One of the primary tasks in the regular maintenance of underground shelters is to ensure proper internal environmental conditions, as humidity is a major obstacle for sustainable use. This study aimed to develop a passive method that combined hygroscopic materials with natural ventilation to improve the indoor humidity of underground shelters. Using a coupled model that included heat and moisture transfer in hygroscopic materials, dynamic heat and moisture transfer in underground buildings, and multizone airflow, this study analyzed the moisture buffering performance of hygroscopic materials under different ventilation conditions. This study also introduces the annual moisture buffering effect as an indicator of humidity stability, which allows a more comprehensive reflection of the material's overall performance in responding to repeated humidity fluctuations in real-world environments, making it particularly suitable for engineering structures such as underground shelters. Simulation results showed that straw-based boards exhibited 2.4–3.1 times higher moisture buffering effect than inorganic materials. Passive measures combining natural ventilation with hygroscopic materials could fully meet humidity requirements in severely cold, cold, hot summer and cold winter, and temperate zones, but were insufficient to fully resolve the humidity problems in the hot summer and warm winter zone.

District heating system is an essential energy infrastructure. Due to the harsh working environment, sensors in district heating substations are prone to faults, which will mislead the control strategies of substations. We propose an online fault detection and diagnosis (FDD) method for sensors in substations. The proposed method establishes a Sequence-to-Sequence Prediction Model based on Long Short-Term Memory network with Spatial-Temporal Attention (abbreviated as STALSTM-seq2seq model) for each target sensor. The model can learn normal and evolving data patterns from historical time series of sensors and predict current sensor observation. Then, an adaptive threshold selection algorithm is used to autonomously determine current anomaly threshold based on the prediction error vector of the model. If the prediction error exceeds the anomaly threshold, the sensor malfunctions. Otherwise, the sensor operates normally. Through a comprehensive case study, we demonstrate that the adaptive threshold selection algorithm can fully utilize the forecasting ability of the STALSTM-seq2seq model, and thereby ensure the accuracy of sensor FDD. Overall, the online sensor FDD method achieves an average F1 score of 0.8473. The research shows that the proposed method provides an effective and robust solution to timely and accurately identify sensor faults for district heating substations.

This study introduces a metamaterial microwave absorber (MMA)-lightweight envelope (LE), which is an innovative solution for integrating electromagnetic and infrared-compatible camouflage technologies into building structures. Specifically, MMA-LE incorporates a MMA into building designs for microwave/infrared-compatible camouflage. This study evaluated the microwave absorption performance, infrared camouflage capabilities, and energy-saving effects of MMA-LEs by analyzing the microwave absorption characteristics using the impedance matching theory and simulation software. A coupled heat and moisture transfer model was used to assess isothermal moisture absorption, heat transfer coefficients, and annual heating/cooling loads. Furthermore, infrared imaging tests verified the effectiveness of the camouflage. Two MMA-LE designs (single and double absorber layers) achieve over 90 % microwave absorption in the 3.2-11.2 GHz and 1.85-12.67 GHz frequency ranges with relative bandwidths of 111.1 % and 149 %, respectively, and with polarization insensitivity. Moreover, the MMA-LE enhanced the wall heat and moisture transfer performance, reduced the relative humidity, and reduced the thermal load under Guangzhou's climate conditions. However, despite the improved moisture resistance, the double-layer MMA-LE increased the envelope moisture content, thus reducing thermal insulation. In addition, the limited absorbency of the substrate material results in a modest increase in the dielectric constant, consequently decreasing the resonant frequency of the hybrid structure compared to dry samples. Nevertheless, the thermal insulation properties of MMA-LEs effectively insulate the internal heat sources, achieving optimal infrared camouflage. In conclusion, this study provides a novel solution for microwave-infrared-compatible camouflage in building applications, offering significant theoretical and practical value.

