Fixed-bed thermochemical reactors limit heat and water vapor transport between materials and wet air, thereby causing thermal accumulation and power decay during discharging. Embedding heat-exchange tubes mitigates these limitations. However, massive heat carried by discharged air remains underutilized but directly dissipated to the ambient. In this study, a double-pipe reactor, derived from shell-and-tube reactors, was proposed to recover sensible heat for preheating the inlet water via a novel heat recovery strategy. Under mass-heat capacity matching conditions, where air and water inputs deliver equal heat per unit temperature rise, increasing the inlet-water temperature from 23 degrees C to 43 degrees C enhances the discharging efficiency by 65.25% (from 37.75% to 62.38%). In contrast, an equivalent rise in inlet-air temperature increases the discharging efficiency by 22.97%. When the inlet-air and inlet-water temperatures are set equal under mass-heat capacity matching condition, the effective heat absorption capacity of water reaches its maximum. Thermal output performance is also improved when a shell-and-tube reactor is combined with a heat exchanger. Specifically, when the inlet-air and inlet-water temperatures are both 38 degrees C, the effective duration of the double-pipe reactor and shell-and-tube reactor-heat exchanger combination (assuming 100% heat exchanger efficiency) increases by 115.4% and 89.6%, while the effective heat absorption capacity of water increases by 133.1% and 75.2%. The double-pipe reactor and mass-heat capacity matching strategy offer guidance for next-generation thermochemical reactor designs and provide theoretical support for enhancing heat utilization in reactors with a forward-moving reaction front.

This study presents a multi-physics coupled three-dimension CFD combustion model to simulate heat and mass transfer during cremation. It accounts for the heterogeneous characteristics and variable thermophysical properties of the remains. Ansys Fluent, coupled with User-Defined Functions (UDFs), models the dynamic evolution of body composition, combustible substitutes, and combustion reaction stages during cremation, providing a detailed description of the process. Numerical simulations reveal three distinct cremation stages when natural gas is used: 1) The initial phase, with a furnace temperature of 800 K, features rapid water vapor release and a Leidenfrost-like vapor layer that impedes heat transfer between the high-temperature flue gas and the remains' surface. 2) The stable combustion phase, with a temperature of approximately 1100 K, shows concentrated high-temperature zones above the remains and in the furnace midsection, demonstrating significant dependence on airflow velocity. 3) The burnout phase, characterized by a temperature decrease to 900 K as combustibles diminish. The maximum deviation between simulation results and experimental data is within 10%, which confirms the model's accuracy. This computational framework is highly applicable for simulating combustion processes involving heterogeneous materials with variable thermophysical properties.

Flow maldistribution can deteriorate the thermo-hydraulic performance of stacked microchannel heat exchangers used in reverse Brayton cryogenic systems. To improve both intra-layer and inter-layer flow distribution, a hierarchical manifold design combining tapered layer manifolds, tapered inlet headers, and expanded outlet headers is proposed. A three-dimensional numerical model was established in Ansys Fluent, and a thermo-hydraulic-lightweight evaluation framework based on the mass-modified performance evaluation criterion (MPEC) was introduced. The results show that conventional manifold structures exhibit severe inter-layer flow imbalance and flow bypass in intermediate layers. The tapered layer manifold improved intra-layer flow distribution effectively. When the taper ratio decreased from 1 to 0.4, the flow non-uniformity coefficients on the helium and water sides decreased by 25.46% and 28.25% respectively. Further optimization of the main headers reduced the inter-layer flow non-uniformity coefficient from 0.8124 to 0.6325. Compared with the baseline model, the optimized configuration increased the overall heat transfer coefficient by 5.5% while reducing the pressure drop by approximately 60%. The helium-side and water-side MPEC values increased by 49.9% and 41.0% respectively, and the exergy efficiency increased from 6.56% to 7.68%. The proposed hierarchical manifold design provides a feasible approach for compact and lightweight microchannel heat exchangers in reverse Brayton refrigeration systems.

