Properties Of Phase Change Materials Research Articles

Investigation on the optimization strategy of phase change material thermal management system for lithium-ion battery

Due to the lack of detailed comparison and reliability validation of paraffin (PA)-based optimization methods for lithium-ion thermal management systems, in this work, PA was selected as a phase change material (PCM). Both expanded graphite (EG) and the fin were used to optimize the thermal management performance of the PA. Charging and discharging experiments under different optimization methods were conducted, and the thermal properties of both PCMs before and after cycling were recorded to assess reliability. The experimental results indicated that both PCMs had similar thermal properties and maintained good thermal management performance after cycling. PA/EG exhibited better thermal management performance than the PA/Fin due to its excellent thermal conductivity network. Higher ambient temperatures also reduced the thermal management performance of PCM and affected the optimization of EG and Fin in the meantime. PA/EG/Fin offered the best thermal management performance, achieving a maximum 35.5 % reduction in battery temperature and controlling the temperature increase of the battery even at extremely high temperatures. This work may serve as a reference for the design of thermal management systems for lithium-ion battery, providing a basis for the application of intelligent algorithms in the optimization of thermal management of PCMs.

Thermal properties of RT22 HC and RT28 HC phase change materials proposed to reduce energy consumption in heating and cooling systems

The construction sector accounts for 40% of total energy consumption and is increasing. To reduce energy consumption of heating and cooling systems during peak demand while maintaining thermal comfort, phase change materials (PCMs) are used more and more. Appropriate application of PCM and design of latent heat thermal energy storage (LHTES) requires in practice an in-depth knowledge of the thermal properties of PCMs. The aim of the paper is to present the results of experimental determination of the properties of two commercially available, organic PCMs – RT22HC and RT28 HC, using T-history method and pipe Poensgen apparatus. Results of experimental tests showed that these low-temperature PCMs could effectivity store heat and cold in a narrow temperature range of approx. 7 K for RT22 HC and about 3–4 K for RT28 HC. The average measured latent heat values are 190 kJ/kg for RT22 HC and 244 kJ/kg for RT28 HC. The distribution of energy stored in RT22 HC shows the peak in the temperature range of 21–23 °C (with 20–50 kJ/kgK for heating, 22–71 kJ/kgK for cooling). For RT28 HC this range is 27–28 °C (75–130 kJ/kgK for heating, 40–125 kJ/kgK for cooling). The diagrams of enthalpy present small hysteresis (0.5–1 K) in these materials. Thermal conductivity measurements using pipe Poensgen apparatus demonstrated that these PCMs have a low conductivity of 0.12–0.33 W/mK. The presented experimental research is intended to provide the data necessary for the correct design of LHTES with RT22 HC or RT28 HC intended to use in heating and cooling systems and to maintain thermal comfort in buildings.

Phonons of Phase‐Change Materials

Phase‐change materials (PCMs) undergo a reversible transition from a semiconducting to a metallic state, nicely termed “incipient metal.” This transition is driven by a Peierls distortion. A model of covalent bonding is developed in a tight‐binding scheme that accounts for the drastic evolution of some properties of PCMs, among which the Grüneisen parameter. The original vibrational properties of PCM and related Peierls distorted materials are analyzed. A three‐body covalent interaction describes the PCM properties. It explains the simultaneous softening of the optical phonons and the hardening of the acoustic phonons upon crystallization of the PCMs.

Thermophysical properties of n-hexadecane: Combined molecular dynamics and experimental investigations

Investigating properties of phase change materials (PCMs) is an important issue due to their extensive use in heat storage systems and thermal regulation devices. Improvement of the efficiency of such systems should be based on a better knowledge of the microscopic mechanisms governing the thermal and rheological characteristics of PCMs. This may be accomplished by the use of molecular simulations of the aforementioned quantities and their linkage with macroscale investigations. In this work, we studied thermophysical properties of n-hexadecane for different temperatures regimes using molecular dynamics (MD) and carry out several experimental measurements. Particularly, we focused on the evaluation of various rheological and thermal properties such as thermal conductivity, κ, viscosity, η, diffusion coefficient, D, and heat capacities Cp and Cv. Special attention was paid to the comparison of the results of simulations with experimental ones.