Maintaining an ultralow dew point is essential for the operation of transonic cryogenic wind tunnels, as it significantly influences aerodynamic characteristics. Even in extremely dry conditions, minute quantities of frost can form on cryogenic surfaces, which compromises data quality. Conducting experiments on frost desublimation in such ultralow dew point environments poses significant challenges due to the demanding experimental conditions. Therefore, this study aimed to explore the desublimation characteristics of cryogenic surfaces in ultralow dew point environments and to address the challenges of experimental investigations under such extreme conditions. Initially, the study experimentally investigated frost formation by assessing the impact of various factors, such as temperature and water vapor content. It was observed that the type of frost formed depended on the water vapor content, and altering the surface temperature influenced the growth region of the frost crystals. The irregular growth of the frost layer on low-temperature surfaces was evident, as temperature markedly affected both the growth rate and the diffusion direction of frost formation. Moreover, the process of trace water frost formation was simulated using a dispersive multiphase model, predicting the frost layer's thickness. The numerical results suggest that the frost layer is micrometers thick, with a minimum thickness of 20 mu m. A nonlinear relationship was identified between frost growth and dew point level. This research lays the groundwork for a deeper understanding of desublimation characteristics in ultralow dew point environments and for further investigation of low-temperature heat and mass transfer phenomena.

Indoor moisture is a crucial aspect of the environment in naturally ventilated underground shelters that remain unattended for long periods of time. The objective of this study was to investigate the impact of natural ventilation on the indoor temperature and humidity of underground shelters using a multi-zone airflow simulation and thereby evaluate the ability of natural ventilation to maintain the indoor environment of shelters in various climates in China. Firstly, a multi-zone airflow model was coupled with the dynamic heat transfer in an underground shelter to simulate the natural ventilation rate and indoor environment. The accuracy of this coupled simulation was subsequently validated using the data measured at an actual shelter. Next, the verified simulation method was applied to analyse the seasonal fluctuations in the natural ventilation rate of underground shelters in the various climates in China; these results were applied to determine the corresponding annual variations in the indoor temperature and humidity. The analysed results show that the relationship between the ventilation rate and indoor humidity level is dependent on both season and climate, and that the influence of the ventilation rate can be negative during summer, especially in wet climate zone. Finally, these findings were evaluated to provide guidelines for regulating natural ventilation according to climate, informing the management of unattended shelters in China.

Polycarbonate panels (PC panels) are state-of-the-art transparent insulating materials widely used in the construction industry due to their cavity structure, which provides exceptional thermal insulation and optimal optical performance. However, the inherent anisotropy of the three-dimensional cavity structure complicates radiative transfer and requires consideration of both azimuth and zenith angles in optical performance evaluation. This aspect has received limited attention in existing research. This study aims to accurately characterize the optical performance of PC panels through numerical simulations. A three-dimensional radiative transfer model based on the discrete ordinate radiation model is developed to solve the radiation transfer equation. The model's independency regarding mesh division, angular discretization, and accuracy is validated. The effects of incidence angle, geometric parameters, and optical properties of PC panels on optical performance are analyzed. The findings reveal a strong correlation between transmittance and absorption with variations in incident zenith and azimuth angles. The transmittance exhibits a consistent monotonic variation expressible as a rational bifunction. Notably, absorption peaks occur within specific solid angle ranges, with increased structural complexity resulting in heightened absorption and greater uncertainty. For conventional PC materials, maximum transmittance ranges from 46.9 % to 73 %, while maximum absorption ranges from 2.3 % to 13.5 %. Increasing absorption coefficients, refractive index, and surface scattering coefficients nonlinearly decrease transmittance while increasing absorption. Additionally, deviations in transmittance and absorption with azimuth angle amplify with an increase in non-horizontal structures. Sensitivity analysis indicates a significant influence of zenith angle on transmittance, and absorption coefficient predominantly affects absorption.

The mismatch between solar radiation resources and building heating demand on a seasonal scale makes cross-seasonal heat storage a crucial technology, especially for plateau areas. Utilizing phase change materials with high energy density and stable heat output effectively improves energy storage efficiency. This study integrates cascaded phase change with a cross-seasonal heat storage system aimed at achieving low-carbon heating. The simulation analyzes heat distribution and temperature changes from the heat storage system to the heating terminal. The results indicate that although the solar collectors operate for 26.3% of the total heat storage and heating period, the cumulative heat stored is 45.4% higher than the total heating load. Heat transferred by the cross-seasonal heat storage system accounts for up to 61.2% of the total heating load. Therefore, the system reduces fuel consumption by 77.6% compared to conventional fossil fuel heating systems. Moreover, radiant floor heating terminals, with a wide range of operating temperatures, match well with cascaded phase change heat storage and can reduce operation time by 19.5% and heat demand by 5.2% compared to conventional radiators. In addition to demonstrating the feasibility of applying cascaded phase change technology in cross-seasonal heat storage heating, this study reveals the lifecycle sustainability due to the shortened heat storage period. The configuration, parameters, and simulation results provide a reference basis for system application and design.

