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Prefabricated buildings in rural areas of China waste a large amount of energy due to poor thermal insulation. Phase change materials (PCMs) are able to stabilize room temperature by latent heat absorption and release during the phase change process. This study incorporated PCMs in the form of microcapsules into the interior wall coatings of prefabricated buildings, and by taking advantage of PCMs’ energy storage capacity, the thermal storage characteristics of PCM-coated bricks were investigated. The results show that microencapsulated phase change material(MPCM) coatings for prefabricated walls exhibit excellent thermal stability properties and effectively reduce the heat flux of prefabricated walls, with coatings having a MPCM mass fraction of 15% and a thickness of 5 mm providing the highest overall benefits. By fitting the numerical simulation results with experimental data, a novel multifunctional passive solar phase change heat collection and storage wall system was developed. This study innovatively combines energy storage materials with interior wall coatings in prefabricated walls of modular buildings investigating how it enhances the thermal stability of the external insulation walls and effectively reduces the reliance on heating equipment for auxiliary heating in rural residences. This essay aims to provide feasible recommendations for optimizing the dual-stage energy-saving and carbon reduction goals in both the construction and operation of rural areas.

Two-dimensional (2D) computational fluid dynamics (CFD) simulations of water-based microencapsulated phase change material suspension (MPCMS) on the flow boiling in a gas–liquid–solid flow system was performed with volume of fluid (VOF) method and discrete particle model (DPM). The Lagrangian particles were linked to the Eulerian phases through the interchange terms such as the drag force in the respective momentum equations. Influences of particle properties including mass fraction and core phase transition temperature, fluid properties including liquid surface tension force and viscosity, detachment time and rise velocity of gas bubbles and particle entrainment in the gas–liquid–solid flow under ambient conditions were numerically investigated. The effects of particles on bubble nucleation, growth and rupture during boiling were studied by visualization. The results show that MPCM can enhance the boiling heat transfer ability of the base liquid. The maximum heat transfer enhancement rate of MPCMS (28 °C) is 4.8%, the maximum heat transfer enhancement rate of MPCMS (90 °C) is 5.1%, the maximum heat transfer enhancement rate of MPCMS (110 °C) can reach 6.7%. MPCM can promote the formation of new bubbles and the rupture of large bubbles, reduce the departure diameter of bubbles, and enhance the boiling heat transfer capacity of the base liquid. The MPCM with core phase change temperature higher than the boiling temperature of base fluid has the best enhancement effect. Through the combination of numerical simulation methods such as VOF and DPM, the complex phase transition heat transfer process of gas-liquid-solid particle coupling of latent thermal functional thermal fluid can be accurately simulated. The work lays a foundation for further explorations on the gas–liquid–solid flows and possible industry applications. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (mPCM) can absorb or release heat by transforming their core phase. This study investigated the effect of mPCM on the thermal and mechanical properties of silty clay in seasonally frozen strata. It analyzed and researched the thermal and mechanical properties of silty clay blended with different contents (2%, 4%, and 6%) of mPCM, as well as its changing rules, using the DSC thermal cycling test, the specific heat capacity test, the freeze-thaw (F-T) cycling test, the no-limit compressive strength test, and the microscope observation test. In addition, this study utilized hyperspectral equipment to assess the applicability of improved silty clay soils in practical engineering on seasonally frozen ground. The results show that mPCM has no supercooling phenomenon and has stable and reversible transformation characteristics, which improves the thermal stability of silt. The specific heat capacity of silt increased with the increase of mPCM dosage. The unconfined compressive strength of silty clay increased to 162.5 kPa at 2% dosage, which was 16.8% higher than that of silty clay, while the unconfined compressive strength of silty clay at 6% dosage decreased to 119.1 kPa, which was 14.4% lower than that of silty clay after freeze-thaw cycles. Adding mPCM reduces the microscopic damage to the pore structure of silty clay soils caused by the freeze-thaw process and mitigates the macroscopic attenuation of their mechanical strength. The mPCM can effectively reduce the solar radiation reflectivity of silty clay, thus providing long-term utility for winter projects.

This paper determines the best design parameters and uses conditions of lightweight aggregate concrete panels containing microencapsulated phase change materials (MPCM-LWAC panels). The main work of this paper includes the followings: (1) The fundamental properties (dry density, thermal conductivity, and specific heat capacity) of MPCM-LWAC were researched to reveal the effect of MPCM dosage on these properties. (2) A model test was carried out to quantify the effect of MPCM dosage on the thermal response of the MPCM-LWAC panel exposed to realistic climate conditions. (3) The numerical simulation was conducted to investigate the effect of MPCM dosage, panel thickness, and outdoor temperature conditions on the thermal response of the MPCM-LWAC panel, which helps to determine its optimum design parameters and use condition. The results showed that the incorporation of MPCM results in lower dry density and thermal conductivity of MPCM-LWAC but higher specific heat capacity. The more MPCM dosage in the MPCM-LWAC panel with a thickness of 35 mm, the lower the energy demand to keep a comfortable interior temperature. Most notably, when the panel thickness exceeds 105 mm, the MPCM-LWAC panel with 5% MPCM only delays the peak temperature. Moreover, the optimal use condition for MPCM-LWAC panels is an average outdoor temperature of 25 °C, which makes the energy demand attain a minimum. [ABSTRACT FROM AUTHOR]

Recently, the need for a thermo-regulating fabric in the textile industry has motivated both researchers and scientists to explore this new type of smart fabric. This study aimed to develop a smart textile using a polyester fabric coated with microencapsulated trimethylolethane (TME) hydrate as the phase change material. The TME microcapsules were produced via in situ polymerization of melamine-urea-formaldehyde (MUF) at varying emulsification times, stirring rates, and TME hydrate concentrations. A knife-over-roll coating method was incorporated, using polyester resin as the binder for the production of the smart fabric. Fourier Transform Infrared Spectroscopy (FT-IR) analysis, Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC) were conducted to examine the chemical, morphological, and thermal characteristics of the microcapsules and the smart fabric, respectively. Results showed that the highest amount of microencapsulated TME phase change material obtained was 18.883 mg. FT-IR results confirmed the presence of TME hydrate and MUF resin in the microcapsule at 3300, 2870, 1148, and 1390 cm−1. The SEM results revealed an amorphous and rough surface of microcapsules. Furthermore, the DSC results demonstrated favorable thermal characteristics, measuring the latent heat storage capacities of the microcapsules before and after application to the fabric as 205.1674 J/g and 224.7318 J/g, respectively. Finally, the encapsulation efficiency was calculated as 64.715%, indicating potential fabric thermal storage applications. [ABSTRACT FROM AUTHOR]

To create a highly efficient photovoltaic-thermal (PV-T) system and maximise the energy and exergy efficiency, this study aims to propose an innovative configuration of a PV-T system comprising wavy tubes with twisted-tape inserts. Following the validation of a numerical model, a parametric study has been conducted to assess the geometrical effects of twisted tape and wavy tubes, as well as the coolant fluid type and velocity, on the overall performance of a PV-T system, located in Shiraz, Iran. It is found that employing twisted tape improves the energy and exergy efficiency by approx. 6.3%. The best configuration yields 12.4% and 16.8% increase in energy and exergy efficiency compared to conventional PV systems. This is achieved at 15% volumetric concentration of microencapsulated phase change material slurry. The monthly variation of global horizontal irradiance in Shiraz highly affected the energy and exergy efficiency of PV-T, with July and October exhibiting the most efficient months, corresponding to 90% and 11.3%, respectively. [ABSTRACT FROM AUTHOR]

