Multi-principal-element alloys (MPEAs) have emerged as a transformative class of metallic materials, surpassing conventional alloys due to their“four core effects”. The inherent compositional complexity and programmable multifunctionality of MPEAs collectively drive their emergence as a vanguard in materials innovation. By synergistically modulating metastable engineering and magneto-volume effects, we developed a MPEA (Fe,Co,Cr)100−xNix with an ultralow coefficient of thermal expansion (α1 = 1.00 × 10−6 K−1, 100–100 K) and exceptional mechanical properties (tensile strength: 560 MPa, the elongation to failure: 53

The increasing cooling demand in buildings, together with the urgent need to reduce carbon emissions and electricity consumption, has renewed interest in dew-point evaporative cooling system as a low-carbon alternative to conventional vapor-compression air-conditioning. However, the practical deployment of the system is often hindered by non-uniform surface wetting, dependence on grid electricity, and the lack of systematic understanding of the coupled effects of solar radiation and ambient humidity under diverse climatic conditions. In this study, a photovoltaic-driven dew-point evaporative cooling system is proposed and experimentally validated. The system dynamically couples photovoltaic power generation with fan operation to achieve supplydriven airflow control, while moisture-conductive fiber materials are employed to enhance wetting uniformity and heat-mass transfer. A transient three-module simulation framework is developed to evaluate the energy, economic, and environmental performance of the system. Results show that, across seven representative climate zones, the system achieves primary outlet air temperatures below 26 degrees C, with cooling capacities of 45-252 W per channel and wet-bulb and dew-point effectiveness reach 100% and 66%, respectively. For a commercial building case, the system achieves a 76.2% reduction in annual operating cost and a payback period of about 5.6 years compared with conventional air-conditioning. Life-cycle assessment further indicates seasonal COQ emission reductions of up to 81.1%. The proposed system demonstrates strong adaptability in both hot-dry and hot-humid climates. The main novelty lies in the dynamic coupling strategy, the application of moistureconductive fiber to ensure stable high-effectiveness operation, and the comprehensive multi-climate energy, economic, and environmental assessment, extending previous studies toward practical renewable-powered cooling solutions.

Building cooling accounts for a substantial share of energy use, while conventional vapor-compression systems rely on high global warming potential (GWP) refrigerants and face efficiency penalties in hot-humid climates due to large latent loads. Evaporative cooling and shallow geothermal hybrid systems offer low-energy alternatives, but existing hybrid systems either lack effective dehumidification or suffer from soil thermal saturation and limited climatic applicability. Therefore, this study proposes an earth-to-water heat exchanger and dew-point evaporative cooling (EWHE-DPEC) hybrid system and investigates its performance through bidirectional thermodynamic coupling between shallow geothermal cooling and evaporative cooling. A coupled model, validated against multiple independent data sources, integrates sub-surface soil temperature prediction, buried pipe heat transfer, and coupled heat and mass transfer. Parametric simulations quantify the effects of water-side conditions, air-side operating condi-tions, subsurface environment, and regional climate. Results show that EWHE pre-cooling enables the DPEC unit to provide strong sensible cooling and condensation-based dehumidification under hot-humid conditions, while the high evaporative capacity of DPEC allows stable operation at elevated water temperatures, mitigating soil thermal accumulation and reducing buried-pipe length. Cooling and dehumidification are enhanced mainly at low water velocities, and the secondary-to-primary air ratio exhibits a non-monotonic effect, with maximum cooling perfor-mance at 0.2-0.3 and maximum dehumidification at 0.4-0.5. Seasonal simulations for four cli-matic zones demonstrate that supply air temperatures can be maintained below 25-27 degrees C with climate-dependent pipe lengths. The findings provide a thermodynamic basis and practical design guidance for ultra-low-energy, refrigerant-free cooling systems in hot-dry and hot-humid regions.

