Characterization Of Phase Change Materials Research Articles

A review on thermal energy storage with phase change materials enhanced by metal foams

Due to the mismatch between energy demand and energy production, in the last years the study of latent thermal energy storage systems has been significantly growing. This work aims to provide an overview of the studies and the experiments carried out on thermal energy storage systems, that use phase change materials combined with metal foams. A histogram that shows how the number of works on these subjects has been increasing over the years is reported; consequently, a general survey on phase change materials is conducted, identifying the temperature ranges and the latent heat which are most used in thermal energy storage systems and defining the strengths and weaknesses of the various types of phase change materials. Furthermore, the paper illustrates the models and methods currently used to describe the phase transition of phase change materials in metal foams. Subsequently, how metal foams improve the desirable characteristics of phase change materials is described, and then it is represented in what percentage the different pore sizes (PPI) are used and what the most functional porosity is for individual works. Lastly, through the summary of the analyzed papers some specific articles are considered, in order to explain the state-of-the-art and to clarify some fundamental concepts.

Investigation of Thermal Performance of Optimized Tree-Shaped Fins in Latent Heat Storage Units

An innovative tree-shaped fin is proposed to address the problem of low thermal conductivity of phase change materials (PCMs) in latent heat energy storage units. Numerical methods are applied to investigate the thermal properties of the melting process of PCMs. This paper investigates the effects of fin arrangement, fin geometry parameters, and temperature of the heat source on melting characteristics of PCMs in the latent heat energy storage unit. Results show that the melting time of PCMs with the inwardly-tilted fins at the top increases by 21.3% compared to the outwardly-tilted fins at the bottom. The response surface methodology is adopted to obtain the fin parameter combination with lower quality and better performance. The optimal fin dimensions are a thickness of 1.06 mm, a length of 3.38 mm, and a spacing of 12.61 mm. The reduction of the ambient temperature from 35 °C to 30 °C increases the melting time of the latent heat energy storage unit by 85%, and from 35 °C to 40 °C decreases the melting time by 29%.

Phase change materials in textiles: synthesis, properties, types and applications – a critical review

Phase change properties of clothing gain attention of the researcher now for their significant unique ability to absorb, release, store, and deposit temperature during phase transition. Phase change materials have been widely used and utilized now in various fields, as well as in textiles. In apparel products, phase change materials are used to introduce various special features, especially its make garments smart or have technical functions. Various researchers pay attention to this area for its large organic and inorganic resources. This review paper summarizes the road map of phase change materials in textiles, including the way of synthesis, the characteristics of phase change materials, and their applications in smart textiles. In addition, the diverse usage of phase change materials in different textiles is discussed. It also tries to cover the principles of phase change behavior, phase change material types, and their thermal properties. After that, the paper will try to mention the potential benefits and challenges associated with utilizing phase change materials in various applications that have been discussed here. Finally, this paper concludes with the mass acceptance of phase change materials in various technological advancements, along with a short note about future research opportunities.

Thermal performance and optimization of an integrated collector–storage solar air heater based on lap joint-type flat micro-heat pipe arrays

This study seeks to optimize the performance of an integrated collector–storage solar air heater (ICSSAH) based on lap joint-type (LJT) flat micro-heat pipe arrays (FMHPAs) and latent thermal storage through numerical simulation. A novel dynamic heat transfer model is developed by incorporating the heat transfer correlation describing the thermal characteristics of phase change material (PCM) in narrow and elongated confined spaces within plate fins and validated using experimental data to address the issue of deviation caused by the fixed thermal resistance of the PCM in conventional numerical simulation methods. The validated model is used to simulate and predict the dynamic performance of LJT-FMHPA-ICSSAH under different heat transfer structures. Several optimization parameters, including the air gap thickness, the optical properties of the collector and glass cover plates, and fins structure, are considered. Simulation results indicate that the heat lost to the external environment through the glass cover plate accounted for over 70 % of the total heat dissipation. The optimal combination included a 50 mm gas layer; copper-based blue titanium coating; ultra-white glass; and fin spacing, thickness, height, and length of 5, 0.2, 60, and 195 mm, respectively. Under autumn/winter operating conditions, the optimized thermal performance is 1.13–1.35 times higher than the performance prior to optimization.

