Thermal Performance Of Phase Change Materials Research Articles

Advancements in Phase Change Materials: Stabilization Techniques and Applications

Phase Change Materials (PCMs) are innovative materials that absorb and release thermal energy during phase transitions, making them ideal for thermal energy storage applications. This paper provides a comprehensive overview of PCMs, focusing on their functioning mechanisms, classifications, and shape stabilization methods. PCMs operate by storing latent heat during melting and releasing it upon solidification, thereby maintaining a stable temperature during phase changes. They are classified into three main categories: organic, inorganic, and eutectic. Organic PCMs, such as paraffins and fatty acids, offer high latent heat storage but suffer from low thermal conductivity. Inorganic PCMs, including salt hydrates and metals, provide better thermal conductivity but face challenges like supercooling and corrosiveness. Eutectic PCMs, which are mixtures of compounds, offer customizable melting points and enhanced thermal properties. To address leakage and improve thermal conductivity, shape stabilization methods are employed, such as encapsulation, stabilization by porous matrix, and polymer hybridized shape stabilization. These techniques enhance the structural integrity and thermal performance of PCMs, making them more suitable for practical applications. The paper highlights the potential of PCMs to improve energy efficiency and outlines future research directions for optimizing their performance in various industries.

مراجعة على التقييم الاقتصادي لدمج المواد المغلفة متغيرة الطور في أغلفة المباني

The worldwide energy crisis has made energy-saving a topic of concern in almost every country. Previous research has explored the use of thermal energy storage materials (TES), such as phase change materials (PCMs), as an effective energy-saving technique. Among various immersion techniques, macro-encapsulation has proven to be efficient, safe, and convenient. However, choosing the right PCM system can be complicated due to the variety of available PCM types, encapsulation materials, and encapsulation shapes. Moreover, while macro-encapsulated PCM systems are efficient, their feasibility depends on several factors, including energy prices, economic situation, and climatic conditions. Therefore, this research aims to provide a comprehensive overview to help create a deeper understanding of the design and application of macro-encapsulated PCM systems. It explains the different types of PCM, encapsulation materials, and encapsulation shapes, guiding the selection for the most appropriate system regarding the surrounding environment. Additionally, it aims to present a guideline for conducting feasibility studies on energy-saving systems such as PCM. A total of 80 research papers covering the intersection between the thermal performance of PCM and the economic assessment have been categorized, studied, and analyzed in order to identify the most accurate method of assessing the system’s feasibility. By providing a base knowledge regarding the various types of each element of the system and the factors that govern the selection of each, this research will help engineers appropriately design the system. In addition, providing a detailed guideline to the assessment of the system shall aid the decision makers in determining the system’s feasibility which encourages its application. Finally, the research investigates and addresses the key issues for future studies.

Transient Thermal Performance of Phase-Change Material Infused in Cellular Materials Based on Different Unit Cell Topologies

Abstract Phase change material (PCM) employment in thermal management and energy storage applications is limited due to their inherently low thermal conductivity. Significant enhancement in the thermal performance of PCMs can be obtained when infused in porous media with high porosity and high solid-phase thermal conductivity. Earlier studies typically employ high porosity aluminum foams obtained via a conventional manufacturing process, commonly known as foaming. A typical representative unit cell of metal foams obtained via foaming process can be of tetrakaidecahedron shape. The conventional manufacturing process of high porosity metal foams offers limited flexibility over unit cell shape, porosity, and pore density. Metal additive manufacturing advancements have the potential to address this manufacturing limitation and provides freedom in the above design domain. To this end, we have explored four different unit cell topologies, viz., octet, tetrakaidecahedron, face-diagonal cube, and cube, for their role in enhancing the transient thermal performance when infused with PCMs. An enthalpy-porosity method has been employed to model the phase-change process for wide range of variables. It has been found that the presence of solid media results in significant enhancement in PCM's thermal performance, and the Octet-shaped unit cell outperformed the other unit cell topologies explored in this study.

