Microencapsulated Phase Change Materials Research Articles

Light transmitting glass fiber reinforced cementitious composite containing microencapsulated phase change material for thermal energy saving

The energy utilization for artificial lighting, cooling, heating, and air conditioning in buildings results in the release of greenhouse gases and causes climate crises. In this regard, a novel light-transmitting cementitious composite (LTCC) was developed by substituting microencapsulated phase change material (MPCM) to reduce the building energy utilization via transmitted light through the composite and improve the solar thermal energy efficiency. The cementitious matrix is produced with cement, kaolin, silica sand, water, superplasticizer, adhesive polymer, glass fiber, different ratios of MPCM, and plastic optical grids to let inward sunlight transmittance. The current study thoroughly investigates the characteristics of light-transmitting composite, including MPCMs, via physico-mechanical, chemical, microstructural, thermal, light transmittance and solar thermoregulation tests. The thermal conductivity of the composite with 0 wt% MPCM decreased from 1.09 W/mK to 0.96 W/mK with 15 wt% MPCM addition. Incorporating 10 wt% of MPCM reduced the 28 days-compressive strength of specimens by almost 28 % due to the lower strength and density of microcapsules, as well as the voids formed by damaged MPCMs. On the other hand, the incorporation of MPCM did not dramatically affect the flexural strength of the cementitious composite. DSC analysis results revealed that the composite containing 15 wt% MPCM shows a latent heat of fusion of 14.6 J/g with a melting point of 17.65 °C. FTIR analysis disclosed that MPCM maintains its chemical structure in the composite. Composite slabs exhibited up to 12.4 % artificial light transmittance, which would translate to a considerable increase in the lighting efficiency of commercial and residential buildings. Thermoregulation performance test under ambient conditions indicates that the specimen containing 15 wt% MPCM can provide a cooler room temperature for 6.5 h when the room or surface temperatures increase above 21–23 °C, and a warmer room when the temperature decreases below these temperatures. The findings of the current study can be applied to enhance thermal energy saving and artificial lighting efficiency in buildings that inspire the design of environment-friendly constructions.

Experimental evaluation of latent heat use of a microencapsulated phase change material slurry in spraying

A spraying system was constructed with a microencapsulated phase change material (MPCM) slurry as the working medium to weaken the adverse effects of the slurry's high viscosity and low thermal conductivity on heat transfer in a wall tube heat exchanger. The temperature distributions of pure water and MPCM slurry were first obtained through infrared thermal imaging in spraying. Furthermore, the latent heat use of MPCM slurry was investigated through a new method based on the temperature properties of the phase change fluid, in which the working and phase change temperature ranges are matched. The heat-mass transfer characteristics are compared and discussed with those of the base fluid, and the latent heat use of 10wt% MPCM slurry containing the core material n-docosane (C22H46). The experimental results indicate that the phase change enables the MPCM slurry droplets to maintain a higher temperature than a fluid with no phase change or base fluid. Different application modes (static and spraying) have correspondingly different phase change temperature ranges owing to supercooling, and the degree of matching between the working and phase change temperature ranges has a critical impact on the latent heat use of the MPCM slurry. Finally, comparing the heat transfer coefficients and Lewis numbers between the base liquid and MPCM slurry reveals that the phase change not only enhances the heat transfer but also slightly reduces water evaporation compared with pure water spraying.

Paraffin@Silica Microencapsulated Phase Change Materials with Improved Anti‐Leakage Properties