Utilizing coal gasification slag (CGS) and fly ash (FA) as matrix materials and Al-Si alloy as the phase change medium, composite phase change materials (PCMs) for medium-to-high temperature thermal storage were prepared by powder sintering. The effects of matrix ratio, phase change material content, and forming pressure on material properties were systematically investigated. The composites were characterized using a universal testing machine, ash fusion tester, thermal conductivity analyzer, DSC, and metallographic microscope. Results show that the optimal composite—composed of 20 wt

Integrating the cold energy of liquefied natural gas (LNG) into liquid air energy storage (LAES) systems represents a significant application for LAES technology. However, the high regeneration energy consumption of the air purification (AP) process in the LAES system, which accounts for approximately 27 % of the total energy consumption during energy storage, severely limits the system's round-trip efficiency. To address this challenge, an LNG-integrated LAES system with air purification (LNG-AP-LAES) has been proposed. This system utilizes backflow gas and expanded air from the energy storage process as the regeneration purge gas for the AP process, effectively eliminating the time constraints imposed by AP on energy storage. The optimized process not only enhances synergy between the charging and discharging phases of LAES but also drastically reduces the regeneration energy consumption of the AP process to just 1 % of the total energy consumption during storage. As a result, the round-trip efficiency of the LNG-AP-LAES system increases from 50.15 % to 67.87 %, while the exergy efficiency improves from 53.38 % to 67.31 %. Parametric optimization analysis reveals that the optimal energy storage pressure for the LNG-AP-LAES system is 12.7 MPa, and the energy release pressure is 9.4 MPa. Under these conditions, the system achieves a round-trip efficiency of 68.17 % and an exergy efficiency of 67.53 %. Economic analysis reveals a payback period of 5.85 years for the LNG-AP-LAES system when the peak-tovalley electricity price ratio is 5:1. The improved process enables continuous and flexible energy storage and power generation, providing a viable scenario for the commercial demonstration of liquid air energy storage technology.

This study systematically investigates the catalytic mechanism of copper oxide (CuO) on the dehydration kinetics of magnesium chloride hexahydrate (MgCl₂·6H₂O) to address insufficient heat storage density in medium-temperature thermochemical energy storage. Composite materials with varying CuO content (0, 5, and 10 wt%) were prepared via a solution-mixing method. The multi-scale evolution of the composites was characterized using TG-DSC, XRD, SEM, XPS, FTIR, and Pyridine-adsorbed FTIR. Results demonstrate that CuO significantly advances the dehydration and enhances the thermochemical energy storage density. Notably, at the critical 130 ℃ threshold, even 5 wt% CuO triggers a transition from the hexahydrate state into a heterogeneous mixture of hexa-, tetra-, di-, and monohydrate phases, rising energy density by 381% (144.38 kJ/kg), effectively shifting the dominant storage mechanism from phase-change to thermochemical. Increasing the loading to 10 wt% further pushes the system into deep dehydration predominantly beyond the tetrahydrate stage toward the di-/monohydrate regime, delivering a 497% leap (179 kJ/kg) accompanied by a 58.6% reduction in apparent activation energy (Ea). While thermal conductivity experiences a modest improvement (9.07%), XPS and pyridine-FTIR jointly reveal that the kinetic acceleration is consistent with surface-mediated Lewis acid catalysis: electron-deficient Cu2+ sites coordinate with the oxygen atoms of H2O ligands, polarizing and weakening the Mg–OH2 coordination bond. This work provides a robust molecular-level strategy for designing high-performance hydrated salt composites for thermochemical energy storage.

Seawater spray cooling offers high efficiency, but the complex salt mixture in seawater requires deeper investigation into boiling regime transitions and heat transfer processes on high-superheat surfaces due to varying ion concentrations. To elucidate boiling regime transition mechanisms of a saline droplet on heated surfaces, an experimental system for quantitative vapor diffusion detection is constructed based on light deflection principles induced by density gradients. By reconstructing fluid velocity fields through quantified light deflection, vapor flow fields during boiling regime transitions are captured, and an evaporation dynamics model for a droplet in film boiling is proposed. The results show that the boiling mode of the droplet changes from film boiling to two boiling modes in sequence with the change in concentration and ratio of the multi-component salt in the droplet. Unlike the aluminum surface, there are no boiling mode shifts for the droplet on the Teflon surface. Two boiling modes in sequence expands the range of salt concentrations at which crystallization and scaling occur compared to single-film boiling. This means that Teflon surfaces inhibit crystallization and greatly reduce the area of crystallization. The droplet heat transfer efficiency on the aluminum surface increases with increasing NaCl concentrations in the NaCl-CaSO4 droplet. The droplet lifetime decreased by 61 % when the concentration of NaCl was increased by 20 times at 190 degrees C. When the concentration of NaCl is 20 g/kg, the droplet evaporation rate could reach up to 2.7 mg/s. On the Teflon surface, the droplet heat transfer efficiency increased with the increase in the concentration of CaSO4 in the NaCl-CaSO4 droplet. And the effect of CaSO4 is more obvious, especially at low salt concentrations. Finally, the evaporation kinetics model of a droplet during film boiling is obtained through the energy equation. Therefore, in order to avoid crystallization and scaling of the heat exchanger and to ensure high heat transfer efficiency, it is necessary to take into account the multiple effects of the salt component and the material of the heat transfer surface.

