Paraffin Phase Change Materials Research Articles

Enhancing the performance of paraffin's phase change material through a hybrid scheme utilizing sand core matrix

Smart waste management and valorisation is presented in the current investigation. Iron is collected from mining wastewater stream and augmented with sand as a supporting material to produce sand core. The sand core pellets encapsulated in paraffin’s to enhance its feasibility as phase change material (PCM). Sand core was characterized using X-ray diffraction and Scanning Electron Microscope (SEM) augmented with energy dispersive X-ray spectrum analysis. Experimental test is achieved by mixing sand core/iron and paraffin that is signified as an encapsulated phase change material. The encapsulated sand core-PCM is embedded in varies mass weights of percentages of 0.5, 1.0, 1.5 and 2.0% and labeled as 0.5%-sand core-PCM, 1.0%-sand core-PCM, 1.5%-sand core-PCM and 2.0%-sand core-PCM. The encapsulated sand core-PCM is embedded into a heat exchanger of the vertical type model that is connected with a flat plate solar collector. Such collector is heating the heat transfer carrier, which is exposed to the heat exchanger for melting the PCM. The experimental work is conducted across the solar noon where the solar intensity in the region is reached to 1162 W/m2 at the time of conducting experiments. Water is applied and supposed as the working heat transfer fluid transporter and pumped into the system at the rate of 0.0014 kg per second. The experimental result revealed that the heat gained recorded an enhancement from 7 to 48 kJ/min when the 1.5%-sand core-PCM system is applied. Thus, the results showed the system is a good candidate by increasing the system efficiency with 92% as a potential solution of solar energy storage at the off-time periods.

Preparation and properties of ultra-thin-walled energy storage paraffin microcapsules for naval applications

Due to the special nature of weather conditions at sea, the tricky status quo of heat loss in readiness or operational clothing, there is an urgent need for special insulated clothing materials to withstand harsh environments, maintain body temperature, and increase comfort for naval personnel who have been at sea for a long period of time in preparation for battle or combat. Paraffin is a special kind of phase change energy storage material, And the preparation of paraffin microcapsules is an effective way to solve the above problems, in which the ultra-thin-walled energy storage paraffin capsules have the advantages of large volume, accommodating more paraffin phase change materials, good energy storage effect and low cost. In this study, three kinds of paraffin microcapsules with core-shell structure were prepared by encapsulating a membrane with stable performance on the surface of paraffin particles using microencapsulation and layer-by-layer self-assembly techniques. We characterized their thermal storage capacity, composition and morphology by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier infrared spectroscopy, and optical microscopy, and compared their performances. The results show that the paraffin microcapsules prepared by layer-by-layer (LBL) self-assembly technique in this study have good thermal storage performance and stability, and their thickness increases with the increase of the number of layers, and the materials used in the experiment wrapped the liquid paraffin layer by layer, which is expected to be practically applied in the field of naval energy storage materials.

Effects of surface wettability and density change during solidification of paraffin phase change materials

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.

The effects of fins number, metal foam, and helical coil on the thermal storage enhancement of the phase change material: An experimental study

Phase change materials (PCMs) are commonly used to store thermal energy as latent heat storage. The low thermal conductivity of PCMs elongates the charging/discharging process time. Using porous media and fins to improve the PCMs’ conductivity are two suggested solutions that have been evaluated in recent research studies. The present work experimentally analyzed the effect of fins usage over a helical tube, the number of fins, and filling the coil internal space with porous media during the energy storage in Paraffin PCM. The thermal conductivity of the PCM is enhanced through the utilization of porous metal foams made of copper, which have a porosity of 0.9 and a pore density of 12 pores per inch. The sole effects of using porous media or fins, in line with their simultaneous effects, and the number of fins on the system’s heat transfer enhancement are investigated. The heat transfer enhancement has been evaluated by examining parameters like the temperature distribution of different points of the heat storage tank, the charging/discharging time, the mean temperature response, the Stefan number, and the obtained discharge power. Results indicate that using either fins or porous media in the storage tank can remarkably improve thermal performance. Furthermore, the best heat transfer enhancement is obtained when using fins and porous media simultaneously. Also, using more fins beside the porous media could further reduce the charge/discharge time. For instance, comparing the cases with only 25 fins, only porous media and the case combined cases reveal respectively about 8.5%, 11%, and 25% decrease in the time of charging process. Also, the best case with 35 fins beside the porous metal foam can reduce the charging/discharging time by about 25%-28%.

