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• Simulated effects of vegetation on microclimate of different urban blocks in winter. • Simulated effects of vegetation on building heating energy in different urban blocks. • Vegetation brought a building heating load increase of 7.16 % in a sunny day at most. • Vegetation brought a building heating load decrease of 2.80 % in a cloudy day at most. • Offered evergreen urban vegetation strategies for high-density cities in cold region. As an important landscape, the evergreen vegetation is prevailing, even in cold region cities. However, the impacts of promoting vegetation on microclimate and building heating load (BHL) are still inexplicit. This study validated the feasibility of a new-developed coupled model that linked ENVI-met and EnergyPlus, for predicting the microclimate and BHL in winter. The impacts of vegetation configuration changes on the performances of three typical urban blocks in Xi'an, a high-density city in the cold region of China, were then evaluated. When the leaf area index of green lands increased from 0.79 to 4.77 m2/m2, a decrease of 3.27 °C on mean radiant temperature, a decrease of 0.48 m/s on wind speed, and an increase of 0.47 °C on air temperature at the block scale could be observed. To the three blocks, the BHL of thermal zones in the height range of tree canopy increased by 7.16 %, 1.52 % and 3.57 % during a sunny day, and decreased by 2.80 %, 0.55 %, and 0.06 % during a cloudy day maximally. Overall, the evergreen vegetation produced negative impacts on the building energy efficiency of cold region cities. For urban planners, it's advisable to concentrate evergreen plants in high-rise blocks to mitigate such disadvantages. [ABSTRACT FROM AUTHOR]

High-rise buildings have been promoted in high-density cities. The impact degree of urban high-rises on the building energy demand at the urban block scale is determined by many factors, including the effects of the vertical meteorological pattern (VMP), which have been discussed insufficiently. In this study, the VMP of urban areas in Xi'an, China was observed, and a building energy simulation model that revealed the "urban block form–outdoor climate–building energy" nexus was developed with the URBANopt plugin on the Grasshopper platform. The impacts of the VMP on the building heating and cooling energy demands of different urban blocks were then predicted. In January, the VMP led to building heating load increases of 0.7–1.6 kWh/m2 (16–52%) and 0.0–1.1 kWh/m2 (0–35%) in the residential and mixed-use blocks, respectively. In July, the ranges of the building cooling load changes produced by the effects of the VMP were 0.0–0.1 kWh/m2 (0–1%) and −0.3–0.2 kWh/m2 (−2%) in the residential and mixed-use blocks, respectively. Furthermore, the VMP affected the relationship between the urban block form and the building energy demand. Based on the relationship, we provided form-optimization advice for different functional urban blocks. The urban high-rise mechanisms in high-density cities and their impacts on the building energy demand were discovered in this study. This can help decision-makers to optimize urban planning while promoting urban sustainability. • A vertical meteorological pattern (VMP) for building energy simulations is developed. • Effects of VMP increase the building heating loads of urban blocks by 52% maximally. • Effects of VMP decrease the building cooling loads of urban blocks by 2% maximally. • Impacts of VMP on the block form – building energy demand relationship are evaluated. [ABSTRACT FROM AUTHOR]

Abstract A liquid desiccant-indirect evaporative cooling (LD-IEC) system has been proposed. The design is able to dehumidify and cool the product air simultaneously in one unit. A computational model has been developed to determine the performance of the heat and mass transfer process. The validation of the model demonstrated good agreement with the experimental data to within 10%. The detailed air treatment process has been theoretically studied. The thermal performance of the LD-IEC has been evaluated. Simulation results showed that the outlet temperature and humidity ratio were influenced by the liquid desiccant film length, intake air temperature, and intake air humidity ratio. For a specific inlet temperature and humidity ratio condition, a desired outlet condition can be obtained by adjusting the length of the liquid desiccant film. [ABSTRACT FROM AUTHOR]

Abstract A hybrid evaporative pre-cooled air-conditioning system is introduced for tropical climate applications. The indirect evaporative heat exchanger is employed to pre-cool the ambient humid air before passing through the vapor compression system. A computational model has been developed for the evaporative pre-cooling process. We validated the model by comparing the simulated outlet air temperature against experimental data. The validated model is then used to investigate the performance of the indirect evaporative heat exchanger in terms of the air temperature and humidity profiles. The pre-cooling process is able to reduce the product air temperature and condense water in the product channel. Consequently, the hybrid evaporative pre-cooled air-conditioning system is able to achieve a potential energy saving due the pre-cooling effect and the improvement of the chiller's efficiency. [ABSTRACT FROM AUTHOR]

