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In this study, ultrafine linear nanostructured SiC with high wettability and large specific surface area were synthesized via the carbothermal reduction method. These nanowires were impregnated with Na2SO4 ⋅ 10H2O, CaCl2 ⋅ 6H2O, MgCl2 ⋅ 6H2O, and CaMg2Cl6 ⋅ 12H2O to obtain composite phase change materials (CPCMs), which demonstrated improved phase separation and significantly reduced supercooling. In particular, the supercooling degree of CaCl2 ⋅ 6H2O was minimized to 0.1 °C. The SiC nanowires effectively prevented issues of dehydration and deliquescence in hydrated salts. The thermal storage capacities of the CPCMs exceeded 90 %, with Na2SO4 ⋅ 10H2O and MgCl2 ⋅ 6H2O reaching 107.10 % and 103.35 %, respectively. Furthermore, the CPCMs exhibited greater sensitivity to changes in temperature compared with the pure hydrated salt phase change materials (PCMs). These results indicate that ultra‐fine SiC nanowires can act as a versatile carrier for hydrated salt PCMs at low and intermediate temperatures. [ABSTRACT FROM AUTHOR]

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In this study, carbon-based nanofluids (CBNFs) were prepared using a revised vortex trap method and applied in the direct absorption solar collector (DASC) to evaluate the feasibility of CBNFs in DASC. The thermal storage performance of water and different concentrations of CBNFs (0.01, 0.025 and 0.05 wt%) was assessed with a 1000 W halogen lamp as a simulated light source under different volumetric flow rates (1.5, 3.0, and 4.5 L per minute [LPM]) at a constant thermal storage load (2.4 kg of water) and ambient temperature of 26 °C. The thermal storage capacity, system efficiency factor (SEF), and heating rate of the CBNFs as the working fluid were higher than those of water in most cases. The thermal storage capacity and SEF of 0.05 wt% CBNF at a volumetric flow rate of 3.0 LPM were 10.36% and 9.36% higher than that of water, respectively. The relevant experimental results demonstrate the great potential of CBNFs in DASC. [ABSTRACT FROM AUTHOR]

• Thermal properties of a PUSSPCM were improved by adding graphite flakes. • Size effect of graphite flakes on phase change properties of PUSSPCMs was clarified. • Innovatively use a GPCM as solid–solid phase change filler in asphalt mastics. • Effect of the preferable GPCM on rheological properties of asphalt mastics was revealed. • The preferable GPCM had potential to cool asphalt mastics in summer. The goal of this work is to improve the latent heat storage capacity and the thermal response rate of a polyurethane solid–solid phase change material (PUSSPCM) for evaluating its applicability as an alternative filler to cool an asphalt mastic. For this purpose, graphite/PUSSPCM (GPCM) structures with various mesh values and contents of graphite were synthesized. The latent heat was initially increased and then decreased with the increasing graphite content. By selecting the optimum content, a GPCM with a larger mesh can possess a higher latent heat. The existence of a relatively large content and mesh of graphite could lead to a higher thermal conductivity for GPCM. The latent heat storage capacity and the thermal conductivity of the synthesized GPCM-8000–1 were 23.2 % and 254.7 % higher than those of PUSSPCM, respectively. Meanwhile, the GPCM-8000–1 material configuration with excellent thermal stability at 200 °C can withstand the high-temperature construction environment of asphalt pavement without liquid leakage and decomposition. As a result, it is recommended as a solid–solid phase change filler to fabricate phase change asphalt mastics. The extracted outcomes from the rheological test results show that the high-temperature deformation resistance, low-temperature cracking resistance and fatigue resistance of the phase change asphalt mastics are improved in contrast to the traditional asphalt mastic. Finally, the cooling effect of the phase change asphalt mastics was evaluated, with the maximum cooling amplitude reaching the value of 5.6 °C. [ABSTRACT FROM AUTHOR]