This study investigated the spatial and temporal variations of PM2.5 concentrations in Harbin, China, under the influence of meteorological parameters and gaseous pollutants. The complex relationship between meteorological parameters and pollutants was explored using Pearson correlation analysis and interaction effect analysis. Using the correlation analysis and interaction analysis methods, four mechanical learning models, PCC-Is-CNN, PCC-Is-LSTM, PCC-Is-CNN-LSTM and PCC-Is-BP neural network, were developed for predicting PM2.5 concentration in different time scales by combining the long-term and short-term data with the basic mechanical learning models. The results show that the PCC-Is-CNN-LSTM model has superior prediction performance, especially when integrating short-term and long-term historical data. Meanwhile, applying the model to cities in other climatic zones, the results show that the model performs well in the Dwa climatic zone, while the prediction performance is lower in the CWa climatic zone. This suggests that although the model is well adapted in regions with a similar climate to Harbin, model performance may be limited in areas with complex climatic conditions and diverse pollutant sources. This study emphasizes the importance of considering meteorological and pollutant interactions to improve the accuracy of PM2.5 predictions, providing valuable insights into air quality management in cold regions.

Within the frigid and elevated landscape of the Tibet plateau, the attachment of sunspaces to buildings can provide a pivotal opportunity to enhance the thermal environment and curtail energy expenditure. With the goal of assessing the annual energy-saving potential of a sunspace that employs passive soil heat storage in a plateau region, this study employs the Computational Fluid Dynamics (CFD) method. To facilitate a comprehensive analysis of the system, the study develops a numerical model that incorporates the RNG k-e turbulence model and the discrete ordinate (DO) radiation model, which takes into account the absorption and reflection phenomenon of solar-band and thermal-band radiation. The study's results demonstrate that soil, serving as a thermal inertia, exerts a positive influence on maintaining the temperature within the sunspace, consequently reducing wall heat flux. In summary, the sunspace in question exhibits an annual average heat load of 87 kWh/m2, and achieves a remarkable 45.78% energy saving. These findings provide valuable insights for the design of energy-efficient buildings, offering a complete CFD approach that utilizes solar radiation and soil-based sunspaces to effectively reduce energy consumption and enhance sustainability.

以某地下工程的水环热泵系统为例,从环路水量控制的角度优化水环热泵系统的控制模式,提高节能效果.利用Trnsys软件对该工程的水环热泵系统进行建模和运行模拟,对定流量、变流量、利用BP神经网络和PSO算法优化的变流量方案模式下的能耗情况进行对比分析.结果表明:与定流量系统相比,变流量系统的节能率为13.3%,利用BP神经网络和PSO算法优化的变流量系统的节能率为19.5%,优化后的方案比优化前的方案节能7.2%.

Cooling towers and internal reservoirs are two conventional heat transfer methods used in protection engineering. However, they have the drawbacks of easy exposure and limited capacity. Although the traditional ground source heat pump system can become a new heat transfer method, its high installation cost and space requirements are obstacles to the development of this technology. To address this problem, the heat exchange pipe of the ground source heat pump system being directly laid in the tunnel lining was proposed in this study. A heat transfer performance test platform for a lined buried pipe heat exchanger based on an arch tunnel was built, and the water velocity, wind velocity, and temperature of each measuring point were recorded under appropriate working conditions. The effects of the inlet water temperature, inlet water velocity, ventilation velocity, and initial soil temperature on the heat transfer performance were analyzed. The results have shown that the heat transfer performance of the tunnel reached its maximum when system operation commenced and then decreased gradually with time, and the rate of decrease gradually slowed. Along the radial direction of the tunnel, the shorter the distance to the buried heat exchanger, the greater the increase in soil temperature, and the shorter the time for the temperature to reach the peak value. As the distance increased, the temperature gradient gradually decreased. Along the circumferential direction of the tunnel, the lining temperature on the inlet side of the buried heat exchanger was higher than that on the outlet side. The temperature distribution on both sides of the symmetrical surface of the tunnel was not uniform, resulting in additional temperature stress in the horizontal direction. The time required for the heat transfer capacity of the tunnel to return to its initial value was approximately eight times that of the system. Compared with the ventilation and water velocities, the inlet water temperature and initial soil temperature had a greater impact on heat transfer. The heat-transfer law of an arch tunnel differs from that of a circular tunnel. There were some deviations when comparing the experimental data of the circular tunnel with those of the actual arch tunnel.