Abstract Outdoor thermal comfort has been receiving more and more attentions due to the increased demand of outdoor activities during last decades. People require good thermal comfort when they are exposed to the outdoor thermal environment. However, the natural environment is severely suffering from the pollution of air, water as well as the extremely hot weather. Therefore, construction of ecological living environment is of great importance. To evaluate and improve the built environment, a campus area located in Northwest China was selected. Numerical simulations based on the software ENVI-met V4.0 were conducted and the effect of growing plants upon the outdoor thermal comfort was analyzed. Numerical results were compared using different thermal Indexes: Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI). Results demonstrated that UTCI gave a lower prediction than that of PET and was more suitable for evaluating the outdoor thermal comfort. Growing trees can significantly reduce the uncomfortable hours during hot summer but the improvement will reach the limitation after growing amount of trees. [ABSTRACT FROM AUTHOR]

With the construction of new villages in China, energy-saving technologies for rural buildings have been attracted extensive attention. According to the characteristic of severe cold climate in Hailar, Inner Mongolia, and the structure of rural residential buildings in Taohai Pasture and the energy use customs in these houses, the energy efficiencies of passive energy-saving technologies which are applied to demonstration houses in Taohai Pasture are analyzed. Based on BIM, the calculation models of three types of houses, including the demonstration house applied passive energy-saving technologies, the traditional house and the energy-saving standard model based on local rural residential energy-saving design standard, are established. Then energy simulation software is used to calculate dynamic heating loads of these houses. Furthermore some indexes such as heating load and annual energy consumption per unit building area are compared. The calculated results show that the heating load of the demonstration house in Taohai Pasture is decreased obviously through the passive energy-saving strategies of the thermal insulation of building envelopes, the effective setting of a solar room and the reasonable distribution of indoor functional zones. Compared to the annual heating loads of the traditional house and the energy-saving standard model, that of the demonstration house is reduced about 74.8 % and 28.9%, respectively. The investment increase of the envelope of the demonstration house can be recovered within 11.4 years through the reduction of annual energy use for heating. [ABSTRACT FROM AUTHOR]

Urban vegetation is an important factor for urban heat island mitigation, which also contributes to indoor cooling energy reduction. In this study, a one-way coupled simulation method which linked the ENVI-met and Energyplus models was developed to evaluate the impacts of urban vegetation on micro-climate parameters and the building cooling energy consumptions. The simulation results from 27 cases (three typical scenarios with nine vegetation configurations) under extreme hot weather in the summer of Xi'an city, China were compared and analyzed. Compared to that in high-rise blocks, the vegetation in low-rise blocks showed a larger potential at cooling-energy saving. The maximum air temperature reduction around the buildings reached to 0.40 °C, the maximum mean radiant temperature reduction reached to 1.78 °C, and the sensible cooling load of some thermal zones dropped by 2.13%. Although the overall effect of vegetation on decreasing the district cooling load is positive, the evaporation effect and the limited area of vegetation cooling may induce a limited rate on the cooling energy saving, especially in the high-rise blocks. This study provides a method for evaluating the potential of environmental and energy-saving benefits of vegetation planting in different urban blocks, and the result is valuable for planners to balance the costs and benefits of green configurations. • A coupled model was developed to evaluate microclimate impact on building energy. • The cooling mechanisms and benefits of planting in different scenarios were analyzed. • Planting brought a 2.13% (1.81%) sensible (latent) cooling load change in maximum. • The overall energy saving potential by planting in different districts were evaluated. [ABSTRACT FROM AUTHOR]

Latent thermal energy storage (LTES) is widely used in excess energy reservation. The performance of a LTES unit is critical for its application. In this study, the spiral tube embedded LTES tank is investigated experimentally, with a composite of paraffin as the phase change material (PCM). Temperature distribution of PCM in the tank was obtained, for both charging and discharging processes. The results showed that during the charging process, the temperature of upper part of PCM increases faster than that in the lower part, which is considered as the effect of natural convection of PCM that dominates the charging process. Inlet water temperature has a greater influence rather than flow rate on heat transfer performance since the increase of temperature difference between HTF and PCM reduces all thermal resistance in the heat transfer, however it could not be increased infinitely to enhance heat transfer performance. [ABSTRACT FROM AUTHOR]

This study presented a pore-scaled numerical simulation on the melting phase change heat transfer of a phase change material (PCM) impregnated in open-cell metal foam. Idealized tetrakaidecahedron was selected as the representing unit cell (UC) to mimic the real foam microstructure and an assembly of tetrakaidecahedron UCs with six lines and three rows was built for computation. Phase change heat transfer in PCM and coupled heat transfer between PCM and metallic ligaments were directly simulated. To address the contribution of natural convection in the melting phase to the overall melting time and pore-scaled melting interface, natural convection in the interstitial fluid was modeled and compared with the conduction-dominated case. Results demonstrated that micro-foam can significantly accelerate the melting phase change rate and further enhancement was observed at pore scale when natural convection in the melting phase was triggered on. [ABSTRACT FROM AUTHOR]