Investigation on Thermophysical Properties of Multi-Walled Carbon Nanotubes Enhanced Salt Hydrate Phase Change Material

Thermal Energy Storage (TES) is a valuable tool for improving the energy efficiency of renewable energy conversion systems. One of the most effective methods for harnessing thermal energy from solar sources is through energy storage using phase change materials (PCMs). However, the thermal performance of PCMs is hindered by their low thermal conductivity. This research focuses on enhancing the thermal performance of salt hydrate PCM using multi-walled carbon nanotubes (MWCNTs) and surfactants. Through experimental investigations, a salt hydrate PCM with varying concentrations of MWCNTs (ranging from 0.1% to 0.9%) was prepared using a two-step technique and their thermophysical properties were thoroughly characterized. Various techniques such as field emission scanning electron microscope, thermal conductivity analyzer, ultraviolet-visible spectrum, thermogravimetric analyzer, and Fourier transform infrared spectroscopy were utilized to study the effect of surfactant on the nanocomposites and examine their morphology, thermal conductivity, optical properties, thermal stability, and chemical stability. The results indicated that the inclusion of MWCNTs with salt hydrate significantly improved the thermal conductivity by 68.09% at a concentration of 0.7 wt %, compared to pure salt hydrate. However, this enhancement in thermal performance was accompanied by a reduction in optical transmittance in the developed nanocomposite PCM. Additionally, the formulated nanocomposite demonstrated excellent thermal and chemical stability up to temperatures as high as 468 °C. As a result, this nanocomposite shows great promise as a potential candidate for solar TES applications, offering favourable characteristics for efficient energy storage from solar sources.

Characterization by differential scanning calorimetry of thermal storage properties of organic PCMs with operating temperature of 150 °C

The involvement of Phase Change Materials (PCMs) in energy storage systems leads to more sustainable and efficient use of energy. Medium operating temperature (melting point 100–400 °C) find various applications in industrial waste heat recovery and hybrid compressed air - thermal energy storage systems. However, there is still a lack of detailed knowledge in terms of their thermal storage properties that hinders them from being more integrated in industry. In this study, thermal properties such as melting point, enthalpy and heat capacity of three medium temperature PCMs were characterized using Differential Scanning Calorimetry (DSC). The enthalpy-temperature graph for each PCM is presented that contains key information on sensible and latent heat contribution in the total energy storage. The selected organic PCMs are adipic acid with two different purities 99%, 99.5%, and its chemical equivalent PureTemp151® with a melting point of (150.5 ± 0.5 °C) and a latent heat of (230 ± 10 J/g). Furthermore, the effect of heating rate and sample mass in DSC procedures on transition temperatures and enthalpy were evaluated. Finally, thermal performance of PCMs was quantified through 150 cycles of melting and solidification. The tested PCMs show a significant storage capacity and good thermal stability with less than 10 % enthalpy loss.

On-site testing of dynamic facade system with the solar energy storage

Decarbonistation goals for building stock calls for innovative solutions on both supply and demand side. Thermal envelopes with in-build energy storage could gather on-site solar energy and reduce cooling or heating loads of the buildings. Results of on-site testing of dynamic facade system with the solar energy storage are presented in the paper. Proposed solar façade consists of phase change material to rise the heat capacity of the building envelope, aerogel for insulation, Fresnel lens for solar energy concentration accompanied by moving reflective blades for heat transfer enhancement. Comparative study was conducted in PASLINK type test booths– the performance of proposed solar façade was compared to the reference element – the highest performance triple glazed window suitable for low energy buildings. The detailed measuring setup provide information on the thermal performance of phase-change material enhanced building envelope under different outdoor conditions (summer, autumn, winter) in Northern European climate. The gained results indicate that proposed solar façade module provides lower energy demand during the cooling season compared to the window, in mid-season it performs similarly, however in heating season proposed solar façade in its current composition is outperformed by high performance triple glased window.