AbstractA series of paraffin (Pn)@silica (SiO2) microencapsulated phase change materials (MEPCM) were synthesized by sol‐gel process using tetraethyl orthosilicate (TEOS) and silane coupling agent as precursors. The morphology and chemical compositions of Pn@SiO2 microcapsules were characterized by SEM and FT‐IR, and thermal energy storage capacity was tested by DSC. The results showed that the Pn@SiO2 microcapsules modified with 3‐methacryloxypropyltrimethoxysilane (MPS) had a desirable phase transition enthalpy (184.12 J/g). Meanwhile, the contact angle and leakage rate of Pn@SiO2 microcapsules were analyzed, and the data indicated the contact angle of Pn@SiO2 microcapsules was significantly improved and the leakage rate of Pn@SiO2 microcapsules was reduced to different degrees by modification with silane coupling agents. The main reason is that the modification of silane coupling agents improves the wettability of silica on the surface of paraffin wax, which makes the aggregation of silica on the surface of paraffin more efficient. Among them, the Pn@SiO2 microcapsules modified by MPS showed the most significant reduction in leakage rate, which was reduced from 8.38 % to 1.24 %. Pn@SiO2 microcapsules modified by MPS not only showed outstanding latent heat‐storage/release capability with a high capacity but also exhibited good shape stability, high thermal stability and excellent phase‐change reliability and durability.

Experimental study of the surface vapor pressure of a microencapsulated phase change material slurry liquid desiccant within the entire temperature range of a dehumidification system

The surface vapor pressure is a critical physical property of a liquid desiccant, which has a direct influence on the mass transfer driving force in the dehumidification and regeneration process. In this study, a measurement system for the surface vapor pressure of the microencapsulated phase change materials slurry (MPCMS) was built using a static method. The surface vapor pressure of the MPCMS at 293.2 K–353.2 K was measured, which covered the entire range of dehumidification and regeneration. Experimental results showed that the surface vapor pressure of the MPCMS decreased compared with that of the pure LiCl solution. The surface vapor pressure drop ratio of the MPCMS increased with increasing MicroPCM and LiCl mass concentrations. The phase transition of the MicroPCMs intensified the drop in the MPCMS surface vapor pressure. When the MicroPCM and LiCl mass concentrations were 2 % and 40 %, respectively, and at the phase transition temperature of 303.2 K, the vapor pressure drop ratio reached a maximum of 17 %. A correlation for the MPCMS surface vapor pressure calculation was proposed, and the deviation between the calculated and measured values was less than 10 %. The results of this study provide basic data for the future development of the MPCMS liquid desiccant system.

Experimental and Photothermal Performance Evaluation of Multi-Wall Carbon-Nanotube-Enhanced Microencapsulation Phase Change Slurry for Efficient Photothermal Conversion and Storage

Melamine formaldehyde was used as the shell material and n-eicosane as the core material with the method of in situ polymerization to synthesize microencapsulated phase change materials (MPCMs). To enhance the thermophysical characteristics and photothermal conversion performance of the MPCM slurry, multi-wall carbon nanotubes were added, and the microscopic morphology and thermophysical parameters of the MWCNT-MPCM slurry were analyzed. The thermal conductivity, viscosity, and photothermal conversion properties of the slurry were examined. The results indicated that the synthesized MPCMs were nucleated and unbroken, with a spherical form and a latent heat of phase transition of up to 135.92 kJ/kg. The MPCM was stable when dispersed in water, and its thermal conductivity rose with the temperature but slightly decreased during the phase transition period. The viscosity rose with the addition of the MPCM, with a jump at 20% MPCM content. The addition of MWCNTs had a minor effect on the material’s thermophysical properties. The thermal conductivity increased from 0.55 W/m·°C to 0.6 W/m·°C when MWCNTs were added to the material. The viscosity of a 20% MPCM slurry exceeded 3000 mPa·s when 0.5% MWCNTs were introduced. Under 1 sun of sunlight, the mixture’s peak temperature could reach 60 °C at 0.5% MWCNT concentration. The MWCNT-MPCM slurry is capable of producing efficient solar photothermal conversion without sacrificing other thermophysical properties, and it has several applications in solar energy consumption and thermal engineering.