The construction of eco-city is a hot spot nowadays, aiming to build harmony between human and nature. Ecological city is able to deal with the relationship between human and the environment, whose key point is to establish a comfortable outdoor thermal environment. To evaluate the built microclimate environment, a campus area located in Northwest China was selected. Different scenarios with extra greening, high albedo pavement materials, water body and their combinations were numerically analyzed through Universal Thermal Climate Index (UTCI) incorporated in the software ENVI-met V4.0. Results demonstrated that the scenarios with water body or high albedo materials was found to have little contribution to reduce UTCI, while the green scenario significantly reduced the UTCI peak (6.9 ̊ C) and also the duration (4.5 hours) of heat stress. The present study may be used as a guide for urban planning and construction for ecological city. [ABSTRACT FROM AUTHOR]

• Results from 33 measurement points in 5 selected urban districts were analyzed. • Urban morphology explains 34% of the variation in air temperature. • Suggested morphological indices are proposed to mitigate the high temperature. • 20m buffer zone is proper to analyze microclimate in high anthropogenic heat areas. • The microclimatic prediction models were established for sustainable development. The negative impacts of urban heat island (UHI) have attracted more and more academic attention. Currently, few studies have considered the effects of anthropogenic heat emission (AHE) in different urban districts. To explore the spatial and temporal differences in microclimate in high-AHE areas, five high-anthropogenic-heat-emission blocks in Xi'an, China were selected, and the microclimatic indices of air temperature (AT) and relative humidity (RH) were measured in 33 urban points in the five typical urban blocks. Meanwhile, the urban morphological indices of 33 points were calculated in the 20 m and 50 m buffer areas (BAs). Results show that the green cover ratio (GCR), the impervious surface area ratio (ISAR), sky view factor (SVF) and reflectivity (REF) were important variables affecting microclimate. These indices explained up to 35% and 31% of the changes in AT and RH, respectively. In addition, the ISAR should be controlled within 44% and the REF should be controlled above 21.5%, in order to ensure that the maximum AT remained less than 37°C (high-temperature orange warning) inside the block on a typical summer day. This study improves the prediction method of high summer temperatures in high-AHE blocks and provides hints for developing UHI mitigation strategies. [ABSTRACT FROM AUTHOR]

• A counter-flow hollow fiber membrane-based evaporative cooler is proposed. • A numerical model is established and validated by experimental data. • The regression models for performance prediction are derived by response surface methodology. • The desirability function is adopted to perform multi-objective optimization. • The accurate regression models can facilitate the regional applicability analysis. The proposed hollow fiber membrane-based evaporative cooler (HFMEC) is expected to be an alternative to the conventional direct evaporative cooler because of its advantages such as the isolation of air from liquid water and the large specific surface area. For the common counter-flow HFMEC with many influencing parameters, it is a bit laborious or even incompetent to rely on experiment or numerical simulation for the parametric study and optimization. Therefore, this study aims to develop accurate and rapid performance prediction models for the proposed HFMEC with the statistical method. An experimental test system for a counter-flow HFMEC was set up. 120 sets of simulations were carried out based on the experimentally validated numerical model and the response surface methodology. Five accurate and practical empirical equations were derived using simulated data: the considered eight input factors consisted of four operating parameters and four membrane module design parameters; the five output responses included the outlet air temperature, outlet air relative humidity, saturation effectiveness, cooling capacity per unit volume, and COP. These simplified equations were adopted to facilitate parameter sensitivity analysis and multi-objective optimization. A case study on the regional applicability of the counter-flow HFMEC demonstrated the ability of the derived equations to conveniently make performance predictions. The results indicated that the regression models could contribute to the rapid performance prediction of the counter-flow HFMEC, aiding in optimization and design. [ABSTRACT FROM AUTHOR]

This paper proposes a gravity heat pipe exchanger used for cooling the communication base station to replace the air conditioning in winter and transition seasons. Tests were made on the gravity heat pipe exchanger of DHHP 3000 produced by Harbin Dawnhappy Heat Pipe Technology Incorporated. The experiment was performed in order to study the effects of the inlet air flow rate, temperature and the exchanger inclination angle on cooling capacity and efficiency of the heat pipe exchanger. As the indoor and outdoor air flow rate are equal, the cooling capacity of heat pipe exchanger increases with the air flow rate and it also increases with the increase of indoor air temperature and with the decrease of outdoor air temperature; The cooling efficiency decreases with the increase of air flow rate and it gradually reduces with the outdoor air temperature increases from 2 °C to 18 °C. Among the ratios of indoor to outdoor air flow rate of 0.4 kg/s:0.5 kg/s, 0.4 kg/s:0.6 kg/s and 0.5 kg/s:0.6 kg/s, the cooling efficiency of 0.4 kg/s:0.6 kg/s achieves the highest value. In addition, as the inclination angle varies from 5° to 50°, the maximum cooling efficiency can be obtained at angle of 20°. [ABSTRACT FROM AUTHOR]

