Search Results (81)

To address hydrogen separation from hydrogen-blended natural gas, this work develops a mathematical model for a novel thermal-transpiration-effect-based circulating-flow gas separator according to the Navier–Stokes equations, following the joint modification with velocity-slip and temperature-jump boundary conditions, and a binary gas diffusion model derived from the Maxwell–Stefan equations. The model is then used to investigate the component transport and flow of a CH₄-H₂ mixture at the slip flow regime. The average hydrogen mole fraction in the component enrichment zone increases monotonically as the temperature difference increases, reaching 0.429 at a hot channel temperature of 400 K. An optimum inlet gas velocity of 0.93 m/s is identified to achieve the maximum average hydrogen mole fraction in the enrichment zone. In addition, decreasing the microchannel diameter enhances the hydrogen enrichment performance, with the average hydrogen mole fraction reaching 0.578 at a microchannel diameter of 1 μm whereas increasing the microchannel diameter improves the product gas flow rate, indicating a trade-off between separation performance and processing capacity. These insights provide guidance for understanding the component transport mechanism and for the preliminary design of this type of gas separator for hydrogen separation applications. Full article

In coastal residential areas, the combined effects of high temperature, high humidity, and weak wind conditions during summer intensify outdoor heat exposure and reduce pedestrian thermal comfort. To investigate the influence mechanisms of tree height and spatial layout on pedestrian-level thermal comfort, this study selected a typical residential community in Chengyang District, Qingdao, as the research site. Based on field meteorological observations, an ENVI-met model was established and validated. Using the existing composite greening scenario as the baseline, three tree layout types (row, cluster, and free layouts) and four height scenarios (4 m, 6 m, 8 m, and 10 m) were configured to quantitatively compare variations in physiological equivalent temperature (PET) under different planting schemes. The results indicate that tree configuration significantly affects summer thermal comfort. Its regulatory mechanism is governed not only by air temperature reduction but also by shortwave radiation interception, longwave radiation accumulation, and shading continuity. Although low-to-medium height trees can reduce local air temperature through transpiration, their limited canopy height and shading continuity restrict their ability to effectively attenuate direct shortwave radiation at pedestrian level, and in some cases may even increase mean radiant temperature (Tmrt) and PET. In contrast, 10 m tall trees arranged in row and cluster layouts can form continuous shaded cores, with the 10 m cluster layout demonstrating the best overall performance by significantly reducing Tmrt and PET. The free layout, characterized by dispersed canopies and fragmented shading, provides relatively limited thermal comfort improvement. The findings suggest that residential greening optimization should strengthen the coordination between tree height, canopy structure, and activity spaces. Tall trees should be prioritized in children’s play areas, elderly resting areas, residential entrances, main pedestrian pathways, and west-facing sun-exposed zones, while integrating building shadows and road orientation to create a continuous yet not overly enclosed shading network, thereby enhancing summer thermal adaptability in residential areas. Full article

Accurate estimation of crop development, water use and yield is essential for improving irrigation management in Mediterranean agricultural systems under increasing climate variability. However, many crop models require extensive input data and technical expertise, limiting their operational use by farmers and technicians. This study proposes an integrated agro-modelling framework that combines thermal time modelling, satellite-derived vegetation indices and simplified yield estimation approaches to assess maize phenology, crop water use and productivity under real farming conditions. A key component of the framework is the use of the Sentinel-2 Normalized Difference Vegetation Index (NDVI) time series to dynamically identify crop growth stages and derive actual basal crop coefficients (K_{cb act}), enabling the estimation of actual crop transpiration (T_{c act}). These NDVI-based estimates of actual K_cb and T_c were evaluated against simulations from the previously calibrated soil water balance model SIMDualKc. The results showed that the temporal profiles of the NDVI successfully captured the progression of the maize growth stages, although some discrepancies were observed during early stages of development due to the effects of the soil background and the satellite revisit intervals. An empirical relationship between the NDVI and K_cb was developed using multi-year observations and model simulations, improving crop transpiration estimation under field conditions. The NDVI-based approach adequately reproduced daily transpiration dynamics with good agreement with SIMDualKc simulations, yielding RMSE values of 0.11–0.69 mm d⁻¹ and errors generally below 21% of the mean transpiration rate. Seasonal transpiration estimates showed stronger agreement once canopy cover reached its maximum. The integrated AEZ–Stewart modelling framework incorporating NDVI-based transpiration estimations provided accurate yield predictions, with RMSE values of 1.7–2.3 t ha⁻¹ (representing less than 14% of the observed yields). Overall, the proposed framework demonstrates strong potential as a practical and scalable decision-support tool for irrigation management and yield assessment in Mediterranean maize systems. Its novelty lies in the operational integration of NDVI-derived crop development and transpiration estimates within a simplified yield modelling structure, offering a transferable approach applicable to other regions and cropping systems where satellite data are available. Full article