为了提高高寒地区住房的太阳能利用率,降低建筑能耗,增加住房的蓄热能力,提升住房的热舒适性,提出将太阳能平板集热器与重力热管集成于外墙的方法;通过分析太阳能重力热管相变传热过程,建立了重力热管相变传热的数学模型,并通过试验对模型进行了验证.结果显示:利用验证的模型对太阳能重力热管的结构进行优化设计,提高了太阳能的利用效率.

Structural insulation panels (SIPs) are considered promising building products that achieve the low-energy goal, and its potential energy performance can be further improved by combining it with a vacuum insulation panel (VIP) in cold climates. The aim of this study is to determine the optimal SIP with VIP (VIP-SIP) thickness and to minimize the energy cost. We conduct a VIP-SIP thickness optimization and cost analysis for five cold sub-regions using P-1-P-2 methods. First, we develop an energy model using the building energy simulation software OpenStudio considering the VIP aging effect, and the accuracy of this model is validated using field test data. Results indicate that as climates become colder from Cold area B to Severe Cold area A, the optimal VIP thickness increases from 3.5 mm to 31 mm, whereas the optimal PU thickness decreases from 66.875 mm to 174.2 mm. In addition, the total cost saving rate increases from 40.5% to 47.9%, and the discounted payback period decreases from 12.59 years to 8.98 years, indicating improved economic feasibility. Furthermore, the influence of the P-1 value and VIP price on the optimal thickness and total cost are also discussed. The findings of this study confirm the economic feasibility of combining SIP with VIP in cold areas, and provide feasible parameters for the design of low-energy buildings in cold areas of China.

针对夏季帐篷过热问题,提出一种新型外遮阳网改善帐篷内热环境.通过理论设计得到不同纬度遮阳网的设计参数,对比新型外遮阳与六针外遮阳对太阳总辐射和直接辐射的透过率以及帐篷外壁面温度的变化.研究表明,新型外遮阳相比无遮阳和传统的六针遮阳网可以大幅降低帐篷的太阳直射辐射得热和外壁面温度,从而有效改善帐篷内部热环境.在此基础上使用Fluent软件对不同遮阳工况下帐篷内的温度场和速度场进行模拟,得出新型外遮阳能有效降低帐篷内的平均辐射温度和PMV.

The urban heat island (UHI) and urban moisture island (UMI) effect can be significant in Hong Kong due to its high-density land utilization, and this can strongly affect building energy performance. While the UHI’ energy impact has been rather intensively studied recently, the UMI effect on latent energy is still underexplored, especially for humid subtropical climate like Hong Kong. This study investigated the intensity of UHI and UMI in Hong Kong, and its impacts on the sensible and latent cooling demand of residential buildings in summer. Firstly, a ten-year weather dataset from 2004–2013 for the six stations selected based on the local climate zone (LCZ) scheme was analysed. The results show that the urban area of Hong Kong appears as both a heat and moisture island during summer nights but as cooling and dry islands during daytime, and the nocturnal UHI and UMI intensity vary significantly with different LCZs. Furthermore, the energy performance of a typical residential building in Hong Kong was simulated with measured weather data for the selected stations as an input. The urban building shows a higher sensible cooling demand, approximately twice that of the comparative rural one, and the latent cooling demand could be up to 96% higher. Both sensible and latent cooling energy demand decrease with increasing LCZ grades. Our study highlights that both UHI and UMI effect should be considered in the estimation of building energy in Hong Kong due to their significant impacts on the cooling energy demand.