PCM emulsions have attracted considerable interest as the media for thermal energy storage (TES) owing to their high thermal storage capacity, desirable fluidity and thermal conductivity. However, the direct transportation of PCM emulsions in TES systems for both charging and discharging is rarely reported. In this work, a PCM-in-water nano-emulsion was prepared with n-hexadecane and suitable surfactants for cooling energy storage at a charging and discharging temperature range of 20–5 °C and 5–15 °C, respectively. It was applied to a tubular heat exchanger system to evaluate its TES performance for a cooling panel of 0.2 m2 total surface area. The thermal storage performance was notably increased with the flow rate of emulsion through the exchanger tube. The volumetric thermal storage capacity of charging was 50% higher than that of water. The cooling energy could be rapidly released in the discharging process, 79% of the stored energy at averaging 25 W during most of the discharging period. The emulsion remained stable throughout the test period. Overall, the results demonstrated that the PCM nano-emulsion has the unique characteristics of high static stability, and high energy releasing efficiency and the promising potential for air-conditioning application in buildings.

The multi-energy system (MES) is believed to have bright prospects in the future for its advantages of high energy efficiency, flexible operation condition, and environmentally friendly. The heating network and the heat load play an important role in the MES and have great potentials in improving the system performance. In this paper, an optimal planning method is proposed for the MES that considers the thermal storage capacity of the heating network and the heat load. The objective includes the investment cost, the fuel cost, the grid cost, the maintenance cost, and the environmental cost. The constraints of the cogeneration, the heating network, and the heat load are all taken into consideration. The simulation based on the typical working conditions in annual operation is performed to verify the effectiveness of the proposed planning method. Four cases are set in order to comprehensively investigate the effect of the thermal storage capacity of the heating network and the heat load on the MES planning. The results indicate that the proposed method can decrease the capacity of the devices and reduce the fuel cost.