Medium- and low-temperature thermochemical energy storage materials are vulnerable to deliquescence, agglomeration, and structural fracturing under hyperhumid conditions, yet the fundamental origins of excess environmental moisture within reactors remain insufficiently characterized. This study systematically elucidates water vapor transport mechanisms between air and physical adsorption materials in thermochemical reactors, with emphasis on transient humidity transfer phenomena during incomplete charging and discharging cycles. Moisture saturation was defined as the key parameter for standardized humidity analysis. Results indicate that uncontrolled saturation arises from thermally driven vapor depression, in which water vapor desorbed from materials or transported by inlet air undergoes progressive condensation during downstream migration. Moisture saturation dynamics were governed by coupled effects of inlet air temperature, flow velocity, and relative humidity. Reverse charging was shown to effectively reduce maximum moisture saturation in cases where materials remained incompletely hydrated after prior discharging. Optimization of inlet air conditions through controlled transitions from low-temperature, high-velocity states to a predesigned charging protocol achieved a 45.7% reduction in maximum moisture saturation (from 1.38 to 0.75). In addition, preheating prior to discharging significantly suppressed reactor moisture saturation, thereby mitigating material failure risks.

The silicon direct nitriding method exhibits low production efficiency, lacks support for continuous production, and often leads to heat buildup in the reaction bed due to silicon nitride decomposition. This results in a low nitriding rate and excessive reaction bed temperatures. To address these issues, a new two-stage transport reaction bed structure with high-temperature entrance was developed in this study. The structure couples radiative heat transfer (Discrete Phase Model, DPM) with a chemical reaction model. Numerical simulations of the nitriding reaction of silicon powder in the new bed were conducted using Ansys Fluent. The results showed that the height of the two-stage reaction bed was reduced by 36 % compared to that of the traditional bed. Additionally, when the temperature of the inner wall surface of the reaction bed increased from 1400 degrees C to 1600 degrees C, the nitriding rate at the outlet reached 96.0 %, an increase of 55.3 %. Furthermore, the nitriding rate of silicon powder improved as the silicon particle size decreased. The nitriding rate of 2.0 mu m silicon particles at the outlet increased to 91.7 %, a rise of 37.6 % compared to 8.0 mu m particles. For complete nitriding of 2.0 mu m silicon powder, a temperature of 1550 degrees C for approximately 300 s at the inner wall surface of the reaction bed should be maintained.

A droplet impacts on high temperature surface may lead to film boiling. Hydrophobic coating used for corrosion prevention is easy to cause film boiling at low temperature, which results in a remarkable decrease in evaporation efficiency and heat transfer coefficient. However, there is a lack of quantitative visual experimental data on the flow field around the droplet to understand the heat transfer characteristics during film boiling. In this study, schlieren photography combined with high-speed imaging technology is used to observe the evolution process of a droplet impact, rebound, oscillation, and stable boiling. The effects of temperature on lifetime, vapour velocity and heat transfer coefficient of a salt droplet with different concentrations are studied for aluminum and Teflon surfaces. The distribution characteristics of vapour velocity are quantitatively analyzed using cross-correlation algorithm, and the calculation formulas of heat transfer coefficient under nucleate and film boiling modes are proposed. It is found that increasing the concentration of a salt droplet can improve the heat transfer coefficient during film boiling. This work will provide a theoretical basis for the improvement of heat exchanger efficiency in areas such as sea water spray cooling.

This study is dedicated to improving the efficiency of the integrated system of Air Separation Unit (ASU) and Liquid Air Energy Storage (LAES) by introducing two-temperature level Cold Thermal Energy Storage (CTES). In the energy storage stage, the cold thermal energy is released from the CTES, while the ASU load increases, which increases the rate of air liquefaction and realizes the storage of liquid air. In the energy release, the ASU load is reduced, and the stored liquid air is pressurized directly into the column and used for distillation. The enriched cold thermal energy of the product gas is recovered and then stored in the CTES. The CTES of two temperature levels can make the flows in the main exchanger of ASU match well and improve the performance of the system. The presented system shows excellent efficiency, of which the exergy efficiency achieves 79.36% and the overall efficiency can reach up to 90.66 % in our given conditions.

