8, 12, and 16 paraffin capsules have been placed in the test tank, respectively. While the hot water output has increased with the increasing number of capsules up to 12 capsules, it has decreased dramatically when 16 capsules have been placed in the tank. In order to determine the optimum paraffin amount, 13 and 14 capsules have been placed in the tank, respectively. While 13 capsules have increased the hot water output, 14 capsules have decreased it. At the end of the study, the optimum number of capsules has been observed as 13. Placing 13 paraffin capsules has increased hot water output by 20% than the standard tank. Additionally, the MIX number and Richardson number have indicated that placing paraffin capsules has not been affected the thermal stratification significantly. They have varied approximately ±1.5% in all cases studied. [ABSTRACT FROM AUTHOR]

Thermal management of photovoltaic (PV) panels is crucial due to the deterioration of their electrical efficiency at elevated operating temperatures. Therefore, thermal protection of PV against overheating is highly required. This study investigated the applicability of the shape-stabilized phase change material (PCM) composites for temperature regulation of PV modules (PVM). Paraffin waxes (PW) with specific melting temperatures infiltrate graphite foam (GF) to prepare the GF_PW composite. The PCM composites are coated with expanded graphite-modified epoxy resin to prevent PW leakage after melting and to maintain product stability, integrity, and mechanical strength. The performance improvement of PVMs integrated with two types of GF_PW composites with different phase change temperatures of 35 and 44 °C (labeled RT35 and RT44, respectively) was studied. The adequate latent heat and thermal conductivity of the epoxy-coated GF_PW composites ranged from 126.5 to 138.1 J/g and from 2.03 to 2.15 W/m°C, respectively. The GF_RT44 and GF_RT35 composites, used as passive heat absorbing elements, reduced the PVM surface temperature by 27 and 32 °C, respectively, enhancing the PVM efficiency by 10.9 and 18.5 % of the reference configuration consisting of the PVM alone. To our knowledge, the PVM efficiency enhancement obtained in this study is the highest among PVMs integrated with PCM composites reported in the literature. [Display omitted] • Thermal management of PV modules against overheating using PCM composite. • Shape-stabilized phase change composites by paraffin infiltration into graphite foam. • Epoxy coating to prevent paraffin leakage during phase change. • 18.5 % improvement in the PV panel efficiency with the PCM composite. [ABSTRACT FROM AUTHOR]

Phase change materials could store and release heat energy through phase change. However, the shortcomings of low thermal conductivity in the photothermal conversion process and easy leakage in the solid-liquid conversion seriously hinder the application of heat energy utilization. Graphene had high thermal conductivity, and it was an ideal material for improving the solar absorption, solar energy conversion and thermal conductivity of phase change materials. In this paper, a graphene aerogel composed of copper nanowires (CuNWs)/2-acrylamide-2-methylpropanesulfonic acid (AMPS) was designed. The thermal conductivity and shape stability of phase change materials for solar-thermal-electrical conversion applications were enhanced by composite CuNWs. Furthermore, PAMPS was coated on the surface of copper nanowires to avoid the oxidation of copper nanowires, and the sulfonic acid group of PAMPS was used to induce CuNWs to disperse uniformLy on the graphene sheets, which further constructed a good conductive network. After vacuum impregnation of PW, the best thermal conductivity phase change composite (PW-CuNWs@PAMPS-GA (1:1)) was obtained. The PCC loaded with CuNWs with the same graphene content achieved a thermal conductivity of 1.46 W/(m·K) and a high latent heat of 206.8 J/g. The latent heat retention rate was as high as 99.57 %. The photothermal conversion efficiency of PW-CuNWs@PAMPS-GA (1:1) was remarkable at 96.4 %. Due to its excellent solar-thermal-electrical conversion efficiency, the output voltage and output current were 800.8 mV and 85.8 mA, respectively, at a solar analog intensity of 5 kW/m2. Even after the sunlight was stopped, the voltage output could be maintained for a while by releasing the heat energy stored in the phase change composite. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a novel water-based hybrid nanofluid was developed using poly-hydroxyethyl methacrylate-encased graphene quantum dot-paraffin nanocomposite (HEMA GQD-P). Graphene quantum dots (GQD) with an average size of 10 to 15 nm were synthesized by citric acid nucleation and the HEMA GQD-P nanocomposites were synthesized by an emulsion polymerization reaction. The emission spectra of GQD obtained using photo-luminescent spectroscopy confirm the occurrence of quantum confinement effect. The synthesis of HEMA GQD-P was carefully carried out to ensure its optimal properties. The synergistic effect due to high thermal conductivity of GQD and high latent heat capacity of paraffin were recognized in the enhanced properties of nanocomposite and hybrid nanofluid. The latent heat capacity of the synthesized nanocomposite was found to be 21.8 % higher than the pure paraffin. The prepared hybrid nanofluid possesses high dispersion stability at pH 7 and the thermal conductivity of the hybrid nanofluid enhances with an increase in nanoparticle concentration. A maximum thermal conductivity enhancement of 53 % (±2) was obtained for the hybrid nanofluid (0.3 vol%) at 30 °C. The present work reveals that the encapsulation of GQD-paraffin in a poly-hydroxyethyl methacrylate shell creates nanocomposites with high heat transfer properties. The synergistic effect of the HEMA GQD-P enhances their potential in the preparation of hybrid nanofluids with enhanced properties for desired thermal management applications. [Display omitted] • Graphene quantum dot-paraffin nanocomposites coated by poly-hydroxyethyl methacrylate were synthesized. • The synergistic effect of graphene quantum dot and paraffin enhance the thermal properties of hybrid nanofluid. • The latent heat capacity of the nanocomposite was found to be 21.8 % higher than the pure paraffin. • Nanofluid shows high dispersion stability and 53 % enhancement in thermal conductivity compared to water. [ABSTRACT FROM AUTHOR]

• The solar drying process is an eco-friendly method for preserving agricultural produce, with a focus on drying Mango pulp. • Organic paraffin wax as a Phase Change Material (PCM) in a portable solar dryer as the heat storing material. • During peak sunshine hours, the excess heat can be stored and used in the off-sunshine hours. • When compared to the sun-dried products, the solar-dried products had better colour, aroma, and quality. Food drying is an important phase in the safeguarding of agricultural by products that assist as raw materials for a variety of end applications. In the Thermal Energy Storage (TES) application a Phase Change Material (PCM) is the suitable material. In this research, paraffin wax was utilized in the planning and building of the solar dryer. The novelty of this work is to reduce the drying duration and increases the drying efficiency. Ripened mango was grinded and dried using different method to preserve and improve the shelf life of that dried product. To create nutritious dried mango cubes for snacking. When compared to conventional drying methods, solar drying with PCM for drying mango pulp has shown good quality retention. The outcome revealed that PCM integrated in the solar dryer has the lowest drying duration compared with open sun dry and without PCM. In terms of quality, color, and scent, solar-dried items outperform sun-dried ones. [ABSTRACT FROM AUTHOR]

