The thermal response performance of radiant terminals plays a crucial role in the optimal design and control of prefabricated radiant heating and cooling systems, directly affecting both thermal comfort and energy efficiency. Based on the concept of effective thermal resistance within a thermal resistance network, a simplified model for predicting the thermal response of radiant panels was developed. Subsequently, the definition and calculation method for thermal response time were established. The predicted dynamic surface temperatures and thermal response times showed good agreement with experimental data, with a root-mean-square error below 0.3 degrees C and a relative error within 5%, respectively. Furthermore, quantitative analysis indicated that the thermal response time gradually increased with increasing pipe spacing but the increment gradually diminished, and decreased nearly linearly with increasing pipe diameter. Additionally, the thermal response time initially decreased and then increased with increasing thickness of the heat distribution plate, creating an inflection point and the minimum value at 0.3 mm-0.4 mm, while it increased greatly with increasing surface layer thickness. The proposed thermal response prediction model can support the design of radiant panels with improved thermal response performance and offer a feasible method for precise dynamic control of surface temperature of radiant terminals in engineering applications.

Evaporative cooling (EC) has gained increasing recognition as a low-carbon and energy-efficient solution to meet the rising urban cooling demands under climate stress. However, conventional regenerative evaporative cooling (REC) systems suffer from performance bottlenecks due to near-saturation within airflow channels and limited flexibility in tuning multiple design parameters. Additionally, existing studies often overlook the intricate interactions between geometric and operational parameters, relying instead on single-variable optimization strategies. To address these challenges, this study proposes a novel perforated counter-flow regenerative evaporative cooler (PCF-REC) that enables regulation of variable thermodynamic parameters for performance enhancement. A dimensionless nonlinear model is first developed and solved using the Newton iteration method. Validated numerical data are subsequently employed to train an artificial neural network (ANN) surrogate model, enabling rapid performance prediction with a correlation coefficient exceeding 0.99851 and a mean squared error below 1.28 x 10(-3). Building on this, a multi-objective optimization framework is constructed by integrating the ANN with the enhanced non-dominated sorting genetic algorithm II (NSGA-II) that incorporates Sobol sampling, dynamic mutation, and K-means clustering strategies. This framework aims to balance multiple conflicting performance parameters and employs analysis of variance to quantify and consider 7-13 significant variables. The final Pareto-optimal solutions, selected through the entropy-weighted TOPSIS method, yield maximum individual improvements of 71.68 % in COP, 104.91 % in dew-point efficiency, and 88.42 % in water consumption reduction compared to the baseline case (L = 0.6 m, h(h) = 0.25 mm, gamma = 0.6, T-in = 31.2.C, omega(in) = 10.15 g/kg). This work establishes a scalable and efficient digital twin-based design optimization approach, offering new insights for next-generation REC system development.

Traditional ventilation mode for dust removal has obvious shortcomings, such as low efficiency, high energy consumption, and is particularly ineffective in dealing with the instantaneous high-intensity dust pollution caused by blasting construction in underground tunnel. To meet the control requirements for such pollution, this study develops one innovative ultrasonic spray system, including ultrasonic spray generator and water and gas source power unit, which is coupled with forced ventilation to form an effective solution for removing dust pollution during underground tunnel blasting construction. Meanwhile, as to the high-intensity dust pollution caused by blasting construction in large-section tunnel, the effectiveness of this solution in controlling blasting construction dust pollution and its operation strategy are experimentally analyzed. The result indicates that this solution significantly improves the agglomeration effect between the fine liquid droplets and dust particles, and the droplets can remain suspended in the air for a long time, effectively inhibiting the dust diffusion. Moreover, the innovative ultrasonic spray system can form a great droplet field, simultaneously achieving the dual effects of blocking the long-distance spread of dust and rapid dust removal. The dust removal rate for PM10 and PM2.5 reaches 95.56% and 76%, respectively. Additionally, the reasonable operation strategy of the innovative ultrasonic spray system is to start running before the blasting construction in tunnel.

