PCM Microcapsules Research Articles

Power consumption of model houses with and without PCM plaster lining using different heating methods

Thermal behaviour and power demand of two container model houses were studied. One of them was equipped with plaster lining with incorporated PCM microcapsules, and the second one served as reference during two successive winter periods. In the first winter period of 2019/20, an electric radiator was applied for heating the houses during the daytime, and then they were let cool down from evening to the next morning. The dynamic thermal behaviour and power demand of the model houses were investigated during the heating up periods, then in a quasi-thermal equilibrium, as well as along their spontaneous cooling down process at changing environmental temperatures. The indoor and environmental air temperatures, internal and external wall surface temperatures were collected by data logger during the whole winter periods for both model houses. Through the second winter period of 2020/21 the same methodology was used; nevertheless, the model houses were heated by air-air heat pumps. The performance coefficient (COP) of heat pumps was compared to the electric radiators. The estimated COP showed significant correlation with the temperature differences between the outdoor and indoor air temperatures, considerable worsening from COP = 3.1–3.4 to COP = 2.0–2.1 with increasing temperature drop to be overcome by the applied air-air heat pumps. However, there was no considerable dependence observed between the reference and PCM plaster lined houses. Equations were suggested to estimate the power demand in quasi-thermal equilibrium for both model houses and both heating methods as a function of the temperature differences between indoor and outdoor air. The power demand of PCM plaster lined model house compared to the reference house was lower by 10.3 % and 7.0 % using electric radiators or heat pumps, respectively, throughout the whole winter period, considering a medium temperature drop of 20 °C through the walls.

Core-satellite assembly of phase-changing material microcapsules enabled with broadband light absorption and localized surface plasmonic resonance for effective photothermal energy harvesting

To enhance the comprehensive photo-thermal energy accretion of the confined phase-changing materials (EPCM), engineered plasmonic nanoparticles (PG) and photosensitizer (PDA) were assimilated and structured in a core-satellite manner to form a highly active composite shell (DS-PDA/PG). In this communication, we devise a heterogeneous core-satellite assembly by the conjugation of the PCMs core and PG satellite assisted by a PDA arresting media. The constructed core-satellite can distinctly demonstrate superior photothermal performance compared to their respective precursor. This structural framework enunciates substantial improvement in photothermal energy conversion and heat dissipation mechanism due to the synergistic effect between the PG satellite and the PDA linker. Particularly, the heat channeling effect of PG nanoparticles onto the structured framework due to its localized surface plasmonic resonance (LSPR) mitigation which effectively dissipates heat to the encapsulating shell. The curated approach achieved a phase transition enthalpy of 139.20 J/g, with a thermal discrepancy of 28.89 ± 1.21 °C attaining an augmented photo to heat energy conversion efficiency of 96.95% due to wideband solar absorption and effective heat dissipation through the core-satellite assembly. The structured consolidation of PG and PDA was recognized to be a functional strategy that reinforce substantial improvements toward direct photo energy cultivation in an assortment of applications such as temperature management of greenhouses, solar water heating systems, solar cookers, and solar-thermal electricity generating systems. • A core-satellite assembly of PCM microcapsules was presented. • Broadband solar spectrum absorption on Uv–Vis–NIR range. • Efficient light to heat conversion through LSPR and molecule thermal vibration. • This work provides new insight into the PCM shell design for an effective solar-thermal conversion system. • Presented a new shell synergy insight for efficient light to the thermal conversion of EPCM.