The water transport behaviors of cement-based materials are altered after hydrophobic modification. The influence of hydrophobic modification on the water transport behaviors of mortar was investigated through 1H NMR and the absorption test. The results indicate that the incorporation of paraffin significantly reduces both the capillary and moisture absorption masses of mortar. The ratio of moisture absorption mass to capillary absorption mass increases with higher hydrophobicity, attributed to the paraffin coverage around the pores and the subsequent increase in contact angle. When incorporating 10 wt% paraffin, the increase in capillary absorption mass of mortar is mainly attributed to vapor diffusion and capillary condensation, accounting for 90.3 %. And the content of interlayer water, gel water, and inter-hydrate water in the two mentioned specimens is approximately equal, attributed to increased resistance to the ingress of liquid water. The reinforcement corrosion protection performance improves by one to two orders of magnitude due to the alteration of water transport behaviors. • Hydrophobic modification alters the proportion of various water transport behaviors. • 1H NMR is employed to characterize the distribution of water content in different water absorption environments. • When the hydrophobicity of the mortar increases, the capillary and moisture absorption specimens exhibit similar mass increments and absorption rates. [ABSTRACT FROM AUTHOR]

• Polymer gyroid heat exchanger (HX) with PCM for thermal energy storage. • The gyroid HX outperformed the conventional shell-and-tube (S&T) HX. • Gyroid HX shows lower pressure drops than S&T HX across the flow rate range. • Metal gyroid HXs exhibit high heat transfer rates. • Polymer gyroid HX exhibits reasonable thermal performance and is light in weight. Latent heat thermal energy storage (LHTES) systems utilizing phase-change materials (PCMs) in conjunction with heat exchangers (HXs) have been widely investigated for efficient thermal energy utilization. This study experimentally evaluated the heat transfer performance and pressure loss of a PCM-based gyroid HX fabricated using a polymer 3D printer. Initially, the study compared the phase change time, heat storage and release characteristics, and pressure drop of the gyroid HX with those of a conventional shell-and-tube HX (S&T HX). The results demonstrate that the gyroid HX achieved up to 20 % shorter thermal charge and discharge times than the S&T HX, which is attributed to a higher heat transfer rate. Additionally, the measured pressure drop of the gyroid HX was up to 44 % lower than that of the S&T HX. Consequently, considering both the heat transfer rate and pressure drop, the gyroid HX showed an average improvement of 57 % and 31 % in the overall enhancement factor during charging and discharging, respectively, compared to the S&T HX. Further, metal gyroid HXs fabricated from steel and aluminum using metal 3D printing were experimentally compared with the polymer gyroid HX. Despite the polymer thermal conductivity being only 1/90 and 1/790 that of steel and aluminum, respectively, the heat transfer rate per unit mass of the polymer gyroid HX was 1.7 times that of the steel gyroid HX and approximately half that of the aluminum gyroid HX. This finding suggests that the polymer gyroid HX is suitable for LHTES applications where lightweight characteristics are crucial. [ABSTRACT FROM AUTHOR]

A novel analytical solution to the time-dependent heat transfer equation for a multi-layer wall considering the contribution of phase change is obtained. Based on this solution a new numerical algorithm is developed for the analysis of variations in temperature and heat flux in a three-layer wall of a building in the presence of transient ambient temperature. In this algorithm, the new analytical solution at the end of the previous time step is used as the initial condition for the following time step with adjusted values of input parameters (ambient temperature). The novel algorithm is verified based on a comparison of the predictions of COMSOL Multiphysics (version 6.1) with its predictions for the same input parameters assuming that the time dependence of the ambient temperature follows the sine law. The new code is used for the analysis of heat transfer through a three-layer building wall assuming typical continental climate conditions. The inner and outer layers were filled with polyurethane foam, while a thin middle layer, located in the centre of the wall, was filled with the phase-change material (paraffin). Using the new numerical algorithm it is demonstrated that the presence of the thin paraffin layer in the wall leads to two orders of magnitude reduction in the amplitude of temperature oscillations on the room side of the wall compared to those on its outer side. It is shown that the presence of paraffin layer in the wall leads to an increase in the phase shift between the temperature on the outer side of the wall and the heat flux on the room side from about 1 hour (homogeneous wall) to about 5.5 hours (wall with the paraffin layer). • Analytical solution to the transient heat transfer equation for a three-layer wall. • Contribution of phase change is considered. • New analytical solution in incorporated in the numerical algorithm. • The new algorithm is verified based on a comparison of the predictions of COMSOL. • Heat transfer through a three-layer building wall in continental climate conditions. [ABSTRACT FROM AUTHOR]

Phase change materials (PCM) have been widely studied in the field of building energy storage. However, industrial grade high latent heat phase change paraffin (PW) has the problem of high melting point and easy leakage, and at the same time, it is necessary to absorb municipal solid waste on a large scale and reduce the damage of waste cellular concrete (WCC) to the urban ecological environment. Using binary paraffin wax (BP) prepared by hot fusion of solid paraffin (SP) and liquid paraffin (LP) as composite phase change materials, polypropylene (PP) and porous material WCC as support materials, a new WCC/PP/BP stereotyped phase change material (FCPCM) with low leakage rate and good stability was prepared by melt blending method and vacuum adsorption method, to meet the energy storage needs of buildings. The chemical compatibility, thermal performance and morphological stability of the prepared FCPCM were tested, and the heat storage/release performance test experiments were carried out to explore the thermal performance of the prepared energy storage concrete. The results show that the Encapsulated WCC/PP/BP has no new substance and good chemical compatibility. The results of scanning electron microscope (SEM) and mercury injection instrument (MIP) show that WCC has good adsorption properties for PP/BP. The melting phase change temperature increases by 14.08%, the latent heat of phase change decreases by 42.94%, and the initial phase change thermal properties are still maintained after several phases of phase change. It can maintain a stable form at 150℃. The 24 h leakage rate remained below 1%, which was nearly 44% lower than that of FCPCM with PP as the support material. Thermogravimetric curve (TGA) shows that the thermal stability of encapsulated FCPCM increases by 25.59%. In addition, the thermal performance test of energy storage concrete shows that compared with traditional concrete, energy storage concrete has greater heat storage density and stronger temperature control ability, which can effectively realize building energy saving. • Waste cellular concrete was first proposed as a porous material. • The thermal properties of prepared FSPCM with low leakage rate were studied. • Preparation and heat storage/release performance test of energy storage concrete. • The 24 h leakage rate of the low leakage rate PCM is kept below 1%. • The thermal stability of the encapsulated FSPCM was improved by 25.59%. [ABSTRACT FROM AUTHOR]