Pore-scale study of melting characteristic of phase change material embedded with novel open-celled metal foam

Metallic porous structure is a prevailing heat transfer enhancer for the melting of phase change material (PCM), while the effect of the structure on the enhancement performance is yet to be understood. In this work, a pore-scale numerical study on PCM melting embedded in a truncated cuboctahedron porous structure, referred as TCD metal foam, was performed. The solid–liquid interface, temperature and the variation of liquid fraction were analyzed and compared with those with the tetrakaidecahedron porous structure, referred as TKD metal foam. The effects of natural convection, porosity, pore density and heating temperature are explored. It is found the natural convection shortens the PCM melting time by about 7 % with the considered porosity range and thus cannot be ignored. Results also show that the TCD metal foam better enhances PCM melting near the porous cell corners compared to the TKD metal foam. Further analysis shows the TCD metal foam can better enhance melting at the former stage due to the larger surface area, while the TKD metal foam can better enhance melting at the later stage due to the thicker metallic ligaments. With essentially the same melting time at ɛ = 0.941, the half-melting takes 17.2 % of the complete melting time for TCD metal foam and 20.3 % of the complete melting time for TKD metal foam. A critical porosity value exists when comparing the enhancement performance of these two metal foams, below which the better melting enhancement is shifted from the case with TCD metal foam to the case with TKD one. The critical porosities are 0.941, 0.923 and 0.899 at the pore densities of 10, 20 and 30 PPI respectively.

Experimental investigation on the stability and heat transfer enhancement of phase change materials composited with nanoparticles and metal foams

Conventional phase change materials (PCMs) possess the challenge of low thermal conductivity, which hinders the energy exchange rate and storage efficiency. PCMs composited nanoparticles and metal foams have been a proven solution to enhance the thermal characteristics of PCMs. In this work, three enhanced PCM composites including nanoparticle/paraffin, metal-foam/paraffin and nanoparticle/metal-foam/paraffin were prepared using fusion blending and vacuum impregnation method. The effects of different nanoparticles with different mass fractions on the stability and heat storage and release characteristics of nanoparticle/paraffin were investigated. Compared with paraffin, the melting time and solidification time of nano-metal/paraffin are reduced by a maximum of 30.18 % and 43.15 %, respectively. In addition, the effect of pore density of metal foam on natural convective heat transfer process was evaluated. The results showed that the stability in descending order is as follows: nano‑aluminum, nano‑copper and nano‑silver. The optimal mass fraction of nanoparticles with good stability was 1.5 wt% (copper), 1.0 wt% (silver), 1.5 wt% (aluminum), respectively. The metal foam makes the internal temperature distribution of PCMs more uniform in the heat transfer process, while inhibiting the convective heat transfer process. With the increase of pore density, the effect on natural convection heat transfer process rises. When the PPI (pores per linear inch) of foamed metal is greater than 40, the natural convection process can be inhibited, obviously. The foam metal has a more significant effect on the heat transfer performance of nanoparticle/metal-foam/paraffin than that of the nanoparticles. The economic benefits of nanoparticle/paraffin, metal-foam/paraffin and nanoparticle and metal foam composite phase change materials are progressively decrease, with MFP being suitable for applications with high economic budgets.

Melting and Solidification Characteristics of PCM in Oscillated Bundled-Tube Thermal Energy Storage System

Phase change material (PCM) based thermal energy storage (TES) is an important solution to the waste of heat and intermittency of new energy sources. However, the thermal conductivity of most PCMs is low, which severely affects the thermal energy storage performance. Oscillation of the tube bundles in a TES unit can intensify the convection of liquid PCM and, therefore, enhance heat transfer. However, the energy storage performance of bundled-tube TES systems in response to oscillation at different amplitudes and frequencies has not been well understood yet, and the optimum time to apply the oscillation during phase transition remains unexplored. To address this issue, this present study was carried out. First, the melting behaviour of PCM with oscillation starting at different times was investigated. Then, the influences of oscillation frequency and amplitude on the melting performance were explored. Finally, the solidification behaviour of PCM with oscillation starting at different times was examined. Results show that the oscillation can accelerate the phase transition process by enhancing convective heat transfer. Compared to the case without oscillation, the complete melting and solidification times are reduced by 8.2 and 6.7% for the case with oscillation starting at 200 s, respectively. The effect of oscillation frequency on the melting enhancement is negligible, while the oscillation amplitude has an important effect on the melting enhancement.