Manipulating the crystal structure and microstructure is fundamentally paramount for designing advanced materials with enhanced functionalities. Kagome‐lattice metals attracted considerable attention due to desirable electronic and magnetic properties but are rarely considered for application as structural materials. In this study, a concept of kagome composite is proposed to realize mechanically zero thermal expansion (ZTE) alloy over a wide temperature window, exemplified by the Lu‐Fe‐Co ternary alloys prepared by two‐step synthesis. Using magnetic Co doping, the kagome lattice magnetic order is stabilized in the parent hexagonal Lu 2 Fe 17 structure, and its thermal expansion regulated simultaneously. By in situ precipitation of the α‐(Fe/Co) phase in the matrix, a soft/hard heterogeneous structure emerges and an ultra‐wide temperature window axial ZTE composite ( α l = +0.98 × 10 −6 K −1 , 110–800 K) with good compressive strength (1.11 GPa) is achieved. This work opens up the prospect of kagome intermetallic composite in the integration of structure and function.

Manipulating interlayer interactions in two-dimensional (2D) materials has led to intriguing behaviors. Borrowing these 2D signatures to bulk materials is likely to unlock exceptional properties. Here, we report an emergent 2D-like bilayer Kagome ferrimagnet through reducing the interbilayer magnetic interaction to nearly zero. This concept is realized within bulk TbMn6(Ge,Ga)6 compounds, characterized by an isolated and pure Mn Kagome lattice, simply by the chemical substitution of Ge with Ga. Specifically, the targeted compound TbMn6Ge5Ga1 exhibits a giant spontaneous exchange bias (SEB) of approximately 1.6 T, which is more than twice that observed in known materials. Field-dependent neutron diffraction reveals the robust nature of the compensated ferrimagnetic (FiM), characterized by almost two-thirds of the moments being pinned and irreversible under fields up to 9 T. Through magnetic and structural analysis, alongside theoretical calculations, we demonstrate that the substantial SEB is related to the intense competition between local robust and weak FiM states within the bilayer Kagome configuration, which are stabilized by an incommensurate spin arrangement. The concept of a bilayer Kagome magnet offers new opportunities for discovering attractive properties in 2D-like materials.

A key challenge for spin-dominated functional materials is their suboptimal structural properties, a problem that restricts their widespread applications. Here, this limitation is addressed by introducing additional lattice degree of freedom. This is exemplified in a novel cobalt-based alloy, which is targeted to demonstrate both the spin-state transformation-induced zero thermal expansion (Invar effect, ensuring precision) and lattice transformation-induced plasticity (TRIP effect, enhancing safety), referred to as TRIP-Invar. An unusual martensitic transformation exhibiting three-phase coexistence has been observed under stressing at 77 K, which results in pronounced work hardening behavior and exceptional cryogenic toughness. Notably, reversible spin/lattice transformations enable intrinsic thermal repairability. This findings not only expand the categories within the Invar family, but also provide a reference for the discovery of other integrated structural and functional materials, enabling humanity's exploration of extreme environments like the poles and deep space.

Dew-point indirect evaporative cooling (DPIEC) technology is designed and applied as a low carbon-emission and high energy-efficient air conditioning (AC) solution without employing non-environmentally friendly refrigerant and mechanical compressor for cooling in building sector. A more realistic three-dimensional (3-D) model of the DPIEC that better captures the fundamental thermodynamic of its operation is proposed. It considers the variability of air thermal properties and is employed to investigate the DPIEC's performance for three possible arrangements. The 3-D model is classified as configurations 1, 2 and 3 based on the relative flow direction between primary/secondary air and spray water. Experimental results indicate that the model can well evaluate the thermodynamic performance. Additionally, the influence of crucial factors on the performance is parametrically studied by employing three performance indexes. Comparison reveals that configuration 1 can achieve the highest effectiveness and cooling capacity. Results also show that the secondary-to-primary air ratio should be confined to around 0.3 to achieve maximum cooling capacity, and the optimal channel gap should be limited to the range from 3 to 4 mm. Comparatively, the relative flow direction between the spray water and the primary/secondary air has a greater effect on the thermodynamic performance than the spray water inlet velocity.