Evapotranspiration and crop coefficients are key variables for designing efficient irrigation strategies in tree crops, yet standard tabulated coefficients derived for mature, fully covering orchards often fail to represent the water use of young, high-density hazelnut systems. In recent years, updated crop coefficients for temperate fruit trees, including hazelnut, and transpiration-based models have been proposed, while several studies have successfully linked Vegetation Indices and thermal metrics to single and basal crop coefficients in vineyards, orchards and field crops. However, no information is available on the use of UAV-derived spectral and thermal indices to estimate crop coefficients in high-density hazelnut orchards. This study compares crop coefficients obtained from traditional approaches (the FAO56 single crop coefficient, a transpiration-based coefficient, and ground cover reduction factors) with coefficients estimated from UAV-derived Normalized Difference Water Index (NDWI) and Crop Water Stress Index (CWSI) in a subsurface-drip-irrigated hazelnut orchard (cv. Tonda Francescana^®) with two planting densities (625 and 1250 trees ha⁻¹) in central Italy. Multispectral and thermal UAV surveys carried out between 2021 and 2024 were used to derive canopy geometrical traits, ground cover, NDWI, and CWSI, while a local weather station provided reference evapotranspiration. Empirical relationships were calibrated between crop coefficients and ground cover, NDWI, and CWSI, and mid-season coefficients were applied to estimate daily crop evapotranspiration, which was then compared with the irrigation volumes supplied during the 2024 season. The standard FAO56 crop coefficient (Kc = 0.9) overestimated evapotranspiration, especially at the lower planting density, whereas ground cover-based reduction factors recalibrated for hazelnut and the transpiration-based coefficient provided estimates more consistent with the applied irrigation. UAV-based NDWI- and CWSI-derived crop coefficients produced mid-season values close to those obtained with the transpiration-based method for both planting densities, confirming that spectral and thermal information can effectively capture the combined effects of canopy development and water status. These results indicate that combining traditional methods with UAV-derived indices offers a flexible framework to refine crop coefficients in high-density hazelnut orchards and support more accurate and spatially explicit irrigation scheduling. Full article

The canopy temperature of winter jujube serves as a direct indicator of plant water status and transpiration efficiency, making its accurate prediction a critical prerequisite for effective water management and optimized growth conditions in greenhouse environments. This study developed a data-driven model to forecast canopy temperature. The model serially integrates a Long Short-Term Memory (LSTM) network and a Random Forest (RF) algorithm, leveraging their complementary strengths in capturing temporal dependencies and robust nonlinear fitting. A three-stage framework comprising temporal feature extraction, multi-source feature fusion, and direct prediction was implemented to enable reliable nowcasting. Data acquisition and preprocessing were tailored to the greenhouse environment, involving multi-sensor data and thermal imagery processed with Robust Principal Component Analysis (RPCA) for dimensionality reduction. Key environmental variables were selected through Spearman correlation analysis. Experimental results demonstrated that the proposed LSTM–RF model achieved superior performance, with a determination coefficient (R²) of 0.974, mean absolute error (MAE) of 0.844 °C, and root mean square error (RMSE) of 1.155 °C, outperforming benchmark models including standalone LSTM, RF, Transformer, and TimesNet. SHAP (SHapley Additive exPlanations)-based interpretability analysis further quantified the influence of key factors, including the “thermodynamic state of air” driver group and latent temporal features, offering actionable insights for irrigation management. The model establishes a reliable, interpretable foundation for real-time water stress monitoring and precision irrigation control in protected winter jujube production systems. Full article

Among the various active cooling methods, transpiration cooling currently attracts significant attention because of its efficient cooling effect and less coolant consumption, in applications such as the combustion chamber of the rockets, turbine blades, leading edges of a hypersonic vehicle, etc. With the development of advanced manufacturing technology and extremely high thermal protection demand, transpiration cooling has become more promising in the future thermal management of aerospace high-temperature components. Compared with other CFD simulations, the calculation of transpiration cooling is more complex, which couples heat transfer and fluid flow in porous media, phase change, etc. This work reviews the mathematical modeling of transpiration cooling in aerospace applications, which mainly includes four aspects: structural modeling of porous media, heat transfer modeling, turbulence modeling, and phase change modeling. For each aspect, the modeling details are provided and the advantage and limitations of each modeling method is summarized. Finally, this paper analyzes the current challenges and future research directions for transpiration cooling. Full article