High-Safety Lithium-Ion Battery Separator with Adjustable Temperature Function Inspired by the Sugar Gourd Structure.

As the power core of an electric vehicle, the performance of lithium-ion batteries (LIBs) is directly related to the vehicle quality and driving range. However, the charge-discharge performance and cycling performance are affected by the temperature. Excessive temperature can cause internal short circuits and even lead to safety issues, such as thermal runaway. The separator plays a crucial role in protecting the battery from regular operation, preventing direct touch between the cathode and the anode while allowing the transport of lithium ions. In this study, we have designed a thermoregulating separator in the shape of calabash, which uses melamine-encapsulated paraffin phase change material (PCM) with a wide enthalpy (0-168.52 J g-1) to dissipate the heat generated inside the battery promptly. Under extra-long-use conditions, the heat emitted by the battery is absorbed by the PCM without causing a significant temperature rise that triggers thermal runaway. The PCM separator can effectively suppress the temperature increase caused by battery penetration. Due to the unique structure of the PCM, the battery is short-circuited; it can significantly delay the internal temperature rise of the battery and quickly dissipate the heat, which is consistent with the characteristics of natural calabash in nutrient absorption and water diffusion, improving the melting and heat storage efficiency of the PCM. The design of the phase change separator provides an effective reference for overheat protection and improved safety in lithium-ion batteries.

Energy storage density enhancement in paraffin phase change material emulsions: A comparative study with two different base fluids

This investigation examined the thermophysical properties of emulsions comprising paraffin 56/58 phase change material (PCM) dispersed in water and ethylene glycol (60 wt%) aqueous solution to optimize energy storage density for low-temperature thermal applications. Dynamic Light Scattering analysis revealed a uniform dispersion of paraffin 56/58 PCM droplets in the basefluids, with an average diameter of approximately 150 nm achieved by incorporating sodium dodecyl sulfate surfactant. The latent heat of fusion for emulsions containing paraffin 56/58 PCM in ethylene glycol (60 wt%) exhibited values of 37.5/41.7, 58.5/63.9, 73.8/75.43, and 93/90.25 J/g for concentrations of 20, 30, 40, and 50 wt%, respectively, during melting/solidification phases. Furthermore, the highest energy storage densities of 306.95 and 361.3 kJ/kg were attained at a PCM concentration of 50 wt% in ethylene glycol (60 wt%) and water-based emulsions, respectively, surpassing those of similar working fluids. It is also indicated that water-based paraffin 56/58 PCMs offer superior energy storage density. However, under severe operating conditions such as extreme temperatures, ethylene glycol (60 wt%) based paraffin 56/58 emulsions demonstrate greater suitability, as the evaporation and freezing points of the basefluid can be adjusted by modulating the ethylene glycol concentration ratio.

Experimental study on the thermal response of a metal foam dual phase change unit thermal storage tank

Adding fins or metal foam to phase change units can effectively enhance the heat storage efficiency of thermal energy storage (TES) tanks, thereby improving the reliability of TES tanks in coordinating renewable energy supply and demand. In this study, an experimental TES tank platform was designed and constructed to investigate how the addition of straight fins, metal foam, and straight fin/metal foam composite materials to paraffin affects the temperature response during the heat storage process. High-temperature water was selected as the heat transfer fluid (HTF) and injected from the top into the TES tank at the same paraffin fill level, and T-type thermocouples were arranged along the central axis of the phase change unit. TES tanks filled with either pure paraffin or composite phase change materials were tested by varying the HTF inlet temperature and velocity, and temperature response data were captured and recorded using a KEYSIGHT DAQ970A data logger. The results indicated that increasing the HTF inlet temperature significantly enhanced the heat storage rate while increasing the HTF inlet velocity had varying effects on different phase change units. A comprehensive analysis suggested that an inlet velocity of 1.3 m3/h (from a range of 0.8–1.8 m3/h) was reasonable. The addition of enhancement measures improved the temperature drift phenomena and effectively increased the temperature response rates and distribution uniformity. Moreover, the straight fin/metal foam composite material exhibited the best performance.