Dopamine as a bioinspired adhesion promoter for the metallization of multi-responsive phase change microcapsules

This work reports on an environmentally friendly method to produce encapsulated phase change material with a thin nickel coating, applicable for heat conversion, storage and thermal management of heat-sensitive components and suitable for active heating by electromagnetic radiation. A critical issue for the metallization is the adhesion between the polymer capsule shell and the metal layer. Based on previous studies using the bio-molecule dopamine as adhesion promoter in composites and for plastics metallization, commercial paraffin microcapsules were coated with an ultrathin polydopamine film via a simple wet chemical process. Subsequently, a thin, uniform and compact nickel layer was produced by electroless metallization. The successful deposition of both layers was verified with a broad range of imaging and spectroscopic techniques. For the first time, surface-enhanced IR spectroscopy was used to study the deposition of ultrathin PDA films. The combination of SEM and energy-dispersive X-ray spectroscopy allowed resolving the spatial distribution of the elements Ni, N, and O in the MC shell. Electrically conducting paths in the Ni shell were verified by conductive AFM. Thermal analysis revealed that the coated microcapsules show a phase change enthalpy of approx. 170 J/g, suitable for thermal storage and management. Additionally, the nickel layer enhanced the thermal diffusivity of the microcapsule powders and enables a fast heating of the PCM microcapsules by microwave radiation, demonstrating the applicability of the metallized MCs for controlled heating applications.Graphical abstract

Experimental performance of a LED thermal management system with suspended microencapsulated phase change material

• Experimental study of thermal management with suspended microencapsulated PCM. • Using suspended PCM microcapsules instead of water improved thermal management. • Optimal MPCMS concentration was analyzed by a dimensionless thermophysical factor. • Variations of cooling performance were attributed to phase change of MPCM. Effective thermal management is crucial for electronic devices, while microencapsulated phase change material (MPCM) has great potential in the field of electronic heat dissipation. However, no existing study has conducted experimental research on the influence of MPCM suspension (MPCMS) on the thermal management performance of electronic devices. In the present study, improvement in the thermal management of LED by using MPCMS as coolant was experimentally demonstrated. The morphology, phase-change and thermophysical properties of the MPCM were observed. Experimental results indicate that the TEC-MHS system that uses MPCMS as coolant exhibited enhanced cooling capacity compared with the system that uses water. A dimensionless thermophysical factor was defined to study the effect of variation in thermophysical properties on cooling performance. Interestingly, the highest thermophysical factor and the best cooling performance were achieved at the same MPCMS concentration. The variation of cooling performance with the ambient temperature and flow rate of MPCMS were found to be attributed to the phase change of MPCM. The experimental results indicate that increased MPCMS concentration does not always lead to improvement of the cooling performance, while the thermophysical and phase change properties of MPCM play critical roles.

Multilayer Nonwoven Inserts with Aerogel/PCMs for the Improvement of Thermophysiological Comfort in Protective Clothing against the Cold

This study aimed to assess the developed nonwoven inserts with aerogel/PCM (phase change material) microcapsules for use in protective clothing against cold in terms of properties related to thermophysiological comfort. These inserts were obtained by the thermal bonding of a multilayer system consisting of needled-punched nonwovens and silica aerogel particles and/or PCM microcapsules evenly distributed between them. The influence of aerogel and PCM microcapsules on the basic physical properties of inserts, their microstructure, air permeability, and water vapor resistance was investigated and analyzed. The thermal insulation properties of inserts were assessed based on thermal conductivity results. The inserts with PCMs were also tested for their ability to regulate the temperature in the undergarment microclimate using the differential scanning calorimeter (DSC) and the “skin model” device. The research showed that the use of aerogel allowed for reducing the thermal conductivity of the insert by approximately 13% compared to the insert without additives. The high values obtained of the melting and crystallization enthalpy of inserts with PCMs confirmed their high efficiency in the heat absorption and release. Thus, the use of aerogel and PCMs in protective clothing against cold seems to be an effective solution for improving its protective properties and actively adapting its thermal insulation to the changing temperature conditions and the activity level of employees.