Cooling with phase change material has been identified as one of the most promising cooling approaches for lowering solar photovoltaic module temperature and enhancing system performance. To the best of the authors' knowledge, the specific contribution of Paraffin based phase change material with its prospective thermal enhancement strategies in solar photovoltaic cooling systems has not been reported. This study comprising four phases aims to provide a comprehensive assessment of the use of Paraffin-based phase change materials, an active cooling approach and metal oxide-based nanoparticles in solar photovoltaic cooling systems through the use of recent and relevant research studies. The comprehensive and comparative discussions, in contrast to former reviews, are provided at the end of each phase to summarize their technical considerations. Furthermore, for each examined study, limitations and implications are discussed in order to identify research gaps for further improvements. This comprehensive assessment findings show that a Paraffin-based phase change material cooling approach can cope with a greater drop in solar photovoltaic module temperature ranging from 3 to 26.6 °C, which stimulates an increase in module electrical efficiency ranging from 1 to 56 %. Challenges and environment impact of the existing systems are summarized. Opportunities and future perspective in this field pave the way for utilizing the possibilities for developing more thermal efficient and economic viable solar photovoltaic cooling systems for a sustainable environment. [Display omitted] • A comprehensive review paves a way toward better solar photovoltaic system (SPVS). • The utility of the specific Paraffin based PCM (PP) in SPVS is explored. • Strategies to enhance SPVS performance using PP are addressed. • The ability of active cooling hybrid SPV thermal (HSPVT) system with PP is studied. • The future perspective of the targeted systems is coined for better sustainability. [ABSTRACT FROM AUTHOR]

In this study, a new PCM composite of paraffin with beef tallow/coconut oil mixture are used to augment the heat removal from the surface of a PV module. At first, the composite of paraffin-beef tallow/coconut oil (PBTCO) is used as the PCM to thermal regulation of a PV module. The effects of the weight of PCMs (W = 2.1–4.1 kg) on surface temperature and power output of PV module are investigated. In the second step, expanded graphite powders (EG) (X 3 = 0.5–10.5 %wt.) are added to PBTCO to augment its thermal conductivity. Response surface methodology is applied to achieve optimal parameters and conditions for the PV/EG-PBTCO system. Measurements show that temperature and output power are as high as 64.02 °C and 4.875 W, respectively, for an uncooled system. The composite of 63.1% paraffin and 36.9% BTCO (mass fraction of BT = 39% and mass fraction of CO = 61%) is the more efficient PCM. In addition, results show that adding EG particles to PBTCO composite has significant added benefits over no using them. The predicted temperature and output power at the optimum point are found to be 32.9 °C and 8.923 W, respectively, at X 3 = 9.94 %wt and PCM weight of 3.57 kg. • A novel PCM composite is introduced for thermal management of a PV module. • Mixture of beef tallow-coconut oil-paraffin (PBTCO) is used as an efficient PCM. • Increasing thermal conductivity of PBTCO using expanded graphite (EG) particles. • Temperature of PV module is reduced from 64.04°C to 32.92 °C by 9.94% wt EGPBTCO. • The maximum efficiency of the PV-EG/PBTCO system at the optimum point is 14.89%. [ABSTRACT FROM AUTHOR]

The technology of latent heat storage with phase change materials (PCMs) is one of the promising means to improve the utilization of renewable energy. Nevertheless, its broad application will be limited due to the low thermal conductivity of PCMs. In this work, paraffin/expanded graphite (EG) composite PCMs by paraffin having a melting point of 62 °C and expanded graphite with three kinds of particle sizes were prepared and characterized. Environmental scanning electron microscope (ESEM) micrographs showed that EG was dispersed homogeneously in composite PCMs. Meanwhile, the distribution uniformity of expanded graphite in composite PCMs was evaluated quantitatively. The thermal conductivities of composite PCMs increase as the mass fraction of EG increases, and the thermal conductivity of paraffin/EG80 (5 wt.%) was 1.492 W/(m·K) in comparison with the value of pure paraffin was 0.355 W/(m·K). X-ray diffraction (XRD) analysis indicated that the fabrication process of composite PCMs was a purely physical process without a new substance produced. Differential scanning calorimeter (DSC) demonstrated that the latent heat of composite PCM was slightly less than the theoretical value. The addition of EG could lead to the improvement of the melting temperature of composite PCMs, while the decrease of the freezing temperature. [ABSTRACT FROM AUTHOR]

• Paraffin microemulsion is prepared and used to make ice slurry. • No ice slurry is found to adhere to the wall. • Paraffin microemulsion is stable after 300 melting/freezing cycling of ice slurry. • The ice crystals at -1°C and -2°C are disc-shape and dendritic-shape, respectively. • The ice crystals are first disc-shape and dendritic-shape, and then evolve disc-shape at -3°C. Ice can be used as the secondary refrigerant. A kind of paraffin microemulsion is prepared as a new ice slurry medium. The crystallization temperature of the microemulsion is no lower than 0.7 °C. The ice percent factor (IPF) of ice slurry prepared with oil-water mass ratio of 1:8 is smaller than that with oil-water mass ratio of 1:9. The addition of hexanol can effectively prevent the ice slurry from adhering to the wall and improve the fluidity. The apparent viscosity of ice slurry increases with the increase of IPF. No phase separation of the microemulsion is found during ice slurry melting/freezing cycling. The morphology and growth process of ice crystals in the formation of ice slurry are different with different experimental temperatures. The higher the supercooling degree, the faster the ice crystals grow. [ABSTRACT FROM AUTHOR]

• A sunlight capturer sponge (PBG) was designed for immobilization of organic PCMs. • The PBG was derived from waste polybutadiene using sugar cube as the self-sacrificial template. • The PBG effectively improved solar-thermal conversion capability of phase change composites (PCCs). • PCCs exhibit excellent leak-proof capability and operational durability. Polybutadiene (PB) waste recycling helps to reduce the ever-growing fossil energy demands because it is usually made from petroleum and natural gas. However, designing and developing a facile and low-cost way to achieve the efficient recycling of PB waste is still a formidable challenge because considerable energy is required to break the polymer chains. Herein, a 3D continuous porous sunlight capturer sponge derived from PB and octadecylamine-functionalized reduced graphene oxide (ODA-rGO) via self-sacrificial template strategy is proposed as supporting skeletons and high-efficiency solar-thermal conversion platform to construct a series of novel phase change composites (PCCs). The prepared PCCs are characterized by excellent leak-proof capability and thermal stability with a heat storage capacity as high as 171.5 J/g. More importantly, highly stable and reversible solar-thermal energy conversion and heat storage capacity without heat loss to the surrounding environment for the PCCs are also demonstrated. Hence the developed PCCs have a potential application in solar energy utilization systems and provide an excellent opportunity for the efficient recycling of PB waste. [ABSTRACT FROM AUTHOR]

[Display omitted] • Si 3 N 4 aerogel can be easily synthesized from preceramic precursors with no catalyst. • Infiltration of phase change material is spontaneous and immediate. • Thermal performances can be optimized tailoring shape-stabilizer pore distribution. • Si 3 N 4 aerogel withstand oxidation over 1000 °C in air. This work presents a new skeleton material for thermal energy storage (TES), a silicon nitride aerogel obtained through the pyrolysis of a pre-ceramic polymer. Silicon nitride offers a good combination of thermal conductivity, high-temperature resistance, and chemical inertness. The aerogel porosity can be spontaneously infiltrated with molten NaNO 3 , which is a typical phase change material (PCM) in high-temperature TES. The Si 3 N 4 /NaNO 3 composite exhibits excellent thermal properties with a thermal energy storage efficiency of 82 %, a limited molten salt leakage, and good stability to thermal cycling. The aerogel withstands oxidation up to high temperature and is chemically inert even in contact with salts. This novel aerogel shows also a notable paraffin absorption ability (used in room temperature TES) with negligible leakage even when in contact with absorbent paper. The so-obtained composite reached ≈ 82.4 vol % of organic PCM and a thermal energy storage efficiency of ≈ 62 % compared to neat paraffin. [ABSTRACT FROM AUTHOR]