In the era of environmental concerns, many attempts were proposed to optimize energy efficiency for buildings and consequently reduce their carbon footprint. As a sustainable approach, it is a promising solution to incorporate phase change materials (PCMs) in construction materials (i.e., ultra-high-performance concrete (UHPC)) to increase its thermal storage capacity and reduce the operation energy. However, incorporating microencapsulated phase change materials (MPCMs) into cementitious materials negatively impacts the fresh and hardened properties. UHPC's improved mechanical strength allows for the creation of slimmer and lighter structures, which may result in less demand in concrete manufacturing and fewer emissions. Hence, the properties of UHPC incorporated with MPCMs (MPCM-UHPC) need more investigations. To fill the gap in the literature about the lack of information about MPCM-UHPC performance, this paper provides a comprehensive work to study the mechanical, thermal, and impact resistance properties of (MPCM-UHPC). Proportions of 5% and 10% of MPCMs were incorporated as a replacement of sand by volume. Proportions of 0.5%, 1.0%, and 1.5% of micro steel fiber reinforcement were used as a percentage of the mixture's total volume. The results revealed the importance of fiber reinforcement in compensating for the negative effect of MPCMs inclusion for improving the thermal properties. Increasing the amount of MPCMs enhanced the thermal performance of the produced UHPC panels through the ability to absorb and release the energy during the phase change process. [ABSTRACT FROM AUTHOR]

Phase change energy storage materials have been recognized as potential energy-saving materials for balancing cooling and heating demands in buildings. However, individual phase change materials (PCM) with single phase change temperature cannot be adapted to different temperature requirements. To this end, the concept of fabricating different kinds of microencapsulated PCM (MEPCM) and combing them to form a multiphase change material (MPCM) for multi-seasonal applications in buildings has been proposed. To prove the feasibility of this idea, three kinds of MEPCMs were fabricated and used for the development of three different composite MPCMs, classified as MPCM-1, MPCM-2, and MPCM-3. Analysis of the results shows that each MPCM sample was able to release latent heat at two different temperatures thus making them suitable for multi-temperature thermal energy storage applications. The phase change temperatures of the MPCMs were however found to be slightly reduced by 0.09–0.31 °C as compared with the MEPCMs samples. The measured energy storage capacities for the MPCMs were also reduced in the range of 6.3–11.4% as compared with the theoretical values but they displayed relatively good thermal stability behaviour of up to 197.8–218.8 °C. It was further identified that the phase change temperatures and latent heat of the MPCM was attributed to the weight percentages of individual components, as the theoretical values for the three MPCM samples were all in good accordance with the measured values. Therefore, optimizing the weight ratios of the MEPCM in MPCM samples and their corresponding thermophysical properties based on specific climatic conditions would be a necessary step to take in future investigations. Thermal performance enhancement of the MPCM is also being recommended as an essential part of further research. [ABSTRACT FROM AUTHOR]

Freeze–thaw (F-T) cycles are one of the most important factors affecting the performance of silty soils with high kaolin content in seasonally freezing regions. This study investigates the improvement of a high-plasticity clayey silt soil (MH) with microencapsulated phase change material (mPCM) to prevent changes in mechanical properties when subjected to freeze–thaw cycles. Unconfined compression, one-dimensional compression, and freeze and thaw tests were performed to evaluate the behavior of treated soil under different freeze/thaw cycles and with different mPCM ratios. It has been observed that the mPCM additive decreased the unconfined compression strength (UCS); however, the strength of the soil held constant during the increasing F-T cycles, and the increase in the mPCM additive content increased the strength of the soil. The inclusion of mPCM affected the compression of the soil and increased settlement (∆H), although the settlement remained constant with increasing freeze–thaw cycles. It has been noted that the compression behavior, which is least affected by the unconfined compressive strength and freeze/thaw cycles, is achieved with the addition of 10% mPCM. As a result of the tests, it was determined that the most suitable additive mPCM ratio is 10% for the compression and strength behaviors. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change material (MPCM) in the form of particles suspended in conventional cooling fluids such as water has shown enhanced heat transfer characteristics when compared to conventional single phase heat transfer fluids. This is attributed to the latent heat of fusion of the MPCM, which results in higher heat capacity of the heat transfer fluid. The thermal performance of MPCM slurry as a heat transfer fluid can be further improved when used in a channel consisting of staggered pins. Use of MPCM slurry in heat transfer channels can result in efficient cooling performance of photovoltaic (PV) systems, where significant thermal loads are prevalent due to high levels of irradiance or working in hot climate conditions. The present work investigates numerically the impact of using MPCM slurry at different mass fractions on the cooling performance of a heat transfer channel attached to a PV panel. The numerical simulations were performed using the ANSYS-FLUENT solver in combination with user-defined functions used to account for the thermophysical properties of MPCM slurry. It was observed that the Nusselt number of MPCM slurry was much higher than for water as single-phase fluid, especially at higher mass fractions at the same flow rate. Moreover, the PV panel temperature was found to be significantly reduced when phase change material in the MPCM slurry experienced melting. Moreover, using staggered circular pins in the channel resulted in a significant reduction of the PV panel temperature even under concentrated irradiance conditions. However, an increase in pumping power was noticeable at high mass fraction of MPCM slurry. Finally, a remarkable increase in the PV panel efficiency was achieved under normal and concentrated irradiance levels by using MPCM slurry in the cooling channel with and without staggered circular pins. [ABSTRACT FROM AUTHOR]

Due to its core phase change characteristics, microencapsulated phase change material (MPCM) can make many base fluids have better heat transfer characteristics. In this paper, the flow boiling heat transfer characteristics of fluorinated liquid-based microencapsulated phase change material suspension (MPCMS) through vertical transparent quartz channel were studied. The effects of MPCM core phase change temperature and suspension flow velocity on boiling heat transfer coefficient and critical heat flux were discussed, respectively. The results show that the appropriate concentration of MPCMS can enhance both the boiling heat transfer coefficient and the critical heat flux. The strengthening effect becomes weak with the increase of suspension flow velocity. The maximum strengthening rates of critical heat flux appear at 0.05 m/s, which are 25% (MPCMS (70°C)), 16% (MPCMS (58°C)) and 10% (MPCMS (28°C)). The phase change temperature of the MPCM core has important effects on the boiling heat transfer coefficient and the critical heat flux. The results showed that the MPCM with core phase change temperature higher than the boiling temperature of base fluid has the best enhancement effect. Different bubble behavior in vertical tube with different heat flux can be observed by high-speed photography system. The particle core phase change in MPCMS inhibits the aggregation of bubbles and forms many small bubbles to enhance heat transfer. The work lays a foundation for further exploring the industrial application of MPCMS. [ABSTRACT FROM AUTHOR]

