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Reactant gas and liquid water transport phenomena in the flow channels are complex and critical to the performance and durability of polymer electrolyte membrane fuel cells. The polymer membrane needs water at an optimum level for proton conductivity. Water management involves the prevention of dehydration, waterlogging, and the cell’s subsequent performance decline and degradation. This process requires the study and understanding of internal two-phase flows. Different experimental visualization techniques are used to study two-phase flows in polymer electrolyte membrane fuel cells. However, the experiments have limitations in in situ measurements; they are also expensive and time exhaustive. In contrast, numerical modeling is cheaper and faster, providing insights into the complex multiscale processes occurring across the components of the polymer electrolyte membrane fuel cells. This paper introduces the recent design of flow channels. It reviews the numerical modeling techniques adopted for the transport phenomena therein: the two-fluid, multiphase mixture, volume of fluid, lattice Boltzmann, and pressure drop models. Furthermore, this work describes, compares, and analyses the models’ approaches and reviews the representative results of some selected aspects. Finally, the paper summarizes the modeling perspectives, emphasizing future directions with some recommendations. [ABSTRACT FROM AUTHOR]

Purpose: To present the detailed implementation processes of the IDEAL algorithm for two-dimensional compressible flows based on Delaunay triangular mesh, and compare the performance of the SIMPLE and IDEAL algorithms for solving compressible problems. What's more, the implementation processes of Delaunay mesh generation and derivation of the pressure correction equation are also introduced. Design/methodology/approach: Programming completely in C++. Findings: Five compressible examples are used to test the SIMPLE and IDEAL algorithms, and the comparison with measurement data shows good agreement. The IDEAL algorithm has much better performance in both convergence rate and stability over the SIMPLE algorithm. Originality/value: The detail solution procedure of implementing the IDEAL algorithm for compressible flows based on Delaunay triangular mesh is presented in this work, seemingly first in the literature. [ABSTRACT FROM AUTHOR]

The utilization of biochar derived from biomass residue to enhance anaerobic digestion (AD) for bioenergy recovery offers a sustainable approach to advance sustainable energy and mitigate climate change. However, conducting comprehensive research on the optimal conditions for AD experiments with biochar addition poses a challenge due to diverse experimental objectives. Machine learning (ML) has demonstrated its effectiveness in addressing this issue. Therefore, it is essential to provide an overview of current ML-optimized energy recovery processes for biochar-enhanced AD in order to facilitate a more systematic utilization of ML tools. This review comprehensively examines the material and energy flow of biochar preparation and its impact on AD is comprehension reviewed to optimize biochar-enhanced bioenergy recovery from a production process perspective. Specifically, it summarizes the application of the ML techniques, based on artificial intelligence, for predicting biochar yield and properties of biomass residues, as well as their utilization in AD. Overall, this review offers a comprehensive analysis to address the current challenges in biochar utilization and sustainable energy recovery. In future research, it is crucial to tackle the challenges that hinder the implementation of biochar in pilot-scale reactors. It is recommended to further investigate the correlation between the physicochemical properties of biochar and the bioenergy recovery process. Additionally, enhancing the role of ML throughout the entire biochar-enhanced bioenergy recovery process holds promise for achieving economically and environmentally optimized bioenergy recovery efficiency. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are promising for indoor humidity regulation due to steep stepwise water uptake and moderate regeneration temperature. Current approaches for performance improvement of MOFs such as impregnating hygroscopic salts and grafting functional groups face the challenge of corrosion and instability. Herein, a template‐guided tuning strategy is proposed to synthesize binary nanocomposite. Highly ordered mesoporous channels of MCM‐41 provide uniform nucleation sites for MOF growth, enabling a 21.5% promotion of specific surface area (3188.14 m2 g−1) and 23.4% improvement of water uptake (1.53 g g−1 at 20°C/90% relative humidity) for the nanocomposite compared with parent MIL‐101(Cr). The fast kinetics and superior stability together guarantee its practical application. Further, a paradigm of continuous indoor humidity regulation driven by sunlight is demonstrated, which realizes smart regulation of the indoor humidity to the human comfort zone (40–60%) with near‐zero energy input. [ABSTRACT FROM AUTHOR]