The high-entropy strategy has gained increasing popularity in the design of functional materials due to its four core effects. In this study, we introduce the concept of a "high-entropy magnet (HEM)", which integrates diverse magnetic compounds within a single phase and is anticipated to demonstrate unique magnetism-related properties beyond that of its individual components. This concept is exemplified in AB2-type layered Kagome intermetallic compounds (Ti,Zr,Hf,Nb,Fe)Fe2. It is revealed that the competition among individual magnetic states and the presence of magnetic Fe in originally nonmagnetic high-entropy sites lead to intricate magnetic transitions with temperature. Consequently, unusual transformations in thermal expansion property (from positive to zero, negative, and back to near zero) are observed. Specifically, a near-zero thermal expansion is achieved over a wide temperature range (10-360 K, αv = -0.62 × 10-6 K-1) in the A-site equal-atomic ratio (Ti1/5Zr1/5Hf1/5Nb1/5Fe1/5)Fe2 compound, which is associated with successive deflection of average Fe moments. The HEM strategy holds promise for discovering new functionalities in solid materials.

Zero thermal expansion (ZTE) metals have drawn considerable scientific and practical interest due to their excellent dimensional stability. However, the narrow temperature window and inherent brittleness of the ZTE compounds severely limit their processing and application. Herein, an axial ZTE alloy (Ho2Fe13.8Ni3.2, αl = -0.3 × 10-6 K-1 and 110-545 K) is realized in the Ni-doped Ho2Fe17 magnets, which effectively broadens the ZTE temperature window. Combining the variable-temperature neutron diffraction and magnetization measurements, we reveal that the content of Ni tailors the ferromagnetic ordering of the Fe sublattice and regulates lattice negative thermal expansion. Good compressive strength is subsequently achieved by introducing excess Fe in the axial ZTE composition, namely, the dual-phase alloy of Ho2Fe13.8Ni3.2-Fe5 (αl = +0.3 × 10-6 K-1, 110-535 K, and 1.19 ± 0.2 GPa). Neutron diffraction and scanning electron microscopy reveal that the α phase (Fe-Ni) precipitates in the hexagonal phase matrix play a critical role in maintaining ZTE characteristics and enhancing compressive strength. The present chemical design approach may be applicable for obtaining high-performance axial ZTE alloys.

Indirect evaporative cooling (IEC) is sustainable and energy-efficient for air cooling. The tubular indirect evaporative cooler (TIEC) is widely used because of its stable and efficient cooling efficiency. However, the conventional TIEC has problems such as poor wetting performance of the wet channel surface and high spray water flow rate. Therefore, this study proposes a novel TIEC based on moisture-conducting fiber to improve the distribution of water film outside the tube by taking the advantage of the characteristics of moisture-conducting fiber. Firstly, the moisture conductivity of different fiber materials is tested to select the moisture-conducting fiber for TIEC. Secondly, the performance of TIEC based on moisture-conducting fiber is experimentally inves-tigated under various working conditions and configurations to obtain the TIEC configuration scheme with a relatively optimal performance. The results show that Coolmax moisture-conductive fiber is the best selection for TIEC applications because of its excellent ability to induce moisture transport and diffusion. The overall per-formance of the configuration scheme of TIEC based on moisture-conducting fiber supplemented with inter-mittent spraying strategy is relatively optimal. The proposed moisture-conducting fiber-assisted TIEC is able to enhance water migration and diffusion, thus improving the wetting performance, saving water and enhancing the cooling efficiency.

Distributed Energy Systems (DES) offer a promising alternative to centralized energy systems, but the use of fossil fuels in DES raises concerns about carbon neutrality. To address this, future development should focus on reducing dependency on fossil fuels and promoting the integration of renewable energy sources. This study proposes a pure photovoltaic-driven combined cooling, heating, and power (PV-CCHP) system to fully decarbonize community energy usage. The system incorporates four types of energy storage devices: battery (BAT), chilled water tank (CWT), hot water tank (HWT), and hydrogen gas tank (HGT) to enhance reliability and reduce costs. The study also investigates the impact of time series aggregation methods on optimization results and conducts a sensitivity analysis for electricity prices. Key findings reveal that BAT is suitable for intra-day energy storage, while CWT and HWT offer cost-effective alternatives. Additionally, HGT proves economical for managing inter-day and seasonal renewable energy uncertainties. The hybrid storage configuration results in a 33.8% reduction in annual total cost (ATC) compared to a BAT-only configuration under a 100% self-sufficiency rate requirement. It is important to consider the aggregated period length in the analysis, as a too-short period may lead to significant underestimation of the ATC, up to 35.9% at most. Furthermore, the study highlights the impact of the feed-in tariff on system configuration. As the electricity feed-in tariff decreases from 0.09 $/kWh to 0, the installed PV capacity drops by 36.6%, while the ATC increases by 21.1%.