Development of thermo‐regulating fabrics with enhanced heat dissipation via graphene‐modified n‐octadecane microcapsules

AbstractPhase change materials (PCMs) are of great importance in thermal regulation applications, but low thermal conductivity is the most critical disadvantage of these materials. Especially in the textile field, while there are many studies on the production of PCM‐coated fabrics, studies on improving heat dissipation are quite limited. Therefore, in this study, first, n‐octadecane was encapsulated with melamine formaldehyde shell modified with graphene as a thermal conductivity enhancer, and then, synthesized PCM microcapsules were coated on polyester fabrics. Chemical, morphological, thermal properties, as well as phase change behavior of microcapsules and coated fabrics were analyzed. The thermal conductivity of the PCM microcapsule‐coated PET fabrics was increased by 31% with the addition of very low amount of graphene (0.1%).

Effect of phase change microcapsules on the thermo-mechanical, fracture and heat storage properties of unidirectional carbon/epoxy laminates

This work aims at producing and characterizing unidirectional carbon/epoxy composites containing different fractions of paraffin microcapsules (MC) for thermal management applications. The viscosity of the epoxy/MC mixtures increases with the MC content, thereby increasing the final matrix weight and volume fraction and reducing that of the fibers. This is at the basis of the decrease in mechanical properties of the laminates with high MC concentration (the elastic modulus decreases up to 53% and the flexural strength up to 67%), but the application of theoretical models shows that this decrease is only due to the lower fiber volume fraction, and not to a change in the properties of the constituents or the fiber/matrix interaction. The MC phase is preferentially distributed in the interlaminar zone, which leads to a thickening of this region and a decrease in matrix-related properties, such as the interlaminar shear strength, which decreases of up to 70%. However, a modest MC fraction causes an increase in the mode I interlaminar fracture toughness of 48%, due to the introduction of new toughening mechanisms. On the other hand, an excessive MC content lets the crack propagating through the matrix and not at the fiber/matrix interface, thereby reducing the toughening mechanism provided by fiber bridging. For the thermal properties, the phase change enthalpy increases with the MC fraction up to 48.7 J/g, and this is reflected in better thermal management performance, as proven by thermal imaging tests. These results are promising for the development of multifunctional polymer composites with thermal energy storage and thermal management properties, and future works will be focused on a deeper study of the micromechanical properties of PCM microcapsules and on the improvement of the capsule/matrix adhesion.

Microencapsulated phase change material via Pickering emulsion stabilized by graphene oxide for photothermal conversion

In this study, Pickering suspension polymerization was used to synthesize thermally stable microencapsulated phase change materials (microPCMs) with n-eicosane as the PCM, polyurea (PUA) as the shell, and graphene oxide (GO) as the colloidal stabilizer. Accordingly, the GO-modified microPCMs (GO@PUAmPCM) prepared at different GO emulsion concentrations were investigated and compared. These microcapsules exhibited high thermal storage of about 70% (180 J/g), leakage prevention, and high solar harvesting capacity with efficient photothermal conversion efficiency (60%). GO@PUAmPCM also showed good thermal reliability, and no leakage was observed after 100 heating and cooling cycles. The process developed herein can be embraced to fabricate highly efficient and reliable PCM microcapsules for solar energy harvesting.

Co-solvent free interfacial polycondensation and properties of polyurea PCM microcapsules with dodecanol dodecanoate as core material

A kind of eco-friendly micro-encapsulated phase change materials (MEPCM) with dodecanol dodecanoate as core material were synthesized via the interfacial polymerization of toluene-2, 4-diisocyanate (TDI) and diethylenetriamine (DETA). During the preparation, a facile solvent free synthesis route was developed owing to the good compatibility of TDI and dodecanol dodecanoate. The synthesized MEPCM were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Particle Size Distribution (PSD) analyzer, Differential Scanning Calorimetry (DSC), Thermogravimetric/Infrared spectrometry (TG-IR) and thermal constants analyzer. It is found that the resultant MEPCM in nearly spherical shape are in the size scope from 10.0 to 40.0 μm, have the average latent heat in the range of 103.4–140.3 J/g, and exhibit high temperature resistance with an onset evaporation temperature at 234.0 °C. Moreover, the MEPCM possess good thermal conductivity from 0.17 W/m K to 0.21 W/m K. Therefore, it is confirmed that the prepared MEPCM can be regarded as a promising thermal energy storage material appropriate to the thermo-regulating fields such as renewable solar heating system.