• Temporal and spatial distribution characteristics of urban climate in Xi'an were assessed. • The assignment method was proposed for drawing single meteorological factor distribution map. • The divided climate zones were classified by applying the k-means clustering analysis in winter and summer. • A method of drawing the UC-Map based on the spatial statistical analysis of multivariate data was developed. • Multivariate data were converted into the urban planning management unit to facilitate the urban management work. Rapid urbanization have increased the sensitivity of urban environment to extreme weather. To improve the deteriorating urban environment, the current situation of urban climate should be evaluated systematically and applied to the planning process. This study reports on the temporal and spatial variability of urban climate and introduces a method for constructing an urban climate map based on spatial statistical analysis of field measurement data. Taking Xi'an, a metropolis in northern China, as the case study, we first conducted a 3-year meteorological investigation, including air temperature, relative humidity, and wind speed in both summer and winter. Meanwhile, five indicators with potential impacts on urban climate were selected to describe the urban characteristics. Then, the geographic information system was applied to integrate the meteorological data and urban characteristic data in order to assign more meteorological data. Next, three types of meteorological single-factor and thermal comfort spatial distribution maps were derived. The k-means clustering analysis method was then employed to classify three types of meteorological factors into seven zones in horizontal spatial dimension. Finally, urban climate maps were generated. This study can help planners quickly distinguish urban climate-sensitive and valuable zones in order to make better strategies for future development. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) has attracted huge attention in new energy vehicle, communication equipment fields, due to the high-thermal conductivity and reliable insulating ability. One of the most crucial factors is the preparation of high-performance AlN powders, and more significantly, the two-dimensional nanostructure would change the phonon vibration mode and transport process, bringing in the novel heat conduction and electricity properties. In this paper, kilogram of two-dimensional aluminum nitride nanosheets (AlNNS) with thicknesses around 30 nm and particle sizes around 400 nm were prepared by a new strategy for the nano sanding process, in which they still keep high purity (impurity content ppm grade) without further purification. Furthermore, the technological parameters of the sanding time and line speed are found as the key factors, that would affect the transformation process fro m hexagonal AlN into super-thin AlNNS. The morphology of the nanosheets is more complete at the line speed of 8 m/s. In addition, AlNNS have an increase of 7% in thermal conductivity (at 50 °C) compared to that of raw powders. Moreover, AlNNS have stronger sintering activity due to the larger specific surface area, in which show an increase of 16.8% in shrinkage. Therefore, AlNNS would represent excellent physical properties more than thermal conductivity, providing a new dimension research in high-thermal conductivity ceramics. Last but not least, nano sanding strategy as a purely physical process, avoids the subsequent chemical purification process, and has the advantages of simple and efficient, low energy consumption and environmental protection. [ABSTRACT FROM AUTHOR]

Water-mediated evaporative cooling systems often suffer from cross-contamination, droplet carryover, and high maintenance costs. This study proposes a novel liquid cooling solution, the hollow fiber membrane-based water cooler (HFMWC), to address these issues. The primary innovation of this study lies in the optimization of key design parameters of the countercurrent HFMWC, aligning them with stringent engineering requirements. Two standard working conditions for wet cooling towers are considered. Numerical modeling and response surface methodology are used to develop regression models correlating six key parameters (water velocity, air/water ratio, fiber length, fiber inner diameter, membrane thickness, and packing fraction) with two performance evaluation indexes (outlet water temperature and consumptive electric power ratio). A genetic algorithm-based multi-objective optimization is employed to obtain Pareto fronts, representing optimal trade-offs between the two indexes. Using the ideal point method, relative optimal solutions are identified, resulting in water temperature drops of 7.56 °C and 13.07 °C, with consumptive electric power ratios of 0.0128 kW h/m3 and 0.0138 kW h/m3 for conditions Ⅰ and Ⅱ, respectively. Most solutions achieve the highest energy efficiency rating while satisfying the design temperature difference. The average deviations between optimized and simulated data for the two indexes are 0.88 % and 3.88 %, demonstrating the reliability of the derived optimal solutions for engineering design. These findings not only offer a promising way to overcome the limitations of traditional evaporative cooling systems, but also contribute to the broader field of sustainable and efficient thermal management technologies. [ABSTRACT FROM AUTHOR]