This article investigates the influence of the thermal performance of building envelopes on annual energy consumption in a ground-buried office building by means of the DeST-based dynamic building energy simulation, aiming at offering reasonable guidelines for the energy efficient design of the envelopes of underground office buildings for various climatic zones in China. In this study, the accuracy of dealing with the thermal process adopted for underground buildings by using DeST is validated by measured data. The analysed results show that the annual energy consumptions for this type of buildings vary significantly, and it is based on the value of the overall heat transfer coefficient (U-value) of the envelopes. Thus, it is necessary to optimize the U-value for underground office buildings located in various climatic zones in China. With respect to the roof, an improvement in its thermal performance is significantly beneficial to the building in terms of annual energy demand. With respect to the external walls, the optimized U-values completely change with the distribution of the climate zones. The recommended optimal values for various climate zones of China are also specified as design references for this type of underground buildings in terms of the building energy efficiency.

Based on the local climate zone (LCZ) scheme, nine typical urban areas in Shenzhen, China were chosen to conduct a field survey to quantitatively analyze the outdoor thermal comfort levels under different urban spatial characteristics. Four integrated indicators, F-1, F-2, F-3, and F-4, were defined based on the Fuzzy-AHP method by considering four different considerations for expressing nine different LCZs. Through physical meteorological measurements and simultaneous human responses on local environments, thermal "neutral" value ranges of three thermal comfort indicators (TCI) were obtained, varying from 27 degrees C to 29.5 degrees C in PET, from 21 degrees C to 24 degrees C in OUT-SET*, and from 28 degrees C to 29.5 degrees C in UTCI. Quantitative equations between F-i and TCI were expressed by applying Linear, Logarithmic and Cubic models to the calculated F(i )and TCI values in the nine LCZs. Sampling experiments were conducted to generate near-random sampling F-i parameters from a four-dimensional distribution. By referring to thermal "neutral" TCI ranges, six optimal F(i )combinations were determined and results show that the LCZ 1 B appears a preferable LCZ class for optimizing local-scale thermal comfort conditions in the high-temperature environments in subtropical regions of China. Additionally, the optimal F-i combinations provide quantitative theoretical guidance in sustainable urban design and planning.

Moisture problem is one of most serious impediments for the development and sustainable utilisation of civil defence shelters due to poor moisture management. The aim of this study is to develop a passive approach to improve the indoor moisture environment of the shelter, fitting straw-based board on the inner surfaces of walls. The study first conducted long-term field monitoring of room temperature and relative humidity in a typical civil defence shelter in Beijing, and analysed the impact of straw-based board on indoor thermal and moisture environment. The measured results show that straw-based board can dampen the increase in humidity level and improve moisture environment of the shelter significantly, especially in summer. Additionally, a coupling method which combines a well-developed hygrothermal model and dynamic heat transfer in a typical civil defence shelter is used for simulating moisture buffering effect of straw-based board, and the accuracy of the method is validated by the measured data. Finally, using the coupling method, a parametric study is carried out to predict the hygrothermal behaviour of straw-based board for the assessment of its buffering effect in various climate zones of China and for better understanding of its application effect in the civil defence shelter.

The surface energy balance over Harbin, one of the major cities in severe cold regions of China, is examined during the snow‐covered and snow‐melt periods (January 11 to April 20, 2017) using radiation and eddy covariance measurements. Comparisons of radiation and energy fluxes from fresh snow, cold snow, melting snow, and snow‐free periods revealed that the presence of snow cover has a considerable impact on the radiation and energy balances. The daytime net radiation was mostly dissipated as sensible heat flux with a fraction of 43% during the fresh snow periods. During the cold snow periods, the daytime fraction of sensible heat flux decreased to 31% and most available energy was stored in the urban surfaces. During the melting snow periods, since the snowmelt process consumed a considerable portion of available energy, the daytime fraction of sensible heat flux decreased about 20% when compared to the cold snow periods, while the daytime fraction of latent heat flux increased about 50% due to the evaporation of melt water. After the snow melted, the ratio of daytime latent heat flux decreased because vegetation was not yet active during the snow‐free periods and the Bowen ratio increased from 2.3 (melting snow periods) to 5.9 (snow‐free periods).