Freezing efficiency was the main factor affecting the efficiency of cold chain logistics and transportation. To further the ice storage performance, three mathematical models of the ice storage equipments were established to explore the influence of the number and the diameter of the tubes on the freezing time, heat flux, and natural convection by analyzing the distribution of the ice fraction and velocity. The results showed that the total freezing time of Type II and Type III, which were arranged the micro-tube, were 76.42 min and 137.50 min, which was more than 90% less than that of type I. Due to a ring cavity of water appearing near the shell of the ice storage tank increased the water natural convection, the freezing time required to increase the ice fraction by 0.05 gradually increased especially with the ice fraction greater than 0.95. To better evaluate the ice storage performance, the freezing efficiency was introduced. The freezing efficiency of Type II and Type III was lower than that of Type I by more than 2.24% and 2.14%, respectively, for the ice fraction range of 0.75 ~ 1. Given the freezing time and ice storage efficiency, it could be found that using type II and making the ice storage rate reach 0.95 could shorten the freezing time and improve the ice storage efficiency. [ABSTRACT FROM AUTHOR]

Thermal analysis of data centers is in urgent need to ensure that computer chips remain below the critical temperature while the energy consumption for cooling can be reduced. It is difficult to obtain detailed hotspot locations and temperatures of chips in large data centers containing hundreds of racks or more by direct measurement. In this paper, a multi-scale thermal analysis method is proposed that can predict the temperature distribution of chips and solder balls in data centers. The multi-scale model is divided into six scales: room, rack, server, Insulated-Gate Bipolar Transistor (IGBT), chip and solder ball. A concept of sub-model is proposed and the six levels are organized into four simulation sub-models. Sub-model 1 contains Room, Rack and Server (RRS); Sub-model 2 contains Server and IGBT (SI); Sub-model 3 contains IGBT and Chip (IC), and Sub-model 4 contains Chip and Solder-ball (CS). These four sub-models are one-way coupled by transmitting their results as boundary conditions between levels. The full-field simulation method is employed to verify the efficiency and accuracy of multi-scale simulation method for a single-rack data center. The two simulation results show that the highest temperature emerges in the same location. The Single-rack Full-field Model (SRFFM) costs 2.5 times more computational time than that with Single-rack Multi-scale Model (SRMSM). The deviation of the highest temperature of chips and solder balls are 1.57°C and 0.2°C between the two models which indicates that the multi-scale simulation method has good prospect in the data center thermal simulation. Finally, the multi-scale thermal analysis method is applied to a ship data center with 15 racks. [ABSTRACT FROM AUTHOR]

Isothermal chemical conversion of biomass pellets under the atmospheres of Ar, CO 2 and O 2 were conducted in this study to explore the effects of atmosphere and temperature on the gaseous releasing process and kinetics, and the structure of the solid char/ash products. Results showed that the gas production was promoted while the solid yield was decreased with the raising temperature. The CO 2 reaction with char during gasification process mainly happened after 800 °C that the CO formation lasted for a longer time than pyrolysis. The surface area of char under CO 2 atmosphere was increased to 215.57 m2/g with the increased temperature to 800 °C, but it was sharply reduced to 5.10 m2/g when the temperature further raising to 900 °C due to the destroyed carbon skeleton. The CO 2 formation was largely promoted with a low activation energy of 11.98 kJ/mol during O 2 oxidation process. Compared with the crystal structure of solid residues obtained under Ar and CO 2 atmospheres, O 2 oxidation process resulted in more complex crystal peaks with the main compositions of SiO 2 , K 2 SO 4 , and CaO. This study should be helpful to further understand the thermal conversion of biomass in a complex reaction atmosphere. [Display omitted] • Thermochemical conversion of biomass was conducted at different atmospheres. • Gas yield was increased while the solid yield was decreased with the rising temperature. • The reaction of CO 2 with char mainly happened after 800 °C for gasification process. • The destroyed carbon skeleton for gasification at 900 °C resulted in the low surface area of char. • CO 2 formation was promoted with a low activation energy of 11.98 kJ/mol for oxidation process. [ABSTRACT FROM AUTHOR]