Optical properties of as-deposited, annealed and laser-treated Ge2Sb2Te5 thin films

Knowledge of the correct optical properties of phase change materials (PCM) is important in the development of many devices. Here, we report on the differences in optical properties of as-deposited, annealed, laser-reamorphized and laser-recrystallized G e 2 S b 2 T e 5 thin films. While as-deposited and laser-reamorphized G e 2 S b 2 T e 5 show a similar spectral dependences of refractive indices and extinction coefficients with a small decrease in optical band gap from 0.63 to 0.59 eV, spectral dependences of annealed and laser-recrystallized G e 2 S b 2 T e 5 differ significantly from each other in the entire measured spectral region with values of optical band gap 0.51 and 0.45 eV, respectively. We discuss the main differences in the optical functions between both crystalline phases using X-ray diffraction studies. We further present that the laser-reamorphized phase transforms to the crystalline phase at about 12 °C lower temperature in contrast to the as-deposited amorphous phase.

PHASE CHANGE MATERIALS: TYPES, PROPERTIES and APPLICATIONS in BUILDINGS

The need to reduce the use of fossil energy, which is running out and harmful to the environment, in response to the increasing energy demand with rapid urbanization, population growth and developing technologies reveals the necessity of research and application of technologies using renewable energy. Phase-change materials (PCM) are one of the most suitable methods for the efficient use of thermal energy originating from clean and sustainable energy sources. PCMs play important roles in a more energy-efficient world. The development of PCMs is one of the most challenging areas of study for more efficient thermal energy storage (TES) systems. This paper first explains the concept of PCMs and then describes the properties of these materials. After mentioned studies for improving the properties of PCMs, then PCM types and advantages-disadvantages are explained. Also, usage areas of PCMs in various sectors are also explained.

Thermophysical Properties of Inorganic Phase-Change Materials Based on MnCl2·4H2O

Manganese (II) chloride tetrahydrate, classified as an inorganic phase-change material (PCM), can be used as a thermal energy storage material, saving and releasing thermal energy during its phase transitions. In this study, thermophysical properties, such as phase change temperatures, latent heat, and thermal conductivities, of four types of MnCl2·4H2O PCMs were investigated under single and dual phases (liquid-, solid-, and dual-phase PCMs) using differential scanning calorimetry (DSC) and a heat flow meter. PCMs with a liquid or dual phases exhibited superheating issues, and their melting temperatures were 7 to 10 °C higher than the reference melting temperatures. The PCMs had latent heats between 146 and 176 J/g in the temperature range of 23 to 45 °C under the endothermic process. Severe supercooling during the exothermic process was observed in all as-received specimens, but was mitigated in the homogenization-treated specimen, which sustained an increase in solidification temperature of about 15 °C compared with the as-received and treated PCMs. The diffusivities of PCMs were between 9.76 × 10−6 and 2.35 × 10−5 mm2/s. The diffusivities of the PCMs in the solid phase were higher than those in the liquid phase. During the initial holding time of the endothermic process, the PCM in the liquid phase could not be fully solidified due to an insufficient initial holding time and very low diffusivity, which caused superheating during the DSC measurement. Moreover, in the exothermic process, a fast cooling rate of 5 °C/min and low thermal diffusivity caused supercooling. In particular, the diffusivity of the liquid PCM was lower than those of the solid PCM and other PCMs, which caused extremely high supercooling during the DSC measurement. This paper provides the thermophysical properties of MnCl2·4H2O PCMs, which are not available in the literature. The homogeneity of PCMs in their initial states and their heating/cooling rates were identified, and constitute important factors for accurately measuring the thermophysical properties of PCMs.

Measurement of thermophysical properties with nanomaterials on the Melting/Freezing characteristics of phase change material

In the present work, four formulations of the composite phase change materials (PCMs) were produced by adding 0.5 wt% of nanoparticles (NPs), and each formulation comprised one of the types of nanoparticles. Myristic acid was considered as the base material; 0.5 wt% of Al2O3, SiO2, CuO, and Ag were reckoned as the supporting materials. Al2O3, SiO2, CuO, and Ag NPs were synthesized and they were studied by different characterization techniques. The melting and freezing temperatures of myristic acid were determined in the range from 55.54 °C to 55.94 °C and from 48.42 °C to 48.71 °C, respectively. Likewise, the latent heats for melting and freezing were found to be 192.31 kJ/kg and 192.53 kJ/kg, respectively. The thermal properties of composite PCMs were evaluated with respect to weight fractions of NPs and thermal cycles. With nanomaterial dispersion, the laser flash analyzer (LFA) confirmed the thermal conductivity enhancement of myristic acid. The composite PCMs have faster melting and freezing times than pure PCMs, as stated in the results of this study.