Supercooling elimination of cryogenic-temperature microencapsulated phase change materials (MPCMs) and the rheological behaviors of their suspension

Phase change materials (PCMs) when amalgamated in a shell material to form microencapsulated-PCMs (MPCMs) usually exhibit high levels of supercooling due to the limited crystallization process. In the present study, various efforts were made to reduce this phenomenon, including increasing the MPCM size, employing nucleating agents, and embedding copper nanoparticles into the MPCM shells. It was observed that with an increase in the microcapsule size from 43 μm to 76 μm, the supercooling was reduced by a value of 10.2 °C from melting/freeing point peak temperature differences of 37.6 to 27.4 for the 1200 rpm and 800 rpm samples respectively. Comparatively, the implementation of octadecanol nucleating agent 30 wt % resulted in a reduction of supercooling by 22.9 °C. The introduction of Cu nanoparticles with a decane core can also reduce the supercooling degree by 4.6 °C, while the thermal conductivity the MPCM samples with a hexadecane core increased from 0.173 to 0.182 W m−1 K−1 before and after the addiction of the Cu nanoparticles. Furthermore, di(propylene glycol) methyl ether was used as a carrier fluid for the MPCMs to study the slurry rheological behaviors with various MPCM compositions. It was observed that the MPCM suspension with 10–20% MPCM mass concentration did not exhibit shear thinning, while the 30% sample conveyed shear thinning properties. Furthermore, near the crystallization temperature of the PCM, the slurry viscosity sharply rose, attributed to the volume changes and non-cooperative motion of MPCM microcapsules.

Optimization of microencapsulated phase change material slurry-based porous heat exchanger

Microencapsulated phase change material (MPCM) is one of the promising methods for thermal energy storage systems. However, the feasibility of their implementation in different systems, especially heat exchangers, is still questionable. In this study, the MPCM slurry flow within a porous double-pipe heat exchanger is evaluated and optimized. To have a better understanding of characteristic parameters impact, including Reynolds number, Darcy number, MPCM mass concentration and inlet temperature difference, on the performance of the heat exchanger, response surface methodology is applied. The effectiveness and Performance Evaluation Criterion (PEC) with three levels are selected as the response variables. The results showed that the simultaneous use of MPCM and a porous medium is not reasonable in terms of pressure losses inside the pipes. However, increasing the permeability of porous media can increment and decrement the PEC and effectiveness by 83 and 5.2 %, respectively, at any MPCM mass concentration. Also, MPCM can improve the cost-effectiveness at lower PEC which demands finding optimum values depending on the application. Increasing the mass concentration of MPCM has shown a high negative impact on PEC at high Reynolds numbers in which up to 13 % reduction is observed by changing the mass concentration from 5 to 15 %.

Fabrication of phase change microcapsules with controllable size via regenerated nanochitin stabilized pickering and their applications for lyocell fiber

Lyocell fiber has attracted much attention in the textile fields as a greener alternative to viscose. Thermo-regulating Lyocell fiber, which composited with phase change materials (PCMs) and Lyocell fibers, would be desirable for making smart clothing with improved comfort. Herein, microencapsulated phase change materials (MPCMs) with polyurea shell and n-octadecane as core material were fabricated using regenerated nanochitin (RCh) as stabilizer via Pickering emulsion strategy. The size of MPCMs can be controlled by a tunable oil/water mass ratio (O/W). When the O/W ratio was above 1/25, the MPCMs exhibited melting enthalpy as high as 189.92 J/g with average size of less than 5 µm, which was suitable for spinning thermo-regulating Lyocell fibers. The thermo-regulating Lyocell fibers that were fabricated by a dry-jet wet spinning process showed high heat capacity (21.07 J/g) with a diameter of about 30 µm at 20 % loading microcapsules. They demonstrate good durability, where 95 % of the original heat capacity were retained after 100 heating/cooling cycles.

Al–Ni alloy-based core-shell type microencapsulated phase change material for high temperature thermal energy utilization