Early-age shrinkage is a critical factor governing the dimensional stability and cracking susceptibility of ultra-high-performance concrete (UHPC). However, accurate prediction of UHPC shrinkage remains challenging due to the strong nonlinear interactions among mixture parameters, curing conditions, and hydration-induced internal moisture evolution, particularly when only limited experimental data are available. In this study, a systematic experimental program was conducted to investigate the influence of the binder-to-sand ratio, water-to-binder ratio, polypropylene fiber dosage, and curing environment on both early drying shrinkage and autogenous shrinkage of UHPC. Based on the experimental results, a structured dataset covering all shrinkage test data was constructed to support data-driven modeling. To improve prediction reliability under small-sample conditions, a Bayesian-optimized Extreme Gradient Boosting (BO-XGBoost) framework was developed and benchmarked against several conventional machine learning models, including Backpropagation Neural Networks (BPNNs), Random Forest (RF), and Support Vector Machines (SVMs). Shrinkage test data from other literature validated the prediction accuracy of this model, demonstrating its rationality and practicality. In addition, the Shapley Additive Explanations (SHAP) method was employed to quantitatively interpret the contribution and interaction mechanisms of key variables affecting shrinkage behavior. The results show that the BO-XGBoost model achieves the highest prediction accuracy and stability among the evaluated algorithms. SHAP analysis further reveals that curing age and curing environment dominate drying shrinkage, whereas autogenous shrinkage is primarily governed by the curing age and water-to-binder ratio. The interaction analysis also identifies the coupled effects between low water-to-binder ratio and extended curing age. The proposed framework not only improves prediction robustness for UHPC shrinkage under limited data conditions but also provides interpretable insights into the mechanisms governing early-age deformation. These findings offer a data-driven basis for optimizing UHPC mixture design and mitigating early-age cracking risks in engineering applications.

Lithium-ion batteries are widely deployed in electric vehicles, yet their performance and safety are strongly constrained by elevated operating temperatures, which may accelerate degradation and, in extreme cases, trigger thermal runaway. This study numerically investigates the thermal performance of a Tesla valve-based cold plate for battery thermal management, with the aim of enhancing heat dissipation efficiency through multi-parameter collaborative optimization. An initial screening is conducted using orthogonal experimental design to evaluate the effects of shunt angle (30 degrees-50 degrees), number of unit pairs (3-7), channel asymmetry ratio (0-0.5), and branch channel width (2-4 mm) on maximum temperature difference and pressure drop. The results indicate that the number of unit pairs and the asymmetry ratio are the dominant factors governing thermal and hydraulic performance. To further quantify these relationships, an optimal Latin hypercube sampling strategy is combined with Kriging surrogate modeling to construct response surfaces linking design variables to system performance. Subsequently, a multi-objective optimization based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II) genetic algorithm is performed to simultaneously minimize temperature non-uniformity and pressure drop, yielding a Pareto-optimal solution set. The optimal configuration corresponds to a shunt angle of 30 degrees, 7 unit pairs, a zero asymmetry ratio, and a branch channel width of 4 mm. Compared with the baseline design, this configuration reduces the maximum temperature difference by 9.13% and the average temperature difference by 15.03%, while also decreasing pressure drop by 0.36%.

Aiming to improve thermal performance and decrease cooling energy demand in hot-climate zones, this research seeks to create and assess an integrated building-envelope approach. It focuses on energy-efficient buildings in the Middle East and how phase-change materials (PCMs), reflective roof coatings, and shade from photovoltaic (PV) panels work together as passive cooling solutions. In 2023, the world’s emissions of greenhouse gases (GHG) reached 41.6 billion metric tons of CO₂ equivalent, with a significant portion of those emissions coming from household energy use. As a result, this study investigates passive cooling methods that reduce operating energy consumption while minimizing heat absorption and related emissions. This study compares the effectiveness of PCMs and reflective coatings in conjunction with PV-based roof shading, in contrast to earlier research that examined only one or the other. We used ANSYS FLUENT to perform numerical simulations and to compare our findings with experimental data from published studies. Research shows that reflective coatings and PCM integration both reduce roof heat input by 76.57% and 56.70%, respectively, while PV roof shading achieves the greatest reduction of 92.69%. The enhanced microclimate efficiency is shown by the 84.12% decrease achieved by the combined PCM-reflective coating system. Reflective coating achieved a 4-day reduction in CO₂ emissions of 5.767 kg, a PCM integration reduction of 3.797 kg, a PV shading reduction of 0.671 kg, and an overall system reduction of 2.114 kg. For hot-climate building energy regulations and retrofit strategies, these findings provide quantitative proof. Achieving long-term emission-reduction objectives and promoting climate-resilient urban design can be achieved through integrated passive cooling solutions.