The counter-flow hollow fiber membrane-based direct evaporative cooler (MDEC) was proposed as an energy-efficient and hygienic air cooling solution. The random sequential addition algorithm was used to simulate the randomness of fiber distribution within the MDEC in engineering practice. 3D numerical models were developed with a computational domain determined as a hexagonal prism containing multiple fibers. The experimentally validated model depicted the air state variation along the path under regular and random fiber distributions. The differences in wet-bulb effectiveness (ε wb) and coefficient of performance (COP) of MDEC with two configurations, regular and random fiber distributions, were compared for different packing fractions and air flow rates. Furthermore, dimensionless correlations for the shell-side friction factor (f), Nusselt number (Nu), and Sherwood number (Sh) were derived to generalize the results to other hollow fiber membrane modules employed in liquid/gas systems. The results showed that the channel flow effect and dead zone under the random configuration worsened the heat and moisture handling performance of MDEC. Compared with the regular configuration, both Nu and Sh were degraded by 11.6–55.6%, but f was desirably reduced by 28.8–49.8%. Balancing cooling capability and energy efficiency, a regular configuration with moderate packing fraction was more beneficial for engineering practice. • The counter-flow hollow fiber membrane module is proposed for evaporative cooling. • Random sequential addition algorithm is used to represent the randomness of fiber distribution. • 3D models with different fiber configurations and packing fractions are developed. • Regular fiber distribution with moderate packing fraction enables efficient cooling and energy saving. • Compared to regular distribution, shell-side Nu , Sh , and f are all reduced in random distribution. [ABSTRACT FROM AUTHOR]

The hollow fiber membrane-integrated evaporative cooler (MEC) is considered as a promising strategy for space air conditioning applications. For a counter-flow MEC, the appropriate fiber specification and flow configuration need to be identified to improve its comprehensive performance. A numerical model was developed to capture the coupled heat and mass transfer process, and its feasibility was verified by measured data. The influence of fiber specifications and flow configuration on its cooling, space-saving, energy and water conservation performance were investigated. The results revealed that a reasonable fiber specification required a packing fraction of about 0.1 and a length slightly longer than the air channel's entrance length, while the inner diameter and membrane thickness should be determined based on the priority index. The flow configuration of air flowing via shell-side and water going through tube-side was more suitable for counter-flow MEC, which was more energy efficient while maintaining cooling ability. In addition, the contribution of each component's resistance to the total heat and mass transfer resistance would fluctuate as the influencing factors changed. In general, the total heat transfer resistance was dominated by the air-side convective resistance, while the main contributor to the total mass transfer resistance was the membrane resistance. • The counter-flow hollow fiber membrane module is proposed for evaporative cooling. • A numerical model is developed and validated with experimental measurements. • The composition of the heat and mass transfer resistance is quantified. • Appropriate fiber specification and flow configuration are determined. [ABSTRACT FROM AUTHOR]

Evaporative cooling systems face limitations in producing cold water due to their dependence on ambient air conditions, air-water cross-contamination, and large equipment size. This study introduces a vacuum-assisted hollow fiber membrane integrated evaporative water cooler as a potential solution. To facilitate its deployment in applications such as building air conditioning and industrial processes, a robust design optimization framework was constructed. A numerical model was established and experimentally verified. Combining the response surface method, three regression models were derived for convenient performance prediction. The six input design parameters encompass operating conditions and membrane specifications. The three output performance metrics are outlet water temperature, coefficient of performance, and cooling capacity per unit volume. Multi-objective optimization using a genetic algorithm, under two inlet water temperature conditions, yielded well-balanced cooler designs with superior cooling performance, energy efficiency, and compactness. The regression models demonstrated high prediction accuracy, with R 2 surpassing 0.93. Compared to the original designs, the parameter combinations identified through the ideal point method realized over 40 % reduction in outlet water temperature, over 66 % increase in coefficient of performance, and over 138 % enlargement in cooling capacity per unit volume. Furthermore, validation of the obtained Pareto fronts confirmed the practical reliability of the design references. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon emissions play a pivotal role in driving global warming, with commercial and residential sectors ranking as the third-largest source after industrial and transportation sectors. Consequently, establishing a framework for spatial characterizing and predicting carbon emissions from these sectors is vital for effective carbon reduction planning. This study proposes an optimized Backpropagation Neural Network, incorporating a Spatial Weight Matrix, to model the relationship between land use and carbon emissions, taking spatial effects into account. Additionally, an optimized Random Forest model with variable search step lengths is developed for large-scale and multi-class land use prediction. Beijing, China serves as the study site, yielding the following findings: (1) The optimized Backpropagation Neural Network outperforms traditional models, achieving goodness of fit of 0.999 and 0.997 in training and testing datasets, respectively. (2) The optimized Random Forest model, while reducing prediction precision for ecological areas (Root Mean Square Error increases by 4.12 %), enhances overall model performance by 73.95 % in a single iteration. (3) By 2025, commercial and residential carbon emissions in Beijing are projected to reach 8.91 million tons. (4) The study characterizes the spatial patterns of commercial and residential carbon emissions at a 1 km resolution for the next 15 years, revealing statistical features. (5) Expansion of mixed commercial and residential land relies on service-oriented development, positively impacting regional carbon emission intensity control. • A novel carbon emission prediction model based on land-use subdivision is proposed. • Backpropagation Neural Network is optimized by the Spatial Weight Matrix. • Commercial and residential emissions in Beijing over the next 15 years are predicted. • Future commercial & residential emissions are characterized at resolution of 250 m. [ABSTRACT FROM AUTHOR]