This paper determines the best design parameters and uses conditions of lightweight aggregate concrete panels containing microencapsulated phase change materials (MPCM-LWAC panels). The main work of this paper includes the followings: (1) The fundamental properties (dry density, thermal conductivity, and specific heat capacity) of MPCM-LWAC were researched to reveal the effect of MPCM dosage on these properties. (2) A model test was carried out to quantify the effect of MPCM dosage on the thermal response of the MPCM-LWAC panel exposed to realistic climate conditions. (3) The numerical simulation was conducted to investigate the effect of MPCM dosage, panel thickness, and outdoor temperature conditions on the thermal response of the MPCM-LWAC panel, which helps to determine its optimum design parameters and use condition. The results showed that the incorporation of MPCM results in lower dry density and thermal conductivity of MPCM-LWAC but higher specific heat capacity. The more MPCM dosage in the MPCM-LWAC panel with a thickness of 35 mm, the lower the energy demand to keep a comfortable interior temperature. Most notably, when the panel thickness exceeds 105 mm, the MPCM-LWAC panel with 5% MPCM only delays the peak temperature. Moreover, the optimal use condition for MPCM-LWAC panels is an average outdoor temperature of 25 °C, which makes the energy demand attain a minimum.

In this paper, a novel Myristyl Alcohol (MAL) phase change material (PCM) microencapsulated with calcium carbonate (CaCO3) shell through a self-assembly process is developed. Despite having strong thermal energy storage capabilities, pure MAL PCM has low thermal conductivity and phase change leakage issues, which limit its usefulness for thermal energy storage applications. To avoid leakage and improve thermal conductivity, pure MAL PCM is encapsulated with a CaCO3 shell for different core/shell mass ratios. The morphology, chemical structure, and crystalline structure of the microencapsulated phase change material (MAL-MEPCM) samples are analyzed by the SEM, FTIR, and XRD. The SEM morphology reveals that the generated microcapsules have spherical, needle-shaped, and floral forms. The DSC thermograms reveal the latent heat (melting) values of 223.36 and 155.40 J/g with an encapsulation efficiency of 69.42% for pure MAL PCM and MAL-MEPCM, the maximum core/shell mass ratio. The TGA thermograms confirm good thermal stability. Even after 200 thermal cycles, the samples have consistent chemical stability and phase change properties, as evidenced by FTIR and DSC results. The prepared MAL-MEPCM samples have higher thermal conductivity than the pure MAL PCM and thus enhance thermal energy storage performance. [ABSTRACT FROM AUTHOR]

Phase change materials, PCMS can be also used in thermal energy systems with various building materials in order to increase thermal performance. In this study, artificial marble with microencapsulated PCM (MPCM) was fabricated and its indoor environmental control and energy saving effects were analyzed using field tests in a standard Korean apartment building. The MPCM capsules contained approximately 70% n-octadecane and were fabricated using the in situ polymerization chemical method. The thermal environment was analyzed using internal temperature and the predicted mean cote (PMV) measurements. The results of the wall board with MPCM installed room temperature fluctuation decreased by 1–2 °C that it was possible to maintain a stable indoor temperature due to the thermal buffering effect. The average change of PMV was −0.03 for 12 h that no significant effect on the thermal comfort. The results of convection heating system energy consumption was reduced by 27.7%. Furthermore, we studied the long-term real-scale thermal performance in winter seasons.

In the era of environmental concerns, many attempts were proposed to optimize energy efficiency for buildings and consequently reduce their carbon footprint. As a sustainable approach, it is a promising solution to incorporate phase change materials (PCMs) in construction materials (i.e., ultra-high-performance concrete (UHPC)) to increase its thermal storage capacity and reduce the operation energy. However, incorporating microencapsulated phase change materials (MPCMs) into cementitious materials negatively impacts the fresh and hardened properties. UHPC’s improved mechanical strength allows for the creation of slimmer and lighter structures, which may result in less demand in concrete manufacturing and fewer emissions. Hence, the properties of UHPC incorporated with MPCMs (MPCM-UHPC) need more investigations. To fill the gap in the literature about the lack of information about MPCM-UHPC performance, this paper provides a comprehensive work to study the mechanical, thermal, and impact resistance properties of (MPCM-UHPC). Proportions of 5% and 10% of MPCMs were incorporated as a replacement of sand by volume. Proportions of 0.5%, 1.0%, and 1.5% of micro steel fiber reinforcement were used as a percentage of the mixture’s total volume. The results revealed the importance of fiber reinforcement in compensating for the negative effect of MPCMs inclusion for improving the thermal properties. Increasing the amount of MPCMs enhanced the thermal performance of the produced UHPC panels through the ability to absorb and release the energy during the phase change process.

Recently, the need for a thermo-regulating fabric in the textile industry has motivated both researchers and scientists to explore this new type of smart fabric. This study aimed to develop a smart textile using a polyester fabric coated with microencapsulated trimethylolethane (TME) hydrate as the phase change material. The TME microcapsules were produced via in situ polymerization of melamine-urea-formaldehyde (MUF) at varying emulsification times, stirring rates, and TME hydrate concentrations. A knife-over-roll coating method was incorporated, using polyester resin as the binder for the production of the smart fabric. Fourier Transform Infrared Spectroscopy (FT-IR) analysis, Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC) were conducted to examine the chemical, morphological, and thermal characteristics of the microcapsules and the smart fabric, respectively. Results showed that the highest amount of microencapsulated TME phase change material obtained was 18.883 mg. FT-IR results confirmed the presence of TME hydrate and MUF resin in the microcapsule at 3300, 2870, 1148, and 1390 cm−1. The SEM results revealed an amorphous and rough surface of microcapsules. Furthermore, the DSC results demonstrated favorable thermal characteristics, measuring the latent heat storage capacities of the microcapsules before and after application to the fabric as 205.1674 J/g and 224.7318 J/g, respectively. Finally, the encapsulation efficiency was calculated as 64.715%, indicating potential fabric thermal storage applications.

This article investigates the thermal insulation performance of cement mortar plastering embedded with microencapsulated phase change material for postponing peak load and achieving building energy conservation. However, the direct incorporation of PCM in the pores of cement mortar suffers from leakage during the phase transition period. This article utilizes the in situ polymerization microencapsulation techniques to encapsulate the developed eutectic phase change material without causing leakage in building fabrics. The scanning electron microscope (SEM) analysis demonstrates that the prepared MEPCM was successfully formed in a uniform spherical structure with an average particle diameter of around 1 µm. The 5 mass% MEPCM incorporated cement mortar has a relatively low thermal conductivity of 0.18 W m−1 K−1, and high compressive strength of 23.23 MPa without compromising building strength. Furthermore, the thermal response of MEPCM embedded cement mortar used as exterior wall plastering was tested in a psychrometric chamber, with a maximum temperature swing of 6.3 °C achieved for the Delhi climatic condition compared to the other two climatic conditions found in Jodhpur and Ahmedabad. The maximum heat transfer reduction of 16.69% was achieved for the Delhi climatic condition, while the reductions in Jodhpur and Ahmedabad were 6.5% and 5.9%, respectively, when compared to a normal brick wall during peak solar irradiance periods. As a result, the prepared MEPCM with a phase change temperature of 25 °C would be a good candidate for reducing the wall gain heat load of buildings in composite climatic zones in the Indian subcontinent. [ABSTRACT FROM AUTHOR]