Under the dual effects of outdoor ozone (O3) pollution intrusion and indoor pollution source generation, the formation mechanism, characterization, prevention and control methods of indoor O3 pollution have been one important scientific issue in the field of indoor air quality (IAQ) research. To have a systematic understanding of this issue, this study summarizes the trends and hotspots of indoor ozone pollution research, systematically reviews the sources, hazards, and characteristics of indoor ozone pollution and analyzes the different prevention and control methods of indoor ozone pollution, including active and passive ozone removal technologies. On this basis, the engineering applications of indoor ozone pollution prevention and control methods in residential, educational, and commercial scenarios are further discussed. Furthermore, the development trends and technical challenges of indoor ozone pollution prevention and control are pointed out. The development of efficient and low-cost ozone removal materials, the optimization of intelligent monitoring systems, and integrated pollution control strategies adapted to climate change should be focused on in the future, in order to provide healthier and safer indoor air environment. The insights could inform designers, engineers, and policymakers seeking to integrate ozone-responsive strategies into building ventilation, material selection, IAQ management, and air-cleaning systems.

Under the condition of adopting the existing ventilation system, the problem of high air humidity is common in urban utility tunnel, especially in the area of outdoor high air humidity, the risk of condensation on the inner wall of urban utility tunnel is very high, which may cause corrosion and operation safety problems of the equipment inside the urban utility tunnel. Aiming at how to effectively control the internal thermal environment and anti-condensation risk of urban utility tunnel in areas with outdoor high air humidity, this study selected 8 urban utility tunnels in Chengdu city as the research object, conducted field tests on their internal air temperature and humidity, and analyzed the condensation risk characteristics. Meanwhile, the optimization strategy of ventilation air distribution suitable for the urban utility tunnel in the area with high outdoor air humidity was established. In addition, under the condition of combination of ventilation and dehumidifier, the reasonable arrangement and supply air parameters of dehumidifier were determined. The goal of effectively controlling thermal environment of urban utility tunnel and preventing its condensation risk can be achieved for the condition of combination of ventilation air distribution optimization strategy and reasonable dehumidifier arrangement and supply air parameters.

The efficiency of the thermal management system is crucial for electric vehicles (EVs). This study proposes a novel dual electronic expansion valve (EXV1 and EXV2) sub-area control strategy to improve the heating performance of the CO2 heat pump (HP) system in low temperatures. The study analyzed the impact of the EXV1 opening on the system's operating parameters. A comparison assessment was subsequently conducted on the heating capacity, COP, and gas cooler (GC) outlet air temperature before and after optimizing the control strategy at -20 degrees C. A method for evaluating performance under heating and refrigerating conditions was proposed and validated using a real vehicle in the environmental chamber. Additionally, the study compared the energy consumption differences between the CO2 and R134a systems at -20 degrees C. The effects of these two systems on vehicle range at various temperatures were also compared using the WLTC (World-Light-Vehicle-Test-Cycle). The results show that when the EXV1 opening is exceeds 300 steps (30 %), it has less influence on the operating parameters of the system components. Furthermore, at -20 degrees C, the optimized control strategy improved the average heating capacity, and COP by 11.6 %, and 9.8 %, respectively, and the GC average outlet air temperature by 8.2 degrees C. The target thermal management system can meet the heating and refrigerating demands. The minimum temperature of the outlet air can be 5.24 degrees C at 40 degrees C and the maximum temperature of the outlet air can be 57.16 degrees C at -15 degrees C. The CO2 HP system saves about 34.7 % of energy consumption compared with the R134a system at -20 degrees C. Under the WLTC, the range of the CO2 HP system is improved by 9.3 % and 16.6 % compared to the R134a system at -20 degrees C and -10 degrees C, respectively.

The radiant heating and cooling (RHC) system is one of the important air-conditioning methods that simultaneously achieves indoor thermal comfort and building energy efficiency. It is characterized by utilizing low-grade energy sources to provide low-temperature heating and high-temperature cooling, playing a significant role in promoting the development of green and low-carbon buildings. This study firstly introduces the typical heat transfer calculation methods of the RHC system and analyzes the surface heat transfer coefficients of radiant heating and cooling. Subsequently, the factors affecting the thermal performance of the RHC system are discussed from two aspects: relevant physical property parameters and flow channel structures. Finally, the control strategies of RHC systems are summarized to address issues such as condensation, overheating, and long response times. And several conclusive findings are presented that are worthy of further investigation in the future.