In this paper, a hybrid evaporatively-enhanced cooling system is proposed under commercial operating condi-tions. The indirect evaporative cooler (IEC) is first employed as a pre-cooling equipment to treat ambient air by recovering energy from the indoor exhaust air. The pre-cooled air is then treated to achieve the required thermal condition by employing the latent-heat thermal energy storage (LHTES) containing spherical balls encapsulated with a synthesized phase change material (PCM). Such a novel hybrid process takes full advantage of the IEC's high cooling efficiency and LHTES's power peak load shifting capability. Experimental system comprising the IEC integrated with the LHTES is designed and tested under various air conditions. Additionally, mathematical models are developed to simulate transport phenomena behind the system. Employing experimentally-validated models, thermodynamic analyses are conducted to study the system's performance. Results indicate that (1) the proposed hybrid system is able to pre-cool and dehumidify the ambient air in the tropics simultaneously; (2) the ambient air temperature and humidity ratio can be respectively reduced by 6-10 degrees C and 2-11 g/kg dry air under specific operating ranges; (3) the evaporative cooling technology facilitates the use of a higher chilled water supply temperature which results in an improvement on the chiller efficiency; and (4) a higher water flow rate leads to faster cold energy storage and release rates during the respective charging and discharging periods.

Recent advancements in single-stage evaporative cooling (EC) have showcased their effectiveness as an energy-efficient and sustainable air-conditioning (AC) solution. However, several challenges hinder the widespread adoption of EC in various applications. These challenges include climate sensitivity, substantial spatial requirements, and limitations in achieving desired output temperatures. To address these concerns, there has been a growing focus on integrating EC with solar energy (SE) systems. With traditional energy resources being depleted, the use of SE has gained prominence as a sustainable solution to meet future energy demands while mitigating environmental pollution. This paper presents a comprehensive review of hybrid EC–SE systems, aiming to elucidate the potential synergies, benefits, and challenges associated with this integration. The review explores the principles and mathematical approaches of various configurations of EC systems to assess their compatibility with SE sources. Furthermore, the review delves into the mathematical model of SE, encompassing both solar power generation and thermal collectors, with the aim of integrating it into the EC model. It delves into key aspects of energy consumption and performance, showcasing advancements in achieving higher efficiency and enhanced cooling capacity through the hybrid systems. Additionally, the review highlights research gaps in the existing literature, emphasizing the need for further exploration in this interdisciplinary field. In conclusion, this paper offers valuable insights into the potential of EC–SE systems to address energy and cooling requirements while promoting sustainable development.

This paper entails a study on the transport phenomena of a novel dew-point evaporative cooler with counter-flow closed-loop configuration, a potential alternative to the conventional mechanical vapor compression system. In contrast to the conventional indirect evaporative cooler and the regenerative indirect evaporative cooler, the proposed novel dew-point evaporative cooler is capable of achieving the simultaneous goals of pre-cooling, energy recovery and dehumidification. The novel dew-point evaporative cooler is classified as either type 1 or type 2 based on the relative flow direction between the water and the supply air. A two-dimensional computational fluid dynamics model is judiciously developed and employed to conduct a comparative study which evaluates the performance of the conventional indirect evaporative cooler vis-a-vis both novel type 1 and novel type 2 configurations. Experimental data is then employed to validate the predictive accuracy of the mathematical model. The distributions of both temperature and humidity ratio are plotted for a typical case of the novel cooler incorporating both flow configurations and considering the effects of moisture condensation. Additionally, the impacts made by key parameters on the cooling performance under condensation state are analyzed by using three evaluation indexes, namely, latent efficiency, wet-bulb efficiency, and enlargement coefficient. By regulating several operating parameters, the variations of the three evaluation indexes are plotted via the proposed numerical model. Key results from this study revealed that the novel type 1 flow configuration is capable of achieving the highest latent and wet-bulb efficiencies, and enlargement coefficient. It is also observed that the relative flow direction between the water and the supply air exerts a stronger influence on the cooler performance compared to the changes of the water mass flow rate.