Phase change energy storage materials have been recognized as potential energy-saving materials for balancing cooling and heating demands in buildings. However, individual phase change materials (PCM) with single phase change temperature cannot be adapted to different temperature requirements. To this end, the concept of fabricating different kinds of microencapsulated PCM (MEPCM) and combing them to form a multiphase change material (MPCM) for multi-seasonal applications in buildings has been proposed. To prove the feasibility of this idea, three kinds of MEPCMs were fabricated and used for the development of three different composite MPCMs, classified as MPCM-1, MPCM-2, and MPCM-3. Analysis of the results shows that each MPCM sample was able to release latent heat at two different temperatures thus making them suitable for multi-temperature thermal energy storage applications. The phase change temperatures of the MPCMs were however found to be slightly reduced by 0.09–0.31 °C as compared with the MEPCMs samples. The measured energy storage capacities for the MPCMs were also reduced in the range of 6.3–11.4% as compared with the theoretical values but they displayed relatively good thermal stability behaviour of up to 197.8–218.8 °C. It was further identified that the phase change temperatures and latent heat of the MPCM was attributed to the weight percentages of individual components, as the theoretical values for the three MPCM samples were all in good accordance with the measured values. Therefore, optimizing the weight ratios of the MEPCM in MPCM samples and their corresponding thermophysical properties based on specific climatic conditions would be a necessary step to take in future investigations. Thermal performance enhancement of the MPCM is also being recommended as an essential part of further research.

In this paper, a new type of microencapsulated phase change materials (MPCMs) with docosane as the core and titanium dioxide (TiO2) as the shell was prepared by in situ polymerization. Its phase transition temperature was approximately 40 °C, and it can be used as a phase change material (PCM) in a low-temperature solar heat collection system. The properties of the new material were examined including the microstructure, the chemical elements on the surface of the microcapsules, and thermal conductivity. In addition, to obtain the optimized formula of the microcapsules, single-factor analysis on the emulsifier type, its mass fraction, ultrasonic oscillation time, pH, and core–shell ratio were performed. The results showed that the MPCMs prepared in this paper had a particle size of 2–5 μm and were spherical. Its surface was uniform and smooth without cracks, and the TiO2 was well dispersed around the docosane, completely coating the docosane without impurities. The MPCMs had good performance in terms of thermal properties and heat storage when using 0.40% SDS as an emulsifier, 10 min ultrasonic, a 3.5 pH value, and a 1:1 core–shell ratio. However, the stirring method, time, and experimental reaction temperature also affected the properties of the material, which was not studied in this experiment. We will continue to study these factors in the future. [ABSTRACT FROM AUTHOR]

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To realize the triple functions of “roadway support, thermal insulation and heat regulation” of pumping wet shotcrete (PWS), the microencapsulated phase change material (MPCM) with poly (lauryl methacrylate) as shell and paraffin wax as core was synthetized by interfacial polymerization. The surface morphology, particle size distributions, core-shell compositions, the performances of the thermal stability and phase change of the MPCM were analyzed. The results show that the synthetized MPCM has excellent performances and can be applied in PWS. To obtain the optimal mixed proportions of the key materials (i.e., ceramsite, sand and MPCM) in PWS, the key performance indices were employed in the orthogonal experimental design to test the multiple performances of the PWS containing MPCMs. The results show that these performances are influenced by the dosages of the key materials and the recommended dosages were: 112.5 kg/m3 of ceramsite, 1250 kg/m3 of sand and 100 kg/m3 of MPCM. This study shows that the application of the MPCMs cannot only further reduce the thermal conductivity of PWS but also endow PWS with the function of heat regulation. A broad prospect of the application of MPCMs in underground cooling engineering can be expected.

A new bio-based microencapsulated phase change material (MEPCM) was synthesised by an in situ polymerisation method, and its thermal energy storage properties were experimentally studied. Bio-based n-dodecanoic acid with a high heat storage capacity was encapsulated by a melamine-formaldehyde (MF) polymeric shell. The MEPCM was characterised using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal conductivity analysis (TCA). The microcapsules had a perfectly spherical morphology with a core–shell microstructure. The MEPCM was chemically stable, and its crystallinity was unaltered. Dodecanoic acid encapsulated by the MF shell exhibited a high thermal energy storage capability of 99.3% and was observed to melt at 41.8 °C with a decent enthalpy of 41.7 kJ/kg. The prepared microcapsules were thermally stable up to 165.02 °C, which were also observed to be leak-proof well above the phase transition temperature. Furthermore, the thermal reliability of the MEPCM was good after 1000 thermal cycles. Overall, the MEPCM was a viable candidate for medium-temperature thermal energy storage applications.

To prevent the cracking of silty clay under cyclic wet-dry cycling (W-D), which leads to the increase of deformation and strength attenuation of silty clay, microencapsulated phase change material (mPCM) was used to improve it. The deformation and strength characteristics of silt with different dosages (1 %, 2 % and 4 %) of mPCM and their changing patterns were analyzed and studied by indoor compaction test, crack observation test, consolidation test and straight shear test, and compared with silt without modifier. The results showed that with the increase of mPCM dosage, the optimum water content of silt and the maximum dry density decreased. A 2 % dosage of mPCM inhibited the development of silty clay cracks, reduced crack width and deformation, and increased the compression modulus of the soil samples by nearly 2.3 times. Under dry and wet cycling conditions, the cohesion decay of silty clay is greater than the angle of internal friction. The addition of 2 % mPCM significantly increased the shear strength of silty clay, cohesion by nearly 2.1 times, and internal friction angle by 1.4 times. The mPCM inhibits crack development mainly by regulating the internal temperature field of soil samples, thus improving soil strength. This study provides a reference for inhibiting soil cracking from a new temperature perspective. • A new method for controlling the temperature gradient of silty clay to inhibit soil cracking using microencapsulated phase change materials is proposed. • With the addition of mPCM, the silty clay's optimum water content increased, and the maximum dry density decreased. • Incorporation of mPCM reduces the attenuation of shear strength of silty clay under dry and wet cyclic action. • This method can significantly improve silty clay's cracking resistance and reduce the soil's deformation characteristics. [ABSTRACT FROM AUTHOR]

Phase change material (PCM) is useful for the storage and release of latent heat. However, its ability to conduct has hindered its engineering application. This study prepares a novel microencapsulated phase change material (MEPCM) by suspension polymerization. To improve the adhesion between the shell and the inorganic additive, triethoxyvinylsilane was incorporated copolymerizing with methyl methacrylate. Thermally conductive nanographite particle was added. This MEPCM was then incorporated into high-density polyethylene (HDPE) to form a series of thermally conductive PCM microcapsules that approached sphere shapes with diameters less than 2 μ m. Thermal analysis showed that the thermal stability and heat resistance of the microcapsule were improved. The thermal conductivity of HDPE was increased by 39% to 0.6358 W/m ⋅ K, and the surface resistivity was lowered to 2. 7 8 × 1 0 5   Ω /sq after the addition of MEPCM. The temperature on the top of the composite tested was lower than pristine HDPE. This was close to the onset melting temperature of the MEPCM (38.5 ∘ C), ∼ 5 ∘ C lower than pure HDPE. The reduction is a significant improvement in temperature regulation. This enables MEPCMs to store and release heat much more effectively, and can thus be applied to medical construction materials to meet the temperature requirements of COVID-19 patients. [ABSTRACT FROM AUTHOR]