his study compares two end-cooling systems, convective-radiant combined cooling (FR+FC) and fan coil convection (FC), through continuous experimental investigations, focusing on the impact of window-to-wall ratio (WWR) on indoor thermal comfort, temperature distribution, humidity, and energy consumption. Results show that increasing WWR amplifies indoor temperature fluctuations. While the overall predicted mean vote (PMV) remains within the Level-II comfort range (-1.0 to +1.0), the FC system exhibits pronounced local PMV gradients near west-facing windows, especially at 80% WWR, where transient PMV reaches 1.26 close to the window, 0.89 higher than at the room center. In contrast, the FR+FC system significantly reduces spatial PMV variations, maintaining local PMV within acceptable limits for most of the day. Energy analysis reveals that FC energy consumption rises with WWR, increasing by 7.11% from 40% to 80% WWR, whereas FR+FC energy use decreases by 29.26% over the same range, demonstrating its superior handling of radiant loads. Furthermore, the convective-radiant system exhibits a high average hourly cooling performance coefficient. These findings indicate that FR+FC systems provide better thermal comfort and energy efficiency in high-WWR spaces, making them particularly suitable for summer operation in window-intensive buildings.

The vacuum external undulator is a critical component in synchrotron radiation light sources and free-electron lasers, featuring a small-aperture vacuum chamber that precisely guides the electron beam through the undulator. The uniformity of the wall thickness of the vacuum chamber significantly influences its beam quality. However, accurately measuring the thickness uniformity of long and narrow vacuum chambers poses significant challenges. A testing system utilizing a specific magnetic field has been developed to measure the wall thickness uniformity of vacuum chambers. The system synchronously measures the voltage between the permanent magnet and the iron ball, as well as the distance between the vacuum chamber’s outer surface and the permanent magnet. By calibrating the relationship between voltage and the iron ball’s height variation, the system enables rapid and accurate evaluation of wall thickness uniformity along the beam direction. Successful tests are conducted on an aluminum alloy vacuum chamber with a length of 4 meters and an inner diameter of 8 mm.

Evaporative cooling technology, with its low cost and near-zero carbon emissions, is a promising alternative for refrigeration. However, traditional regenerative evaporative cooler (REC) faces the limitation caused by the contradiction between efficiency and cooling capacity within fixed structure. Therefore, an improved perforated counter-flow regenerative evaporative cooler (PCF-REC) is proposed, aiming to explore the performance enhancement mechanisms of customized perforations in the complex process of heat and mass transfer. Based on Newton iteration calculation, this study establishes a matching prediction model using MATLAB programming and validates it against experimental data, with a relative error within 3.28 %. Subsequently, comparative studies are conducted on REC and four different PCF-RECs. The results demonstrate that PCF-RECs can simultaneously enhance the dew-point efficiency and cooling capacity under low air supply ratio (gamma). The average dew-point efficiency and cooling capacity can be amplified by 13.8 % and 11.40 W/m2, respectively. Additionally, a new dimensionless near-saturation evaluation index is introduced, reporting that an increase in channel length would trigger the premature occurrence of near-saturation. The trade-off between geometric and operational parameters is further revealed through the study of multiple along-channel parameters, including temperature, humidity, evaporation rate, driving force and water consumption. The perforations tend to be designed at the left end of the channel, which ingeniously corresponds to a high-flow, high-temperature localized environment. When gamma =0.4, PCF-REC4 achieves a maximum evaporation rate of 0.257 kg/m2 & sdot;h, a 5.76 % improvement over REC. This perforated regenerative design enables targeted regulation of channel thermal and humidity conditions, providing a novel performance enhancement strategy.

Prefabricated ceiling radiant panel is one type of efficient and lightweight radiant heating and cooling terminal, which has been widely used in many commercial and residential buildings. The surface temperature distribution of radiant terminal is a crucial factor that affects the local thermal discomfort for heating and the surface condensation risk for cooling. However, the existing research on surface temperature distribution lacked a correlation with the average surface temperature prediction model, which was not convenient for guiding the design and control of radiant heating and cooling systems. Therefore, this paper proposed a new simplified model of radiant panels, and the calculation errors of heat transfer and average surface temperature were within +/- 5 % and +/- 1 %, respectively. Furthermore, a surface temperature distribution prediction model was established, and the definition of surface temperature uniformity was also determined through derivation. The calculation results indicated that the root mean square error between the predicted surface temperatures at each measurement point and experimental values was 0.8 degrees C for heating and 0.4 degrees C for cooling, and the corresponding relative errors of surface temperature uniformity were 5.7 % and 8.9 %. Finally, the effects of water supply temperature, water mass flow rate, pipe spacing, pipe diameter and thickness of heat distribution plate on the surface temperature distribution were quantitatively analyzed. The results showed that the water mass flow rate, pipe spacing (more than 150 mm) and the thickness of the heat distribution plate clearly influenced the surface temperature uniformity.

