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In order to obtain a building thermal storage material with excellent thermal performance, sufficient strength and low leakage, the advantages of ternary PCMs (Lauric acid—Palmitic acid—Tetradecyl alcohol, LA-PA-TA) and vitrified beads (VB) as a adsorbent carrier were integrated to prepare a novel LA-PA-TA/VB composite PCM which exhibited favorable phase change temperature (i.e. 20.1–20.5°C) and low sub-cooling (0.4°C). Then, the novel LA-PA-TA/VB was, respectively, encapsulated with five different materials (a true stone paint emulsion, styrene-acrylic emulsion, EVA emulsion, epoxy resin and cement powder) to form a shape-stabilized LA-PA-TA/VB (SS-LA-PA-TA/VB) in order to reduce the leakage. The mass loss and mechanical properties experiments showed that SS-LA-PA-TA/VB encapsulated with the real stone paint emulsion-cement powder presented the optimal stability and reliability with low mass loss ratio of only 2.67% after 50 phase change cycles. The SS-LA-PA-TA/VB with the optimal package was further prepared into a thermal energy storage mortar (TESM) with different SS-LA-PA-TA/VB contents. The results show that the thermal properties of the TESM increased and the mechanical properties decreased with SS-LA-PA-TA/VB contents. However, even with the TESM with 30 wt% SS-LA-PA-TA/VB (30TESM), the compressive strength, flexural strength etc. still satisfy the requirement of the Chinese National Standard. The analysis shows that the hydrophobic functional groups are attached to the surface of the emulsion of the real stone paint, whereby a stable hydrophobic film was formed. In addition, the temperature regular ability and heat insulation performance of 30TESM and the referenced mortar were compared by temperature probe embedded inside the mortar blocks and installed in a small experimental room. The results indicated that the internal temperature of the mortar blocks, backside and central temperature in the small room was 5.4°C,5.6°C and 2.1°C lower than those of the referenced group, respectively. It is thus clear that the novel low cost TESM exhibits a good temperature damping effect and temperature control performance and may have a widespread application in the areas of building energy conservation. [ABSTRACT FROM AUTHOR]

Nonsymmorphic symmetries play a significant role in the emergence of topological nontrivial phases in some 2D materials. Herein, a new 2D material P21/m‐MoTe2 with nontrivial topological properties and nonsymmorphic symmetries is proposed. With the help of first‐principles calculations, it is found that it is dynamically stable, and has relatively high energetic stability. When spin–orbit coupling (SOC) is ignored, this material is a semimetal with two intersects appearing on the high‐symmetry line Γ–Y. Detailed symmetry analysis reveal that they are protected by the screw operator C˜2y. After SOC is turned on, it turns into a topological insulator with a global bandgap of 94 meV. The large gap ensures that the topological nontrivial phase is robust to an external perturbation. The discovery of nonsymmorphic P21/m‐MoTe2 expands the family of transition metal dichalcogenides and provides a new platform to study topological phases in 2D nonsymmorphic materials. [ABSTRACT FROM AUTHOR]

Indirect coal combustion can solve some problems such as low efficiency and air pollution during traditional coal combustion, this research investigates energy release characteristics of indirect combustion and aims to achieve maximum energy utilisation. Firstly, Energy Utilization Diagrams Methodology was used to explore exergy cascade release pathways and exergy losses for typical indirect combustion such as supercritical water gasification re-combustion, steam reforming re-combustion, and chemical-looping combustion, which are compared with direct combustion. It is pointed out that indirect combustion has changed release pathways of chemical exergy, and decreased energy level difference between chemical exergy in fuel and thermal energy in combustion, then exergy losses is reduced and exergy in fuel is released step by step. Secondly, to prove that indirect combustion can indeed reduce exergy losses and improve exergy efficiency in the combustion process, supercritical water gasification re-combustion with least exergy losses was selected and exergy analysis model was established by energy quality coefficient. Results show that thermal efficiency and exergy efficiency of supercritical water gasification re-combustion reaches as high as 94.8% and 79.5%, respectively, 2.23% and 19.61% higher than those of traditional coal-fired boilers. As a result, energy matching and conversion are more reasonable in indirect coal combustion processes. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) is a limiting factor affecting the purification efficiency of subsurface flow (SSF) constructed wetlands (CWs). To clarify the causes of oxygen environments and the response characteristics of plant oxygen release (POR) in SSF CWs, this study set three oxygen source treatments by limiting atmospheric reaeration (AR) and influent oxygen (IO) and compared the differences in plant physiological metabolism, DO distribution characteristics, and the purification effect of the SSF CWs at different depths. The results showed that limiting exogenous oxygen stimulated root redundancy of the wetland plants. The root volume and proportion of fibrous roots of the wetland plants increased significantly (p < 0.05). When only the POR existed, the root zone DO increased significantly to 2.05–4.37 mg/L (p < 0.05), and was positively correlated with the TN and TP removal rates (p < 0.05). Additionally, in the presence of POR only, the average removal rates of TN and TP in the top layer were 86.5% and 76.9%, respectively. The proportion of fibrous roots, root zone DO, and root-shoot ratio were key factors promoting the purification effect of the SSF CWs under limited exogenous oxygen sources. Enhancing POR by inducing root redundancy enhanced nitrification (hao , pmoABC-amoABC), plant absorption, and assimilation-related functional genes (nrtABC , nifKDH), and enriched nitrogen and phosphorus removal bacteria, such as Flavobacterium and Zoogloea. This consequently improved pollutant removal efficiency. Inducing root redundancy to strengthen POR produced an aerobic environment in the SSF CWs. This ensures the efficient and stable operation of the SSF CW and is an effective approach for natural oxygenation. [Display omitted] • Exogenous oxygen limitation increased the root-shoot ratio by 1.12–6.18 times. • When only POR, rootzone DO of SSF CWs increased significantly to 2.05–4.37 mg/L. • Root redundancy make directional selection for rhizosphere microorganisms. • Oxygen release from redundant roots can create aerobic environment of SSF CWs. [ABSTRACT FROM AUTHOR]