Latent heat thermal energy storage (LHTES) using alloy-based phase-change materials (PCMs) is a promising technique for stabilizing the power supply of grid-connected renewable energies. In particular, recently developed alloy-based microencapsulated PCMs (MEPCMs) are attracting considerable attention owing to their ease of handling and ability to overcome the problems of corrosion and melting leakage experienced by alloy PCMs. To expand high-temperature LHTES, more MEPCMs need to be developed. In this study, an MEPCM was developed using Al-5 wt.%Ni alloy (melting point 640°C). Microencapsulation was performed in two steps: 1) Al hydroxide layer formation on the surface of PCM particles by boehmite treatment in boiling water for 1 h or 3 h and 2) Al 2 O 3 shell formation by heat oxidation treatment in an O 2 atmosphere. The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. The sample after 1 h of boehmite treatment and heat oxidation treatment had melting and solidification latent heat capacities of 241 J g –1 and 251 J g –1 , respectively. The developed MEPCM maintained its original shape and high latent heat capacity, even after 100 cycles of melting and solidification. The developed Al–Ni alloy-based MEPCM is expected to be applied to next-generation LHTES, in which a large-scale and ultrafast heat exchange system is employed in a small space by cascade configuration with other MEPCMs with different melting points. In addition, the formation of the Al–Ni alloy core/α-Al 2 O 3 shell structure was investigated thermodynamically, providing insights that will promote the development of Al- X alloy-based MEPCMs in the future. • Al–Ni alloy based microencapsulated phase change materials (MEPCMs) were developed. • The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. • The MEPCM exhibited high thermal storage capacity about 241 - 251 J g -1 . • The MEPCM had melting temperature of 640°C. • They are good candidates for high-temperature thermal energy storage application.

Phase change materials sheets for energy-efficient heat curing process: A potential idea and performance evaluation

Many countries experience long cold winter, which delays many in-situ concreting activities. Shifting to precast concrete systems is a common solution to continue and maintain construction progress. However, the heat curing process for precast elements represents a challenge for the precast industry due to its high energy consumption (i.e. high fossil fuels dependency and associated high carbon emissions). Therefore, this study examines the feasibility of utilizing micro-encapsulated phase change materials (MPCMs) to achieve a sustainable curing process. Both direct incorporation of MPCMs in the cementitious mixtures and covering specimens with MPCMs sheets were examined under a simulated heat-curing cycle. Results showed that covering specimens with MPCMs sheet eliminated drawbacks induced by MPCMs direct incorporation (i.e. leakage of paraffin, voids, and loss of function). Moreover, utilizing the MPCMs sheet allowed shortening the heat curing holding period by 50% (i.e. from 10 hrs to 5 hrs) while achieving 96% of the desired strength. Findings confirmed the high potential of using MPCMs sheets to cure, save energy, and boost the precast concrete industry's sustainability level.

Mechanical and thermophysical properties of cement mortars including bio-based microencapsulated phase change materials

This study investigates the mechanical and thermophysical performance of cement mortars incorporating microencapsulated phase change materials (mPCMs), which consist of an aqueous dispersion of 100% bio-based fine core–shell particles. A specific protocol was used to manufacture the mortar samples, which ensures a homogeneous particle distribution and prevents microcapsule leakage. The addition of mPCMs to the mortar causes both a decrease in density, an increase in porosity, and a substantial loss of mechanical strength. Conversely, hot-disk characterization revealed a large improvement in the thermal performance. The system containing 8 wt% mPCMs exhibits a good balance between its mechanical and thermal properties.

Analysis of the influence of microencapsulated phase change materials on the behavior of a new generation of thermo-regulating shape memory polyurethane fibers

The present work is a first approach in order to achieve thermo-sensitive and waterproof polyurethane fibers useful in the textile industry. For this, two polyurethane formulations with glass transition temperatures (Tg) close to the body temperature have been synthetized and characterized by several techniques such as Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic-Mechanical Analysis (DMA) and Thermo-mechanical analysis (TMA). In this manner their thermal and shape memory behavior were determined. It was also estimated the water vapor transmission rate of both polyurethane films. Then, integration of two different microencapsulated phase change materials (PCMs), one with organic shell and another one, with an inorganic shell, was carried out by extrusion in order to achieve materials with thermo-regulating properties. Fibers for both polyurethanes, pristine or loaded with microencapsulated PCMs, were again characterized to check that the thermal and shape memory properties are maintained, and to study their capability to storage and release energy. The promising results pave the way for a new generation of thermo-regulating materials useful in numerous applications such as the textile sector.