Ｔｈｒｅｅ ｄｉｍｅｎｓｉｏｎａｌ ｒａｎｄｏｍ ｇｅｏｍｅｔｒｉｃ ｓｔｒｕｃｔｕｒｅ ｏｆ ｐｅｌｌｅｔｓ ｐａｃｋｅｄ ｂｅｄ ｗａｓ ｍｏｄｅｌｅｄ ｕｓｉｎｇ ｔｈｅ ｄｉｓｃｒｅｔｅ ｅｌｅｍｅｎｔ ｓｏｆｔｗａｒｅ ＬＩＧＧＧＨＴＳ. Ｌａｒｇｅ ｅｄｄｙ ｓｉｍｕｌａｔｉｏｎ ｍｅｔｈｏｄꎬ ｔｗｏ-ｔｅｍｐｅｒａｔｕｒｅ ｍｏｄｅｌ ａｎｄ ＥＢＵ-Ａｒｒｈｅｎｉｕｓ ｃｏｍｂｕｓｔｉｏｎ ｍｏｄｅｌ ｗｅｒｅ ｅｍｐｌｏｙｅｄ ｔｏ ｓｉｍｕｌａｔｅ ｔｈｅ ｐｒｅｍｉｘｅｄ ｃｏｍｂｕｓｔｉｏｎ ｐｒｏｃｅｓｓ ｏｆ ｍｅｔｈａｎｅ-ａｉｒ ｉｎ ｔｈｅ ｒａｎｄｏｍｌｙ ｐａｃｋｅｄ ｂｅｄ. Ｔｈｅ ｃａｌｃｕｌａｔｅｄ ｒｅｓｕｌｔｓ ａｒｅ ｃｏｍｐａｒｅｄ ｗｉｔｈ ｅｘｐｅｒｉｍｅｎｔ ｄａｔａ ｔｏ ｖｅｒｉｆｙ ｅｆｆｅｃｔｉｖｅｎｅｓｓ ｏｆ ｔｈｅ ｍｏｄｅｌ. Ｔｈｅ ｓｔｒｕｃｔｕｒｅ ａｎｄ ｔｈｅ ｓｈａｐｅ ｏｆ ｔｈｅ ｆｌａｍｅ ａｎｄ ｔｈｅ ｔｅｍｐｅｒａｔｕｒｅ ｄｉｓｔｒｉｂｕｔｉｏｎ ｉｎ ｔｈｅ ｐａｃｋｅｄ ｂｅｄ ｗｅｒｅ ａｎａｌｙｚｅｄ. Ｔｈｅ ｓｉｍｕｌａｔｉｏｎ ｒｅｓｕｌｔｓ ｓｈｏｗ ｔｈａｔ ｔｈｅ ｔｅｍｐｅｒａｔｕｒｅ ｏｆ ｓｏｌｉｄ ｉｓ ｈｉｇｈｅｒ ｔｈａｎ ｔｈａｔ ｏｆ ｇａｓ ｏｎ ｔｈｅ ｓａｍｅ ｈｅｉｇｈｔ ｏｆ ｔｈｅ ｐａｃｋｅｄ ｂｅｄ ｄｕｒｉｎｇ ｔｈｅ ｌａｔｅ ｓｔａｇｅ ｏｆ ｃｏｍｂｕｓｔｉｏｎꎬ ｗｈｉｃｈ ｒｅｆｌｅｃｔｓ ａ ｇｏｏｄ ｔｈｅｒｍａｌ ｓｔｏｒａｇｅ ｃａｐａｃｉｔｙ ｏｆ ｔｈｅ ｐｏｒｏｕｓ ｍｅｄｉｕｍ. Ｔｈｅ ｈｅｉｇｈｔ ｄｉｆｆｅｒｅｎｃｅ ｏｆ ｔｈｅ ｆａｍｅ ｓｕｒｆａｃｅ ｂｅｔｗｅｅｎ ｔｈｅ ｔｕｂｅ ｗａｌｌ ａｎｄ ｔｈｅ ｃｅｎｔｅｒ ｉｎ ｔｈｅ ｐａｃｋｅｄ ｂｅｄ ｉｓ ｍｕｃｈ ｓｍａｌｌｅｒ ｔｈａｎ ｔｈａｔ ｉｎ ｔｕｂｅ ｗｉｔｈｏｕｔ ｐｏｒｏｕｓ ｍｅｄｉａꎬ ｗｈｉｃｈ ｓｕｇｇｅｓｔｓ ｔｈａｔ ｔｈｅ ｆｌａｍｅ ｉｓ ｄｉｖｉｄｅｄ ｂｙ ｔｈｅ ｐａｃｋｅｄ ｂｅｄ ａｎｄ ｔｈｅｎ ｔｈｅ ｕｎｉｆｏｒｍｉｔｙ ａｎｄ ｓｔａｂｉｌｉｔｙ ｏｆ ｔｈｅ ｃｏｍｂｕｓｔｉｏｎ ｗｉｔｈｉｎ ａ ｐｏｒｏｕｓ ｍｅｄｉｕｍ ａｒｅ ｉｍｐｒｏｖｅｄ. [ABSTRACT FROM AUTHOR]

Abstract In this work, a phase change material based photo-thermal cells was prepared and the solar light triggered thermal storage charging and discharging property was investigated. The graphene nanosheet was uniformly dispersed into paraffin to form phase change materials based photo-thermal cells. The thermal conductivity, enthalpy, heat capacity, optical absorptive property and photo-thermal performance of photo-thermal cells were investigated. The results show that adding 50 ppm of graphene nanosheet in the phase change materials could largely improve the optical absorptive property in visible range and thermal storage capacity charging rate. To calculate the effective thermal storage capacity of phase change material, the results show that the phase change material based photo-thermal cells has larger effective thermal storage capacity than water, indicating the phase change material based photo-thermal cells is promising in solar thermal utilization systems. Highlights • The phase change material based photo-thermal cells is successfully prepared. • The optical absorbance of PCM is largely improved. • The effective thermal storage capacity and charging rate of PCM is largely enhanced. [ABSTRACT FROM AUTHOR]