Investigation on heat transfer performance of flat plate micro-heat pipe phase change heat storage/release device

In the domains of low/zero carbon energy, the ship energy storage system, coupled with phase-change storage and release technology, holds significant importance. The utilization of a flat micro-heat pipe as the primary heat transfer element prompts the development of a test platform and a transient heat transfer model for the heat storage device. This is in response to existing challenges such as a single structure, poor temperature uniformity, and low thermal efficiency in current heat storage technology. The study delves into the impact of varying temperatures and flow rates of heat transfer fluids on the overall performance of heat storage devices and heat transfer efficiency. The findings highlight that the staggered double plate micro-heat pipe structure can enhance total heat storage by 11%, average heat storage power by 19%, and heat storage efficiency by 21% compared to the heat storage device with a single flat micro-heat pipe structure. It becomes evident that the heat storage device with the staggered double heat pipe structure outperforms its counterpart. Additionally, Temperature and flow velocity play pivotal roles in determining the heat transfer performance of phase change materials. As the temperature difference between the heat transfer fluid and the phase change material increases, both the phase transition rate and the equivalent Nusselt number also rise, providing a crucial foundation for examining the heat transfer characteristics of phase change materials during different stages of phase transition.

Numerical study of heat transfer characteristics of phase change materials reinforced with porous media based on hybrid mesh

To address the drawbacks of inadequate energy density as well as utilization effectiveness in solar energy utilization, phase change energy storage offers a possible option. However, the low thermal conductivity of traditional phase change materials (PCMs) restricts the extent to which solar energy utilization can be enhanced. In this paper, the impact of the metal foam (MF) on the solid–liquid interface, the flow field, the enhancement heat transfer mechanism during the paraffin wax (PX) melting process and thermal storage characteristics was analyzed. Besides, a three-dimensional mathematical model of MF-PX using the hybrid mesh technique was established and software ANSYS-FLUENT was used for simulation. The results indicated that, the hybrid mesh exhibited a reduction of 52.75 % in mesh count compared to the unstructured mesh, resulting in 45 % reduction in computational time. Moreover, the hybrid mesh also showcased improved mesh quality that the unstructured mesh was mainly distributed in the range of 0.48–0.6, while within the range of 0.84–1.0 for the hybrid mesh. More important, the maximum relative error between experimental and simulation was 8.67 %, indicating that the model can make a reasonable prediction. With the proportions of MF increased from 0.11 % to 0.43 %, both the Rayleigh number (Ra) and its amplification decreased. At 800 s, the Ra decreased from 1.76E+07 to 1.20E+07, while the amplification of the Ra was reduced from 1.88E+07 to 1.30E+07. In addition, the natural convection proportions of CMF decreased from 96.31 % to 80.65 %. These observations indicated that natural convection was the primary heat transfer mechanism, and the conduction was enhanced by the increasing proportion of MF. Finally, in terms of heat storage characteristics, the heat storage capacity and heat storage rate of the composite PCM slightly decreased. The heat storage values decreased from 19.30 kJ to 18.66 kJ. Similarly, the heat storage rates decreased from 19.86 J/s to 18.81 J/s.