Application of the Hot Wire Method to Measure the Thermal Conductivity Coefficient of a Gypsum Composite

Currently, there is much discussion about modern technologies and solutions in construction. There are new solutions that save electricity or heat, usually in buildings additionally equipped with intelligent management systems. High hopes are placed on building materials. Every investment begins with them. The basic building materials include materials such as cement, bricks, hollow bricks or plasterboard, and their modification and the use of admixtures ensure the greatest changes in the parameters of the building. This article focuses on the preparation and testing of gypsum mortar consisting of gypsum, phase change material and polymer. The idea was to replace the proven method of adding microencapsulated phase change material by direct binding. This article presents the study of thermal conductivity by the hot wire method. Using this method, tests of temperature changes during plaster hardening were also carried out. Compressive strength tests were also carried out on the 14th, 21st, 28th, 35th and 105th day from the date of making the samples. For each of these tests, three types of samples with different polymer content were used. After a series of tests, the best results were obtained by a series of samples with 0.1% polymer.

Flexible phase change composite films with improved thermal conductivity and superb thermal reliability for electronic chip thermal management

High-performance flexible composites with excellent thermal management ability are essential to dissipate the heat generated in electronic systems. Herein, micro-encapsulated phase change material (MPCM) with n-Docosane core and MF resin shell is prepared. The obtained MPCM exhibits large phase change enthalpy (192.9 J/g). Subsequently, flexible composites are prepared by incorporating the MPCM, multi-walled carbon nanotubes (MWCNT) and hexagonal boron nitride (h-BN) in styrene-ethylene-propylene-styrene (SEPS) polymer matrix. At 30 wt% MPCM, the phase change enthalpy of 60.6 J/g is achieved. 3 wt%MWCNT/10 wt%h-BN/30 wt%MPCM composites show improved thermal conductivity of 0.44 W m−1 K−1, which is 95.5 % higher than pure SEPS. The composites are applied in chip for thermal energy dissipation, the temperature of chip’s lower surface is only 62.6 °C, which is 22.84 % lower than pure SEPS. Overall, the MWCNT/h-BN/MPCM composites with superior thermal properties and mechanical characteristics are promising in the field of electronic equipment thermal dissipation.

Thermal performance of cement mortar embedded with microencapsulated phase change materials in Indian subcontinental climatic conditions

Thermal performance of cement mortar embedded with microencapsulated phase change materials in Indian subcontinental climatic conditions

Investigation of the effectiveness of microencapsulated phase change materials for bitumen rheology

Investigation of the effectiveness of microencapsulated phase change materials for bitumen rheology

Processing of phase change materials by fused deposition modeling: Toward efficient thermal energy storage designs

Recently, several efforts have emerged that employ additive manufacturing techniques to integrate phase change material (PCM) thermal energy storage into geometrically complex designs for advanced thermal management. In this work, we contribute to this emerging research by reporting on the production of a composite nylon-based filament for fused deposition modeling incorporating encapsulated PCMs for 3D printing heat sink geometries. Microencapsulated PCM (MEPCM) with a 6 °C transition temperature was selected as the material for thermal energy storage. This transition temperature was selected due to its suitability to provide thermal energy storage to target air-conditioning applications in buildings. In an attempt to improve the thermal conductivity of the composite, fine boron nitride fillers were added, although the effect on improvement was found to be negligible in the overall composite mixture. The nylon-MEPCM ratio in the filaments was optimized, and filaments containing up to 40 wt% MEPCM were successfully synthesized, which were found optimal for 3D printing complex heat sink and other geometries. Thermal and mechanical properties of the filaments were characterized, including latent heat of fusion, thermal conductivity, phase change temperature, tensile strength, and more. Thermal infrared imaging of heat sink geometries printed using the MEPCM filaments undergoing thermal discharging was also conducted. This work presents the most promising result to date in the open literature for a 3D-printed PCM composite in the combination of size, energy density, and geometric complexity of printed parts.