Abstract The development of high efficient materials for storage and utilization of sustainable thermal energy is very meaningful. Herein, in this research, an oxalic acid dihydrate/glycolic acid (OG) binary eutectic mixtures with the ratio of 80 wt%/20 wt% was prepared as phase change material (PCM), hydrothermal carbon (HTC) and poly (acrylamide-co-acrylic acid) copolymer (PAAAM) were separately and together used as support materials to solve liquid-state leakage problem and improve thermal conductivity. Three form-stable PCM composites (OG/PAAAM, OG/HTC/PAAAM and OG/HTC) were synthesized. The prepared composites were studied by XRD and FT-IR spectra, their thermophysical properties and PCM storage properties were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The OG/PAAAM, OG/HTC/PAAAM and OG/HTC showed the high loading rate to OG content, which are 1718 wt%, 1329 wt% and 1150 wt%, and the latent heat are 289.6, 313.2 and 318.8 J/g, respectively. In addition, the composites possess excellent recyclability after 101 times melting-freezing cycles. Compared to pure OG, OG/PAAAM and OG/HTC/PAAAM (0.2766, 0.3125 and 0.8538 W/m K), the OG/HTC exhibit a higher thermal conductivity of 1.3867 W/m K. Highlights • Three novel form-stable PCMs (OG/PAAAM, OG/HTC/PAAAM and OG/HTC) were prepared. • Three composites have high loading capacity on PCM and show excellent stability. • Composites doped with the HTC show higher heat storage efficiency. • Thermal conductivity has been significantly improved with the doping of HTC. [ABSTRACT FROM AUTHOR]

Convective Concrete is about a research-driven design process of an innovative thermal mass concept. The goal is to improve building energy efficiency and comfort levels by addressing some of the shortcomings of conventional building slabs with high thermal storage capacity. Such heavyweight constructions tend to have a slow response time and do not make use of the available thermal mass effectively. Convective Concrete explores new ways of using thermal mass in buildings more intelligently. To accomplish this ondemand charging of thermal mass, a network of ducts and fans is embedded in the concrete wall element. This is done by developing customized formwork elements in combination with advanced concrete mixtures. To achieve an efficient airflow rate, the embedded lost formwork and the concrete itself function like a lung.

Form–stable phase change materials (FSPCM) with high thermal energy storage capacity and thermal conductivity were manufactured by adding expanded graphite (EG) into stearyl alcohol (SAL) and high density polyethylene (HDPE) mixtures. In the composites, HDPE was used to prevent SAL leakage, and EG was not only a supporting material just like HDPE but also a thermal conductivity promoter. The influences of EG on the thermal properties of the SAL/HDPE phase change materials were investigated with a series of measuring means. Several lines of evidence showed that SAL and HDPE were mixed uniformly and EG was evenly dispersed in the SAL/HDPE composites. Approximately constant melting temperatures of FSPCM at around 57 °C and high latent heat of at least 200 kJ/kg were presented by the differential scanning calorimeter (DSC). It was found that the leakage rate of the SAL phase change materials decreased obviously when EG was added into the FSPCM. Furthermore, the thermal conductivity of FSPCM with 3% EG could increase up to 0.6698 W (m K) −1 while thermal conductivity of FSPCM without EG was only 0.1966 W (m K) −1 . Finally, the FSPCM with EG could provide considerable thermal energy storage capacity and high thermal conductivity for latent heat storage. [ABSTRACT FROM AUTHOR]

In this work microencapsulation of myristic acid–palmitic acid (MA–PA) eutectic mixture with silica shell using sol−gel method has been attempted. The core phase change material (PCM) for thermal energy storage was myristic acid−palmitic acid eutectic mixture and the shell material to prevent the PCM core from leakage was silica prepared from methyl triethoxysilane (MTES). Thermal properties of the microcapsules were measured by differential scanning calorimeter (DSC). The morphology and particle size of the microcapsules were examined by scanning electronic microscope (SEM). Fourier transformation infrared spectrophotometer (FT–IR) and X–ray diffractometer (XRD) were used to investigate the chemical structure and crystalloid phase of the microcapsules respectively. The DSC results indicated that microencapsulated phase change material (MPCM) melts at 46.08 °C with a latent heat of 169.69 kJ kg −1 and solidifies at 44.35 °C with a latent heat of 159.59 kJ kg −1 . The thermal stability of the microcapsules was analyzed by a thermogravimeter (TGA). The results indicated that the MPCM has good thermal stability and is suitable for thermal energy storage application. [ABSTRACT FROM AUTHOR]