Assessment of Thermal Performance of Textile Materials Modified with PCM Microcapsules Using Combination of DSC and Infrared Thermography Methods.

The aim of the study was the combination of two measurement methods, the differential scanning calorimetry (DSC) and infrared thermography to evaluate thermal performance of woven and knitted fabrics coated with acrylic pastes containing 20% (P/20) and 40% (P/40) of microcapsules of phase change materials (MPCM) with transition temperatures of 28 °C (MPCM28) and 43 °C (MPCM43). The DSC analysis showed that the phase transition processes for materials modified with pastes P/20 occur in a narrower temperature range than those modified with P/40 pastes. The initial temperatures TOnset (S-S) and TOnset (S-L) are higher for materials modified respectively with pastes P/20 and P/40. The melting and crystallization enthalpy values of both P/20 coated materials are lower by about 45% and 35% compared to P/40. Infrared thermography analysis showed that materials modified with P/20 are heating up faster than modified with P/40 for both MPCM. In the cooling process for modified fabrics the highest temperature decrease was observed in the first 30s. Materials modified with paste P/40 were cooled more slowly in comparison with paste P/20, both for MPCM28 and MPCM43.

3D-Finite Element Analysis for Influences of PCM Inserted in Garment on Body Temperature Responses

To investigate the influences of the PCM micro-capsules in the garment on the body temperature responses, a mathematical model of heat and moisture transfer in garments inserted PCM micro-capsules is developed. The model is solved by the finite element method. Then, this garments model is interfaced with the thermal regulatory model of the human body based on the 3D FEM. Furthermore, the temperature distribution of garment and human body is simulated by using the model. The results show that garment with PCM can significantly delay the temperature rise compared with garment without PCM.

Preparation of acrylic PCM microcapsules with dual responsivity to temperature and magnetic field changes

Energy preservation is one of the serious concerns in recent years to reduce fossil fuels consumption and greenhouse gases. Magnetic microcapsules based on n-hexadecane/Fe3O4 core and poly methyl methacrylate (PMMA) shell were designed as an innovative type of dual-functional phase change materials. Fe3O4 nanoparticles were first synthesized by co-precipitation method and then modified with oleic acid. Then, they were incorporated into suspension polymerization in the presence of MMA and n-hexadecane. FTIR and SEM analyses confirmed the presence of all components in the magnetic microcapsules with a wrinkled morphology and uniform size in averagely 180 µm. They revealed reasonable thermal storage properties and high thermal cycling performance according to DSC thermograms. The encapsulation efficiency and thermal storage ability were calculated by the extracted data from DSC analysis for all the samples and their thermal conductivities were measured too. Magnetometry studies approved superparamagnetic properties of the obtained microcapsules with low remanence and coercivity. With such a dual-functional feature, the introduced magnetic microcapsules could show potential applications in some high-tech fields with providing both thermal regulating and magnetic responsive properties.

Fabrication of polymer capsules by an original multifunctional, active, amphiphilic macromolecule, and its application in preparing PCM microcapsules

Based on our recent discovery that D-PGMA solution showed excellent amphiphilic and reinitiation properties, an eco-friendly, facile and scalable method to prepare polymeric capsules was proposed.

Synthesis and characteristics of composite phase change humidity control materials