Turbulent melting characteristics of hybrid nano-enhanced molten salt phase change material in rectangular enclosure

The turbulent melting characteristics of hybrid nano-enhanced phase change material (HNEPCM) in a three-dimensional rectangular enclosure has been numerically investigated. The lower and upper walls are partially heated and cooled using constant surface temperature boundary condition and the other surfaces are specified with adiabatic boundary condition. The rectangular enclosure is filled with molten salt phase change material (PCM) of potassium nitrate (KNO3) with melting temperature of 334 °C. The transient melting rates of PCM are investigated by dispersing hybrid mono-dispersed spherical nanoparticles of Aluminum oxide (Al2O3) combined with Silicon dioxide (SiO2), Titanium dioxide (TiO2) and Multi-walled carbon nanotubes (MWCNT). The Rayleigh number (Ra) and particle volume fraction (ϕ) are varied in the range of 106≤Ra≤1010 and 2%≤ϕ≤5%. The turbulent phase change process of PCM is modeled using enthalpy–porosity approach with Lam–Bremhorst k−ϵ turbulence model. The three-dimensional governing equations are discretized using Finite difference technique and computations are carried out using Fortran 90 in-house code. The stronger thermal buoyancy force accelerates the melting rate and the melting pattern indicates the accumulation of large quantity of molten metal in the upper regions of the rectangular enclosure. The average melting velocity and turbulent kinetic energy of pure KNO3 PCM is increased by 51.17% and 77.84% by the addition of Al2O3−MWCNT hybrid nanoparticles. The impact of hybrid nanoparticles on the melting rate and thermal performance of PCM is significant in higher Rayleigh number flows than transitional flows. The present results are validated and are in close agreement with the benchmark experimental results.

Hybrid thermal performance enhancement of shell and tube latent heat thermal energy storage using nano-additives and metal foam

Phase change materials (PCMs) are popular for effectively storing thermal energy due to their high thermal energy density and nearly constant operating temperature. However, a restriction for their effective application comes up due to their poor thermal conductivity. The main aim of this numerical investigation is to analyze the potential of two heat transfer augmentation methods, (i.e., metal foam and nano-additives) for a shell and tube. A mathematical formulation considering the extensions of Brinkman and Forchheimer made on the model of Darcy for porous media is validated with experimental data available in literature and used for simulations. The model is used via a commercial CFD code for simulations of heat transfer and phase change evolution during both charging and discharging processes in the heat exchanger. The thermal performance of the heat exchanger is examined through liquid fraction evolution, time for complete cycle and stored energy. The effects of operational and structural parameters including inlet temperature, metal foam material, foam porosity (0.95 and 0.98), pore density (10, 40, and 70 ppi), and nanoparticle volume fraction (0, 1 and 3 vol%) are investigated. Results show that the metal foam material and nanoparticle concentration have a significant effect on the thermal performance of PCM in shell and tube. Metal foam and graphene nanoplatelets reduce the charging and discharging times by up to 96.11% and 96.23%, respectively. Furthermore, lower porosity foam expedites the charging/discharging process whereas the pore density has no noticeable effect. The findings of this study are hoped to be helpful for designing efficient thermal energy storage units.

Enhanced thermal performance of phase-change material supported by nano-Ag coated eggplant-based biological porous carbon

In this paper, nano-Ag coated eggplant-based biological porous carbon (BPC) was used as the support material to load PEG to solve the problem of leakage and low thermal conductivity of phase change material (PCM). A series of support materials (caky BPC, caky BPC@Ag, BPC powders, BPC@Ag powders) were prepared. The results show that the shape-stabilized PCM (ss-PCM) obtained by caky BPC had better anti-leakage ability. The thermal conductivity of the support material coated with nano-Ag particles was increased by 40.9 % compared with the uncoated support material. After ten thermal cycles, the composite ss-PCM (ss-CPCM) remained to exhibited excellent thermal reliability, which indicated that the ss-CPCM supported by nano-Ag coated BPC had excellent potential in practical application. In addition, BPC@Ag improved the light-to-heat conversion rate and had more application prospects. In addition, BPC had a high photo-thermal conversion efficiency, and BPC@Ag further improved the photo-thermal conversion.