The oxidation environment has important influence on the transformation of the energy contained in fuel and generation of pollutants. To the problem of nearly 50% exergy losses in coal oxidation at air atmosphere, this research intends to change oxidation atmosphere from air to supercritical water/oxidant and achieve efficient release of exergy in coal at about 650 °C with the aid of a high solubility and unique performance of heat and mass transfer of supercritical water. Therefore, firstly, based on the exergy analysis theory and the energy-utilization diagrams, the release mechanism of exergy of coal in supercritical water oxidation process is revealed. It is pointed out that supercritical water oxidation has changed the release pathways of chemical exergy, and decreased the level difference between chemical exergy and thermal energy, and more exergy is released. Meanwhile, there is also no exergy loss of physical heat transfer. As a result, supercritical water oxidation has higher exergy efficiency than conventional oxidation. Secondly, the exergy losses, level difference between chemical exergy and thermal energy as well as exergy efficiency, are quantitatively investigated. Results show that the exergy efficiency of supercritical water oxidation reactor may be as high as 80.1% and has increased by 27% relative to conventional boilers. Thirdly, based on supercritical water oxidation of coal, a concept power generation system is constructed. Exergy efficiency is calculated and exergy analysis is provided for the supercritical water oxidation power plant. Compared with conventional power plant, exergy efficiency in supercritical water oxidation plant reaches as high as 61.3% and 21% higher than that in conventional power plant. Finally, from the results obtained, it is believed that the commercial breakthrough of the supercritical water oxidation process will be possible when the corrosion and salt deposition in the reactor are solved. [ABSTRACT FROM AUTHOR]

• A hydrophobic and low-cost SiO 2 aerogel had been prepared via acid/base two-step catalytic process followed by ambient pressure drying process. • SiO 2 aerogel is stably distributed in the pores of expanded perlite (EP), and SiO 2 aerogel/EP composites were obtained. • The thermal conductivity and water absorption of EP decreased greatly after aerogel modification. • A new attempt for SiO 2 aerogel modification and application of expanded perlite in thermal insulation materials was proposed. This article aims to complement the advantages of SiO 2 aerogel and expanded perlite (EP) to prepare high-performance building insulation materials. SiO 2 aerogels were prepared via acid/base two-step catalytic process followed by ambient pressure drying (APD) process. The two-step surface modification method is used to improve hydrophobicity of aerogel. And SiO 2 aerogel/EP thermal insulation composites were obtained via introducing wet gel into EP. The effects of the amount of water, the amount of anhydrous alcohol and the pH value of sol on the properties of aerogels were analyzed. And the effects of vacuum degree and adsorption time on the thermal conductivity and compressive strength of SiO 2 /EP composite were studied. The pore size distribution and chemical structure of SiO 2 aerogel were characterized by N 2 adsorption-desorption test and Fourier transform infrared spectroscopy (FTIR). The micromorphology, crystal structure of SiO 2 aerogel and SiO 2 /EP composite were characterized by scanning electron microscope, X-Ray diffraction. The results show that the thermal conductivity of SiO 2 aerogel prepared with tetraethoxysilane (TEOS): methyltriethoxysilane (MTES): ethanol (EtOH):H 2 O = 1:0.3:14:6 (mole ratio) was as low as 0.0212 W/(m·K), the aerogel had high porosity (95.05%) and super hydrophobicity(the contact angle is 158.7°). Meanwhile, it was found that SiO 2 aerogel is stably distributed in the pores of the EP and effectively reduces its thermal conductivity and water absorption. The minimum thermal conductivity of SiO 2 /EP composite was 0.036 W/(m·K), the minimum water absorption was 9.2% and the compressive strength was 214.35 kPa. Hence, SiO 2 aerogel/EP with good performance and low cost has great potential in the field of building insulation. [ABSTRACT FROM AUTHOR]