Thermal Properties of Novel Phase-Change Materials Based on Tamanu and Coconut Oil Encapsulated in Electrospun Fiber Matrices

The accumulation of thermal energy in construction elements during daytime, and its release during a colder night period is an efficient and green way to maintain a comfortable temperature range in buildings and vehicles. One approach to achieving this goal is to store thermal energy as latent heat of the phase transition using the so-called phase-change materials (PCMs). Vegetable oils came recently into focus as cheap, widely available, and environmentally friendly PCMs. In this study, we report the thermal properties of PCMs based on tamanu and coconut oils in three configurations: pure, emulsion, and encapsulated forms. We demonstrate the encapsulation of pure coconut- and tamanu-oil emulsions, and their mixtures and mixtures with commercial PCM paraffins in fiber matrices produced by a coaxial electrospinning technique. Polycaprolactone (PCL) was used as a shell, the PCM emulsion was formed by the studied oils, and sodium dodecyl sulfate (SDS) and polyvinyl alcohol (PVA) were used as emulsifiers. The addition of commercially available paraffin RT18 into a 70/30 mixture of coconut and tamanu oil, successfully encapsulated in the core of a PCL shell, demonstrated latent heats of melting and solidification of 63.8 and 57.6 kJ/kg, respectively.

Integration of phase change materials in improving the performance of heating, cooling, and clean energy storage systems: An overview

Phase change materials (PCMs) have garnered significant attention as low-cost thermal energy storage systems that efficiently capture and store solar energy. Recent review works have largely focused only on thermal conductivity enhancement techniques, and/or applications of PCMs, while others have mainly discussed the performance enhancement of either heating, cooling, or clean energy storage systems integrating with PCMs. However, not enough studies recently reviewed all of these techniques/systems comprehensively to provide insights into them. This paper thus comprehensively reviews the integration of PCMs as an enhancement to most types of heating, cooling, and clean energy storage system performance, and the techniques to enhance thermal conductivity. The integration of PCMs with these systems has shown promising performance. For instance, an improvement of 13.5% is found in the efficiency of photovoltaic (PV) system when it is integrated with PCM/Al2O3 nanoparticles. In addition, the solar air heater's daily energy efficiency reaches 17% on its own, but when combined with PCM, it reaches 33%. However, the major drawback of using PCM–TES (thermal energy storage) for cooling is that PCM does not entirely solidify at night. The literature also shows that the issues related to PCMs' low thermal conductivity, phase separation, and subcooling/supercooling, their poor compatibility with other materials, and the environmental hazards they pose hinder their application on a large scale. It is necessary to implement international standards for assessing the thermophysical properties of PCMs and compile data to better facilitate the utilization of PCMs by end-users.

Energy consumption of a building with phase change material walls – The effect of phase change material properties

The use of Phase Change Material (PCM) in the building envelope is a promising technology for providing energy savings. In this study, the effectiveness of incorporation a honeycomb PCM to the walls of a retrofitted building in Ottawa, Canada is investigated in terms of reduction of heat flux through the walls. The climatic condition of Ottawa has a low air temperature of about −14 °C in the winter season. Reduction in the heat flux through the building envelope reduces the energy consumption of the building. PCM melting temperature, peak effective capacity, and the thickness of PCM layer have been varied to study their respective effect on the effectiveness of the PCM. Incorporating 1-cm thick PCM with peak melting temperature of 20 °C gives the best performance for a typical summer day with outdoor temperature varying from 15.0 to 26.5 °C. The heat gain and heat loss through the studied building walls is reduced by 41 % and 96 %, respectively. Also, the results show no further improvement in the PCM effectiveness when the thickness of the PCM layer and the peak effective heat capacity are increased beyond 1 cm and 20 kJkg−1K−1, respectively.