Investigations on transient thermal performance of phase change materials embedded in metal foams for latent heat thermal energy storage

A feasibly numerical model based on enthalpy-porosity and local thermal non-equilibrium is proposed to explore the transient heat transfer characteristics of phase change materials (PCMs) embedded in metal foams during charging process. Parametric analysis elaborates effects of various parameters on thermal performance of PCMs. Heat transfer and storage performances are further conducted from the perspectives of transient temperature. Results indicate that metal foams are capable of boosting melting rate of PCMs and phase change heat transfer is dominated through thermal conduction with obviously weakened natural convection. Metal foams with less thermal conductivity lead to lower temperature differences between metal foams and PCMs and more uniform temperature distributions of PCMs embedded in metal foams are developed over pure PCMs case. The complete melting times of PCMs can be shorten by approximately of 55.03%, 54.75% and 49.58%, when incorporated in metal foams and superiorities are even more obvious under lower porosity, larger pore density or higher heat flux. Greatest results in profiles and contours of temperature difference correspond well to mushy zones of phase transitions. Thermal energy is primarily reserved in PCMs in the form of latent heat. In conclusion, this paper is expected to be explicitly beneficial to broaden phase change energy storage applications.

A complete numerical model for low temperature composite form-stable phase change material slab based on dynamically simplified temperature transforming method

ABSTRACT Phase change material (PCM) that is used in the roof top slab can minimize the heat infiltration into the living space from the building envelope and increase the indoor thermal comfort level. The major disadvantage of PCM is leakage at liquid state. Expanded graphite (EG) is used here as supporting material for PCM to prevent the leakage and maintains the form stability. The composite PCMs are prepared by adding the EG with various mass ratios, i.e. 3%, 6%, and 9%. The thermal properties of all composite PCMs are determined by DSC and thermal conductivity analyzer. The optimum PCM composition was found at 9% of EG. In this study, the shape-stabilized PCM-integrated roof top was analyzed by simplified temperature transforming (TT) numerical model. The main advantage of this model is that it is used to combine the equivalent enthalpy and heat capacity. The numerical results are validated with experimental values and show the lower mean absolute percentage error (MAPE), i.e. 6.91%. This indicates that present model is well suitable to predict the thermal performance of composite PCM incorporated roof top. The effect of various parameters like thickness of the PCM slab, wind velocity, percentage of EG mass ratio, and location of PCM are investigated by simplified TT model. The results showed that the maximum inner surface temperature reach up to 53°C for BG model (concrete and gypsum) by distributing constant heat flux, i.e. 1,000 W/m2 for 180 min. At this same condition, the inner surface temperature of other PCM models PBG (PCM, concrete, gypsum) and BPG (concreate, PCM, Gypsum) reaches to 50°C and 41°C, respectively. PBG model exhibits excellent thermal performance compared to BPG model. The thermal performance of PCM slab is also investigated by varying the thickness of the PCM layer and found that time lag is raised with the thickness of the PCM slab.

Enhanced thermal performance of phase-change materials supported by mesoporous silica modified with polydopamine/nano-metal particles for thermal energy storage

Thermal energy storage using phase change materials (PCMs) plays a crucial role in solving the contradiction between energy supply and demand. In this paper, we proposed a novel approach to design a functionalized process for the matrix which was modified with polydopamine and silver nanoparticles for improving the crystallization process of polyethylene glycol (PEG) PCMs which were bound onto the surface and the interior of the mesoporous silica by adjusting the size and shape of pore systems, the hydrogen bonding force between PEG molecules and carriers. And the results suggested that the prepared supporting materials exhibited prominent chemical compatibility with PEG and a great enhancement for the thermal conductivity (34.0%) with the sequential modification of polydopamine and silver nanoparticles. The composite ss-PCMs also exhibited excellent thermal reliability after 10 thermal cycles, indicating that the emerging composite ss-PCMs had favorable potential in the practical applications.