Dispersion of conducting polymer-based nanocomposite in Phase Change Materials (PCMs) tends to enhance the thermophysical properties. Present work aims to synthesize and disperse conducting polyaniline@cobalt nanocomposite within the Paraffin matrix to improve the thermo-physical property. Polyaniline based nanocomposites with 1.0 and 2.0 wt% cobalt (PC1 and PC2) were sonicated with paraffin at different weight ratio of 0.1%, 0.5%, 1%, and 5% and characterization of nanocomposite dispersed phase change material was performed. Thermo-physical properties were analysed by using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). Thermal conductivity of nanocomposite enhanced paraffin increased with increase in weight% of both PC1 and PC2 till 1% of its weight in paraffin and decreased for 5% of PC1 and PC2 concentration with paraffin. TGA readings observed drop in initial decomposition temperature of PPC1-5% (Paraffin with PC1 in 5% concentration) and PPC2-5% (Paraffin with PC2 in 5% concentration) by an amount of 08% and 12.4% respectively compared with base PCM Paraffin wax. DSC results of PPC1-0.1% and PPC2-0.5% showed 182.04 J/g and 170.86 J/g latent heat of fusion as compared to Paraffin wax. The samples were tested for 200 thermal cycles and the chemical stability and thermal property were compared with the fresh samples. [Display omitted] [ABSTRACT FROM AUTHOR]

• Metal foam reduces full melting time by 73.7% compared with pure paraffin. • Dividing metal foam into two parts (upper and lower) improves heat transfer. • Metal foam with increased porosity in positive y-direction enhances heat transfer. • Full melting time was reduced by 75.5% by using metal foam with two parts. Latent Heat Thermal Energy Storage (LHTES) is a promising solution to alleviate the supply-demand mismatch in the field of energy utilization. LHTES relies on high-quality phase change materials (PCMs) for high thermal capacity and narrow temperature variation. As an important class of PCMs, paraffin shows advantages of safe, non-corrosive, low-cost, but has limited applications because of relatively low thermal conductivity. The heat transfer performance of LHTES could be remarkably improved by embedding metal foams into PCMs. In the present work, water, paraffin (RT54HC) and copper foam were used to study the heat transfer enhancement, which acted as heat transfer fluid (HTF), PCM and heat transfer enhancer, respectively. The non-thermal-equilibrium energy model was applied in the numerical investigation. The liquid fraction profile was compared between pure PCM and composite PCM. The melting process, interface evolution and the average heat flux density under copper foams with different porosity changing modes were investigated. Results indicated that the incorporation of copper foams into PCM significantly increased the heat transfer performance of LHTES. The full melting time was reduced by 73.7% compared to that of pure PCM. The average heat flux density was improved from 96.38 W to 330.16 W. The optimal method was that dividing the copper foam into upper and lower parts, where the porosity increased separately along with the positive x-direction and positive y-direction. Compared with fixed porosity, the full melting time and average heat flux density were reduced by 6.78% and increased by 4.26%, respectively. [ABSTRACT FROM AUTHOR]

Composite phase change materials (PCMs) possess excellent temperature-regulating capabilities, which can effectively reduce building energy consumption, ultimately contribute to energy saving and carbon reduction. In this study, oleophobic modification was carried out on the Zn modified - white pine biochar. The resultant oleophobic material (Zn-WPC-A) showed excellent supporting capability in the preparation of paraffin wax (PW)/biochar composite PCMs (PW/Zn-WPC-A). The oleophobic properties of biochar could effectively prevent PW leakage, and resulted in a high PW loading rate of 84.26% and an encapsulation efficiency of 82.26%. Zn-WPC-A demonstrated good physical and chemical compatibility with PW. The inclusion of Zn-WPC-A effectively promoted the nucleation in the crystallization process of PW. PW/Zn-WPC-A exhibited a thermal conductivity 3.28 times that of pure PW, displaying excellent thermal responsiveness. The fusion enthalpy of PW/Zn-WPC-A was 107.2 J/g. Furthermore, it displayed excellent stability within the working temperature range with no leakage observed. Simulated housing application experiments illustrated that the use of PW/Zn-WPC-A as building insulation material effectively slowed down the variation rate of indoor temperature. Therefore, the composite PCM using oleophobic modified biochar as supporting material showed excellent thermal performance and strong temperature-regulating capability. [Display omitted] • Oleophobic modification greatly improves the supporting performance of biochar. • The mass ratio of PW in Zn-WPC-A/PW composite PCM is as high as 84.26%. • The oleophobic biochar effectively prevents the leakage of PW from composite PCM. • Composite PCM reduces the temperature variation by about 40% in house. • The addition of biochar increases the thermal conductivity of PW by 227.54%. [ABSTRACT FROM AUTHOR]

Glyceryl stearate and cassava starch (CS) composites were prepared by an esterification process. Formulations containing starch at various concentrations were prepared, being 1, 1.5, 3, 5, 10, 15, 20, and 30 % by weight, respectively. The characteristics of pH, moisture content, FTIR, melting point, latent heat, thermal energy storage, and specific heat capacity of composites were elucidated. The optimal formulation contained 1 % w /w CS, this indicated that the composite was able to maintain its temperature for 9.4 ± 0.5 min, with a melting temperature of 51.9 ± 0.3 °C, solidification temperature of 36.1 ± 1.6 °C, latent heat of fusion of 120 ± 10 J/g, and latent heat of solidification of 126 ± 3 J/g, and specific heat capacity of 2.6 ± 0.2 J/g.K. New bonds were formed in the composite structure of glyceryl stearate and CS at these levels. The composite had a pH that was safe for contact with human skin and a moisture content that could be kept stable for a prolonged time. The innovation and the advantages of a composite materials: 1. The main components are derived from natural materials. 2. Costs effective 3. Sustainability 4. Safety, and 5. Efficacy. Therefore, composites have a high potential as are replacement for paraffin wax bath therapy. • Glyceryl stearate/CS composite shows thermal energy storage efficiency for use in relief from arthritis pain. • Glyceryl stearate/CS composite is an alternative for replacement paraffin wax. • A numerical investigation reveals the addition a small amount of CS content can bring the melting temperature similar to paraffin wax. [ABSTRACT FROM AUTHOR]