Preparation of cellulose-paraffin composite foams by an emulsion–gelation method using aqueous inorganic salt solution for thermal energy regulation

Leakage of paraffin phase-change materials during phase transitions limits their application. Cellulose is an environment-friendly material that has the potential to resolve leakage problems. In this study, large-scale, firm, and no leakage cellulose-paraffin composite foams were fabricated via an emulsion–gelation method using a cellulose/LiBr solution. Spherical paraffin particles were embedded into the three-dimensional nanofibrillar network structure of the regenerated cellulose, with no chemical interaction between the paraffin and cellulose. This cellulose-paraffin foam exhibited excellent mechanical properties, with a maximum elastic modulus value of 7.08 MPa. No leakage was observed at 80 °C even when the paraffin content was 80 %. During phase change, the maximum latent heat was 173.2 J g−1. The thermal conductivity was relatively low (46.5–77.2 mW m−1); this represented 23–38 % of the thermal conductivity of pure paraffin. Therefore, foams are promising materials for efficient and reliable thermal energy storage applications.

Direct synthesis of porous aluminum nitride foams for enhancing heat transfer and anti-leakage performance of phase change materials

Organic phase change materials (PCMs) suffer from low thermal conductivity and easy leakage, which limit their application in heat storage and thermal management. In this work, porous AlN skeletons were synthesized to solve these problems of paraffin PCM. Using Al powders as raw material, porous AlN skeletons were prepared through the ice-templated method and the direct nitridation reaction. The skeletons were impregnated with paraffin to prepare phase change composites (PCCs). The thermal conductivity of the PCC with 55.6 wt% AlN reaches 9.1 W m−1 K−1 in the axial direction, which is 4550 % of paraffin. This PCC retains a high enthalpy of 105 J g−1 and has good thermal stability. Moreover, the porous AlN skeletons can effectively absorb paraffin so that all PCCs maintain a stable shape. This study provides a simple and efficient method to synthesize porous AlN and to solve the heat conduction and leakage issues of PCMs.

Enhancing the performance of thermal energy storage by adding nano-particles with paraffin phase change materials

Abstract Phase change materials (PCMs) are now being extensively used in thermal energy storage (TES) applications. Numerous researchers conducted experiments using various circumstances and materials to optimize storage performance. A study was conducted to compare the numerical research of the melting process of paraffin wax using a hybrid nano-integrated paraffin PCM with graphene oxide (GO) and single-walled carbon nanotubes (SWCNTs) in a TES unit. Hence, this research focuses on a sustainable TES system using hybrid nanomaterials (PCM + GO, PCM + SWCNTs, PCM + GO + SWCNT) with varying concentrations of nanoparticles. The objective is to improve the thermal characteristics of PCMs. The main aim of this study is to examine the numerical analysis of the system inside a TES that has a rectangular form. The numerical experiments were conducted using the finite-volume solver Ansys Fluent. The obtained findings show the thermophysical characteristics fluctuations with respect to the solid volume fractions, liquid fraction, temperature, and velocity inside the TES system. Implementing an effective heat transfer mechanism from the point of capture to storage and later consumption necessitates the employment of a heat transfer fluid. The inclusion of SWCNT particles at a concentration of just 10% has been seen to expedite the melting phenomenon. Furthermore, incorporating GO in conjunction with SWCNT alleviates this phenomenon, resulting in a melting behavior that resembles that of unadulterated paraffin. Additionally, the introduction of just 1% GO, combined with SWCNT, leads to a rapid alteration in surface heat transfer coefficient compared to the scenario with single SWCNT and paraffin. These insights hold practical relevance for the development of TES systems in various applications.