Thermal performance of concrete sandwich panels incorporating phase change materials: An experimental study

The employment of phase change materials (PCMs) in the construction of concrete building components has engaged many researchers’ interest. In this study, a novel reduced-scale experiment is employed to perform a parametric investigation of the thermal performance of PCM-integrated wall specimens considering two types of concrete, two types of PCM, and different thicknesses of the concrete and PCM layers. Moreover, three different ambient temperature profiles of a summer day in three different cities were considered as the outside ambient temperature to evaluate the performance of each PCM under different temperature conditions. The test procedure is capable of evaluating the thermal performance of different wall configurations under various temperature conditions. The inside temperature variations of the wall specimens were monitored as the thermal performance criteria. In consequence, integrating the PCM layer with normal concrete or with slimmer concrete layers resulted in better thermal performance of PCM in absorbing heat in comparison to lightweight concrete or thicker specimens due to the considerable effect of density and specific heat capacity of different types of concrete. Moreover, the compatibility of the melting temperature of PCMs with the ambient temperature of the considered cities in summer is assessed and discussed.

Influence of the copper foam shape on thermal performance of phase-change material

Most Phase-Change Material (PCM) possessed the poor thermal conductivity, leading to a modest thermal performance in the Latent Thermal Energy Storage (LTES) system. Filling metal foam was widely used to overcome this deficit. To optimize the thermal transfer enhancement benefit of PCM filled with copper foam partly, six physical models with the filling ratio of 50% were built and the numerical simulation was employed with the two-temperature non-equilibrium model. Results showed temperature had the higher response rate in the composite PCM than that in the pure PCM and then heat was transferred from composite PCM to pure PCM. The smaller the divided PCM zone by copper foam, the smaller the thermal resistance of the pure PCM zone and thereby, the larger the thermal transfer enhancement benefit. By optimizing the foam shapes, the full melting time could be reduced by 4143 s, and the average values could be increased by 0.00459 °C/s for temperature response and 336.83 w/m2 for the heat flow. By comparing the thermal transfer performance of six physical models, PCM could melt difficultly in the lower right corner, which would also be the focus of copper foam arrangement. In the future design of LTES system, the optimized foam shapes have a good reference value.

Influence of the Copper Foam Fin (CFF) shapes on thermal performance of Phase-Change Material (PCM) in an enclosed cavity

Phase-Change Material (PCM) attracted much attention due to its high thermal storage density under the small temperature variation, its poor thermal conductivity limited the thermal charging/discharging efficiency significantly. To overcome this deficit, fins were produced by copper foam to improve the thermal performance of PCM and seven Copper Foam Fin (CFF) shapes were considered with the same filling ratio of 50%. The numerical simulation was employed with the two-temperature non-equilibrium model. Results showed the solidifying process with the liquid fraction variation from 100% to 30% had the similar rules with the melting process with the liquid fraction variation from 0% to 70%, but the solidifying time with the liquid fraction variation from 30% to 0% was much higher than the melting time with the liquid fraction variation from 70% to 100%. The preferable CFF shape was gained with the longer left-side length, close to the hot and cold source. And there was the natural-convection heat transfer in solidifying and melting processes, but the natural convection intensity was too small to be considered in the solidifying process.

Fabrication of phase-change core/shell nanofibers based on a eutectic fatty acid mixture to control body temperature fluctuations

A sustainable eutectic mixture of two fatty acids, i.e. Lauric acid (LA) and Palmitic acid (PA), was produced as Phase Change Materials (PCMs) to control body temperature fluctuations. Based on thermodynamic calculations and related experimental analyses, the mass ratio of the mixture was chosen as LA:PA = 69:31. A core-shell structure was prepared through coaxial electrospinning, so as to prevent the leakage of PCM during phase change from the solid state to liquid one. Nylon 6 covered the core as the shell of the prepared nanofiber. The optimized nanofibers were obtained with the diameter of 152.7 nm. The produced PCM possessed an onset melting temperature of 32.17 °C, which was close to the normal body temperature (i.e., 37 °C). Thermal performance of PCM in the nanofiber core-shell structure analyzed by an image processing technique showed that the sample containing PCMs exhibited enhanced thermal properties during the cooling down process.