In paraffin-based phase change concrete, rice straw can be used as the carrier for paraffin, however, the compatibility between rice straw and cement matrix is poor. In this study, Nano-SiO 2 was grafted on straw-paraffin to improve the interfacial compatibility, and its influences on thermal performance and mechanical properties of phase change cement paste were investigated. Firstly, the phase change potential heat and tensile property of Nano-SiO 2 grafted straw-paraffin were tested. Then, the thermal performance and mechanical properties of cement paste with Nano-SiO 2 grafted straw-paraffin were tested. The results indicate that: (1) The melting temperature of Nano-SiO 2 grafted straw-paraffin (PRS-1%) is 51.15℃, 0.39% lower than paraffin-straw without Nano-SiO 2 (PR), the enthalpy value is 85.64 J/g, 8.74% higher than PR. (2) The tensile strength of PRS-1% is 38.63 MPa, which is 18.63% higher than PR. After 100 phase change cycles, its tensile strength is 23.98% higher than PR. (3) The Nano-SiO 2 grafting can reduce the volume of pores and cracks at straw-paste interface, decrease the content of Ca(OH) 2 and increase the content of C-S-H gel at the interface. (4) Compared with cement paste with PR, the compressive strength and flexural strength of cement paste with PRS-1% increase by 21.05% and 16.55%, respectively. (5) The Nano-SiO 2 grafting (1%) can increase the specific heat capacity and thermal conductivity of straw-paraffin based phase change cement paste by 2.24% and 9.64%, respectively. • Nano-SiO2 reduces the volume of pores and cracks at straw-paste interface. • Nano-SiO2 improves compressive and flexural strength of cement paste with straw-paraffin. • Nano-SiO2 improves specific heat capacity and thermal conductivity of cement paste with straw-paraffin. [ABSTRACT FROM AUTHOR]

In this study two phase change materials (PCMs) mixed with sand were evaluated for distributed latent heat thermal energy storage (LHTES) coupled with a novel Flat-Panel ground heat exchanger (GHE) for shallow geothermal applications. N-Octadecane and a commercial paraffin-based PCM were mixed (30% v/v) separately with sand, which is commonly used as backfilling material for GHE. Both two mixtures underwent 16 thermal cycles and specimen's temperatures and their variation over time were analyzed to evaluate phase change stability and supercooling. Grain size laser diffraction and pore analysis were performed together with optical microscopy, environmental scanning electron microscopy coupled with X-Ray spectrometry (ESEM-EDS) and Fourier transform infrared spectroscopy (FTIR) analysis to evaluate PCMs-sand dynamic interaction over time and temperature. Results shown that sand addition halves n-Octadecane phase change time, although leading to a limited supercooling equal to 1 °C. Sand addition to commercial PCM leaded to a similar increasing in heat transfer, however in absence of supercooling phenomena. These performances were constant through 16 thermal cycles. Therefore, PCMs mixing in sand as mixture for GHEs backfilling material can be considered a strategy to enhance thermal storage of backfilling material, by increasing the underground thermal energy storage and then the exploitation carried out by shallow geothermal applications. • Paraffin-sand mixtures are PCMs suitable for LHTES coupled with shallow ground GHE. • Paraffins' PCM thermal diffusivity is enhanced by sand addition (30:100). • Thermal cycling over Paraffin-sand mixtures lead to sand grain size decreasing. • Different chemical bonding occurs among pure and commercial paraffins. [ABSTRACT FROM AUTHOR]

Phase Change Materials (PCM) possess high heat storage density, but commonly have low thermal conductivity that results in poor heat transfer. Another common problem is the shape stabilization of the storage medium. These problems could be solved by loading the medium with thermally conductive fillers, such as graphite, and encapsulating it in a thermally conductive polymer matrix shell, hence enhancing the thermal properties of both. We suggest a ternary system in which a graphite-epoxy composite provides an encapsulating scaffold to the paraffin, which is also loaded with graphite-based filler. Various graphite-based fillers differing in sizes and geometry were explored, aiming at optimizing their intrinsic properties, such as defect density, and consequently enhancing the thermal properties of the PCM as a whole. It was demonstrated that by judicious choice of the filler, enhancement is achieved for the thermal conductivity of: (1) the shell (epoxy-graphite flakes composite) by 4000% compared to the neat epoxy; (2) the medium (paraffin-graphite flakes composite) by > 2000% compared to the neat paraffin; and (3) the integrated PCM system (paraffin-epoxy-graphite flakes composite) by 1000% compared to that of neat paraffin. The PCM composite is completely preserved during phase change cycling. • Various graphite-based fillers differing in size and geometry were explored for PCM. • Graphite flakes (GF) were found to be the best filler for the overall properties. • Ternary paraffin-GF-epoxy thermally conductive shape-stabilized system was achieved. • Properties of the ternary system were completely preserved during thermal cycling. [ABSTRACT FROM AUTHOR]

This paper discusses how the arrangement of fins can affect the charging process. Mixture of paraffin and copper oxide nanomaterial has been utilized. Several configurations of fins with various position, thickness and length were discussed. Volume fraction of NEPCM in domain is constant, thus reducing melting time is criterion for good efficiency. Outputs reveal that with incorporating fins in both sides, melting process becomes more uniform. Lower melting time with using longer fins is a result of more effective buoyancy forces by dividing the whole domain into smaller blocks. Using fins over both inner and outer pipes shorten the melting time. The main purpose of current modeling is finding the optimized style of fins to gain the highest performance. Nice accommodation of outputs with empirical previous data indicates the verification of code. Unlabelled Image • Melting process with reporting entropy generation was studied. • Y-shaped fins and nanoparticles are utilized to reduce melting time. • FVM is employed for simulation of various fins arrangement. • The fourth case has the highest melting rate. [ABSTRACT FROM AUTHOR]

• Effects of graphite (GP) on thermal performance of composite PCMs were studied. • GP is beneficial for the improvement of thermal performance of composite PCMs. • Thermal conductivity of EP/P50/GP80 is 4 times higher than that of pure P50. • Composite PCMs could keep stable thermal behavior after 200 thermal cycles. Phase change materials (PCMs) with paraffin waxes have been widely used in solar energy systems attributed to their favorable latent heat thermal energy storage (LHTES) properties. However, long-standing drawbacks of serious leakage in the melting state and low heat transfer property significantly limit their practical application in TES. Herein, we report a novel expanded perlite/paraffin/graphite powder (EP/P50/GP) composite form-stable PCM (FSPCM) with enhanced thermal conductivity overcoming the drawbacks of paraffin. The effects of graphite particle (GP) size on the properties of composite FSPCM were investigated by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM). XRD and FTIR analysis suggested that there was favorable chemical compatibility among the composite FSPCMs. GP addition exhibited a positive influence on the thermal stability of EP/P50/GP composite FSPCMs. The smaller the GP size is, the better the dispersion of GP in the composite FSPCMs is. The thermal energy storage capacity per unit volume and cost of EP/P50/GP80 composite were also calculated as 1.95 × 107 kJ/m3 and 23.49 $/kJ. The thermal conductivity of EP/P50/GP80 composite FSPCM was determined as 1.34 W/m∙K, which showed the highest heat transfer rate in the all EP/P50/GP composite FSPCMs and was 4.15 times higher than that of P50 (0.26 W/m∙K). After the thermal cycling tests, the prepared samples exhibited good thermal reliability, and the thermal conductivities were also further improved. Overall, GP showed apparent effects on the heat transfer rate and thermal behavior of the composite FSCPMs. The as-synthesized FSPCMs could have considerable promising in the solar energy systems. [ABSTRACT FROM AUTHOR]