Melting and Heat Transfer Characteristics of Phase Change Material: A Comparative Study on Wire Mesh Finned Structure and Other Fin Configurations

Abstract In the present paper, a two-dimensional transient numerical study has been performed to investigate the influence of different fin designs on the melting and heat transfer characteristics of a phase change material (PCM), i.e., Paraffin wax, filled in square enclosures equipped with fin structures. Five distinct fin designs were examined: single rectangular, double rectangular, double triangular, double angled, and wire mesh. It is worth noting that all these fin designs have the equal heat transfer area. An isothermal heat source of temperature 350 K is provided at the left wall of the square enclosure and the remaining walls are assumed to be adiabatic. Six parameters were evaluated to determine the best fin configurations: melting time, enhancement ratio (ER), time savings, energy stored, mean power, and Nusselt number. The results show that all the fin designs outperformed as compared to model 1 (no fin configuration). Among the finned configurations, model 2 had the poorest performance, taking 1314 s to complete the melting, while model 6 had the most efficient fin design, with a melting time reduced by 67.53% compared to model 1. Model 6 also had the highest ER and mean power, i.e., 70.43% and 199.51%, respectively and as the melting process continued, the Nusselt number decreased. In addition to the above, we optimized the element size of the wire-mesh fin design using RSM methodology. This optimized design decreases the melting period by 70.04%. Overall, present study provides a comprehensive analysis of different finned configurations for improving the melting performance of the PCM in square enclosures and found wire-mesh fin design most appropriate and promising.

Melting characteristics of phase change material inside graded aluminum foam based on tetrakaidecahedron model: Pore-scale simulations

Metallic ligaments in open-cell metal foams have effectively improved the heat conduction of phase change materials (PCMs). However, when the gradient direction of porosity is perpendicular to the direction of heat conduction, the mechanism by which graded foam (GF) influences the phase transition of PCM remains elusive. To address this issue, this study employs the pore-scale numerical simulation and develops a numerical model to study the impact of GF on the charging of PCM-foam composites. The analysis identifies the local convection and heat conduction as the most crucial factors influencing heat transfer during phase transition. To effectively examine the role of metallic ligaments in the phase transition, simplified tetrakaidecahedron cells are adopted. The results demonstrate that the GF delays the charging of PCM. Specifically, compared to the homogeneous foam, the full melting time (FMT) of PCM in the GF increases by over 29%. Additionally, the integral-mean temperature response rate (ITRR) of PCM in the GF decreases by 20.2% to 22.1%. Within the GF, the PCM requires more time to melt completely in the tetrakaidecahedron cells with high porosity. Moreover, local convection plays a pivotal role, considerably reducing the FMTs of PCMs by over 85% and increasing the ITRRs of these structures by 588.1% to 599.0%.

Impact of Fin Arrangement on Heat Transfer and Melting Characteristics of Phase Change Material

Impact of Fin Arrangement on Heat Transfer and Melting Characteristics of Phase Change Material

Evaluation of the Thermal Characteristics of Phase Change Material Integrated into the Roof of Buildings by a Numerical Model

Evaluation of the Thermal Characteristics of Phase Change Material Integrated into the Roof of Buildings by a Numerical Model

PCM microcapsules applicable foam to improve the properties of thermal insulation and energy storage for cement-based material

In the field of material science, foaming agents common are commonly used for enhancing the thermal insulation and phase change materials (PCM) for heat storage. However, PCM tends to agglomerate in the cement slurry with the directly addition, presenting an obstacle to effective dispersion. Moreover, the addition of PCM leads to rapid defoaming. To overcome this issue, a novel nanoparticle-stabilized foam was designed in this study to create a three-component system that enhances the interaction of viscosity modifiers, surfactants, and foam stabilizers. The effect of cement density on thermal insulation was evaluated by analyzing thermal conductivity and heat transfer performance tests, as well as exploring the mechanical properties of the cement-based materials. Scanning electron microscope (SEM) images show that the foam designed in this study remarkably promotes the dispersion of PCM microcapsules, indicating the bridging interactions of foam in the cement paste. The result shows that the thermal conductivity of foam cement with 15 vol% PCM microcapsules drops from 0.11 W/m·k to 0.07 W/m·k compared to that without PCM addition, with a dry density around 600kg/m3. Furthermore, the specimens with the addition of PCM achieve the endothermic and exothermic peaks under experimental images. This discovery is of great significance to heat absorption ability of low-density concrete, where the addition of PCM leads to a slower foam bursting under the nanoparticle-reinforced foam system. The dispersion and connectivity of foams, as well as the physical characteristics of PCM, provide new perspectives for coexistence in a relatively stable system in this way.