A new kind of phase change humidity control material (PCHCM) was prepared by using PCM microcapsules and different hygroscopic porous materials. The PCHCM composite can regulate the indoor hygrothermal environment by absorbing or releasing both heat and moisture. The PCM microcapsules were synthesized with methyl triethoxysilane by the sol–gel method. The vesuvianite, sepiolite and zeolite were used as hygroscopic materials. The scanning electron microscopy (SEM) was used to measure the morphology profiles of the microcapsules and PCHCM. The differential scanning calorimetry (DSC) and the thermal gravimetric analysis (TGA) were used to determine the thermal properties and thermal stability. Both the moisture transfer coefficient and moisture buffer value (MBV) of different PCHCMs were measured by the improved cup method. The DSC results showed that the SiO2 shell can reduce the super-cooling degree of PCM. The super-cooling degrees of microcapsules and PCHCM are lower than that of the pure PCM. The onset temperature of thermal degradation of the microcapsules and PCHCMs is higher than that of pure PCM. Both the moisture transfer coefficient and MBV of PCHCMs are higher than that of the pure hygroscopic materials. The results indicated the PCHCMs have better thermal properties and moisture buffer ability.

The impact of the heating/cooling rate on the thermoregulating properties of textile materials modified with PCM microcapsules

The aim of the study was to analyze the impact of the different values of heating/cooling rate (1, 5, 10, 15°C/min) on thermal properties of textile materials modified with PCM microcapsules (MPCM). Polyester knitted and woven fabrics were coated with polymer pastes containing 40wt% of MPCM with the melting temperatures 18°C (MPCM18), 28°C (MPCM28) and their equilibrium mixture (MPCM18/28). SEM analysis revealed that the knitted fabric the surface is evenly coated with MPCM and on the woven fabric there are uncovered areas.DSC results have shown, that melting temperatures increased and crystallization temperatures decreased with the increase of the heating/cooling rate. For modified knitted fabrics the value of phase transitions enthalpy amounted 56–60J/g regardless of the type of MPCM used. In the case of the woven fabrics the value of enthalpy amounted 21–23J/g, 25–28J/g and 14–16J/g respectively for woven fabrics modified with MPCM18, MPCM28 and MPCM18/28. Presented research will evaluate the possibility of their use under changing ambient temperature conditions. The use of blends will allow the extension of MPCM modified textile materials working ranges. Analysis of the size of the heat effects and phase transitions temperature changes depending on the scanning rate will allow to the exact knowledge about the temperature ranges in which MPCM work, the thermal effects values which accompanied to this work by a changing ambient temperature conditions.

Efficacy of using slurry of metal-coated microencapsulated PCM for cooling in a micro-channel heat exchanger

This paper provides a method of heat transfer enhancement using microencapsulated phase change material (MPCM) slurries, utilizing the latent heat of PCM during melting. The values of heat transfer coefficient obtained for water are in a good agreement with those estimated using heat transfer correlation available in the literature. Two types of PCM microcapsules, non-metal coated and metal coated, were tested through a short tube MCHE with different slurry concentrations (5 and 10wt.% PCM) and fluid flow rates. The calculated melting times for PCM microcapsules are less than their resident time at the same flow rate; which confirm their melting in the MCHE. The results show that heat transfer coefficient, hf increases as slurry flow rate and MPCM concentration in it increases. The hf increased by ∼3.5 times of that of pure water when 10% non-metal coated MPCM slurry was used. The metal coated MPCM slurry showed a further 10% increase in hf compared to the non-metal coated at same MPCM concentration and Reynolds number. The results show that the major enhancement in hf is due to the increase in the fluid thermal capacity caused by PCM melting and also to less extend by micro mixing caused by the capsules. The use of MPCM slurry increases pressure drop, however the heat transfer enhancement override such increase in pressure drop.

Thermal and morphological studies on novel PCM microcapsules containing n-hexadecane as the core in a flexible shell

Herein, a series of microcapsules, containing n-hexadecane (HD) as the core, and polymethyl methacrylate (PMMA) and poly(butyl acrylate-co-methyl methacrylate) (poly(BA-co-MMA)) as the shells were prepared through suspension polymerization. The aim of this work was to investigate the effect of shell flexibility on the encapsulation efficiency and thermal performance of the microcapsules. Kinetics and thermodynamic studies based on propagation rate constants for the monomers and the polarity of the system were employed to predict final morphology of the microcapsules. To this aim, contact angle and interfacial tension analysis were performed, and the results of morphology prediction were affirmed by SEM. A multi-nucleus morphology was observed for microcapsules with PMMA shell and a matrix-type morphology was detected for poly(BA-co-MMA) with high BA content. Thermal properties of the microcapsules were evaluated by DSC and DMTA was performed to assess the rigidity of shells with two distinct Tgs for poly(BA-co-MMA). Appropriate thermal storage behavior plus flexibility of the shell in PCM microcapsules must be considered simultaneously for efficient applications. Here, poly(BA-co-MMA) (with BA content below 25wt%) as the shell was nominated for this reason.