For improving the performance of heat release unit, porous foam has been offered in this article. To reach the better conduction mode, copper oxide has been mixed with paraffin which its melting point is 28 °C. The air flows within the duct and wavy duct was made of aluminum which was full of RT28 in liquid phase at t = 0. For first case, as time rises from 20 to 30 h, solid fraction rises from 0.419 to 0.731 and outlet air temperature declines from 292.83 to 292.14 K. With same change in time for second case, solid fraction augments from 0.731 to 0.959 and temperature of air declines about 0.27%. At t = 15 h, solid fraction for first and second cases are 0.26 and 0.574 and outlet air temperature are 293.09 and 294.64 K, respectively. Amounts of solid fraction after 30 h are 28.9 and 4.98 times greater than those of t = 5 h for first and second cases, respectively. Unlabelled Image • For improving the performance of heat release unit, porous foam has been offered. • Copper oxide has been mixed with paraffin. • Finite volume method is employed to model this unsteady process. • SF for porous case after 30 h is 4.98 times greater than those of t = 5 h. [ABSTRACT FROM AUTHOR]

In this study, the surrogates of long chain paraffins produced from waste cooking oil through hydro-processing was hydro-cracked and hydro-isomerized for studying the process for producing renewable aviation fuel, through carrying out the experiments with varying reaction temperature, pressure, H 2 -to-alkane ratio and weight hourly space velocity (WHSV) over the home-made NiAg/SAPO(silicoaluminophosphate)-11catalyst. The data of conversion, selectivity, isomer yield and isomer-to-normal (I-to-N) alkane ratio were determined for evaluating the performance of the catalyst. The catalyst characterizations of the fresh and spent catalysts were examined through the technologies of Scanning Electron Microscopy (SEM), powder X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and fourier-transform infrared (FTIR) spectroscopy. It was found that the rearrangement of vapor-liquid equilibrium and increase in residence time by adjusting the operating conditions improved the performance of hydro-cracking/isomerization. In addition, based on the results of catalyst characterizations, the unreacted feed was dispersed onto the surface of the catalyst, expected to deactivate the catalyst. • Surrogate of hydro-processed alkanes was converted by max. 71% over NiAg/SAPO-11. • The selectivity of jet fuel, I-to-N alkane ratio reached 88% and 1.5 respectively. • Catalyst activity would be reduced due to the blockage of pore by unreacted feed. [ABSTRACT FROM AUTHOR]

• MIL-101 successfully doped with Cu and Ni nanoparticles. • The loading effect of nanoparticles on separation of ethylene/ethane was investigated. • The effect of temperature on the performance of as-synthesized adsorbents were studied. • The selectivity and capacity of doped MIL-101 adsorbents enhanced toward ethylene. • MIL-101 with 6% Cu loading received maximum ethylene capacity and selectivity among other adsorbents. In the present study, MIL-101 doped with copper and nickel nano particles were successfully synthesized and applied as promising adsorbents for separation of ethylene/ethane mixture. The as-synthesized adsorbents were characterized using XRD, N 2 adsorption–desorption and FESEM analysis. Afterward, the single-component isotherms of C 2 H 4 and C 2 H 6 were measured with manometric adsorption apparatus at temperatures of 293, 303, 323 and 343 K and pressures from atmospheric to 2 bar. The results showed that MIL-101 loaded with Cu nano particles has higher adsorption capacity (2.78 mmol/g) as well as higher selectivity (12.9) toward ethylene when compared to MIL-101 and MIL-101 loaded with Ni nano particles. It was found that Sips model could better predict the experimental data than the Langmuir and Freundlich models. Finally, to investigate the performance of adsorbents in the selective separation of ethylene/ethane mixtures with different compositions, Ideal Adsorbed Solution Theory (IAST) method was used. [ABSTRACT FROM AUTHOR]

The Chinese Kang is indispensable for domestic heating during the winter in the rural residence of northern China. However, it still has certain drawbacks such as the huge surface temperature difference and limited effective heating time. A novel phase change material Chinese Kang (PCMCK) is developed by combining paraffin and the traditional Kang to overcome such disadvantages. A comparison test was conducted to analyze the thermal performance of PCMCK and traditional Kang. According to the data, the coefficient of variation of the PCMCK is significantly lower than that of the traditional Kang during each time period. Thus, the PCMCK surface temperature distribution is much more uniform. Additionally, after the burning ceased, the indoor temperature of a PCMCK-heated room still kept rising until midnight due to the excessive heat absorbed by #48 paraffin. The mean indoor temperature is 2.94 °C higher than that of the traditional Kang-heated room. As a result, the thermal character of phase change material is fully utilized. The PCMCK can effectively improve the indoor thermal comfort, the uniformity of Kang surface temperature and extend the heating period significantly as well. • The PCMCK surface temperature distribution is much more uniform comparatively. • The indoor mean temperature of the PCMCK room is raised about 3 °C comparatively. • The indoor temperature of PCMCK-heated room kept rising until midnight. • The temperature of the PCMCK dropped more slowly when it decreased after midnight. [ABSTRACT FROM AUTHOR]

Energy shortages and rapid increase in its demand are amongst the major problems facing the world today. In response to the rapid depletion of fossils fuels, other alternative energy sources have been explored. One of the methods of generating energy is converting plastics into usable fuel. Two major problems facing the world today prompting to pyrolysis are disposal of plastic waste due to their non -biodegradable nature and depletion of fossil fuels as a result of the continuously rising demand. The feedstock for the pyrolysis plant was selected to be Polyethylene Terephthalate (PET) in the form of flakes ranging from 8 – 12 mm and were supplied by PETRECO. The binary dominance matrix was used to examine the optimal heat exchanger. The helical heat exchanger was designed to reduce cost by elimination of a water pump as the heat transfer fluid lost heat to the atmosphere. It was easier to obtain liquid paraffin from the chosen raw materials since it was already in the paraffin chemical structure. In the pyrolysis plant, the temperature in the reactor increased at a maximum rate of 6˚C/min regulated by a temperature controller and each batch took 60 minutes. The percentage weight of paraffin yield was a maximum of 40% weight of the feedstock. Therefore, 1 kg of plastic waste was converted to 286 ml of paraffin fuel. The presence of oxygen in the PET structure enhanced the solid residue of the product. The properties of the solid residue left in the reactor were sufficient to recommend for PET bricks. The solid residue had a maximum compressive strength of 10 N/mm2 which was within the standard range and had less water absorbing tendencies and hence a longer lifespan. Catalytic pyrolysis can also be explored for future research in order to improve product quality. [ABSTRACT FROM AUTHOR]