• Thermal behaviors of vapor chamber are explored by hybrid Lattice Boltzmann method. • Surface wettability has a non-monotonic effect on the thermal performance of VC. • Hydrophilic boiling surface is recommended for higher boiling heat transfer limits. • Hydrophobic boiling surface is recommended for lower heat flux conditions. • Hydrophilic condensation surface is beneficial for faster boiling thermal response. Vapor chamber (VC) has been recognized as an effective passive cooling solution for thermal management. Due to complexity of phase-change processes in VC, boiling and condensation have been the focus of attention. In this paper, a hybrid lattice Boltzmann method was employed to explore the effects of surface wettability on thermal behavior/performance of VC. Taking the bubble/droplet dynamics, boiling heat transfer coefficient (BHTC), critical heat flux (CHF), thermal response and resistance as key factors, selections of proper surface wettability to address heat dissipation requirements were discussed. The results show that the influences of wettability on phase-change processes are not monotonic. For high heat fluxes, compared with neutral surface of 89.0° contact angle (CA), the CHF of the hydrophilic boiling surface (CA=23.9°) is enhanced by 92.57%. For low heat fluxes, the VC with a hydrophobic boiling surface (CA=115.5°) results in the highest BHTC by 260.34% compared with the neutral one. The heat flux should be carefully applied to the hydrophobic surface to prevent burnout. For condensation surface modification, the hydrophilic condensation surface is preferred for the faster thermal response. These findings are expected to provide a promising method for enhancing thermal performance of VC by surface modification. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon emissions are a significant factor contributing to global climate change, and their characterization and prediction are of great significance for regional sustainable development. This study proposes a novel carbon emission characterization and prediction model based on interpretable machine learning and land use. It does not rely on socio-economic indicators, thus enabling carbon emission predictions after the decoupling effect. It can also reflect spatial distribution characteristics of carbon emissions, and demonstrates high accuracy and interpretability. The Yangtze River Delta (YRD) region serves as the application case for the model. Utilizing GIS-Kernel Density for land-use subdivision and Optimized Extra Tree Regression, the model achieves high precision (R2 = 0.99 for training, R2 = 0.86 for testing). Shapley Additive exPlanations (SHAP) model was employed to interpret the model, revealing the impact curves of different land areas on carbon emissions. Optimized Land Expansion Analysis Strategy (Opti-LEAS) and Cellular Automaton based on Multiple Random Seeds (CARS) models simulated land use under baseline scenarios, confirming an overall accuracy exceeding 85%. The total carbon emissions in the YRD in 2030 are projected to reach 1580.70 million tons, with Shanghai leading at 223.84 million tons, followed by Suzhou at 172.20 million tons. County-level carbon emissions were characterized, and a spatial econometrics model was employed to reveal the spatial distribution characteristics of future carbon emissions, indicating a clustering effect (Moran's I = 0.6076). As industrial land disperses, clustering shifts towards regional centers, with areas like Wuzhong District identified as 99% confident carbon emission hotspots. • A novel model utilizes land use for carbon emission prediction has been proposed; • The model provides specific carbon reduction strategies due to its interpretability; • The advantages of the model for multi-scale CO 2 emission prediction are elucidated; • Yangtze River Delta region, China was chosen as the model application case. [ABSTRACT FROM AUTHOR]

Data centers have tended to develop towards large scale and high density, with overall power consumption reaching up to 3 % of the total national electricity consumption. It is vital to establish energy-efficient electronic cooling devices for data center improvement. Phase-change heat transfer has emerged as a highly efficient method for addressing the heat dissipation problem. As the demand for micro-electronic cooling devices grows, enhancing the phase-change heat transfer has been a key focus of engineering research for several decades. Surface modification can effectively facilitate heat transfer favored by the surface area expansion and free energy transition. This review delved into the multiple processes involved in phase-change heat transfer, containing boiling and condensation. Considering the surface roughness and free energy, the wettability theories and manipulations of hydrophilic and hydrophobic surfaces were presented. The fabrication techniques available for modified surfaces mainly comprise coating, etching, template, sol-gen, and layer-by-layer assembly methods. The effects of patterned surface, wettability gradient surface, electrowetting surface, and wettability controllable surface on phase-change heat transfer enhancement were elaborated, particularly for the critical heat flux and heat transfer coefficients. This review of experimental and simulation results showed that surface wettability modification possesses a promising prospect in improving heat transfer performance. In this review, recommendations for the design of surface modification to promote the development of energy-efficient technologies in specific artificial environments were proposed. Further theoretical and experimental efforts need to create novel surfaces that can facilitate high-performance phase-change heat transfer across a range of applications. • Detailed methods used to achieve surface modification were elaborated. • Design methods of highly-effective surfaces were discussed and recommended. • Various improvements of condensation and boiling heat transfer were examined. • Hybrid surfaces are proven to enhance thermal performance better than single ones. • Electrowetting surfaces exhibit the best performance in modified applications. [ABSTRACT FROM AUTHOR]