Evaluation of the energy flexibility potential of radiant ceiling panels with thermal energy storage

This study focuses on evaluating the energy flexibility potential of an innovative cooling technology that consists of a standard radiant ceiling panel incorporating macro-encapsulated phase change materials (PCM). The incorporated PCM allows shifting the energy demand for building cooling. A simulation case study is implemented to investigate the energy flexibility of an office building conditioned by the proposed system in a hot and humid climate. At first, the thermal storage properties of the macro-encapsulated PCM were determined by using the standard ASTM C1784-20. The obtained properties were then used in a whole-building simulation model validated using measurements in a real size walk-in chamber. Three different performance indicators were used to quantify energy flexibility: available storage capacity, storage efficiency, and power shifting capacity. Results show that with an average panel to ceiling ratio of around 66%, the radiant ceiling panel has an average sensible heat storage capacity of around 430 Wh/m2day and average annual storage efficiency of 86%. Results also show that the proposed system can shift the electric power demand for conditioning by 8 h compared to a conventional all-air system. These results confirm the benefit for implementing Demand-Side Management strategies that can exploit the energy demand flexibility of radiant ceiling panels incorporating PCM.

Experimental investigation of photothermal properties of phase change material enhanced by Zn–TiN binary nanoparticles

By the widely application in solar energy conversion systems for phase change materials (PCM), the photothermal properties of PCM are important for the efficiency of systems. As a typical PCM, the applications of paraffin in solar utilization are limited by it poor photothermal properties. In order to improve the photothermal performance of pure PCM, Zn–TiN binary nanoparticles are chosen for the enhancement in the present work. Furthermore, the photothermal properties of Zn–TiN binary nanoparticles enhanced phase change material (NePCM) with various volume fraction are evaluated by thermal properties, capacity of solar energy absorbed, and photothermal conversion performance. In addition, the stability of NePCM effected by dispersants and the temperature variation regularity of samples effected by solar radiation intensity and temperature monitoring locations are also studied. As the results: CTAB is a suitable dispersant for the NePCM. Under the same concentration (0.001 vol%), Zn–TiN binary nanoparticles can improve the solar absorption capacity of pure PCM significantly which enhanced almost 8 times. However, due to the aggregation of nanoparticles, the efficiency of photothermal conversion decreases with the increase of volume fraction, therefore, 0.001 vol% Zn–TiN binary NePCM gives the maximum efficiency of 22%, that is twice than that of the pure PCM. Photothermal conversion performance improved with the increase of intensity of solar radiation. Under the intensity of 600 W/m 2 , the peak temperature of 0.01 vol% Zn–TiN binary NePCM is 62.57 °C which appears in the center of the sample. • A new binary NePCM consisted by Zn, TiN nanoparticles and PCM is prepared. • Photothermal properties of binary NePCM are explored by mathematical and experimental method. • A system for researching photothermal conversion capacity is set up. • The influencing factors of photothermal conversion capacity of Zn–TiN NePCM are researched.

Incorporating phase change materials into glazing units for building applications: Current progress and challenges

• Both light and heat transfer characteristics of glazing systems should be considered. • Usage of phase change materials helps reducing energy loss through glazing systems. • Measurement and numerical models are inadequate to study photo-thermal transmission. • More research on effect of phase change materials on acoustic performance is needed. • Database lacks optical properties of solid and molten nano-phase change materials. Building envelopes consist of transparent and non-transparent components, and pose distinct opportunities and challenges in energy conservation. Glazing envelopes, which are transparent, are mainly responsible for the lighting and ventilation of buildings, but the acoustic performance may be weakened. Since glazing envelopes suffer from the defects of high solar transmittance, poor thermal insulation, and low thermal inertia, their energy-saving technologies are significantly different from those of non-transparent envelopes. Different energy-saving technologies have been studied to improve the optical and thermal performance of glazing envelopes. However, there is a lack of a review study involving the phase transition process and the improvement of photo-thermal transmission in glazing envelopes containing phase change materials. The present work provides a comprehensive overview of research advances in optical transmittance, thermal resistance, and thermal inertia along with photo-thermal transmittance in glazing envelopes, with a special focus on the integration of phase change materials. The study reveals that measurement and numerical models are inadequate to study photo-thermal transmission. Besides, it is identified that there is a research gap in the acoustic performance of glazing systems incorporating phase change materials, and there is a lack of database on the optical properties of phase change materials containing nanoparticles.