Microchannels with microencapsulated phase change slurry (mPCM) have gained attention due to their compactness and large surface area to volume of fluid ratio. The phase change process also helps in sustaining high heat exchange over small temperature changes. This paper is focused on numerical investigation of heat transfer characteristics of mPCM slurry flow during its freezing phase in microchannels under convective boundary conditions. The phase change process was incorporated in numerical modeling by considering the rectangular profile of an effective specific heat capacity model. Numerical simulations were peformed for mPCM slurry with 5 to 15% mass concentration, and the results were compared with those obtained with pure water. The effects of mass concentration of mPCM slurry on pressure drop, local Nusselt number, and local temperatures along the length of the channel were investigated. It was noticed that the increase in mass concentration enhanced the local Nusselt number than pure water. At the outlet of microchannel for flow velocity of 0.55 m/s, the bulk and surface temperatures were found to be 3.12 K and 1.2 K higher than those recorded with pure water. With a mass concentration in 5–15% range the pressure drop for mPCM slurry was found to be 5.1–36% higher than the pure water case. [ABSTRACT FROM AUTHOR]

Summary: An optimal mix proportion design program was developed firstly in this research by analyzing most relevant factors affecting the mix ratio, such as water‐cement ratio, workability, drying mass, adding and mixing method of MPCM, etc. Then, the influences of MPCM on density, porosity, compressive strength, thermal conductivity, specific heat capacity, and thermal diffusivity of LWAC were investigated by changing curing time, MPCM content, and MPCM state. Results shown that the porosity of MPCM‐LWAC linearly increases and corresponding density linearly decreases with the increase of MPCM content. SEM images of MPCM‐LWAC reveal weaker connection and higher porosity between aggregate and mortar caused by more MPCM. The addition of MPCM to LWAC causes a compressive strength loss proportional to the MPCM content. The compressive strength of MPCM‐LWAC increases with the increasing curing time; however, growth rate of compressive strength decreases with the increasing MPCM content. When the MPCM content reaches a maximum of 10%, the compressive strength of MPCM‐LWAC at 50°C is 4.7% less than that of MPCM‐LWAC at 20°C. For the 10% MPCM addition, the specific heat capacity increased by 32.09%, and the thermal conductivity and thermal diffusion reduced by 19.0% and 23.9%, respectively. [ABSTRACT FROM AUTHOR]

• Storage of solar heat in fluidized bed with microcapsulated PCM was investigated. • Microcapsulated PCM with diameter around100 μm kept their morphology during fluidization. • Efficiency of the fluidized bed reached as high as 80% • During recovery cold air temperature was increased by 8 °C in less than 30 min. Fluidized beds are widely used in effective heat and mass transfer applications for chemical processes. The beds can also used for storing thermal energy (TES) and offer a rapid and effective way to exploit solar energy especially for heating applications. Microencapsulated PCMs serve as the TES medium and the fluid phase in these applications. There exist few experimental studies that have investigated uses of fluidized beds for thermal storage. The works show that properties of microencapsulated PCMs have to be fine-tuned for them to become effective in fluidized beds. This paper investigates the performance of an experimental air-fluidized bed using microencapsulated PCM as the thermal storage system for two different storage temperatures of 55 °C and 65 °C. The results show that TES using microencapsulated PCM with mean particle size of 100 μm that corresponds to A-type particle according to Geldart chart showing fluidization behavior of particles is possible. The fluidization process did not change the morphology of the microencapsulated PCM. Fast storage and recovery can easily be accomplished at efficiencies as high as 80%. [ABSTRACT FROM AUTHOR]

Summary: As an energy storage material, microencapsulated phase change materials (MPCMs) have become a research hotspot in recent years due to their unique thermophysical properties. However, this material usually has limitations in terms of its performance, such as low encapsulation efficiency, leakage during phase change, poor cycle stability, and high degree of supercooling. To solve these problems, nanoparticle as‐modified material to improve the performance of MPCMs has attracted the attention of both domestic and overseas scholars. This paper aims to review the research progress of MPCMs modified by nanoparticle from three aspects: preparation, performance, and application. In this paper, the preparation method and principle of nanoparticles used for the modification of MPCMs are first introduced. Then, based on different properties (mechanical properties, thermal conductivity, thermal stability, and supercooling), the research works of nanoparticle‐modified MPCMs in recent years are reviewed. Finally, the practical applications of nanocomposite MPCM in the field of slurry, building, asphalt pavement, and battery thermal management are reported. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (MPCMs) are increasingly seen as an adequate tool for heat management. The addition of a MPCM layer into a typical firefighters' protective clothing can be used to mitigate burn injuries, increasing the time to second degree burns. A numerical approach is introduced to simulate the heat transfer in multilayer fabrics with MPCM. An overview of temperature field and total heat flux distribution for the multilayer fabric system with and without the MPCM is presented. Additionally, the effects of MPCM mass fraction, latent heat, specific heat and thickness are investigated to assess the thermal protective performance. The results demonstrate that the addition of a MPCM layer into the multilayer fabric assembly can be used to decrease the temperature obtained at the comfort liner boundary. Effect of heat intensity and radiation distance between the fabric system and heating source is also analyzed and discussed. The findings obtained in this study can provide some useful information on the beneficial design of clothing containing MPCMs. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (MicroPCM) were prepared via sol–gel method using paraffin as heat storage core and silica as inorganic shell. The morphology feature, chemical structure, thermal properties and thermal stability of MicroPCM were characterized by the field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), the differential scanning calorimeter (DSC), simultaneous thermal analyzer (STA) and the thermal conductivity meter. The results indicated that MicroPCM were spherical in shape with the shell thickness in the range from 236 nm to 303 nm. The stirring speed and TEOS dosage were key factor on the latent heat and supercool effect of MicroPCM. The maximum latent heat of MicroPCM was 240.2 J ⋅ g − 1 with the heat loss of only 0.2 J ⋅ g − 1 in phase transformation when it was prepared at the stirring speed of 400 r/min and TEOS dosage of 20 ml. MicroPCM was a promising material for thermal energy storage (TES). A series of novel MicroPCM with good thermal properties was prepared by sol–gel method using paraffin as the heat storage core material and silica as the inorganic shell material by controlling the stirring speed and adjusting TEOS dosage. MicroPCM was spherical in shape with the shell thickness in the range between 230 nm and 300 nm. The result indicated that MicroPCM had a high latent heat with a range from 229 to 240.2 J·g–1. [ABSTRACT FROM AUTHOR]