In this article, an in-depth study and analysis of economic structure are carried out using a neural network fusion release algorithm. The method system defines the weight space and structure space of neural networks from the perspective of optimization theory, proposes a bionic optimization algorithm under the weight space and structure space, and establishes a neuroevolutionary method with shallow neural network and deep neural network as the research objects. In the shallow neuroevolutionary, the improved genetic algorithm (IGA) based on elite heuristic operation and migration strategy and the improved coyote optimization algorithm (ICOA) based on adaptive influence weights are proposed, and the shallow neuroevolutionary method based on IGA and the shallow neuroevolutionary method based on ICOA are applied to the weight space of backpropagation (BP) neural networks. In deep neuroevolutionary method, the structure space of convolutional neural network is proposed to solve the search space design of neural structure search (NAS), and the GA-based deep neuroevolutionary method under the structure space of convolutional neural network is proposed to solve the problem that numerous hyperparameters and network structure parameters can produce explosive combinations when designing deep learning models. The neural network fusion bionic algorithm used has the application value of exploring the spatial structure and dynamics of the socioeconomic system, improving the perception of the socioeconomic situation, and understanding the development law of society, etc. The idea is also verifiable through the present computer technology. [ABSTRACT FROM AUTHOR]

Purpose: To help minimize the negative impact of chemical fertilizers on the environment, recycle nitrogen and phosphorus nutrients of anaerobic digestate and reduce loss of nutrients via leaching, an eco-friendly slow-release fertilizer was prepared through recovery of nitrogen and phosphorus nutrition from digestate using superabsorbent fibers extracted from soybean curd residue as an adsorbent. Methods: The preparation method was proposed, and the fiber composite-based adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. Results: The successful incorporation of N and P into the fiber composite-based adsorbent via adsorption was confirmed by results of these analyses. The prepared fertilizer showed a relatively high N content (3.65 wt%) and a limited P content (0.14 wt%). Also, the swelling capacity as well as water retention capability of the obtained fiber composite-based adsorbent were evaluated. The release behavior of N and P from impregnated fiber composites was examined and was found to be partially in good accordance with the standard of the Committee of European Normalization, showing good slow-release and water-retention properties. Furthermore, in order to assess the fertilizer quality of the prepared materials, the effects of different fertilizers (commercially available fertilizer and prepared slow-release fertilizer) on tomato plant growth and soil microbial communities were investigated. Conclusions: The obtained results demonstrated the potential of fiber composite-based slow-release fertilizer system for recycling N and P nutrition from digestate, improving the effectiveness of fertilizer as well as protecting the environment. [ABSTRACT FROM AUTHOR]

Removing benzene from indoor space plays an important role in indoor air purification. A novel filter with vegetal fiber paper (VFP) as matrix hosting silica gel is proposed in this paper for benzene removal. In order to investigate the feasibility and performance of this idea, firstly, three pieces of VFP samples impregnated with different amounts of silica gel are fabricated and their benzene adsorption quantities are tested. The results show that three times is recommended as the optimal number for impregnating. The VFP sample impregnated with silica gel after the third impregnating exhibits commendable coating stability and good benzene adsorption performance. Additionally, at low relative pressure (Pb/Ps ≤ 0.05), the experimental data of benzene adsorption isotherms fit well with the Langmuir model with R2 greater than 0.97. Then, two actual filters made of VFP impregnated with silica gel after the third impregnating were fabricated. It is found that the pressure drop of the actual filter is only 1200 Pa/m when the air velocity is 2 m/s. Besides, the one‐pass efficiency of the filter can reach to 19.44%. It is expected that the silica gel coated on the filter can be modified to improve the purification performance of the filter. [ABSTRACT FROM AUTHOR]

In order to improve the supply air quality, more and more investigations have been conducted on enthalpy exchanger (or total heat exchanger). Enthalpy exchanger consists of functional layers and support layers. The functional layers, which exchange the heat and moisture between fresh air and exhausted air, play a critical role in improving efficiencies of the exchanger. A paper matrix with low cost and easy fabrication is widely used as the functional layers in current enthalpy exchangers. In this study, modified paper by spraying calcium chloride solution is proposed to improve the hygroscopicity of conventional material. Novel functional layers with different solution concentrations of 5, 10, 20, 30, and 40% are fabricated and analyzed. Performance of exchangers made by the modified functional layers and by original layers are tested and compared. Results show that when airflow velocity is 0.3 m/s (corresponding to 50 m3/h), sensible efficiency, latent efficiency, and enthalpy efficiency of modified enthalpy exchanger with use of 30% solution increase from 62, 44, and 49% to 75, 69, and 71% in the winter conditions and from 53, 51, and 52% to 75.8, 71.5, and 73% in the summer conditions compared with original exchanger, the increasing of pressure drop caused by treatment can be ignored. Besides, application of the modified enthalpy exchanger is tested and it is proven that the modified exchanger can obtain better performance compared with original exchanger. [ABSTRACT FROM PUBLISHER]