Latent heat energy storage using nanomaterials as a heat sink for the prevention of thermal runaway: A study in conjugate heat dissipation

Phase change material (PCM) based heat sinks are the passive cooling technologies that achieve required thermal management. PCM increases the energy storage capacity, and adding nanomaterial to the PCM improves the heat sink capacity. However, there are very few studies on the effect of heat load on thermal performance in this field. This research focuses on the experimental investigation of the thermal characteristics of Nano-PCM-based heat sinks with varying base roughness and load. To enhance the heat transfer characteristics of paraffin PCM, two distinctive nanoparticles, i.e., graphene and Silver Titanium Dioxide (Ag-TiO2), are used. Two different heat sinks containing one of the nanoparticles mixed PCM were tested. However, one more heat sink containing only PCM was also used in the study. Scanning electron microscope analysis, thermogravimetric analysis, differential scanning calorimetry, and energy dispersive X-ray analysis were performed, and the performance was measured at various heat loads (25 W, 35 W, and 45 W), and different roughness configurations (R1, R2, and R3) with PCM and Nano-PCM. The study's findings indicate that the R3 configuration containing graphene-PCM performs better than the others. It had a longer charging time (heating), a shorter discharging time (cooling), and a more constant temperature during discharging. Comparing the discharging cycles of AgTiO2-PCM, graphene-PCM reveals a minor difference. The cooling rate depends on the heat load and a heat load of 45 W results in a faster cooling rate.

Experimental study on the performance enhancement of PV/T by adding graphene oxide in paraffin phase change material emulsions

Traditional water-based PV/T systems have low heat storage density, high PV backsheet temperatures, and low energy utilization in practical applications. In this work, nanoparticles were applied to improve thermal conductivity and simultaneously emulsions were added to enhance energy storage density of the conventional heat transfer media. Furthermore, the synergistic effect of nanocomposite Phase Change Material Emulsions (PCME) as the heat transfer medium on the thermoelectric efficiency of PV/T was studied in a real system. Specifically, the water-based 30 % paraffin emulsions with graphene oxide (GO) concentration of 0.01, 0.02 and 0.03 wt% were prepared by ultrasonic stirring and their thermophysical properties were characterized. The results show that the 30 wt% paraffin emulsion with addition of 0.02 wt% GO has the phase change temperature of 35 °C, latent heat of 42.93 J/g, thermal conductivity of 0.505 W/(m·K) and viscosity coefficient of 0.91. It shows the thermal efficiency of the paraffin/GO emulsion increased by 92.28 %, the electrical efficiency increased by 8.87 %, the comprehensive efficiency increased by 45.75 %, and 15.8 % increase in heat collection for the heat exchange tank in comparison with the water. It is concluded application of PCME would improves the thermoelectric performance of the system than traditional water-based PV/T systems.

Form-Stable Composite Phase Change Materials Based on Porous Copper-Graphene Heterostructures for Solar Thermal Energy Conversion and Storage.

Solar-thermal energy conversion and storage technology has attracted great interest in the past few decades. Phase change materials (PCMs), by storing and releasing solar energy, are able to effectively address the imbalance between energy supply and demand, but they still have the disadvantage of low thermal conductivity and leakage problems. In this work, new form-stable solar thermal storage materials by impregnating paraffin PCMs within porous copper-graphene (G-Cu) heterostructures were designed, which integrated high thermal conductivity, high solar energy absorption, and anti-leakage properties. In this new structure, graphene can directly absorb and store solar energy in the paraffin PCMs by means of phase change heat transfer. The porous structure provided good heat conduction, and the large surface area increased the loading capacity of solar thermal storage materials. The small pores and superhydrophobic surfaces of the modified porous G-Cu heterostructures effectively hindered the leakage issues during the phase change process. The experimental results exhibited that the thermal conductivity of the prepared form-stable PCM composites was up to 2.99 W/(m·K), and no leakage took place in the solar-thermal charging process. At last, we demonstrated that the PCM composites as an energy source were easily integrated with a thermoelectric chip to generate electric energy by absorbing and converting solar energy.