This study explores the synthesis and characterization of microencapsulation of organic and eutectic phase change materials with a melting point ranging from 5 to 30 ℃ for low-temperature applications. Emulsion polymerization utilizing methyl methacrylate monomer as the shell material is employed for effective encapsulation. Comprehensive characterization of microcapsules is undertaken, including chemical composition (using Fourier transform infrared (FT-IR) spectroscopy), morphology (employing scanning electronic microscopy (SEM) and metallurgical microscope), particle size distribution (measured by ImageJ software), enthalpy (evaluated through differential scanning calorimetry (DSC)) and thermal degradation (explored via thermogravimetric analysis (TGA)). The successful production of microencapsulated phase change materials (MPCM) is confirmed by their two-phase decomposition process, the presence of specific chemical bonds, and the spherical morphology of particles with an average diameter between 25.63 and 49.62 μ m. However, in the case of eutectic core material, irregular microcapsules are shaped with a larger mean diameter. It has also affected the encapsulation efficiency in which around 29.43% and 30.1% efficiencies are reached for eutectic cores compared to 45.11% and 47% in organic ones. Simultaneously, thermophysical properties of MPCMs, such as density, thermal conductivity, and specific heat, are determined using the displacement method, transient line heat source, transient hot wire, and DSC. These properties are expressed through regression equations based on the determined effective factors. The derived equations enhance the capability to implement MPCMs in practical applications and numerical simulations. [Display omitted] • Microencapsulation of eutectic and organic phase change material. • Chemical and physical analysis of particles revealed issues in encapsulating eutectic materials. • Thermo-physical properties of microcapsules are measured. • Corresponding regression equations for thermal properties are reported to be applied in future studies. • Microcapsules can be nominated as promising candidates for cold chain applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A method of solar-driven spray flash evaporation assisted by microencapsulated phase change material (MPCM) is proposed for solution regeneration. • The spray flash evaporation experimental platform working with NaCl-MPCM suspension is constructed. • The regeneration amount per unit mass flow rate of the NaCl-MPCM suspension is 24.8 g/kg, which is about 19 % higher than that of the NaCl solution. • This study aims to provide guidance for the efficient utilization of solar-driven flash evaporation assisted by MPCM. Solution regeneration belongs to a separation and purification technology for multi-component liquid systems, which is involved in many fields such as liquid desiccant air-conditioning, desalination, and sewage treatment. Solar-driven evaporation technology has enormous energy-saving potential in solution regeneration, but it has the disadvantages of instability and slow regeneration rate. In this work, the method of solar-driven spray flash evaporation assisted by microencapsulated phase change material (MPCM) is proposed for solution regeneration. The spray flash evaporation experimental platform working with NaCl-MPCM suspension is constructed, and the spray characteristics and heat and mass transfer characteristics of NaCl-MPCM suspension are examined under different operating parameters. The results show that the addition of MPCM to the solution can significantly improve its equivalent specific heat capacity, which mitigates dispersed and discontinuous defects of solar energy. Furthermore, it can effectively reduce the severe temperature drop of the solution during the flash evaporation process, which ensures a high driving potential difference between the solution and flash evaporation environment. It is worth mentioning that under the same operating conditions, the regeneration amount per unit mass flow rate of the NaCl-MPCM suspension (w MPCM = 10 wt%) is 24.8 g/kg, which is about 19 % higher than that of the NaCl solution. Additionally, the flash performance of the NaCl-MPCM suspension can be further improved by reducing the initial fluid velocity at the nozzle or the flash evaporation pressure. This study aims to provide guidance for the efficient utilization of solar-driven flash evaporation assisted by MPCM. [ABSTRACT FROM AUTHOR]

A novel type of bi-functional microencapsulated phase change material (MEPCM) microcapsules with thermal energy storage (TES) and carbon dioxide (CO2) photoreduction was designed and fabricated. The polyaniline (PANI)/titanium dioxide (TiO2)/PCN-222(Fe) hybrid shell encloses phase change material (PCM) paraffin by the facile and environment-friendly Pickering emulsion polymerization, in which TiO2 and PCN-222(Fe) nanoparticles (NPs) were used as Pickering stabilizer. Furthermore, a ternary heterojunction of PANI/(TiO2)/PCN-222(Fe) was constructed due to the tight contact of the three components on the hybrid shell. The results indicate that the maximum enthalpy of MEPCMs is 174.7 J·g−1 with encapsulation efficiency of 77.2%, and the thermal properties, chemical composition, and morphological structure were well maintained after 500 high–low temperature cycles test. Besides, the MEPCM was employed to reduce CO2 into carbon monoxide (CO) and methane (CH4) under natural light irradiation. The CO evolution rate reached up to 45.16 μmol g−1 h−1 because of the suitable band gap and efficient charge migration efficiency, which is 5.4, 11, and 62 times higher than pure PCN-222(Fe), PANI, and TiO2, respectively. Moreover, the CO evolution rate decayed inapparently after five CO2 photoreduction cycles. The as-prepared bi-functional MEPCM as the temperature regulating building materials and air purification medium will stimulate a potential application.

Summary: The electronic industry is increasingly investigating different approaches for the cooling of electronic equipment. The use of bulk phase change materials is also a promising approach for energy storage. The introduction of microencapsulated phase change materials combined with nanofluids can be beneficial. The combined use of a nanofluid and a metallic porous material can be used to mitigate problems resulting from small thermal conductivity. This study investigated a ternary mixture of water with a nanofluid and a microencapsulated phase change material in a porous medium. The model was previously validated with experimental data using a 0.5%vol concentration nanofluid in water. The results revealed that heat storage capability can be achieved as long as the microencapsulated phase change materials, which consists of encapsulated eicosane, is at a concentration of 20%. Because the melting temperature of microencapsulated phase change materials is approximately 36°C, energy storage at a low flow rate and heat flux is recommended. [ABSTRACT FROM AUTHOR]

MPCMs and their suspensions, acting as the thermal storage, heat transfer or temperature constancy mediums, have gained concerns in various energy related sectors. However, problems involving high supercooling degree, low thermal conductivity and suspensions instability are barriers for their energy storage applications. The present study focuses on such properties by adding GQDs/nano-aluminum into MPCMs particles. Paraffin was selected as core material and urea–melamine–formaldehyde polymer as shell to prepare 10 MPCMs samples (no modifiers, GQDs, nano-aluminum, GQDs & nano-aluminum) via in situ polymerization. The morphology, thermal conductivity, thermal property and MPCM/suspensions stability were characterized. It was found, the selected modifiers didn't impact on the microcapsules morphology, but GQDs can make particle size smaller and distribution more uniform. Adversely, the mean particle size can be increased by nano-aluminum. GQDs are much more effective than nano-aluminum in improving thermal conductivity. GQDs can suppress supercooling effectively, however, nano-aluminum has no obvious effect on supercooling suppression. The MPCMs suspension modified by the selected amount of GQDs and nano-aluminum (Al-GQDs(4.5–2)) achieved a high physical stability. No structure instability of modified MPCM sample was observed. To sum up, the combined effort of GQDs and nano-aluminum enabled MPCMs to be more applicable in energy storage applications. • GQDs addition made MPCMs micro-capsules smaller and size distribution more uniform. • GQDs are much more effective than nano aluminum in improving thermal conductivity. • GQDs can suppress sub-cooling effectively, however, Nano aluminum has no obvious effect. • The combined effort of GQDs and nano aluminum modified multiple properties of MPCMs. [ABSTRACT FROM AUTHOR]