Experimental and numerical studies of cogasification of woody biomass and sewage sludge have been carried out. The gasification experiments were performed in a fixed-bed downdraft gasifier and the experimental results show that 20 wt % dried sewage sludge in the feedstock was effectively gasified to generate producer gas comprising over 30 vol % of syngas with an average lower heating value of 4.5 MJ/Nm3. Further increasing sewage sludge content to 33 wt % leads to the blockage of gasifier, which is resulted from the formation of agglomerated ash. The numerical models were then developed to simulate the reactions taking place in four different zones of the gasifier (i.e., drying, pyrolysis, combustion, and reduction zones) and to predict the producer gas composition and cold gas efficiency. The deviation between the numerical and experimental results obtained was lower than 10%. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2508-2521, 2015 [ABSTRACT FROM AUTHOR]

A performance comparison of experimental results for CO2trans-critical cycle is presented for an overview of the current level of technology. The published performance data were collected as research objects through comprehensive literature review on experimental research. The methods for data processing, error analysis, and performance evaluation are introduced in the research methodology section. Through the proposed research method, 28 groups of performance results from developed prototypes or test rigs are compared and analyzed using the coefficient of performance and the second law efficiency of thermodynamics. A discussion of the performance comparison between developed CO2devices and commercial products of synthetic working fluid is also presented based on China's national standards (General Administration of Quality Supervision, Insection and Quarantine of the People's Republic of China 2001, 2003). Based on the comparison results, the state-of-art and possible research directions for CO2trans-critical cycle technology are summarized and presented. [ABSTRACT FROM AUTHOR]

Solar energy refrigeration is very attractive for low-temperature grain storage because the cooling load of low-temperature grain storage is roughly in phase with solar energy availability. In this study, a solar-powered adsorption chiller was developed with aim of developing an alternative refrigeration device for low-temperature grain storage. The solar-powered adsorption chiller was put into experimental operation during summer and autumn. Test results show that the solar-powered adsorption chiller can produce a cooling capacity about 66–90 W per m2collector area. Its daily solar-cooling COP (coefficient of performance) is about 0.1–0.13 under the climatic conditions of daily solar radiation being about 16–21 MJ/m2·day. With appropriate ventilation appliance, this kind of solar-powered adsorption chiller could be considered as an alternative for low-temperature grain storage in most areas of China. [ABSTRACT FROM PUBLISHER]

For grain in-store drying, a solar assisted drying process has been developed, which consists of a set including a solar-assisted heat pump, a ventilation system, a grain stirrer, etc. In this way, low power consumption, short cycle time and water content uniformity can be achieved in comparison with the conventional method. A solar-assisted heat pump drying system has been designed and manufactured for a practical granary, and the energy consumption performance of the unit is analyzed. The analysis result shows that the solar fraction of the unit is higher than 20%, the coefficient of performance about system (COPS) is 5.19, and the specific moisture extraction rate (SMER) can reach 3.05 kg/kWh. [ABSTRACT FROM AUTHOR]

The high operating cost is currently a limitation to industrialize microbial lipids production by the yeast Lipomyces starkeyi. To explore economic fermentation technology, the two-stage fermentation of Lipomyces starkeyi using yeast extract peptone dextrose (YPD) medium, orange peel (OP) hydrolysate medium, and their mixed medium were investigated for seven days by monitoring OD600 values, pH values, cell growth status, C/N ratios, total carbon concentration, total nitrogen concentration, residual sugar concentration, lipid content, lipid titer, and fatty acids profiles of lipids. The results showed that two-stage fermentation with YPD and 50% YPD + 50% OP medium contributed to lipid accumulation, leading to larger internal lipid droplets in the yeast cells. However, the cells in pure OP hydrolysate grew abnormally, showing skinny and angular shapes. Compared to the one-stage fermentation, the two-stage fermentation enhanced lipid contents by 18.5%, 27.1%, and 21.4% in the flasks with YPD medium, OP medium, and 50%YPD + 50%OP medium, and enhanced the lipid titer by 77.8%, 13.6%, and 63.0%, respectively. The microbial lipids obtained from both one-stage and two-stage fermentation showed no significant difference in fatty acid compositions, which were mainly dominated by palmitic acid (33.36–38.43%) and oleic acid (46.6–48.12%). Hence, a mixture of commercial medium and lignocellulosic biomass hydrolysate could be a promising option to balance the operating cost and lipid production. [ABSTRACT FROM AUTHOR]