Modelling for the mitigation of lithium ion battery thermal runaway propagation by using phase change material or liquid immersion cooling

In this study, a three-dimensional (3D) thermal runaway (TR) model with conjugate heat transfer submodel is adopted. TR behaviors for a battery pack with 12 prismatic lithium-ion batteries (LIBs) are then simulated. Three thermal safety measures of TR protection from internal shorting in Cell 1 to pack level configuration are compared and evaluated. Paraffin phase change material (PPCM) is firstly proposed to delay the TR propagation between LIBs with solid-liquid phase change as heat transfer mechanism. Different thicknesses of PPCMs are compared to verify the TR mitigation performance of the PPCM under thermal abuse condition. The TR time for the Cell 2 is delayed to be 64 s, 266 s and 414 corresponding to PPCM thickness of 1.8 mm, 3.6 mm and 5.4 mm. As the simulation results shows, this TR time can be further delayed to 798 s by a strategy with combing PPCM with insulation. In addition, this work proposes a novel thermal safety protection based on immersion cooling with pool boiling of fluorinated liquid as heat transfer mechanism. We observe that the average temperature of Cell 2 - Cell 12 tends to be within 34 °C under immersive cooling condition, which indicates the possibility to prevent the TR.

Parametric analysis of a solar parabolic trough collector integrated with hybrid-nano PCM storage tank

ApplicationNewly developed fluid called phase change materials (PCM) used to accumulate solar thermal energy. This paraffin-based fluid is mixed with hybrid nanoparticles composed of titanium dioxide “TiO2″ and copper oxide “CuO”. Using this fluid, we hope to improve the efficiency of industrial solar thermal installations. Purpose and MethodologyA computational fluid dynamics (CFD) model was developed using Ansys Fluent 19, coupled with a home code implemented in the C programming language as a “user-defined function”. Initially, the model was validated against experimental data, then a parametric study was conducted to investigate the impact of pure paraffin PCM and hybrid nanoparticles-paraffin PCM, as well as the effect of varying the mass fraction of nanoparticles and the heat transfer fluid flow rate. geometric parameters such as the number of fins installed in the storage tank were also considered during the analysis. Major findingsOn the basis of the obtained results, it was found that the incorporation of paraffin phase change materials (PCMs) within a storage tank has the potential to significantly prolong the operational duration of solar systems. Additionally, hybrid nanoparticles at 1% concentration increased the average storage tank temperature by 8% and decreased the melting time by 13.29% compared to pure PCM.

Enhancing Thermal Performance of Autoclaved Aerated Concrete (AAC) Incorporating Sugar Sediment Waste and Recycled AAC with Phase Change Material-Coated Applications for Sustainable Energy Conservation in Building

This research focuses on the integration of waste materials derived from sugar sediment and recycled AAC into the manufacturing process of autoclaved aerated concrete (AAC) to enhance its physical, mechanical, and thermal characteristics. Furthermore, the investigation explores the prospect of augmenting the thermal efficiency of the AAC composite by applying different quantities of paraffin phase change material (PCM) coatings to its external surface. Throughout the thermal testing phase, temperature control was consistently maintained at three distinct levels: 40 °C, 50 °C, and 60 °C, facilitated by a heater serving as the thermal source. The investigation unveiled that the optimal composition encompassed a 10% by weight replacement of sand with recycled AAC content. This formulation resulted in a peak compressive strength of around 5.85 N/mm2, along with a maximum tobermorite phase ratio of 25.5%. The elevated strength is directly associated with the heightened crystalline nature of the tobermorite phase. The most favorable configuration incorporated a 20 g PCM-coated material, demonstrating remarkable outcomes, including an extension of the time lag by about 55%, a reduction in the decrement factor by around 56.4%, as well as a substantial reduction in room temperature of roughly 15.8% compared to standard AAC without PCM coating, all at a stable temperature of 60 °C. The integration of sustainable waste materials and PCM technology, as illustrated in this study, notably contributes to resource conservation and the advancement of energy-efficient architectural practices.