Thermal management system is a key component to maintain the performance of lithium-ion batteries in electric vehicles. Cooling technology based on phase change materials with single-phase transition range has been proposed by many researchers but the temperature control of batteries is not ideal for high charge/discharge rates and cycle tests. Herein, we designed a novel phase change material consisting of paraffin with dual-phase transition ranges (around 34 °C and 48 °C), expanded graphite (thermal conductivity = 40 W/m K), and epoxy resin with a mass ratio of 5:2:3. This material was combined with graphite film (in-plane thermal conductivity of 1400 W/m K) to prepare a thermal management module. Graphite film and expanded graphite form an excellent heat conduction structure. Epoxy resin endows this composite with satisfactory mechanical properties, even at 70 °C. The paraffin provides a double buffer effect that minimizes the temperature increase of the batteries and the temperature differences between the batteries in the pack due to the broad phase transition range. As a result, the maximum temperature of the batteries is 33 °C and the maximum temperature difference between the batteries is only 1.4 °C, even at the highest 4C discharge rate. In addition, the maximum temperature of the batteries is only 44.8 °C after six extreme cycles. • The chosen paraffin has a double buffer effect on temperature rising of batteries. • Mechanical properties of this phase change material are prominent, even at 70 °C. • The maximum temperature in battery pack is 33 °C at the highest 4C discharge rate. • The maximum temperature difference is 2.8 °C under all charge/discharge rates. • Highest temperature of the batteries is only 44.8 °C in the extreme cycle test. [ABSTRACT FROM AUTHOR]

To examine if range of motion of the shoulder treated with paraffin will be better than that of the shoulder treated with sustained stretch alone. Pilot randomized controlled trial. Regional burn center. Patients (N=23) who sustained a burn injury, with a shoulder active abduction and/or flexion in the +70° to +150° degree range, who were 14 years or older, were receiving follow-up physical therapy after discharge from hospital, and provided a signed consent to participate. Group A received sustained stretch and paraffin, and group B received sustained stretch only. Both groups had 6 sessions of treatment over 2 weeks. Active range of motion (AROM) and active-assisted range of motion (AAROM) for shoulder flexion (SF) and shoulder abduction (SA) were measured before and after each treatment session. For pretreatment measurements, only the results for SF AAROM had significant time effects. For posttreatment measurements, SF AROM and SF AAROM had significant effects for time. Session 1 was significantly lower than sessions 2, 3, 4, and 6 for both measures, and additionally, session 1 was significantly lower than session 5 for SF AAROM. For SA AROM, a group-by-time interaction effect was significant, with scores for the paraffin group relatively stable across sessions, and the nonparaffin group had peaks at sessions 3 and 6. There were no significant effects for (1) within-session changes to examine improvement during a session or (2) presession scores across the 6 sessions showing maintenance of motion. Total change from the first session presession measurement to the sixth session postsession measurement for the 2 treatment groups were nonsignificantly different. As shown in this study, sustained stretching with paraffin may be a valuable adjunct to range of motion intervention for the shoulder after burn injury. [ABSTRACT FROM AUTHOR]

In this work, paraffin/carbon nanotubes/graphene aerogel (Pa/CNTs/GA) nanocomposite with different CNTs lengths were synthesized. CNTs' length was changed by refluxing them in a mixture of acids for different times, by which the initial micrometer length of CNTs was reduced to 1200 and 205 nm after 0.5 and 1 h refluxing. To complete dispersing CNTs in paraffin, they were functionalized for the second time using dodecylamine. By inserting paraffin composites into the aerogel using vacuum impregnation, the thermal conductivity of the aerogel increases greatly. Melting and freezing latent heat of both samples of graphene aerogel composite containing 0.5 and 1 h refluxed CNTs was reduced compared to that of the pure paraffin and Pa/CNTs composite. The specific heat of the Pa/CNTs/GA composite containing 1 h refluxed CNTs was reduced compared to that of the Pa/CNTs (1 h refluxed) composite, but it was increased for the samples containing 0.5 h refluxed CNTs. Also, Pa/ZnO, Pa/TiO 2 , and Pa/Al 2 O 3 composites were prepared and their thermophysical properties were compared with those of Pa/CNTs composites. [Display omitted] • Pa/CNTs/GA composites with different CNTs lengths were synthesized. • Thermal conductivity of Pa/GA increased up to about 7 times of GA. • Fusion latent heat of Pa/CNTs/GA was reduced comparing with pure paraffin. • Solidifying latent heat of Pa/CNTs/GA was reduced comparing with pure paraffin. • The specific heat of the Pa/CNTs/GA was less than that of the Pa/CNTs. [ABSTRACT FROM AUTHOR]

As an environment-friendly material, bamboo has a wide application prospect in the fields of construction, furniture and decoration. However, the problems of dimensional instability and susceptibility to mildew of bamboo seriously affect the economic values of bamboo and bamboo-based products. The performance of bamboo can be improved by modification treatment, but there are problems such as toxicity of modifier, complicated modification process and high modification cost. Therefore, from the perspective of facile, effective and green modification, bamboo with hydrophobicity, dimensional stability and mold resistance effect was prepared by high-pressure impregnation treatment of a wax-based composite system composed of non-toxic and low-cost paraffin, microcrystalline wax and stearic acid. The results showed that the wax-based composite system significantly improved the hydrophobicity, dimensional stability and mold resistance of bamboo. The 8 days' water absorption of bamboo modified by paraffin, microcrystalline wax and stearic acid (PSM-B) was reduced by 33.14 % compared with the raw bamboo. The swelling resistance coefficient and the surface contact angle of PSM-B reached 81.04 % and 108.8°. PSM-B has almost no mold occurred in the 20-day antifungal test. This study provides a new idea for the protection of bamboo products, which has a broad application prospect. • There have been studies on the modification of wood and bamboo using paraffin, vegetable oil, or a paraffin/vegetable oil composite system, but relevant scholars have focused their research on using a single wax or vegetable oil and a normal temperature and pressure impregnated paraffin/vegetable oil composite system to modify wood and bamboo. There is no research on the heat treatment process to realize the moisture shielding of bamboo by one-step method. In addition, the fine control of wax-based composite system, the controllable preparation method of modified bamboo and its performance influencing mechanism are still unclear, and in-depth systematic research is needed. • The impregnation process of bamboo was improved to make the wax-based composite system impregnate bamboo more adequately (10 MPa, 70 °C, 30 min to 20 MPa, 80 °C, 2 h) in comparison with the study of Piao et al. The addition of microcrystalline wax increased the melting point of the system (62.9 °C to 76.5 °C), which improved the thermal stability of the wax-based composite system and expanded its application in high temperature environments. • This is the first combination of paraffin stearic acid and microcrystalline wax to modify bamboo through a combination of physical and chemical methods, using the optimal ratio to achieve wax composite system can provide theoretical basis and technical support for the preparation and performance control of bamboo green modifiers. • This research does not use mold inhibitors and preservatives, and uses heating and high-pressure immersion treatment methods to study a one-step heat treatment process to achieve bamboo moisture shielding, and prepare bamboo materials with permanent styling and antifungal functions. It is a bamboo material modification with an important innovation in method. • In this research, technologies such as FTIR, XPS and so on, are applied to the wax-based composite system/bamboo heterogeneous interface study, and the research method is innovative, which can provide reference for related or similar research in the future. [ABSTRACT FROM AUTHOR]