Mass transfer and thermal buffering effect of hydrophobic fabrics with single-side coating of MPCMs

The incorporation of microencapsulated phase change materials (MPCMs) into textiles have been realized for personal temperature regulation. However, the hydrophobicity and breathability of MPCM-incorporated fabrics remained improvement. In this work, four commercial fabrics were first treated with a hydrophobic coating and the MPCMs were coated on the hydrophobic fabrics via pad-dry-curing coating method. The morphology, hydrophobicity, thermal energy storage, thermal buffering effect, moisture transfer, and breathability of the MPCM-coated fabrics were investigated. As a result, the MPCMs were well coated on one side of the hydrophobic fabrics. The water contact angles of the MPCM-coated side of MPCM-coated fabrics were higher than 100o, and the anti-fouling property was found. Besides, the breathability was reduced when an MPCM coating was on the hydrophobic fabric. The one-way moisture transfer behavior was little affected when there was an MPCM coating on the knitted and woven fabrics while significantly reduced when the 3D knitted fabric was the substrate. The thermal energy storage of the MPCM-coated fabrics ranged from 1.89 to 8 J/g, which was related to the used fabric type. Correspondingly, the thermal buffering effect of MPCM-coated fabrics was found, and a better thermal buffering effect was proposed when the MPCM-coated side faced the heating source.

Development of core-shell type microencapsulated phase change material with Zn-30 mass% Al alloy and its shell formation mechanism

Latent heat storage (LHS) technology is promising because it can store and release heat at a constant temperature utilizing phase change material (PCM) and is a superior alternative for sensible heat storage (SHS) technology. In this study, we report an improved preparation method for microencapsulated PCM (MEPCM) with Zn–30 mass% Al (melting temperature: 440–512 °C) as the PCM. Conventional MEPCM preparation involves boehmite treatment for 3 h in boiling water to form AlOOH shells on Zn–30 mass% Al alloy particles (average diameter: 35.7 μm) and heat-oxidation treatment to form an oxide shell in oxygen atmosphere at 800 °C. In this study, Al(OH)3 is added to the treatment solution before boehmite treatment; furthermore, precipitation treatment at 75 °C for 16 h is investigated. After heat-oxidation treatment, different Al and Zn oxide shells are formed on the surface of the alloy particles depending on the Al(OH)3 quantity added before boehmite treatment and precipitation treatment. The prepared MEPCM has a heat storage density of 0.48 GJ m−3 and excellent cyclic durability of >100 melting and solidification cycles. In addition to this, investigations related to the fabrication of composite PCM by mixing it with a glass frit was carried out for improving the durability of the MEPCM. Therefore, this material can be utilized in future medium-to-high temperature heat applications such as transportation, chemical processes, and renewable energy.

Characteristics and energy performance of novel MicroPCM C50 energy pile in cooling mode

Energy piles utilize geothermal energy via integrated geothermal heat exchangers (GHEs), which can sustain structural loads while also harvesting geothermal energy to meet the building's heating and cooling requirements. In the study, we report a systematic investigation of the Microencapsulated Phase Change Material (MicroPCM) C50 energy pile, from characterizing the material properties of the MicroPCM C50 concrete to analyzing the energy performance of the MicroPCM C50 based energy piles. Through integrating the MicroPCM into structural concrete, MicroPCM C50 concrete is manufactured and its properties, such as mechanical compressive strength and thermal conductivity, are characterized. With measured material properties implemented into a numerical model of the MicroPCM C50 energy pile, the energy performance when the energy pile works in the cooling mode is assessed. Our results suggest that (1) incorporating MicroPCM into C50 concrete specimens (up to 5 wt%), will dramatically reduce the compressive strength of C50 concrete; (2) Thermal conductivity and heat capacity of C50 concrete specimens are improved as mass fraction increases from 1 to 3 wt%, while reduced as mass fraction increases from 3 to 5 wt% (maximum at 3 wt%); (3) When considering both the mechanical and thermal performance of the energy pile, the energy pile with W shape GHE and 1 wt% MicroPCM addition is the best option for this scenario, followed by the energy pile with U shape GHE and 1 wt% MicroPCM, which will collect around 5% more geothermal energy, compared to normal concrete energy pile, and meanwhile retain a high level of mechanical strength. Our results will provide support for the design and optimization of the MicroPCM C50 energy piles toward real-world applications.