Summary: Based on the low hydration heat and temperature rise requirements of cement slurry used in natural gas hydrate layer, two novel microencapsulated phase change materials (MPCM‐1 and MPCM‐2) with different melting point were designed and synthesized; then, the heat evolution of cement slurry was controlled by MPCM‐1 and MPCM‐2 through physical means; the decomposition of hydrates was avoided. Before synthesizing MPCM‐1 and MPCM‐2, the micromorphology, particle size, and distribution of paraffin wax emulsion were studied. Then, the MPCM‐1 and MPCM‐2 containing paraffin wax with urea formaldehyde resin shell was synthesized by in situ polymerization, and the chemical structure and performances were investigated. The melting point of MPCM‐1 and MPCM‐1 is 23.09°C and 35.85°C; the phase change enthalpy is 97.49 and 85.69 J/g. The MPCM‐1 and MPCM‐2 were added into cement slurry, and the controlling effects on heat evolution were studied. As a result, it was found that the hydration heat and temperature rise of cement slurry were successfully reduced by using MCPM‐1 and MPCM‐2. Simultaneously, the investigations of fly ash and slag cement slurry were accomplished. Moreover, the fly ash and slag cement slurry containing microencapsulated phase change materials was prepared. It was shown that the 24 and 48‐hour hydration heat were reduced by 1.10 × 105 and 10.5 × 105 J, respectively. Highlights: A novel microencapsulated phase change material (MPCM) was synthesized.Heat evolution was controlled at different temperature intervals by MPCM.Limiting the temperature rise was achieved by physical and chemical means.Reducing the hydration heat was realized by physical and chemical means.The application of MPCM was significantly increased. [ABSTRACT FROM AUTHOR]

Abstract In this work, a novel microencapsulated phase change material based on sodium thiosulfate pentahydrate as core and poly(ethyl-2-cyanoacrylate) as shell was successfully synthesized by interfacial polymerization in a water-in-oil emulsion system. The morphology, microstructure, surface elemental distribution, chemical composition and crystalline structure of the resultant microcapsules were determined by scanning and transmission electron microscopies, energy dispersive spectroscopy, Fourier-transform infrared spectroscopy and X-ray diffraction. Besides, their thermal properties were also investigated systematically by differential scanning calorimetry and thermogravimetry analysis. The results showed that the microcapsules presented almost spherical profiles with a diameter of about 1.0 µm and a well-defined core-shell structure. Meanwhile, the microcapsules possessed phase change temperature of 46.44 °C and latent heat of 107.0 kJ·kg−1 at the core material/monomer mass ratio of 4/2. Due to the protective effect of shell material, the thermal stability of the microcapsules was improved. In addition, the thermal cycling test revealed that the microcapsules had good thermal reliability. Considering the above results, this synthetic technique can be considered as a feasible way to prepare microencapsulated salt hydrates and is expected to extend to the encapsulation of other hydrophilic substances. And the obtained microcapsules have great potential as a solar energy storage material. Highlights • Novel microcapsules with STP as core and PECA as shell were fabricated. • The eco-friendly shell has favorable chemical compatibility with salt hydrates. • The microcapsules presented a core-shell structure with a diameter of about 1.0 µm. • The latent heat of the microcapsules reached 107.0 kJ·kg−1. • The microcapsules had an improved thermal stability and a good thermal reliability. [ABSTRACT FROM AUTHOR]

Abstract Large energy storage capacity and high thermal charging/discharging rate are crucial for microencapsulated phase change materials (MEPCM) in thermal energy storage application. The microcapsules with dodecanol core and melamine-formaldehyde (MF) resin shell modified by graphene oxide (GO) and carbon nanotube (CNT) hybrid filler were prepared via in-situ polymerization. The effect of the combination of GO and CNT on morphology and thermal properties of the microcapsules was investigated, and the mechanism for heat transfer enhancement was further studied from both macroscopic and microscopic views. The results indicated that the addition of GO and CNTs largely enhanced the thermal conductivity of the microcapsules, and the GO-CNT hybrid filler was superior to individual GO or CNT. Particularly, with a hybrid filler loading of 0.6 wt%, the thermal conductivity of the microcapsule was improved by 195% with the latent heat slightly decreased. The prepared microcapsules were dispersed into water to form a latent functional thermal fluid, and its photo-thermal conversion performance was studied. The excellent thermal properties and photo-thermal conversion performance made the microcapsule dispersed slurry a potential fluid in direct absorption solar collectors. Highlights • The combination of GO and CNT was used as fillers to improve the thermal conductivity of the microcapsules. • The synergistic effect of GO-CNT hybrid filler on the morphology and thermal properties of the microcapsules was studied. • The thermal conductivity of the microcapsule with 0.6 wt% GO-CNT hybrid filler was enhanced by 195%. • The mechanism for heat transfer enhancement was studied from both macroscopic and microscopic views. • The microencapsulated phase change slurries had good photo-thermal conversion performance for DASCs. [ABSTRACT FROM AUTHOR]

A novel photothermal conversion microencapsulated phase change material (PDA-MPCM) was successfully prepared, contained n-octadecane (n-OD) as the core material, polymethyl methacrylate (PMMA) as the middle layer, and polydopamine (PDA) as the shell material. The incorporation of PDA enabled PDA-MPCM can obtain excellent photothermal conversion efficiency (73.92 %) and maintain good thermal energy storage capacity (1570 J kg−1 K−1). The PDA-MPCM suspension (PDA-MPCMS) prepared by the two-step method has a long time dispersion stability (more than 72 h) and an ultra-low transmittance (close to 0) in the wavelength range of 200–650 nm. To investigate the photothermal conversion ability of suspension, the stuffy bask experiments were carried out under the real sunlight in the direct absorption solar collector (DASC) with PDA-MPCMS. The experimental results showed that the peak temperature rise of 0.10 wt% PDA-MPCMS was 27.80 % higher than that of the base fluid, and the zero-loss collector efficiency reached 93.6 %. The PDA-MPCMS are expected to play an important role in promoting solar applications. • The practical application of new photothermal conversion microcapsules and suspensions in DASC was investigated. • The peak temperature rise of 0.10 wt% PDA-MPCMS was 27.80% higher than that of the base fluid, and the zero-loss collector efficiency reached 93.6%. [ABSTRACT FROM AUTHOR]