SiC w /Al 2 O 3 honeycomb ceramics were engaged as sensible shell materials for encapsulating Al-Si alloys (latent heat materials) in the honeycomb holes to obtain alloy/ceramic composite materials with a high thermal storage capacity for high-temperature solar thermal storage applications. The stability evaluation between the sensible honeycomb ceramics and the latent alloys had been conducted and the failure mechanism for the latent alloys was investigated. Results indicated that the addition of the latent alloys could improve the thermal storage capacity of the sensible honeycomb ceramics significantly by >114% and the thermal storage densities of honeycombs containing Al-12Si and Al-20Si alloys were 1141.3 kJ/kg and 1106 kJ/kg (400–900 °C), respectively. The composite materials exhibited excellent physical and chemical stability. No cracks formed in the honeycomb ceramics and no leakage of alloys was discovered after the composite materials were exposed to 100 thermal cycles in a high-temperature testing environment. The oxidation of Al at >600 °C would lower the latent heat of alloys and the thermal storage densities decreased to 1039.9 kJ/kg and 1013.2 kJ/kg after enduring 100 thermal cycles. This study not only provides a sensible-latent system of thermal storage materials with excellent stability but also gives an insight into the protection of metal containers against the corrosion from Al-based alloys. [ABSTRACT FROM AUTHOR]

• An increase of 57.1% heat transfer rate modulator is observed from re = 100 to re = 103. • The modulator best serves its purpose at the lowest ra and the highest re. • The effect of blade number on the thermal performance improvement is trivial. • Thermal effectiveness and storage capacity have inverse relationship with each other. The transient analysis of the thermal response and frictional loss characteristics for flow-modulated conjugate heat transfer phenomena has been investigated in the present study. The flow domain is a partitioned cavity of a hexagonal structure equipped with a multi-blade flow modulator. The clockwise rotating blade is adiabatic and stirrers the internal flow along with the natural convection caused by the bottom heated floor of uniform heat flux. The conjugate behavior is introduced through the solid subdomains consisting of two brick-made partitions and one glass partition of uniform thickness. The material of the partition wall reflects the physical aspects of industrial applications. The two-dimensional unsteady continuity, momentum, and energy equations are expressed in a non-dimensional form where the buoyant force is modeled through the Boussinesq approximation. The Arbitrary Lagrangian Euler (ALE) finite element is adopted to solve the moving mesh problem by formulating a free triangular discretization scheme. Parametric computational investigations are carried out for air as the working fluid (Pr = 0.71) and 3 different configurations of the rotating modulator while varying the other parameters, i.e., Reynolds number (Re) and Rayleigh number (Ra) for a fixed Biot number (Bi = 104). This dynamic mesh problem encompasses a wide range of parameters, i.e., (100 ≤ Re ≤ 103), and (104 ≤ Ra ≤ 106) for Bi = 104 to evaluate the thermodynamic response of the present thermo-fluid system. Various thermo-fluid system responses are visualized through the spatially average Nusselt number evaluated on the heated surface, system effectiveness, average thermal storage capacity, and frictional power loss of the flow domain. The thermal response is fragmented into individual responses in terms of component signal frequency by the Fast Fourier Transform (FFT) analysis. According to the current analysis, increasing the number of blades increases the rate of heat transfer by a negligible amount. On the other hand, among three different types of modulators, the three-blade modulator shows the lowest power loss coefficient and the lowest power instability. Thus, a three-blade modulator qualifies as the optimum design to impart external motion to the working fluid to introduce forced convection. This research has some scope for improvement. Future studies can be conducted on the improvement of blade designs, thickness, and size of the blades. The present study can shed light on the modeling of a better storage system where heat transfer and moisture control are integrated for the proper functioning of the storage, such as food storage, cold storage, garment inventory, etc. This study is original, and no previous research has been conducted considering the hexagonal domain and variation of the number of blades. The present study reveals that a modulator best serves its purpose at low Rayleigh and high Reynolds numbers. Moreover, the three-blade modulator has the lowest power loss coefficient and lowest power instability, making it the most suitable modulator to impart external excitation to the working fluid. [ABSTRACT FROM AUTHOR]