In this work, a novel building cooling system is proposed, namely DAV-cooling system, which integrates dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification. The DAV-cooling system does not use any organic refrigerants, and can naturally provide fresh air indoors to prevent managers from arbitrarily reducing fresh air, and can be flexibly adjusted to meet different cooling requirements. In addition, the thermodynamic model of the DAV-cooling system is established, and some systematical analysis of parameters of the DAV-cooling system is carried out. The results indicate that there is an optimal ratio of fresh air to primary air for the DAV-cooling system, and the optimal value of this ratio should be in the range of 0.2-0.4. When the DAV-cooling system operates under the condition of a higher flow of primary air, the requirements for the dehumidification efficiency of the vacuum membrane-based dehumidification device can be reduced. Moreover, the relationship between COP and cooling capacity ratio is revealed, and it is found that COP decreases as the cooling capacity ratio increases, but they are not in an absolutely one-to-one relationship. Outdoor temperature and humidity also have a greater impact on the performance of the DAV-cooling system. For Singapore and Changsha in the period from June to August, the COP of the DAV-cooling system is about 5-7 and 4.5-9 respectively when the permeate side pressure is 20 kPa. Finally, the engineering design methods of the DAV-cooling system are discussed, and it is found that the DAV-cooling system can be designed as a temperature and humidity independent control air conditioning system through the proposed design method and the established model. This work can provide a complete solution reference and some new insights for the application of next-generation HVAC systems.

Polymer heat exchangers are gaining increasing attention in the field of air cooling applications. This paper aims to present a parametrical analysis on a membrane-based semi-direct evaporative cooler (MSDEC) with internal baffles. A mathematical model has been established to achieve an in-depth understanding of the heat and mass transfer process of the proposed MSDEC. An experimental system has been employed to study the evaporative cooling performance of the hollow fiber module and validate the mathematical process. Simulation results demonstrated that the installation of baffles can improve the wet-bulb effectiveness by up to 32%. In addition, the developed model is adopted to study the air treatment performance of the MSDEC with baffles by evaluating the influence of various essential parameters including the fiber length, the number of fiber rows, the fiber row spacing, the geometrical dimension of baffles, and the inlet air velocity.

Previous studies obtained the heat and mass transfer coefficients of Indirect evaporative coolers (IECs) with condensation based on the following assumptions: (1) empirical equations in the dry channel without water evaporation or condensation, or the boundary condition is assumed to be a constant surface heat flux or temperature so that constant values of Nusselt number can be employed for evaluating the heat transfer coefficient; and (2) Lewis number is assumed to be unity so that the mass transfer coefficients can be then calculated via the heat and mass transfer analogy. Thus far, the heat and mass transfer coefficients of IECs with condensation under naturally formed boundary condition are lacking. In this paper, an experimental-validated computational fluid dynamics (CFD) model has been established to investigate the heat and mass transfer processes of IECs incorporating the phenomenon of condensation. A single factor analysis and a multiple factor analysis are concurrently carried out to evaluate the effects of the nine parameters on the heat and mass transfer processes of IECs. Key findings revealed that both mean Nusselt and Sherwood numbers under the presented conditions are larger than those obtained under constant surface temperature and heat flux conditions; and the respective values of the primary and secondary Lewis numbers are observed to change from 0.37 to 0.75 and 0.70 to 0.85 which severely deviate from the conventional assumed value of unity. Finally, empirical correlations are developed for the mean heat and mass transfer coefficients based on an orthogonal test method. The simplified linear correlations can serve as new fundamental references to account for IEC that are consistently experiencing with condensation. (C) 2020 Elsevier Ltd. All rights reserved.