Thermal performance of PCM and branch-structured fins for cylindrical power battery in a high-temperature environment

Battery modules with phase change material (PCM) cooling inevitably suffer from heat-storage saturation and poor secondary-heat dissipation, especially in high-temperature environments or hot regions. To optimize thermal management, this study firstly explores the thermal behaviors of PCMs with different phase change temperatures (PCTs) in a high-temperature environment. The experimental results show that a PCM with a PCT of 46 °C offers the best cooling effect at a high ambient temperature of 40 °C in this study. For example, the maximum temperature of a cell without PCM reaches 53.3 °C, whereas that of the cell with PCMs having PCTs 40, 46, and 55 °C, are 59.2, 51.6, and 57.5 °C, respectively, during the dynamic cycling process. Nevertheless, the application of above PCM is still unsatisfying because the maximum temperature of the battery in the PCM module exhibits obvious increasing trend with cycles in 40 °C environment. On this basis, several novel fins with multiple heat-flow channels (of V, Y and X shapes) are designed and introduced into the PCM module to enhance the secondary heat dissipation capability. These fins with innovative branch structures deliver excellent performance in alleviating the battery temperature than the traditional rectangular fins, which can be attributed to the ability of the branch structures to increase the heat transfer area by adding heat transfer channels. The results of this work show that the X-shape delivers the best performance in a high-temperature environment of 40 °C by maintaining the maximum temperature of the cell below 47 °C.

Analysis on phase transition range of the pure and mixed phase change materials (PCM) using a thermostatic chamber test and differentiation

A phase change material (PCM) is a type of thermal storage material. The thermal performance of PCMs is evaluated by latent heat capacity and phase change temperature range. The phase change temperature of the phase change materials (PCM) is a critical factor in selecting a PCM. In this study, the conditions of physical and chemical bonding of PCMs including n-octadecane, n-docosane, palm wax, and two types of mixed PCMs were analyzed using the differential scanning calorimetry and the Fourier transform infrared. The phase change temperature range of these PCMs were analyzed using a thermostatic chamber test. In addition, the analysis method of the phase transition range of these PCMs was studied using the first and second derivatives. As a result, the phase changes of n-octadecane, n-docosane, and palm wax occurred at 27, 43, and 45–62 °C, respectively. It is not possible to determine the exact temperature at which phase change occurs with palm wax because palm wax includes various acids. Also, the results of the mixed PCM of n-octadecane and palm wax indicate several peaks. Finally, through a second derivative, it proved that the mixed PCM of n-octadecane and palm wax melts at 18.3–29.1 and 35.1–42.9 °C and freezes at 48.4–51.8, 31.8–34.1, and 23.7–26.9 °C.

An Experimental Study on the Thermal Performance of Phase-Change Material and Wood-Plastic Composites for Building Roofs

We assessed the usefulness of phase-change material (PCM)-based thermal plates fabricated from wood-plastic composites (WPCs) in mitigating the urban heat island effect. The thermal performance of plates containing PCMs with two different melting temperatures and with two different albedo levels was evaluated. The results showed that the PCM with a melting temperature of 44 °C maintained lower surface and inner temperatures than the PCM with a melting temperature of 25 °C. Moreover, a higher surface albedo resulted in a lower surface temperature. However, the thermal performance of PCMs with different melting temperatures but the same surface albedo did not differ. Using PCM-based materials in roof finishing materials can reduce surface temperatures and improve thermal comfort.

Characterization of paraffin/ultrasonic-treated diatomite for use as phase change material in thermal energy storage of buildings

In this study, paraffin-/ultrasonic-treated diatomite was characterized for use as phase change material (PCM) for thermal energy storage in buildings. The diatomite was treated with ultrasound at various periods of time. The diatomite treated with ultrasound for 60 min (DA-60) was the optimum condition providing the highest surface area without structural degradation. The melting point and latent heat of the paraffin/DA-60 composite PCM were 59 °C and 45.90 J g−1, respectively. The obtained form-stable PCM had good thermal reliability after 500 cycles of thermal cycling test. The thermal performance of PCM was tested by incorporating the paraffin/DA-60 composite PCM into gypsum board. The results showed that the gypsum board containing the paraffin/DA-60 composite PCM had better thermal energy absorption and release characteristics than those of the control sample. The incorporation of paraffin/DA-60 composite PCM into suitable building materials could thus considerably reduce the energy consumption of cooling system in buildings.