Urban densification intensifies the heat island effect, threatening ecological security. Green spaces, as crucial spatial elements in regulating the urban thermal environment, remain poorly understood in terms of their morphological characteristics and regulatory mechanisms, with a lack of systematic quantification and recognition of diurnal variations. This study, focusing on Shanghai’s main urban area, constructs physiological, physical, and morphological variables of green spaces based on high-resolution remote sensing data and the MSPA landscape morphology analysis framework. By integrating machine learning models with the SHAP interpretation algorithm, it analyses the influence mechanism of green spaces on Land Surface Temperature (LST) and its non-linear characteristics from the perspective of diurnal variation. The results indicate the following: (1) Green spaces exhibit pronounced diurnal variation in LST influence. Daytime cooling is primarily driven by vegetation cover, vegetation activity, and surface albedo through evapotranspiration and shading; night-time cooling depends on soil moisture and green space spatial structure and is achieved via thermal storage-radiative heat dissipation and cold air transport. (2) Green space indicators exhibit pronounced nonlinearity and threshold effects on LST. Optimal cooling efficiency occurs under moderate vegetation activity and moderate humidity conditions, whereas extreme high humidity or high vegetation activity may induce heat retention effects. (3) Day–night thermal regulation mechanisms differ markedly. Daytime cooling primarily depends on vegetation transpiration and shading to suppress surface warming; night-time cooling is dominated by soil thermal storage release, longwave radiation dissipation, and ventilation transport, enabling cold air to diffuse across the city and establishing a stable, three-dimensional nocturnal cooling effect. This study systematically reveals the distinct diurnal cooling mechanisms of high-density urban green spaces, providing theoretical support for refined urban thermal environment management. Full article

Within the scope of this article is the presentation of a modelling and measurement approach for the effects of roof greenings and the application of the approach to evaluate the influence of roof greenings upon the thermal conditions inside a typical residential building. It is shown that overheating in summer can be reduced, and thermal comfort for inhabitants can be increased. The cooling is caused by the transpiration of plants and by the evaporation of water from the substrate. Other relevant physical effects are the shading of plants and the increase in the heat capacity of the building. In state-of-the-art buildings, a layer with a high insulating effect is incorporated into the envelope. This leads to the effect that a huge fraction of the cooling power is taken from the outside of the building and only a smaller part is taken from the inside. In order to mitigate this decoupling, a hydraulic connection between the greening and the interior of the building is introduced. To evaluate the effect of the inside cooling, the difference in the number of yearly hours with overheating in residential buildings is estimated. In addition, the reduction in energy demand for the climatisation of a typical residential building is calculated. The used methods are as follows: (1) Performance of laboratory and free field measurements. (2) Simulation of a typical residential building, using a validated approach. In summary, it can be said that green roofs, in particular with hydraulic connections, can significantly increase the interior thermal comfort and potentially reduce the energy required for air conditioning. Full article

The high-latitude cold regions of northeastern China present scarce thermal resources, exhibit a short frost-free period, and lack high-yielding maize (Zea mays L.) varieties suitable for dense planting. These factors have long constrained the realization of maize yield potential under dense planting conditions. This study investigated the effects of intercropping maize varieties with different growth periods on the photosynthetic performance, yield formation, and interspecific competition. The long-season varieties Zhengdan958 (ZD958) and Xianyu335 (XY335), which are representative of the region, were intercropped with the shorter-season variety Yinongyu10 (YNY10), six intercropping row ratios (6:6, 4:4, 2:2, 1:1, 0:1, and 1:0) were set, and monoculture plots (0:1 and 1:0) were used as the controls. The results indicated that as the row ratio decreased in the intercropped plots, the leaf area index, relative leaf chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate increased while the intercellular CO₂ concentration gradually decreased compared with those in the monoculture plots. Simultaneously, dry matter accumulation, allocation, transport efficiency, 100-kernel weight, number of kernels per ear, and grain yield progressively increased, reaching maximum values at a 1:1 intercropping row ratio. Conversely, YNY10 in the intercropped plots exhibited opposite trends in these parameters. The land equivalent ratios for all intercropped row ratios exceeded 1. During the 2023–2024 growing season, the composite population grain yield was significantly higher (p < 0.05) at an intercropping row ratio of 1:1 for ZD958 (4.11–4.26%) and XY335 (3.54–3.65%) compared with the monoculture treatments, demonstrating the strong yield advantage of intercropping. Furthermore, in the intercropping systems, ZD958 and XY335 exhibited positive aggressivity and a competitive ratio greater than 1, thus showing stronger competitive ability than YNY10. Moreover, the increased grain yield of ZD958 and XY335 effectively compensated for the ecological disadvantages of YNY10, thereby leveraging the synergistic effects of close planting and intercropping patterns to promote improvements in maize composite population productivity. Full article