Heat storage technology is critical for optimizing energy systems and improving energy utilization efficiency during the global energy transition. Conventional thermal storage devices are limited by the trade-off between heat transfer efficiency and structural stability. This limits their potential for large-scale applications. This study proposes a magnesium oxide-based electric solid heat storage device design with multi-surface channels. A three-dimensional transient heat transfer model was constructed using computational fluid dynamics to analyze the temperature field evolution and energy conversion efficiency during heat storage and release processes under identical thermal boundary conditions. The performance of the device was analysed by evaluating various channel configurations, including triangular, square, hexagonal and circular, and the effect of the number of heat exchange surfaces due to the change in shape. The results showed that altering the heat exchange channel structure improves the efficiency of heat storage and release. Hexagonal channel was found to increase heat storage by 3.2% and heat release efficiency 9.8%. Additionally, increasing the number of heat exchange surfaces significantly improved the temperature distribution within the heat storage brick stack. When the number of heat exchange surfaces increased from three to infinity, uniformity during the heat storage and release processes improved by 50.2% and 32.5%, respectively. Furthermore, the pressure drop within the heat exchange channels was inversely proportional to the number of heat exchange surfaces. The research findings can accelerate the large-scale application of heat storage systems in renewable energy integration and provide a core technological foundation for enhancing the operational flexibility of next-generation power systems under carbon neutrality goals.

Rising demands for heating and cooling, along with the need for grid peak regulation, pose challenges to modern energy systems. Traditional methods such as Combined Cooling, Heating, and Power (CCHP), off-peak thermal storage, and ammonia-water absorption cooling often operate in isolation, making them insufficient to meet the growing demand. Thus, this study introduces an integrated CCHP system that utilizes solar energy and off-peak electricity to enhance grid stability. A case study of a 1000 m2 office building evaluates turbine and generator steam inlet parameters through sensitivity analyses and multi-objective optimization. The evaluation indicates that, in summer, the system achieves a Coefficient of Performance (COP) of 0.75, with exergy efficiency of 44.74 % and system efficiency of 52.63 %. In winter, the exergy efficiency reaches 63.99 %, and the system efficiency is 82.79 %. The system effectively manages 352.12 kW in summer and 269 kW in winter, saving $23,600 annually in operation and maintenance costs. Additionally, it achieves a Levelized Cost of Storage (LCOS) of $0.17/kWh, surpassing coal-fired and reference CCHP systems in system efficiency.

Thermochemical energy storage (TCES) is a promising long-term heat storage technology with significant potential for applications in the renewable energy sector. Unlike fixed-bed reactors, moving-bed reactors offer optimal alignment between heat release power and temperature, with storage capacity independent of reactor size and quantity. This study develops a three-dimensional model that simulates heat transfer, mass transfer, and chemical reactions during the heat release process in a moving-bed reactor. The effects of various inlet parameters on temperature distribution and material conversion fractions are examined under three-phase flow, consisting of heat storage particles, air, and water. Furthermore, the performance of fixed-bed and moving-bed reactors is compared. The results indicate that the motion of heat storage particles effectively mitigates the reverse heat transfer issue observed in fixed-bed reactors, ensuring more stable heat release. Reducing the air inlet relative humidity from 90 % to 70 % results in an outlet water temperature of 56.1 degrees C, significantly reducing the workload of the humidifier while satisfying temperature output requirements. Notably, the reactor's heat release power is primarily constrained by the water inlet flow rate, while the water temperature rise is largely constrained by heat transfer on the air side. This study provides valuable insights for into the design of thermochemical heat storage systems with stable output performance.

This study addresses two critical limitations of magnesium chloride hexahydrate (MgCl2 & sdot;6H2O) for its low thermochemical energy storage density at 130 degrees C and inadequate thermal conductivity through synergistic modification with copper oxide (CuO) nanoparticles and expanded graphite (EG). Multi-objective optimization identifies an optimal composite demonstrating significantly enhanced performance. The results show that the CuO/EG-modified composites demonstrate significantly improved performance: 5 wt% CuO doping reduces the initial dehydration peak temperature by 67.88 degrees C to 105.8 degrees C while elevating energy storage density to 144.38 kJ/kg at 5 degrees C/min heating rate, representing a 381.3 % increase compared with pristine MgCl2 & sdot;6H2O. Subsequent integration of 1 wt% EG further enhances cyclic stability to 95.14 % retention after 11 cycles and 91.89 % after 20 cycles, concurrently boosting thermal conductivity by 13.8 % to 0.816 W/(m & sdot;K) without compromising energy storage density. Compared with high-density polyethylene (HDPE), a widely used material in medium-temperature solar collectors, modified composite exhibits markedly superior performance at both the material and system levels. The volumetric energy density of the composite reaches 223.4 MJ/m3, which is 32.4 % higher than that of HDPE (168.7 MJ/m3). Its thermal conductivity is 0.816 W/(m & sdot;K), representing a 63.2 % improvement over HDPE (0.5 W/(m & sdot;K)). When integrated into a solar collector-based combined cooling, heating, and power (CCHP) system, the composite further demonstrates system-level advantages, achieving 66.01 % energy efficiency and 54.07 % exergy efficiency, compared to HDPE's 61.88 % and 50.12 %, respectively. These results confirm the composite's strong potential for medium-temperature solar collector applications.