Abstract: A non-stoichiometric thermodynamic model based on minimum free energy is developed to predict the performance of hydrogen production from biomass gasification in SCW (supercritical water). Specially, we take glucose as a test sample of biomass and apply this model to analyze the processes of hydrogen production from glucose gasification in SCW. It is found that there is a “fast water–gas-shift-type pathway ”, and the product gases consist primarily of hydrogen and carbon dioxide with small amounts of methane and carbon monoxide. When the reaction temperature reaches a higher value, the equilibrium gases consist only of hydrogen and carbon dioxide. The gas yields, higher heating value, gasification efficiency and cold gasification efficiency are strongly affected by the reaction temperature and feedstock concentration and less affected by the pressure under the following range of conditions: a temperature of 650–1050K, a pressure of 20–35MPa and a concentration of 0.1–1.0M. The higher the molar ratio of C/O, the higher are the maximum theoretical yields of hydrogen. The trend of the prediction results is in good agreement with the experimental data, especially as we take into consideration the carbon conversion efficiency. [Copyright &y& Elsevier]

[Display omitted] Besides thermal insulation performance, waterproofness and mechanical strength are also important indexes for evaluating thermal insulation materials. In this paper, silica aerogel/rock wool (SA/RW) composite plates and silica aerogel/glass wool (SA/GW) composite plates were prepared by infiltration and atmospheric pressure drying method. The influence of silica aerogel mass fraction and infiltration time on thermal conductivity, short-term water absorption and compressive strength of composite plates were explored, and the modification effects of SA/RW and SA/GW composite plate under the optimum ratio were analyzed. The changes in microstructure before and after modification were obtained by SEM. The results showed that the addition of silica aerogel significantly changed the surface layer of inorganic fibers, which can form a relatively stable composite system. When the mass fraction of silica aerogel reached 8% and the infiltration time was 20 min, the thermal conductivity of SA/RW and SA/GW composite plate was 0.0330 W/(m·k) and 0.0263 W/(m·k), which were 26.7% and 20.3% lower than those before modification, and the apparent density reached 177.55 kg/m3 and 53.61 kg/m3, respectively. The short-term water absorption was 0.78 kg/m3 and 0.65 kg/m3, which was 35% and 36.2% lower than that before modification. The compressive strength was 42.6 kPa and 14 kPa, respectively, increased by 7% and 103% compared with that before modification. [ABSTRACT FROM AUTHOR]

Abstract: There are presently different types of air conditioning products in China such as room air conditioners, variable speed room air conditioners, unity air conditioners, multi-connected air-condition (heat pump) unit, chilled water air conditioning systems. For these air conditioning products, evaluation indexes have been created, respectively including energy efficiency ratio (EER), coefficient of performance (COP), seasonal energy efficiency ratio (SEER) and integrated part load value (IPLV), and their energy efficiency standards have been established. Based on thermodynamic perfectibility, this paper makes the compatible analysis of the energy efficiency and thermodynamic perfectibility gradient of energy efficiency standards for different air conditioning products. According to testing conditions of evaluation indexes, these air conditioning products are classified into two groups, the standard rating conditions group (EER, COP) and the variable working condition group (SEER, IPLV). The results show the thermodynamic perfectibility of different air conditioning products grade as the same level for energy efficiency standards in each group differ from one another. Besides, the average thermodynamic perfectibility gradient of energy efficiency levels for air conditioning product in the standard rating conditions group is basically the same, and that of variable speed room air conditioners and multi-connected air-condition (heat pump) unit are the highest and lowest, respectively. [Copyright &y& Elsevier]

Abstract: Biomass gasification in supercritical water is a promising technology for hydrogen production by utilizing wet biomass. A new experimental system of biomass gasification in supercritical water was built in SKLMF. In this paper, a comprehensive thermodynamic analysis, including chemical equilibrium in the reactor, gas–liquid equilibrium in the high-pressure separator, exergy and energy analysis of the whole system, was conducted. Chemical equilibrium model is based on minimizing Gibbs free energy. By chemical equilibrium analysis in the reactor, rules of the main parametric effects on biomass gasification in supercritical water are obtained. Simultaneously, a high-pressure gas–liquid equilibrium model was proposed based on modified universal functional activity coefficient (UNIFAC) model, Soave–Redlich–Kwong (SRK) equation of state and modified Huron–Vidal second-order (MHV2) mixing rule. Effects of pressure, temperature and water recycled ratio on gas–liquid equilibrium in high-pressure separation were discussed. Finally, results from energy and exergy analysis show that energy and exergy efficiencies of the whole system are in excess of 40% and increase with increasing heat transfer efficiencies. Energy loss of the system is caused mainly by heat transfer and exergy loss is mainly caused by heat transfer and chemical reaction. Our research provided a thermodynamic tool for improvement of design and operation optimization of biomass gasification system in SKLMF, which may be also applicable to other biomass gasification system. [Copyright &y& Elsevier]