Urban growth in hot, arid regions intensifies the urban heat island effect, making green spaces vital for climate mitigation. This research investigates the impact of public gardens on the surrounding urban thermal environment and on the mitigation of the urban heat island (UHI) in a hot arid region. This study selects an important public garden in Biskra, the “5 July 1962” Garden, as a case study of significance at the urban scale. To achieve research objectives, onsite measurement using a digital measurement device (5-in-1 Environmental Meter “Extech EN300”) and satellite remote sensing data from LANDSAT8 are employed, capturing summer measurements of key parameters and indices: Land Surface Temperature (LST), Air Temperature (AT), Relative Humidity (RH), Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI) and Normalized Difference Moisture Index (NDMI). The analysis and correlation of these indices with the LST values allow us to evaluate the zoning and distance impacts of the garden studied. Land surface temperature rises gradually from the garden outward, peaking in the North-East with the strongest heat island effect and remaining lower in the cooler, vegetation-rich South-West. The results reveal that air temperature is the primary driver of land surface temperature (72% impact), while relative humidity (17.3%), vegetation index (7.8%), moisture index (2.9%), and water index (1.7%) contribute to cooling, with vegetation and moisture reducing surface temperatures through shading, transpiration, and latent heat exchange. Full article

The subtropical transitional zone of China exhibits highly complex climatic conditions and diverse forest ecosystems, making it a critical region for understanding vegetation–water interactions. This study employed the Thermal Dissipation Probe (TDP) method to monitor sap flow in three typical forest types—evergreen broad-leaved forest, bamboo forest (Dendrocalamus latiflorus), and Chinese fir (Cunninghamia lanceolata)—in a subtropical transitional watershed in southern China. The aims were to quantify seasonal and annual variations in sap flow, to examine the effects of environmental drivers, and to analyze the hysteretic responses between sap flow and the drivers. The main findings were as follows: (1) bamboo forests exhibited significantly higher sap flow density than evergreen broad-leaved and fir forests at both annual and seasonal scales, though the overall transpiration of bamboo forests was lower than the others due to its limited sapwood area; (2) sap flow was positively correlated with potential evapotranspiration, solar radiation (Ra), vapor pressure deficit (VPD), air temperature, and soil temperature, while it was negatively correlated with relative humidity, atmospheric pressure, soil moisture, and precipitation; (3) Ra and VPD were identified as the dominant drivers of sap flow variations, with nonlinear increases that leveled off once thresholds were reached; (4) clear hysteresis patterns were observed, with sap flow peaks consistently lagging behind Ra but occurring earlier than VPD. These results advance our understanding of forest water-use strategies in the subtropical transitional zone and provide a scientific basis for improving water resource management and ecosystem sustainability in this region. Full article

Canopy conductance (G_c) is an important biological constant for quantifying the water vapor flux at the canopy-atmosphere interface, reflecting the coupling strength between crop transpiration and microclimate. To elucidate how mulching modulates G_c dynamics under varying environments, we measured the transpiration of maize based on thermal equilibrium method from 2020 and 2021, synchronously recording solar radiation (R_s), temperature (T), relative humidity (RH), and vapor pressure deficit (VPD) under no-mulching (NM), transparent film (TFM), black film (BM), and straw mulching (SM) treatments in the North China Plain. The results showed that in the near-surface microenvironment, at early stages (seedling-jointing), compared to the NM treatment, TFM and BM treatments unexpectedly reduced temperature by 0.1–1.1% while increasing humidity by 0.2–4.0%, lowering VPD by 0.7–15.5%, contradicting presumed warming effects. During tasseling-filling stages, both plastic films elevated temperature by 3.5–5.2%, decreased humidity by 5.2–6.9%, and sharply increased VPD by 23.4–27.6%, inducing heat-VPD coupling stress. Throughout the entire growth period, SM treatment resulted in an initial increase followed by a decrease in temperature, but the decrease in humidity and increase in VPD occurred earlier and smoothly compared to film mulching treatment in the near-surface microenvironment. All treatments increased average temperature but decreased average humidity in the near-ground microenvironment throughout growth stages, ultimately leading to an increase in average VPD. In addition, all treatments increased G_c at noon by 10.3–81.2%. Under different solar radiation conditions, TFM, BM, and SM treatments increased the reference conductance (G_cR) but did not always increase G_c sensitivity to VPD (m). We propose a specific mulching strategy: Using black or transparent plastic film mulching in arid/cold regions and straw mulching in high-temperature and drought-prone/rain-fed agricultural areas can reconcile the trade-off between microclimate optimization and physiological adaptation, advancing precision water management in arid-prone croplands. Full article