This study uses a cryogenic distillation method air separation unit (ASU) coupled with liquid air energy storage (LAES) to improve the round-trip efficiency and reduce the initial investment of LAES. We propose an integrated system (ASU-LAES-DER) with different ways of energy release. In the novel system, the liquid air can be reheated and expanded to produce additional power, or the liquid air energy stream and part of the material stream can be used for ASU distillation to produce power saving effects. This novel integration allows the ASU to have load regulation capability and facilitates the implementation of demand-side power management. Furthermore, the flexible and efficient energy release methods improve the energy efficiency and economic value of LAES. The comprehensive round-trip efficiency of the system can reach 52.1%-69.2 % with a payback period of 3.25-6.72 years. The peaking index is used to analyze the peak-to-valley load transfer capability of the novel system. Results show that the peaking index ranges from 25.5 MW to 50.1 MW at different scales, indicating that the system can be used as an important grid peaking unit when applied on a large scale.

Granular bed filters (GBF) represent a highly effective technology for purifying high-temperature dusty flue gases, although their efficiency in capturing submicron particles remains limited. A novel gradient porosity GBF model with varying bed structures and heat exchange capabilities was proposed. In this research, we employed CFD software to elucidate the movement and heat transfer process of 1 mu m dust particles within gradient porosity GBFs and heat exchanger tubes. By optimizing the model under the conditions of a 0.5 m/s inlet flue gas flow rate and 1 mu m dust particle size, we achieved a 345.62% increase in filtration efficiency and a 76.61% reduction in pressure drop. The findings indicate that the proposed GBF outperforms other models across various flue gas flow rates in terms of filtration efficiency. The impact of the flue gas flow rate on the combined filtration efficiency for submicron dust on the proposed GBF model was notably significant.

The transformation of internal filter granules into a heterogeneous size distribution through abrasion alters filtration properties. This research constructs an abraded multi-granularity particle bed filter via unidirectional coupling of the discrete element method and computational fluid dynamics. The study examined the filtration characteristics of fine particulate matter at high temperatures. The findings indicate that the abraded multi-granularity beds were higher than the uniform size granular beds in both pressure drop and filtration efficiency. The abraded multi-granularity bed enhances filtration efficiency with a proportionally minor increase in pressure drop relative to the uniform size granular bed. In comparison to a stratified bed structure, the mixed configuration of the multi-granularity bed yields greater filtration efficiencies with less escalation in pressure drop. To maintain filtration efficiency beyond 90%, higher temperatures necessitate an augmented inlet flow rate, requiring an increase by a factor of 2.23 at 1000 K relative to 300 K.

To address the gap between the thermochemical energy storage (TCES) performance of MgSO4-porous matrix composites in small-scale prototypes and their practical application, a TCES system with an output power of 50 kW was designed and constructed to investigate the feasibility of using MgSO4-silica gel composites in large-scale storage systems for long-term heating applications. Thirty consecutive sets of experiments were performed on both the reactor and the system. Aiming at energy storage system for space heating and hot water supply, four parameters (energy consumption, energy storage density, energy storage efficiency, and specific energy storage capacity) were investigated as the key performance evaluation indicators. The experiment results indicated the energy consumption of the heater and humidifier account for approximately 80 % of total energy consumption. The findings also demonstrated the potential to increase the ESD from 0.47 GJ/m(3) to 0.76 GJ/m(3) by exploiting the heat generated from the additional circulation water in the reactor's shell. The optimized system achieved an efficiency increase of similar to 11 %, reaching over 60 %, and the specific energy storage capacity can reach up to 198.15 Wh/kg. In addition, the supply water temperature can stay above 50 degrees C for roughly 4 h, with a maximum value from 70.1 degrees C to 82.4 degrees C, and the water temperature lift was found to as high as 57.4 degrees C. Additionally, the adsorption heat accounted for approximately 44 % of the total energy storage.