Photothermal properties and performance of hybrid carbon-paraffin/water emulsions

Solar thermal energy has attracted renewed research interest for its excellent energy efficiency among different types of solar technologies. However, the limiting factor of them all is the intermittent nature of solar radiation. To overcome this drawback, it is possible to store absorbed light in form of heat using emulsions with phase-change materials (PCMs) dispersed in solar nanofluids by combining the advantage of solar thermal storage characteristics of PCMs and the higher light absorption capacity of solar nanofluids. In this study, paraffin/water and hybrid carbon-paraffin/water emulsions with 5 wt% paraffin wax RT44HC as PCM are proposed. Low-cost emulsions with proven colloidal stability were successfully produced, with and without small amounts of oxidized carbon black nanoparticles (0.01 wt%) dispersed in the emulsion. Thermal energy storage capacity improved up to 16 %, while maintaining good thermal conductivity properties. Optical properties were evaluated by means of a spectrophotometer with an integrating sphere, including both spectral absorptance and reflectance of the samples. Two experimental setups were developed with concentrated light, to evaluate the photothermal conversion efficiency under simulated and natural sunlight. The improvement of the light to heat conversion properties provided by the oxidized carbon black nanoparticles was confirmed, with PTE values of 1.5- and 2.7-fold better than the base fluid (water) using a solar simulator and natural sunlight, respectively.

Experimental studies on the enhancement in discharging characteristics of phase change material with steatite nanoparticles

Phase change materials are latent heat energy storage systems that can store huge quantities of thermal energy in a small volume. Latent heat energy storage systems are complicated to design due to the low thermal conductivity of phase change materials for discharging to enhance the heat capacity and latent heat storage. The objective of the study is to examine the discharging of phase change material in a latent heat energy storage system for maintaining the temperature of the water. Paraffin wax utilized as the phase change material due to its higher latent heat capacity. The experiments were performed with the flow of the hot water through a phase change material container by using a copper tube to enhance the discharging of phase change material during solidification to maintain the temperature of the water. Furthermore, the steatite nanoparticle has been dispersed with phase change material to enhance the discharging of characteristics. The steatite nanoparticle has been selected due to its low thermal conductivity, and the weight percentages nanoparticles were varied viz. 10 %, 20 %, 30 %, and 40 %. The increase in water temperature from 0.1 °C to 1 °C has been taken 7 h by enhancing the discharging of phase change material with various concentrations of the steatite nanoparticle. The work shows the significant discharging characteristics of phase change material with steatite nanoparticles. The nano-phase change material has the potential to maintain the temperature of water without any external energy for a particular duration, which shows cost-effectiveness.

Simulation study of drilling fluid cooling in long horizontal wells based on phase change heat absorption

ABSTRACT The shale gas resources found in deep formations are abundant and represent a crucial area for current and future shale gas development. However, as shale gas exploration and development intensify in China, an increasing number of high-temperature formations are being encountered during drilling, presenting significant challenges to drilling engineering and severely constraining the development of deep shale gas exploration. In this study, the stability of PCM (phase change material) combined with drilling fluid as a coolant was discussed, and the influence of PCM on wellbore temperature field in drilling fluid was considered. A calculation model of temperature field of drilling fluid containing PCM was established, the cooling characteristics of PCM under the influence of different parameters were simulated, and the cooling effect of PCM integrated with drilling fluid on ultra-deep and high-temperature Wells was analyzed. The investigated PCM has a phase change temperature range of 120 ~ 130°C and a latent heat of 264.15 ~ 265.53 kJ/kg. Our results showed that the cooling impact of PCM exhibits an upward trend as the quantity of PCM utilized increases. Assuming the drilling temperature limit is 135°C, after adding 5% PCM to the drilling fluid, the drilling length of the horizontal section increased by approximately 500 m. With 15% PCM added, the horizontal section could be extended by about 1000 m. We conducted a simulation analysis on a well in southern Sichuan, and found that adding 12% PCM had the best cooling effect, reducing the bottom hole temperature by 12.3°C and extending the horizontal section by 700 m. Compared with conventional drilling fluid cooling methods, incorporating PCM as cooling agents within the drilling fluids provided better cooling effects. It effectively addressed the problem of excessive bottom-hole temperatures in deep wells, extended the drilling length of horizontal sections, and prolonged the service life of downhole instruments. Our research lays the groundwork for the future investigation of cooling techniques for high-temperature deep well drilling fluids.