A study on frost and high-temperature resistance performance of supercooled phase change material-based flat panel solar collector

Easy freezing and overheating of the flat panel solar collector (FPSC) limits its large-scale application. In addition to the characteristics of high heat storage density and low price, inorganic supercooling phase change materials (PCMs) also have a large difference between their melting and freezing points, which fully meets the needs of FPSCs. In this paper, a new type of supercooled PCM as an FPSC was designed and studied, and a computational fluid dynamics (CFD) model was verified by experiments. Simulations were done to analyze the effects of different structures and PCM properties on the thermal efficiency and cooling rate of the collector. The results showed that the efficiency increase rate of the absorber plate was about 15% when the absorber plate was in direct contact with the PCM under neutralization. For the PCM with a melting point of 323.15 K and a supercooling degree of 30 K, the increase rate of the cooling time can reach more than 15% compared with that of a non-supercooled PCM. The structure of FPSC was optimized, and the thickness of PCM was studied in typical geographic areas. Except for Chengdu, the reliability index of the supercooled phase change material FPSC (SPCM-FPSC) in winter and summer was found to increase to more than 0.5 compared with 0.1 for ordinary FPSCs. It was found that the SPCM-FPSC significantly improved the freezing and high-temperature resistance of collectors in various regions. These results provide a strategy for the promotion and application of FPSCs in harsh outdoor environments.

Numerical study of PCM thermal behavior of a novel PCM-heat pipe combined system for Li-ion battery thermal management

A three-dimensional numerical model is developed and validated against experimental data for a cylindrical lithium-ion battery module with a compact hybrid cooling system of phase change material (PCM) and heat pipes. This cooling system is particularly well-suited for small or medium-sized battery module or pack. The PCM process and its effect on battery thermal behavior are numerically investigated for cases based on different C-rate discharge processes (0.5C, 1C and 2C), different PCM properties (different mass fractions of expandable graphite) and different charge–discharge cycles of the battery module. The results indicate that the PCM liquid fraction distribution is not uniform during the discharge process, the PCM starts to melt from its outermost neighboring the batteries and its upper part gets more liquid due to natural advection of liquid PCM. The different melting rates within the PCM lead to slightly enlarged temperature difference between batteries. Increasing discharge C-rate further accentuates this temperature difference. A tested composite PCM of 12 wt% EG (expanded graphite) shows better heat dissipation performance than that of pure PCM, and consequently it is better suited for battery thermal management systems. The simulations for different charge–discharge cycles indicate that lowering C-rate and increasing recovery time can improve thermal performance of the battery module and thermal control is thus more effective.

A comparative study on thermophysical properties of functionalized and non-functionalized Multi-Walled Carbon Nano Tubes (MWCNTs) enhanced salt hydrate phase change material

Thermal energy storage (TES) system is one of the best options for harvesting, storing, and saving energy for long-term or short-term use of a modern energy production system. The nano-enhanced phase change materials (NePCM) are a new type of phase change materials (PCM) formed by suspended nano-sized particles in base PCM to improve the thermophysical properties of the base PCM. The major challenge in nanoparticle dispersion in PCM, especially for solar energy applications, is its poor thermal conductivity and light transmission capability. Present research aims to address the thermal conductivity and light transmission capability issues by dispersing pristine multi-walled carbon nanotube (MWCNT) and functionalized multi-walled carbon nanotube (FMWCNT) particles in various weight concentrations (0.1, 0.3, 0.7, and 1.0%) into the salt hydrate PCM. A two-step technique was implemented to develop the NePCM for various weight percentage of MWCNT and FMWCNT. The Fourier transform infrared (FTIR) spectrum shows the MWCNT and FMWCNT nano-sized particles physically mixed well in salt hydrate PCM and without disturbing the chemical properties. The thermal conductivity of developed composites at 0.7 wt% MWCNT/S50 (S50M-0.7) and 0.7 wt% FMWCNT/S50 (S50F-0.7) are 0.78 W/mK, and 0.92 W/mK, respectively. The Differential Scanning Calorimetry (DSC) results revealed that the maximum improvement in latent heat by 14.66% and 31.17% for 0.1 wt% MWCNT/S50 (S50M-0.1) and 0.3 wt% FMWCNT/S50 (S50F-0.3) respectively. Light transmittance of S50M-0.7 and S50F-0.7 reduced to 92% and 93.49% than pure salt hydrate PCM. It exhibits the reduction in transmittance, greater improvement in solar spectrum absorption, and excellent photothermal conversion. • Study on Functionalized and non-Functionalized MWCNT enhanced PCM. • Comparative thermal performance of MWCNT and FMWCNT enhanced salt hydrate PCM. • A remarkable enhancement in thermal conductivity by 100% for S50F-0.7 • A substantial reduction in light transmittance by 93.49% for S50F-0.7 than base PCM.