This study focused on the effect of glass structures of modern architecture on the indoor thermal environment during summer. In particular, this study examined how solar radiation significantly altered people’s thermal sensations. Laboratory tests on convection–radiation air conditioning systems were conducted, encompassing 12 different scenarios, including diverse indoor open areas, terminal forms, and levels of solar radiation. These tests aimed to explore the physiological and psychological responses of the human body to solar radiation penetrating through windows into the inner room. During the experiments, the participants’ subjective thermal sensations and thermal comfort were recorded, along with continuous monitoring of their physiological and environmental parameters. Results showed that solar radiation significantly increased local skin temperature, with a maximum rise of 2.15 °C. Operative temperature is a reliable indicator of human skin temperature and thermal sensation vote (TSV). This study established two models that could predict the skin temperature of individuals indoors through operative temperature under conditions without or with solar radiation, and identified sensitive ranges of operative temperature for both models, to be specific, 26.32 °C to 28.43 °C and 28.51 °C to 34.11 °C, respectively. Furthermore, this study established the relationship between skin temperature and TSV under conditions with and without solar radiation. The results indicate that solar radiation enhances the human body’s adaptability to indoor environmental parameters; a convection–radiation system (FC+RF) could be used to optimize indoor thermal control under solar radiation, achieving more stable environmental temperatures and improved indoor comfort.

In this study, the thermal comfort and energy consumption of two different terminal units when combined with three different water supply temperatures were studied. Results showed that convection–radiation combined cooling terminals can increase the water supply temperature under the same thermal comfort level compared with convection cooling terminals. When the water supply temperature was fixed at 11 °C, the energy consumption of convection–radiation combined cooling terminals was 9.1

This study investigates the operational characteristics of a convective-radiative cooling system in hot summer and cold winter regions. It focuses on analyzing how the system's structural design and operational strategy affect energy consumption and indoor comfort. Laboratory tests were conducted on two types of dry-wet combined convective-radiative cooling systems (System 1 and System 2). A comprehensive analysis was performed on the effects of different water supply temperatures and operation modes on indoor environmental conditions, energy consumption, and comfort. Findings highlight the significance of terminal structures in improving the efficiency of these systems. Results show that System 1 typically maintains room temperatures about 1 degrees C higher than System 2, which benefits from enhanced stability due to its concrete filling layer. The study also notes a possible hot water mixing issue in System 1's buffer tank. Transmission and distribution system energy for these systems ranges from 12.5 % to 23.3 %, increasing with water temperature. Both systems can reduce energy consumption by 45.9 %-49.2 % in different modes, and increasing the water supply temperature to the main unit can further decrease energy use by 6.7 %-29.5 %. Continuous operation ensures stable Predicted Mean Vote (PMV) levels, while intermittent operation allows the PMV to quickly reach the recommended range. Both systems demonstrate low sensitivity to changes in supply water temperature in terms of operational effectiveness. This study recommends using intermittent operation with high-temperature water cooling, starting system 1-2 h before use for an optimal balance between energy efficiency and comfort. This provides a comprehensive perspective for enhancing convective-radiative systems cooling and offers practical suggestions for their design and operational strategies.

[目的]从时间空间角度量化分析新型雪茄烟叶晾棚中温、湿度状况,并评价其适宜程度.[方法]测定全天内各时段新型晾棚中不同位点处空气温度和相对湿度(RH),利用计算流体力学(computational fluid dynamics,CFD)软件构建新型晾棚的物理模型,并模拟晾棚内温度场、湿度场,进而量化分析棚内不同温湿度区间的空间分布、时间和体积.[结果](1)建立的CFD温度、湿度场模型误差小于7％,拟合效果良好.(2)棚内温湿度总体处于较适宜雪茄烟叶调制的状态,全天各时段的均温在22℃～35℃间、RH均值基本在65％～90％之间.(3)0:00—8:00的挂烟区中有40％～60％的空间因RH>90％处于不宜调制状态,10:00—0:00(次日)挂烟区中90％以上区域达到温湿度较适宜状态,其中在10:00—12:00和20:00—22:00处于温湿度最佳状态.(4)夜间RH偏大和下午RH偏低是影响棚内调制适宜区范围大小的限制性因素.[结论]CFD技术适用于雪茄烟晾棚的温、湿度状况量化分析研究.新型晾棚的工作性能总体良好,棚内温湿度波动明显小于棚外,利于雪茄调制;挂烟区80％～100％的空间在一天内约有20 h处于烟叶调制的较适宜温湿度状态,其中约有3 h处于适宜状态.新型晾棚的主要优化方向是提高RH适宜度.