Influence of PCMs in thermal insulation on thermal behaviour of building envelopes

A model of heat transfer through a wall consisting of a layer of concrete and PCM enhanced thermal insulation is considered. The model accounts for heat conduction in both layers, thermal radiation and heat absorption/release due to phase change in the insulation as well as time variation in the ambient temperature and insolation. Local thermal equilibrium between encapsulated PCM and light-weight thermal insulation was assumed. Radiation emission, absorption and scattering were also accounted for in the model. Comparison of different cases of heat flow through the building envelope was carried out. These cases included presence or absence of PCM and thermal radiation in the insulation, effect of emissivity of the PCM microcapsules as well as an effect of solar radiation or its lack on the ambient side of the envelope. Two ways of the PCM distribution in thermal insulation were also considered. The results of simulations were presented for conditions corresponding to the mean summer and winter seasons in Warsaw. It was found that thermal radiation plays an important role in heat transfer through thermal insulation layer of the wall while the presence of the PCM in it significantly contributes to damping of temperature fluctuations and a decrease in heat fluxes flowing into or lost by the interior of the building. The similar effect was observed for a decrease in emissivity of the microcapsules containing PCM.

Preparation and hygrothermal properties of composite phase change humidity control materials

A novel phase change humidity control material (PCHCM) was prepared by using PCM microcapsules and different hygroscopic porous materials. The PCHCM composite can regulate the indoor hygrothermal environment by absorbing or releasing both heat and moisture. The PCM microcapsules were synthesized with methyl triethoxysilane by the sol–gel method. The vesuvianite, sepiolite and zeolite were used as hygroscopic materials. The scanning electron microscopy (SEM) was used to measure the morphology profiles of the microcapsules and PCHCM. The differential scanning calorimetry (DSC) and the thermal gravimetric analysis (TGA) were used to determine the thermal properties and thermal stability. Both the moisture transfer coefficient and moisture buffer value (MBV) of different PCHCMs were measured by the improved cup method. The DSC results showed that the SiO2 shell can reduce the super-cooling degree of PCM. The super-cooling degrees of microcapsules and PCHCM are lower than that of the pure PCM. The onset temperature of thermal degradation of the microcapsules and PCHCMs is higher than that of pure PCM. Both the moisture transfer coefficient and MBV of PCHCMs are higher than that of the pure hygroscopic materials. The results indicated the PCHCMs have better thermal properties and moisture buffer ability.

Investigation of tactile comfort properties of the fabrics treated with microcapsules containing phase change materials (PCMs microcapsules)

In this study, it was focused on the investigation of comfort-related properties of the fabrics treated with microcapsules containing phase change materials (PCMs microcapsules). There are limited findings about the effect of prepared PCM microcapsules on fabric properties related with the tactile comfort. In this work, we applied our produced microcapsules to the cotton fabrics and researched these fabrics’ tactile comfort-related properties such as bending rigidity, drape, fabric–fabric friction, and tenacity. One of the outstanding properties of our microcapsules is reactive carboxylic acid groups on their wall. They have the ability to bind to the fabrics in terms of their reactive chemical groups. Microcapsules on the fabrics can be durable to the effects of the rubbing and repeated washings. The fabric test results indicated that air permeability, bending rigidity, tensile strength decrease with the microcapsule treatment, whereas the fabric drape and coefficient of friction of the fabrics increase depending on the amount of microcapsules added on the fabric.