This review paper deals with Triply Periodic Minimal Surfaces (TPMS) and lattice structures as a new generation of heat exchangers. Especially, their manufacturing is becoming feasible with technological progress. While some intricate structures are fabricated, challenges persist concerning manufacturing limitations, cost-effectiveness, and performance under transient operating conditions. Studies reported that these complex geometries, such as diamond, gyroid, and hexagonal lattices, outperform traditional finned and porous materials in thermal management, particularly under forced and turbulent convection regimes. However, TPMS necessitates the optimization of geometric parameters such as cell size, porosity, and topology stretching. The complex geometries enhance uniform heat exchange and reduce thermal boundary layers. Moreover, the integration of high thermal conductivity materials (e.g., aluminum and silver) and advanced coolants (including nanofluids and ethylene glycol mixtures) further improves performance. However, the drawback of complex geometries, confirmed by both numerical and experimental investigations, is the critical trade-off between heat transfer performance and pressure drop. The potential of TPMS-based heatsinks transpires as a trend for next-generation thermal management systems, besides identifying key directions for future research, including design optimization, Multiphysics modeling, and practical implementation. Full article

The silkworm (Bombyx mori) is rich in germplasm resources, including thermotolerant strains that live in tropical/subtropical humid climates. In this study, two thermotolerant strains and one sensitive strain were used as materials, with the former exhibiting higher critical thermal maximum (CTmax) values. Under different temperature and humidity stresses, physiological and transcriptomic responses of the fifth instar larvae were compared. It was confirmed that high humidity exacerbates harmful effects only under high temperature conditions. Based on transcriptome and co-expression network analysis, 88 evolved thermoplastic genes (Evo_TPGs) and 1338 evolved non-plastic genes (Evo_non-PGs) were identified, which exhibited specific responses or expressions in the two thermotolerant strains. Eighteen of the Evo_TPGs encode cuticular proteins, 17 of which were specifically downregulated in the two thermotolerant strains after short-term exposure to 35 °C. This may promote cuticular transpiration to dissipate internal heat, thus compensating for the suppression of tracheal ventilation in hot and humid climates. For the Evo_non-PGs, most of the metabolic genes showed lower expression at background levels in the thermotolerant strains, while oxidative stress genes showed the opposite trend, suggesting that silkworms can enhance heat tolerance by suppressing metabolic rates and allocating more resources to overcome heat-induced oxidative damage. Furthermore, the heat resistance-related genes showed higher single nucleotide polymorphisms (SNPs) between resistant and sensitive strains compared to randomly selected genes, suggesting that they may have been subjected to natural selection. Through long-term adaptive evolution, thermotolerant silkworms may reduce their internal temperature by dynamically regulating cuticle respiration in response to high temperature and humidity, while allocating more energy to cope with and repair heat-induced damage. Overall, these findings provide insights into the evolution of heat-resistant adaptations to climate change in insects. Full article

Heat-exacerbated drought stress is becoming increasingly common in crop production systems, including peanuts, yet limited information exists on how peanut cultivars respond to this combined stress. While controlled environments allow for the isolation of these stress effects, their relevance to field conditions remains unclear. In this study, five Virginia-type peanut cultivars were evaluated under four treatments in a growth chamber environment, i.e., control, heat, drought, and combined heat and drought stress; and under two treatments in the field environment, i.e., rainfed control, and combined heat and drought stress using rainout shelters. The physiological traits assessed included stomatal conductance and transpiration rate, as well as leaf temperature difference. In both environments, combined heat and drought resulted in a significant decline in physiological performance compared to control conditions. On average, stomatal conductance decreased by 65% in the growth chamber and 21% in the field under combined heat and drought stress, while transpiration was reduced by 49% and 24%, respectively. In the growth chamber, leaf temperature difference increased by 40% under combined stress, whereas it was not statistically different under field conditions. Correlations of the physiological responses between growth chamber and field were stronger under combined stress conditions than under control conditions. Principal component analysis revealed clear genotypic separation based on gas exchange and thermal traits, with NC 20 and Sullivan consistently associated with higher stomatal conductance and transpiration under stress across environments, indicating greater physiological resilience, while Emery clustered with traits linked to stress susceptibility. These findings underscore the significant impacts of combined stress in peanut production and highlight the importance of evaluating cultivar responses under both controlled and field environments to guide crop improvement strategies. Full article