Exploring the temperature-dependent thermal stability of nano-enhanced phase change materials: An experimental study using eicosane as the base material

Recently, studying phase change materials (PCMs) has brought many researchers' attention to be applied in thermal energy storage and battery thermal management (BTM) applications. Nano-materials have been used recently to improve the advantages of the PCM which makes them suitable materials to be used in thermal management systems. Moreover, the selection of the nanomaterials and the proper concentration of nano-particles in PCM affects the thermophysical characteristics of PCM. According to the fact that PCM requires to be thermally stable, the principal aim of this study is to analyze the thermal stability of PCMs composites by loading different mass fractions of CuO nano-particles. In order to add nano-particles to the eicosane-based PCM, a two-step method has been used. The thermal stability of the Nano-enhanced phase change materials (NePCM) has been measured by using the thermogravimetric analyzer. Results demonstrated that 0.5 wt% is the best value of additive nano-particle which showed a remarkable increment in thermal stability. Therefore, all the presented results indicate the importance of selecting an optimal PCM nano-composite for various applications including NePCM-based thermal energy storage and BTM systems. The brand and model of the device used in this study are Hitachi and STA7000 respectively.

Heat transfer characteristics of phase change materials in double-layer packed bed under dynamic thermal boundary

Dynamic thermal boundary conditions have a significant impact on the thermal storage performance of phase change materials (PCMs) in packed beds. In this paper, an unsteady numerical heat transfer model of a double-layer packed bed is established and verified. The heat storage characteristics of the four PCM combination schemes are calculated and compared, and the sinusoidal wave heat source is used as an input parameter to study the influence of wave amplitude and period changes on the thermal performance of the system. The study shows that when the volume ratio of PCM 1 to PCM 2 is 1/3:2/3, the melting time is shorter and the heat storage rate is faster. The long-period fluctuation can significantly shorten the melting time and improve thermal performance. When the period is 120 min, the melting time is shortened by about 15.2 % compared with the steady state, and the heat storage rate is increased by 19.6 %. The larger the amplitude of the heat source, the stronger the promotion effect on melting. When the amplitude is 16 °C, the melting time is shortened by about 17.7 % compared with the steady state, and the heat storage rate is increased by 16.7 %. The research results can provide some reference for the design of a double-layer packed bed under the dynamic heat source.

Thermal characteristics and optimization of phase change energy storage subgrade in permafrost regions

In permafrost regions, the thawing of permafrost will cause serious damage to the road structure, and delaying the degradation of permafrost is the key to ensure the road performance. Based on the energy storage characteristics of phase change material (PCM) and the anti-seepage performance of geotextile, a phase change geotextile (PCG) with heat absorption and waterproof functions is prepared in this study. PCG is applied to the subgrade structure, and the phase change energy storage subgrade (PCESS) is proposed. This subgrade structure can effectively reduce the temperature and increases the artificial permafrost table in permafrost regions. In order to study the temperature regulation mechanism of PCESS, the effects of thermal properties of PCM and epoxy resin mixture (PCMERM) and structural parameters of PCG were analyzed by numerical models. The mean absolute errors (MAEs) were 0.88 and 1.08 with experiments conducted to validate numerical model. The analysis of influencing factors showed that the phase change temperature of PCMERM exhibits the best value to improve the regulation effect of PCESS under given conditions. Increasing the heat of fusion and dosage of PCMERM can enhance the regulation effect. When PCG was laid on the top of the subgrade, the regulation effect was the best. Compared with the traditional permafrost subgrade, PCESS showed long-term thermal stability. In addition, the prediction model for the artificial permafrost table change was established. The model predicted the artificial table in three cases, and the MAEs were 0.048, 0.019 and 0.039, respectively. These results suggest that the model can accurately predict the changes of the artificial permafrost table.