The traditional carbon accounting method, with a lag of over 2 years due to the release time of statistical yearbooks, impedes timely policy adjustments in urban planning and management. Hence, there is an urgent need to establish a real-time carbon emissions characterization model. Xi'an which has a complex land-use structure was chosen as the study site and its carbon emissions were calculated using the Emission Factor Method. The GIS-Kernel Density (KD) model was constructed, and land use was subdivided based on Point of Interest (POI) and road network data. Based on the results of carbon emissions accounting and land-use subdivision, a Multilayer perceptron (MLP) model was established. The remote sensing (RS) images of Xi'an underwent supervised classification, and the carbon emissions of Xi'an were characterized based on the subdivision results and MLP model. The results show that: (1) The accuracy of the characterization model is more than 90%, and with the improvement of RS technology, the accuracy will be further improved; (2) Compared with the existing model, this model can real time reflect the spatial distribution of carbon emissions; (3) Atmospheric emission of Xi'an will be 41.92 million tons at the end of 2022, a decrease of 2.80 million tons compared with that of 2020, but an increase of 0.33 million tons from 2021. The north of Xi'an and periphery of the central urban area are the main carbon sink loss areas, while the east of Xi'an and north foot of the Qinling Mountains are carbon sink growth areas. • A model that can characterize carbon emissions in real time is proposed. • Land use subdivision was considered and the accuracy of the model reached 90%. • The model can realize the spatial characterization of carbon emissions. • Xi'an, China was selected as a case to demonstrate the advantages of the model. [ABSTRACT FROM AUTHOR]

Flat thermosyphon (FTS) has gained wide attention in solving heat dissipation problems of data centers. The miniaturization of densely packed electronics has led to a demand for compact heat sinks. In this paper, a confined FTS consisting of an evaporator, condenser and customized quartz-glass chamber was developed. Bubble behaviors were investigated by the visualization approach under vacuum conditions. Effects of the space height, nominal heating power, and liquid filling ratio on the thermal characteristics were involved. Experimental results found that the bubble behaviors with 10 mm height are different from others. For 10 mm height, bubble contacts the condensation surface and then bounces back to the evaporator. The quantitative analysis shows that the boiling heat transfer coefficient with 10 mm height is 65.5 % of that with 25 mm height , and a condensation heat transfer coefficient with 10 mm height is 58.9 % of that with 20 mm height. Increasing heating power deteriorates the condensation heat transfer via forming a bubble film on the condensation surface. A small filling ratio (30 %) with 10 mm height is beneficial for the phase change heat transfer. It is hoped that these results can offer guidance for designing effective cooling devices. [Display omitted] • Bubble behaviors of confined flat thermosyphon (FTS) is explored. • Effects of space height, heat power, and filling ratio are involved in analysis. • The bubble directly bounces back to the evaporator of FTS with 10 mm height. • Small filling ratio (30 %) is beneficial for phase change of FTS with 10 mm height. • Reduced space height attenuates the thermal performance of confined FTS. [ABSTRACT FROM AUTHOR]

• A carbon emission prediction model with high accuracy and precision was established. • The proposed prediction model can reflect spatial distribution of carbon emissions. • The resolution of the model is proved to be suitable for prefecture-level region. • A case study of Xi'an, China, demonstrates the advantages of the model. • Provides strategies for carbon reduction planning and energy management in Xi'an. Climate change has become a global concern, and the prediction of carbon emissions is key to achieving carbon-reduction goals. The existing framework cannot accurately reflect the spatial distribution of carbon emissions, making it difficult to guide urban planning and management. Therefore, in this study, a carbon emission spatial simulation and prediction model was established. The model includes the GIS-Kernel Density sub-model for subdividing built-up area, the Land Use-Carbon Emission sub-model for establishing the correlation between land use and carbon emissions, the Multi Objective Programming-Principal Component Analysis-BP neural network sub-model for presetting development scenarios, and the Patch-generating Land-use Simulation sub-model for predicting. Xi'an was chosen as the study site, and two extreme scenarios were determined. A total of 373,318 development paths were segmented from the interval, and the optimal path was selected. All scenarios were simulated, and the carbon emissions and their spatial distribution were calculated. The results showed that the overall accuracy of the simulation exceeded 90%. Under the optimal path, Xi'an's carbon emissions reach 60.6 million tons at peak time, which will be reduced to 47.38 million tons by 2060. In addition, the model analyzed the temporal and spatial changes of carbon sources and sinks and drew up the path of carbon reduction by technology and urban planning. This model can provide a reference for regional carbon-reduction planning and carbon reduction technology implantation. It can propose strategies from the perspective of planning and management. [ABSTRACT FROM AUTHOR]