Proposed specific heat capacity model for a concrete wall containing phase change material (PCM) under field experiment conditions

This study compares (1) the specific heat capacity (CP) model obtained from the differential scanning calorimetry (DSC) measurement, (2) the conventional CP model using the step function and normal distribution function, and (3) the newly proposed CP model using the non-central F-distribution function. The CP models were implemented into the numerical conductive heat transfer model for the PCM-containing Portland cement (PC) concrete wall. Except for the heat capacity of PCM, other experimental data such as density, thermal conductivity, heat flux, or inner temperature profiles were obtained from the previous studies to build the numerical model. Through the validation process, the CP model using the non-central F-distribution function was selected as the best model, including the thermal properties of PCM. The proposed model was applied to the parametric study to investigate the best thermal efficiency, such as thermal comfort and diurnal temperature difference when applying PCM to PC concrete walls.

Development in multiple-phase change materials cascaded low-grade thermal energy storage applications: A review

The efficient use of thermal energy is one of the most important aspects that govern the development of any nation. But the disparity between demand and supply of thermal energy has stimulated researchers to design efficient thermal energy storage (TES) systems. The latent heat TES (LHTES) utilizing phase change material (PCM) is one of the most effective methods for the storage of energy in confined space. The LHTES encounters the issue of the non-uniform driving temperature difference between PCM and heat transfer fluid that causes a slow rate of heat transfer, and asynchronous phase transition. To achieve uniformity in temperature distribution and for instant storage and release of thermal energy, the concept of cascading of multiple-phase change materials (M-PCMs) in the LHTES system has been established. The review paper summarizes the development in M-PCMs cascaded LHTES (C-LHTES) utilized for low-grade thermal energy storage applications (cold: below 20 °C and low-temperature heat: between 20 °C and 100 °C). The effect of thermodynamic properties of PCMs, selection, and stacking of PCM, operating and geometric parameters have been reviewed on the performance parameter of M-PCMs C-LHTES. To improve the heat transfer rate, energy, and exergy efficiency of LHTES, the innovative designs, and arrangements, and the use of M-PCMs in conjunction with thermal conductivity enhancers and surface enhancers have also been discussed. The results of research work in the field of M-PCMs C-LHTES are summarized in tabular form according to the applications. The key findings of the review for each application and guidelines for selecting phase change temperature of M-PCMs, preferred number of stages, order of M-PCMs for cascading, etc. are presented in conclusion. The scope of future work in the field of M-PCMs C-LHTES systems has also been presented.

Anomalous liquids on a new landscape: From water to phase-change materials

A liquid that is cooled below its melting temperature, referred to as a supercooled liquid, can solidify into an amorphous rigid state (i.e., glass), if cooling is fast enough and crystallization is avoided. The phenomenology of supercooled liquids has been in general established. However, there are pronounced exceptions (e.g., water) which do not fall into the class of ‘normal’ liquids but exhibit a transition behavior in their liquid states. The latest advances connect the unusual aspect of liquids to the properties of phase-change materials (PCMs) that are the basis for non-volatile memory and neuromorphic technologies. In this article, we review the liquid anomalies in the alloys based on group-IV, V, VI elements including technologically important compositions. Their different behaviors are rationalized in terms of liquid–liquid (metal-semiconductor, and fragile-strong) transitions. We discuss their implications for understanding unusual phase switching behaviors in these materials. Lastly, unsolved problems and new opportunities are outlined.