The utilization of geopolymer mortar (GPM) made from fly ash (FA) as a sustainable construction material with minimal carbon footprint is a viable option. Incorporating microencapsulated phase change materials (mPCM) into GPM presents a promising solution to reduce the energy consumption of buildings. In this study, phase-change GPM (PC-GPM) was manufactured using FA as the main raw material. The thermal conductivity and latent heat of PC-GPM were improved through addition of mPCM, and the mechanical properties were enhanced through inclusion of basalt fiber (BF) and polypropylene fiber (PF). The mineral components and microstructural characteristics of PC-GPM reinforced by fibers were also investigated. The results indicate that an increase in the mPCM content led to a reduction in the dry density and compressive strength of PC-GPM. The addition of mPCM contributed to an increase in water absorption and a reduction in thermal conductivity. The physical-mechanical properties of PC-GPM were dependent on the content, length and type of fibers. The latent heat of PC-GPM was observed to be approximately 0.77 kJ/kg. The formation of sodium-alumina-silicate-hydrate (N-A-S-H) and calcium-alumina-silicate-hydrate (C-A-S-H) gels was found to enhance the mechanical properties of PC-GPM. The PC-GPM sample achieved a maximum compressive strength of 36.86 MPa, associated with a thermal conductivity of 1.198 W/(m·K) when the mPCM and BF contents were 25% and 0.75%, respectively. The experimental findings can offer valuable contributions to the advancement of environmentally friendly and sustainable phase-change building materials. [Display omitted] ● The thermo-physical properties of PC-GPM with fibers were investigated. ● An increase in mPCM content led to a reduction in dry density. ● Water absorption of PC-GPM-BF was lower than that of PC-GPM-PF. ● Thermal conductivity of PC-GPM-BF was higher than that of PC-GPM-PF. ● N-A-S-H and C-A-S-H gels improved the compressive strength of PC-GPM. [ABSTRACT FROM AUTHOR]

Highlights • Performance of an active PCM system installed in an 11 storey building was studied. • Operational parameters of the active PCM system were monitored for 25 months. • PCM reduced chiller cooling load by 12–37% in winter but remained inactive in summer. • PCM only utilized 15% of its heat storage capacity to shift the peak cooling load. • The factors that contributed to the underperformance of active PCM were reported. Abstract While the energy saving performance of an active phase change materials (PCMs) system in buildings has been widely investigated using prototype-scale experiments and numerical assessments, their performance during the operational phase of a real building has been less understood. This study assessed the energy-saving performance of an active PCM system installed in an eleven storey building in Melbourne. Macro-encapsulated PCM with the phase transition temperature of 15 °C was installed in a large PCM tank. Water was used as the heat transfer fluid (HTF) to extract and store cooling energy from the PCM tank. The performance of the active PCM system was monitored for 25 consecutive months, and the results were analyzed on a seasonal basis. Building design documents and the maintenance manuals were studied to understand the difference between design intent and actual operation. The analyzed results revealed that the active PCM system reduced cooling load on the chiller by 12–37% only during colder months, but, remained dormant during the summer. Even in the case of maximum effectiveness, the PCM tank only utilized 15% of its available heat storage capacity to reduce the cooling load. The factors that contributed to the underperformance of active PCM system include mismatch between designed and actual operation of the PCM system, inefficient operation logic of the system, poor material quality, and limited knowledge of maintenance staffs during the operation stage. The lessons learned from the operation of this active PCM system in this multi-storey building were reported and discussed. [ABSTRACT FROM AUTHOR]

Highlights • Higher concentration or lower melting point results in higher overall energy efficiency. • Higher concentration or melting point is beneficial to exergy efficiency enhancement. • Maximum improvement in exergy efficiency is achieved by adjusting the inlet velocity. • Proposed slurry increases energy efficiency by 8.3% and exergy efficiency by 3.23%. Abstract Microencapsulated phase change material (MPCM) slurry has proven to have potential in elevating the overall performance of a photovoltaic/thermal (PV/T) module as a working fluid. In order to make full use of the superiority of MPCM slurry and further improve energy and exergy efficiencies of the PV/T module, the effects of MPCM concentration and melting temperature under a wide inlet fluid velocity range were explored based on a three-dimensional numerical model of coupled heat transfer in this study. The results show that both the energy and exergy efficiencies increased with the concentration. A lower melting temperature resulted in higher energy efficiency, whereas a higher melting temperature is helpful for exergy efficiency improvement. The slurry with an excessively low melting temperature (e.g. 27 °C) even led to lower exergy efficiency than pure water. The melting temperature needs to be precisely tailored to make a compromise between energy and exergy efficiencies. In comparison with pure water, the improvement in energy efficiency provided by the slurry was further enhanced at a lower inlet velocity, while the improvement in exergy efficiency was optimized by adjusting the inlet velocity to a certain value. The maximum improvement in energy efficiency provided by the slurry was 8.3%, whilst that in exergy efficiency was 3.23% in this work. From the above, the superiority of MPCM slurry can be further promoted by selecting suitable material properties and operating parameters. [ABSTRACT FROM AUTHOR]

Abstract Phase change materials (PCM) have stable operation temperature and large storage capacity. However, PCM have problems of leakage and low thermal conductivity. For improving performances of PCM, stearic acid (SA) was encapsulated in silica shell by sol-gel method to form microencapsulated phase change materials (MPCM), and graphene oxide (GO) was attached to surface of silica by a self-assembly process to form GO@MPCM, so as to further improve performances of MPCM. The morphology of MPCM was observed through a scanning electronic microscope (SEM). The chemical structure and crystal phase of MPCM were measured by Fourier transformation infrared spectroscope (FT–IR) and X–ray diffractometer (XRD). Raman spectrometer was used to further verify that GO was attached to the MPCM. Thermogravimetric analyzer (TGA) analysis confirmed that MPCM have good thermal stability. Thermal properties of MPCM were measured by Differential scanning calorimeter (DSC), where melting temperature and latent heat of MPCM2 is 67.78 °C and 179.29 J/g. The melting temperature of GO@MPCM is similar to that of MPCM2, and the melting latent heat of GO1 @MPCM and GO2@MPCM is 146.72 J/g and 134.42 J/g, respectively. Besides, thermal conductivity of MPCM with GO is higher than that of pure SA. Highlights • SA is microencapsulated with silica shell via sol–gel technique. • GO is attached to silica shell by a self-assembly process for improving thermal conductivity. • The melting temperature and latent heat of GO1@MCPM is 65.12 °C and 146.72 J/g. • The synthesized microcapsules have good thermal stability. • Thermal conductivity of GO1@MCPM is increased by 62.5% as compared with pure SA. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (MEPCMs) have been recognized as potential energy storage materials for applications such as balancing of heating and cooling loads in buildings. However, current MEPCMs do suffer from low thermal conductivity and low mechanical strength thus limiting their full potential. Past investigations have shown that nanomaterials could be used as a surfactant for the preparation of O/W emulsion and for thermal enhancement in encapsulation processes of phase change materials. For that reason nanosilicon dioxide hydrosol was selected as a surfactant for the encapsulation of samples of n -octadecane due to its excellent thermal stability and good combination properties with both organic and inorganic phase change materials. To this end, the focus of the study was on the synthesis and characterization of the fabricated MEPCM samples. Analysis of the results did show good particle dispersion and shell integrity with the best fabricated sample (MF-2) achieving a significant increase in thermal stability temperature by approximately 78°C (i.e. from 133°C to 211°C) and also higher core material content ranging from 8% to 25% in comparison with other samples. However, there was a reduction of about 17% in the energy storage capacity and a slight reduction of 0.57°C in its melting temperature when compared with the original sample of n -octadecane. The results also revealed that the nucleating agent (ammonium chloride) did affect the morphology, particle size distribution and the content of the base materials. Further enhancement studies are therefore encouraged. [ABSTRACT FROM AUTHOR]