There are few systematic studies to investigate the inherent reason behind the evolution law of ejector performance, only some simple qualitative or roundabout analysis. In this paper, a double-choking theory is proposed to provide an in-depth explanation of the evolution laws of ejector performance. The systematic investigation and quantitative analysis focus on the influences of various operational and geometrical parameters on the ejector choking flows. Key results revealed that the flow area of the primary jet flow at the choking cross-section A(py) almost linearly increases with higher primary flow pressure p(p0), while the entrainment choking area A(ey) declines instead, and thus the entrainment ratio epsilon decreases. The mixing pressure p(y) significantly increases with entrainment pressure p(e0), and A(py) partly reduces. Consequently, A(ey) becomes larger and epsilon is accordingly with an over-double increase. A(py) undergoes a continuous decrease when the area ratio of primary nozzle lambda(t) increases, and thus e rises consistently although A(ey1) eventually experiences a slight decrease. However, the choking state of the entrained flow would discontinue as lambda(t) exceeds its critical value lambda(tc). Additionally, A(ey) increases substantially when the area ratio of the constant-area section lambda(3) enlarges, while A(py) and p(y) always remain unchanged. Accordingly, epsilon follows the same increasing trajectory as A(ey). These impactful results could serve as an essential guide for optimizing the ejector design, and also ensure a clearer perspective to understand the fundamental link between the ejectors entrainment performance and choking flow.

针对传统空调系统热湿耦合处理所带来的问题,提出一种两级压缩双温空调系统.该空调系统主要由2个压缩机、2个蒸发器(高温蒸发器和低温蒸发器)、冷凝器和2个电子膨胀阀构成.通过Simulink软件建立该空调系统的稳态数学仿真模型,并对换热器和压缩机的数学模型进行验证.分析高、低温蒸发器的换热面积比(RA)对该空调系统性能系数(COP)的影响,计算该空调系统在不同室外气候条件下的COP和节能潜力.研究结果表明:当2个蒸发器总换热面积一定时,随着RA增大,该空调系统的COP先增大后减小,且随着室外空气的温度或相对湿度降低,该空调系统的COP逐渐增大,最高可达6.32;在制冷工况下,两级压缩双温空调系统比带新风的传统空调系统节能12.60％～30.97％,整个供冷季节的空调能耗可减少16.74％.

This paper entails a comparative study on the performance of counter-flow dew point evaporative coolers with two different configurations (type A and type B). Type A refers to the flow configuration where the supply air flows parallel to the water film, while type B refers to the flow configuration where the supply air flows counter to the water film. Both cooler types, when compared with a conventional indirect evaporative cooler, have better potential of lowering the product air temperature below its wet bulb temperature approaching the dew point temperature. A two-dimensional computational fluid dynamics model based on the continuity, momentum, energy and diffusion equations is firstly formulated and then employed to simulate the heat and mass transfer processes. The model, when validated with experimental date, shows a maximum discrepancy of 6.0%. A similarity analysis is then performed to structure the original governing equations of the model into dimensionless forms so as to evolve a fundamental platform that allows key dimensionless parameters to be determined. By regulating these key dimensionless parameters, distributions of the dew point and wet bulb effectiveness and the dimensionless product temperature are plotted via numerical simulation method. Additionally, key simulated data are regressed to obtain the empirical correlation of the dimensionless product air temperature. The key findings that emerged from the present study include: (1) the key dimensionless parameters that are essential to evaluate the performance of the counter-flow dew point evaporative cooler are supply air Reynolds number, water Reynolds number, working air to supply air mass flow rate ratio, water inlet dimensionless temperature, channel length to half width of dry channel ratio and half width of wet channel to half width of dry channel ratio; (2) comparatively, type B configuration has a higher cooling effectiveness and lower product temperature than type A configuration; and (3) the developed dimensionless product air temperature correlation for type B adhered closely to simulated results.