SiC porous ceramic carriers with adjustable porosity of 79.9%–90.7% were prepared by foam gel-casting forming and carbothermal reduction reaction sintering, using industrial waste fine-grained iron tailings and graphite powder as raw materials. Then paraffin/SiC shape-stable phase change materials were prepared by spontaneous infiltration employing paraffin as phase change material. Thermal conductivity of the SiC carriers (0.17–0.31 W/m·K) is 2.7–3.7 times higher than that of iron tailings porous ceramics with the same porosity. A thermal conductivity model of the SiC carrier is established and verified by experimental data. Phase composition, microstructure, molecular structure, mechanical properties and thermal properties of the shape-stable phase change materials were characterized by XRD, SEM, FT-IR, WDW, Hot Disk and DSC, respectively. There is only a physical combination between paraffin and SiC carriers. The compressive strength of the shape-stable phase change materials (2.0–2.3 MPa), weight loss and latent heat loss are less than 5% and 4.7% after 100 thermal cycles, respectively, which can meet the application requirements as a functional material. Thermal conductivity of the shape-stable phase change materials (0.7–0.73 W/m·K) is significantly improved, a latent heat of 138.5 J/g, and the efficiency of energy storage and release is 2.3–3.3 times as good as than that of paraffin, suggesting that this material is capable of recycling and reusing waste heat as a highly efficient thermal energy storage system. • SiC porous ceramics carrier was prepared from iron tailings. • The thermal conductivity of SiC carrier is 2.7–3.7 times higher than that of iron tailings with the same porosity. • A novel application method of industrial waste iron tailings to preparing SSPCM. • SSPCM shows enhanced thermal conductivity and efficiency in storing and releasing thermal energy. • SSPCM maintains excellent performance even after 100 thermal cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • SEBS blends containing paraffin with same content but different T m was prepared. • Shape memory performance of different SEBS/paraffin blends was investigated. • Blends with low or high T m paraffin showed different shape fixing ratios. • The shape fixing ability was related to the existing forms of paraffin crystals. Poly(styrene-b-[ethylene-co-butylene]-b-styrene) (SEBS)/paraffin system is a promising class of shape memory polymers and the transition temperature of such materials could be flexibly regulated by choosing different paraffins. However, the difference in shape memory performance of SEBS/paraffin blends containing paraffin with same content but different melting temperature (T m) has not been comparatively studied. In this work, two series of SEBS/paraffin blends containing same content paraffin (30 and 70 wt%, respectively) with T m of 28.5 and 61.3 °C (denoted as P L and P H , respectively) were prepared and their shape fixing ratios (R f s) under conventional shape memory (CSM) and reversible plasticity shape memory (RPSM) programming methods were investigated. It was found that these blends with the same paraffin content showed different R f s regardless of the programming method. For example, the 30 wt% P H -containing sample exhibited higher R f under CSM programming, while the 70 wt% P L -containing sample showed higher R f under RPSM programming. By investigating microstructural changes, a possible explanation for the shape memory performance of SEBS/paraffin blends containing paraffin with different T m was proposed. This work was helpful to deepen the understanding of shape memory mechanism and broaden the application of SEBS/paraffin-based shape memory polymers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Influence of carbon doping concentration on the mechanical properties of PRSA is investigated. • PRSA, under the influence of carbon doping, has dual performance. • Mechanical behavior of the PRSA matrix can be manipulated with carbon doping for actual applications. Aerogels are different types of porous and solid materials that exhibit a strange set of extraordinary material properties. Aerogels have great potential for use in the fields of heat, sound, electronics, and especially thermal insulation. This paper investigates the influence of carbon doping concentration on the mechanical properties of paraffin-reinforced silica aerogel (PRSA). To do this investigation, Young's module (YM), stress–strain curve, and ultimate strength (US) values at various carbon-doped particles of 1 to 10 % were reported by molecular dynamics (MD) simulation. The results show that the PRSA, under the influence of carbon doping, has dual performance. To be more precise, by adding the amount of carbon doped from 1 to 3 %, the US and YM of the PRSA rose from 329.96 and 1137.20 MPa to 353.73 and 1268.44 MPa. In other words, the mechanical strength of the PRSA increases in a limited ratio. However, by increasing carbon doping from 3 to 10 %, the US and YM of the PRSA reduced to 306.233 and 1041.88 MPa, respectively. So, it is expected that the mechanical behavior of the PRSA matrix to be manipulated with carbon doping for actual applications. [ABSTRACT FROM AUTHOR]

Thermal storage technology based on phase change material (PCM) holds significant potential for temperature regulation and energy storage application. However, solid–liquid PCMs are often limited by leakage issues during phase changes and are not sufficiently functional to meet the demands of diverse applications. Fortunately, it has been recognized that many polymer materials can effectively address these problems in the field of phase-change energy storage. These polymers exhibit exceptional performances and provide versatile options for energy storage applications. Due to the wide range of available polymers, different structures and properties are be utilized in various ways for energy storage purposes. This review focuses on three key aspects of polymer utilization in phase change energy storage: (1) Polymers as direct thermal storage materials, serving as PCMs themselves; (2) strategies for the development of shape-stable PCMs based on polymers, including vacuum impregnation, direct blending, chemical grafting, electrospinning, microencapsulation, and the homogeneous-to-heterogeneous-strategy; and (3) polymer-enhanced multifunctional PCMs, which can exhibit additional properties such as flexibility, hydrophobicity, and photo-thermal conversion. The objective of this review is to expand the application of polymers in the field of phase change energy storage and to provide more research ideas for the development of novel, high-performance multifunctional shape-stable PCMs with excellent performances. [Display omitted] • Detailed strategy for polymer-based shape-stabilized PCM. • Development of polymer-enhanced multifunctional PCMs. • Polymer-based composite PCMs for intelligent applications. • The prospects for the future development of polymer-based composite PCMs. • A guide to expand polymer applications in phase change energy storage. [ABSTRACT FROM AUTHOR]

• A promising microfluidic encapsulation technique is proposed. • A novel phase change heat storage microcapsule was developed. • Microencapsulated phase change materials for storage/release of thermal energy such as solar energy. Phase change materials (PCMs), renowned for their exceptional heat storage capabilities, have been extensively utilized in solar energy utilization. However, the persistent challenge of liquid leakage during their use remains unresolved. In this study, a promising microfluidic encapsulation technology is presented, leading to the development of a novel phase change heat storage microcapsule. Differential scanning calorimetry measurements confirm the retention of over 88% of the latent heat of the phase change material (up to 171.8 J/g). Additionally, CFD modeling demonstrates that the geometric structure of the microcapsules significantly enhances heat transfer, effectively addressing the issue of low heat transfer efficiency in PCM systems. Leakage tests have demonstrated the exceptional cyclic stability of microcapsule encapsulation, as it exhibits no leakage even after undergoing 100 consecutive melting-freezing cycles. Moreover, it experiences only a minimal 4.2% loss in latent heat. The incorporation of microcapsule encapsulation into phase change heat storage technology opens up exciting opportunities for harnessing the full potential of phase change materials. [ABSTRACT FROM AUTHOR]