Paraffin Phase Change Materials Research Articles

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

Experimental investigation of longevity and temperature of a lithium-ion battery cell using phase change material based battery thermal management system

Nowadays, conventional lead acid batteries are being replaced by Lithium-ion batteries due to their high energy density, low cost, and high electric capacities. But when subjected to high discharge conditions, these batteries undergo a rapid increase in temperature which can make them unstable and change their internal chemistry to the point of fire or explosion due to thermal runaway and reduce their working life (electrical capacity). To prevent this, battery thermal management systems need to be used. The current work is focused on investigating the performance of a phase change material-based thermal battery management system for controlling battery temperature and battery life. In this experimental study, RT-47 Paraffin phase change material is wrapped around a 1.2Ah, 3.7 V lithium-ion battery cell with a thickness of 4 mm. The results of temperature and electrical current were recorded for 1200 s during which the battery was discharged at a constant resistance load. It was found that using a phase change material based thermal management system the temperature of the battery cell was better maintained and it lasted approximately double the time as compared to a bare battery cell under the same loading conditions.

Synthesis, characterization, thermophysical properties and shape stability of paraffin/CNTs nanocomposite phase change materials

Paraffin/carbon nanotube (Pa/CNTs) nanocomposite with different CNTs lengths was prepared in order to investigate the change of thermophysical properties of paraffin phase change material (PCM). For this purpose, CNTs were first treated with sulfuric and nitric acids, which reduced the length of CNTs. Then, for complete dispersion of CNTs in paraffin, secondary functionalization was done using dodecylamine and they were added to paraffin with different wt.%. In order to stabilize the shape of paraffin, composites were inserted into graphene aerogel by vacuum impregnation method. Experiments showed that with the increase in the wt.% of CNTs, the thermal conductivity of composites increases, and the highest increase of 26.92% was observed for the composite containing 1 h refluxed CNTs with 1.2 wt.% in solid paraffin. Also, with an increase in the wt.% of CNTs, the latent heat of melting and solidifying of the composite increased, but the specific heat decreased. The absorption capacity of paraffin by graphene aerogel was investigated and the maximum absorption capacity was observed for the composite containing 1 h refluxed CNTs with 0.6 wt.% which showed 36.11% increase compared to the pure paraffin. In addition, by performing the leakage test, it was observed that the GA/Pa/CNTs structure has very good shape stability.

The regulation mechanism and heat transfer enhancement of composite mixed paraffin and copper foam phase change materials

The regulation mechanism and heat transfer enhancement of composite mixed paraffin and copper foam phase change materials

Economics and lifecycle carbon assessment of coconut oil as an alternative to paraffin phase change materials in North America

Globally, almost 40% of carbon emissions are attributable to building operation and embodied carbon. Phase change materials (PCMs) can store solar energy during peak periods to decrease summer cooling loads and overnight winter heating loads and emissions. At present, most PCMs are non-renewable paraffins with high embodied carbon; plant-based oils such as coconut oil may maintain the conditioning load reductions, while reducing the sustainability and embodied carbon of PCMs. The objective of this study was to determine the economic and emissions of coconut oil as an alternative to paraffins via full house simulations in three North American locations within different climate zones. It was found that paraffin PCM had greater embodied carbon and annual heating and cooling reductions than the coconut oil, causing the lifecycle carbon footprint to be lower with paraffin PCM than with the coconut oil over the house lifetime. This indicates the importance of developing bio-based PCMs with latent heat capacity that more closely compare to paraffins, in order to minimize total building carbon footprint. It was also found that the economic payback period of both PCMs may exceed the lifetime of the house and thus render the PCMs infeasible without reductions in capital costs or increased carbon pricing.

Prevention and suppression effects of phase change material on thermal runaway in batteries

With the rapid improvement in the electric vehicle industry, lithium-ion batteries are being used in increasing numbers. However, lithium-ion batteries are prone to thermal runaway under various factors, leading to fires and explosions that seriously affect the security of electric vehicles. Therefore, a method for effectively preventing and suppressing thermal runaway in batteries is an important problem that needs to be solved. The phase change material can absorb a large quantity of heat during the solid‒liquid transition process, exhibiting strong potential for thermal runaway protection in lithium-ion batteries. In this research, a lithium-ion battery module is proposed with cylindrical cells and paraffin phase change material. The prevention and suppression effects of the phase change material on thermal runaway in the cells are analyzed by a numerical method. The phase change material can effectively reduce the maximum temperature of the trigger cell and stop the propagation of thermal runaway in the module. By varying the thermal conductivity, latent heat, melting temperature and thickness of the phase change material, their influences on the heat generation and temperature of the trigger cell during thermal runaway are analyzed. Design recommendations for phase change materials to protect lithium-ion batteries from thermal runaway are provided based on the results.