The melting performance of a rotating triplex-tube latent heat thermal energy storage unit is studied by numerical simulation method. The Taguchi design and response surface method are applied to its optimized design. Firstly, the Taguchi design method is used to quantitatively reveal the specific effects of fin distribution, fin number, and fin material on the melting performance of the unit. Compared with all-inner tube-fin or all-outer tube-fin structures, the melting time of alternating inside and outside fin structures is shortened by 52.64% and 32.42%, the average heat absorption rate is greatly increased by 105.56% and 47.26%, and the total heat is reduced by 2.64% and 2.17%, respectively. Then, the response surface method is applied to the eight alternating fins obtained by the Taguchi design, and the effects of fin length, width, and rotation angle on the melting time and average heat absorption rate of the unit are studied. Compared with the original structure, the optimal structure reduces the total melting time by 7.37% and increases the average heat absorption rate by 7.23%. The geometric parameters' interaction with the relevant target response is studied, and the corresponding fluid-structure interaction equation is fitted. Finally, the melt growth phenomenon near the wall is found in the initial melting stage of the optimized model by mechanism analysis. • The rotation condition is applied to a triplex-tube LHES unit. • The TDM and RSM are used to optimize the melting performance of LHTES. • The fluid-structure coupling functions of melting time for each parameter are fitted. • The melt growth phenomenon near the wall is found in the initial melting stage. [ABSTRACT FROM AUTHOR]

Although solar energy is a clean and abundant resource, it has an unstable nature. It is demonstrated that latent thermal energy storage (LTES) systems have been an excellent way to utilize solar energy fully and widely. However, LTES has the problem of insufficient thermal conductivity. For this reason, it is inevitable to consider effective methods to intensify the thermal conductivity of LTES system. In the current study, experiment and numerical simulation are used to study the influence of non-uniform metal foams on heat transfer during phase transition. In this study, a horizontal shell-and-tube LTES test system is established. Moreover, the phase change melting rate of radially filled metal foams with different porosity gradients is compared. According to the numerical simulation results of phase interface, velocity field and temperature field, natural convection can accelerate the melting of PCM. However, there is no distinct effect on the solidification process. When the equivalent porosity is 0.94, the optimal combination (melting process is 0.84-0.92-0.99 and solidification process is 0.87-0.94-0.97), compared with the uniform structure, can shorten the total consumption time by 9.7% and 6.2%, respectively. • The radial positive gradient structure accelerates the melting, but it has little effect on the solidification. • In the current study, the optimal melting/solidification combinations are 0.84-0.92-0.99 and 0.87–0.94-0.97, respectively. • The optimized design of metal foam gradient can reduce the cost of mobile thermal storage system. [ABSTRACT FROM AUTHOR]

Archaeology museums play an important role in protecting unearthed cultural relics from natural weathering. However, many of the unearthed relics are still suffering from deterioration or even ruin due to improper environmental control in archaeology museums. In this study, we demonstrate that the disregard of environmental control for relics and the imbalances of energy and mass across in situ air-relic-soil interfaces in pits are important causes for the deterioration of relics. Thus, individual environmental management strategies for visitor passages and relic preservation are proposed for the long-term preservation of unearthed relics. Experimental investigations using the test pit, with radiant panels for control of the environmental interfaces, validated these management strategies for the preservation and display of relics in archaeology museums. These results have significant implications for understanding the mechanism of relic deterioration and for formulating appropriate strategies to create sustainable environments for long-term preservation of unearthed relics in archaeology museums. [ABSTRACT FROM AUTHOR]

Increased artificial constructions due to urbanization absorb more solar radiation, making urban surface and air temperatures rise and affecting the energy performance of urban buildings and the human health. Many studies have reported that green facades and roofs, materials with high albedos can noticeably reduce building surface temperatures and cool the air in summer. However, little is known about the cooling effects and assessment of different mitigation strategies when they are adopted in a block scale. This study focuses on assessing and comparing the effects in the high-rise communities in Xi'an, China, which are a good representation of the city because they are composed of a high density of buildings, and they cover the majority of the current urban sprawl land. Simulations of three community prototypes through ENVI-met software were carried out in order to assess the mitigation techniques in terms of the ground surface, building surface, and vertical canopy air temperature decrease. The main techniques adopted were cool pavements, cool coating facades and roofs, green facades with ivy and green roofs with funkia and 15 cm substrates, and combinations of those. The statistical analysis results revealed that green roof can cool the roof more than the cool roof, while cool facade can cool the facade more than green facade. As to single mitigation strategy, the cool pavement have the most significant potential to decrease canopy air temperature. In general, the combination of different strategies had much more positive effects than single solution. These positive results indicate that the cooling strategies are urgently needed in the current urban construction to alleviate the urban heat island effect. Image 1 • The cooling potentials of various strategies and their combinations were compared in three high-rise community. • The performance of computational simulation software ENVI-met were tested by comparing measured data. • Decrease of land surface temperature, building surface temperature and canopy air temperature were achieved and evaluated. • The community characteristics affect the cooling effects. [ABSTRACT FROM AUTHOR]