To offer a solution for low heat transfer and solar energy-storage performance of conventional phase-change fluids, we designed a direct absorption solar energy collecting system based on n -octadecane/phosphorene (PR) nanosheet phase-change nanofluids for capturing solar energy with high energy conversion efficiency and rapid heat response and transfer. The phase-change nanofluids were fabricated through homogenously dispersing PR nanosheets in the n -octadecane aqueous emulsion. The resultant nanofluids exhibit good dispersion stability and suitable viscosity under an optimal emulsifier content of 9.0 wt % and a homogenization rate of 16,000 rpm. Although the nanofluids show a relatively lower latent-heat capacity compared to pristine n -octadecane emulsion, their thermal response and heat transfer were enhanced significantly due to the introduction of PR nanosheets, leading to an increase in thermal conductivity by 98.59% for the nanofluids containing 1.0 wt % PR nanosheets. More importantly, the n -octadecane/PR nanosheet nanofluids exhibit an excellent optical absorption capacity for solar photothermal conversion and thermal energy storage. The nanofluid containing 1.0 wt % phosphorene nanosheets presents a relative thermal storage capacity of 152% by taking pristine n -octadecane emulsion as a control. The nanofluids also show good working stability for the long-term use in solar photothermal conversion and thermal energy storage. The phase-change nanofluids developed in this study exhibit great application potential in solar energy capture and photothermal energy utilization thanks to their enhanced thermal conductivity, high energy-storage density, suitable viscosity, thermal reliability, and excellent photothermal conversion and energy-storage capability. [Display omitted] • A novel type of phase-change nanofluids was developed for high-efficient solar energy utilization. • The nanofluids were fabricated by a combination of n -octadecane emulsion and phosphorene. • The nanofluids present good dispersion stability, high thermal conductance, and suitable viscosity. • The nanofluids exhibit an excellent solar photothermal conversion and energy-storage capability. • The nanofluids find great potential for solar energy capture and harvest applications. [ABSTRACT FROM AUTHOR]

Abstract: Ice storage is currently the dominant cooling energy storage method. To more effectively utilize natural, renewable cooling sources, such as evaporative cooling and sky-radiative cooling, diurnal storage media operated on a daily basis at the temperate range between 10 and 20°C are the most desirable. This paper will present the experimental investigation of microencapsulated paraffin slurry as cooling storage media for building cooling applications. The water slurry of microencapsulated n-hexadecane with a melting temperature of 18°C was cooled to 5°C and heated to 25°C cyclically in a storage tank of 230l, and it was observed that full latent heat storage can only be realized at around 7°C due to supercooling, and the effective cooling storage capacity at the cooling temperature range between 5 and 18°C are obtained, which can be used to realistically estimate cooling storage capacity with various natural cooling schemes. [Copyright &y& Elsevier]

The inherent leakage of molten paraffin during the solid-liquid transition and the immature state of industrial technology currently limit its practical applications for temperature regulation in smart energy-saving buildings. Here, a 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane modification of diatomite with an oleophobic surface was used as a supporting material of molten paraffin for enhancing thermal storage capacity of paraffin/diatomite composite. The results show that an optimal encapsulation ratio of the paraffin/diatomite composite is up to 84.5%, with excellent thermal reliability after a 50-cycle of melting and freezing. The simulation test demonstrates that the indoor temperature is reduced by 5.3 °C in a phase change material room with the paraffin/diatomite composite window as compared to that of an ordinary simulation room. Diatomite with oleophobic surface as a molten paraffin supporting material is effective in improving the thermal storage capacity of the composite. The paraffin/diatomite composite is a potential material with the applications in energy-saving buildings. • Provide a novel strategy for improving the thermal storage capacity of paraffin. • Diatomite using oleophobic modification was first used as a supporting material. • Optimal encapsulation ratio of paraffin/diatomite composite was up to 84.5%. • The indoor temperature with paraffin/diatomite composite window was reduced 5.3 °C. [ABSTRACT FROM AUTHOR]