Discharge performance assessment of a vertical double-pipe latent heat storage unit equipped with circular Y-shaped fins

This paper aims to study the effect of circular Y-shaped fin arrangement to improve the low thermal response rates of a double-tube heat exchanger containing Paraffin phase change material (PCM). ANSYS software is employed to perform the computational fluid dynamic (CFD) simulations of the heat exchanger, including fluid flow, heat transfer, and the phase change process. The optimum state of the fin configuration is derived through sensitivity analysis by evaluating the geometrical parameters of the Y-shaped fin. For the same height of the fins (10 mm), the solidification time is reduced by almost 22%, and the discharging rate is enhanced by almost 26% using Y-shaped fins compared with the straight fins. The results demonstrate that the solidification time is inversely proportional to the fin's length. The heat release rate for the case with the longest fins (stem length of 10 mm) is 39 W, almost 2.8 times higher than that with the fins' stem length of 5 mm. The case with the tributary's angle of 22.5o solidified in 55 min, faster than the other studied angles. Increasing the number of fins significantly affects the solidification time and discharging rate. By increasing the number of fins from 3 to 9, the heat transfer rate improves by 194%. The advantages of circular Y-shaped fins are well known in heat transfer applications and therefore are characterized toward higher performance in this study for the first time during the solidification process.

Controllable Friction of an Epoxy Composite via Thermal Treatment

Smart surfaces with controllable friction have generated considerable attention lately. However, most composites prepared with traditional fillers cannot achieve “real-time” friction conversion. Herein, a new smart surface was designed to achieve different friction coefficients (0.65 and 0.12). Different coefficients of friction were reversibly and precisely controlled via heating. Via friction and heating, 1H,1H,2H,2H-perfluorohexyl hexadecane (PHHD), a kind of phase-change material—paraffin wax—was released from the microcapsules, and a stable and complete film was formed. It changed the interface from “solid-solid” to “solid-liquid” in a dry friction state. The composite contains microcapsules that prevent phase separation between PHHD and matrix, which enables the composite to have a long service time and switchable friction performance. In addition, this composite can maintain its extraordinary ability even in harsh environments like UV irradiation. By demonstrating switchable friction based on changes in the interactions between contact interfaces, this work provides a new principle for designing smart tribological composites.

Melting and solidification analysis of paraffin phase change material in a circular space, molecular dynamics simulation

The increasing use of renewable energy sources has led to more studies in the field of eliminating the weaknesses of these sources. The use of energy storage systems is one of these things that increase the sustainability of renewable resources and reduce the share of fossil fuel resources in daily energy consumption. One of the most important things in heat storage systems is the use of suitable phase change materials (PCM). In this research, the behavior of paraffin, as a well-known PCM, is investigated on a molecular scale. For this purpose, an annular space has been selected as a nanochannel and the behavior of this material inside it has been investigated in different states. First, the thermal performance of this PCM is investigated. Then, the effect of its temperature on index parameters such as viscosity, heat flux, thermal conductivity, charge time, discharge time, and phase change time are evaluated. The research results show that increasing initial temperature (from 300 K to 350 K) improves the performance of PCM (the duration of charging and discharging are increased from 1.78 and 2.15 ns to 1.41 and 2.24 ns, respectively.). In addition, increasing the speed of the material also reduces the charging and discharging time to 1.65 and 2.09 ns, respectively. Increasing the diameter ratios also changes the indicator times to 2.18 and 2.03 ns, respectively.

Thermal energy harvesting of highly conductive graphene-enhanced paraffin phase change material

Thermal energy harvesting of highly conductive graphene-enhanced paraffin phase change material