•Numerical modeling of PCM panels used in building envelope was studied.•Numerical result was validated well with the experiment data.•Temperature variations of the PCM wall and roof were analyzed ...numerically.•Internal temperature developments were researched for the PCM wall and roof.•Thermal energy savings for the PCM systems were analyzed.
The phase change material (PCM) used in the building envelope can decrease the building energy consumption and improve the thermal comfort by enhancing the thermal energy storage capacity of the wall and the roof. In this research, two new PCM systems, i.e., PCMOW (capric acid contained in the panels installed on the outside surface of building) and PCMIW (capric acid and 1-dodecanol contained in the panels installed on the inside surface of building), have been developed numerically. The main study constitutes four parts: (1) the model and its validation; (2) the analysis on temperature variations of the wall and the roof; (3) the analysis on the internal temperature developments of the wall and the roof; (4) the study of thermal energy saving. A mathematical model and its corresponding numerical solution were presented. Relative error analysis inclusive of maximum and average errors and Bland–Altman analysis were employed for validation. It is found that the numerical simulation achieved good validity. The theoretical analysis of temperature variations of the walls and the roofs for the PCMOW, PCMIW and reference rooms has been conducted. Then, the internal temperature developments of PCMOM and PCMIW systems were analyzed to reveal the operation of the PCM panel in the wall and the roof. This study also explored the analysis method of thermal energy savings for the two PCM systems to maintain the indoor temperature within thermal comfort zone.
Robust and accurate nuclei localization in microscopy image can provide crucial clues for accurate computer-aid diagnosis. In this paper, we propose a convolutional neural network (CNN) based hough ...voting method to localize nucleus centroids with heavy cluttering and morphologic variations in microscopy images. Our method, which we name as deep voting, mainly consists of two steps. (1) Given an input image, our method assigns each local patch several pairs of voting
vectors which indicate the positions it votes to, and the corresponding voting
(used to weight each votes), our model can be viewed as an implicit hough-voting codebook. (2) We collect the weighted votes from all the testing patches and compute the final voting density map in a way similar to Parzen-window estimation. The final nucleus positions are identified by searching the local maxima of the density map. Our method only requires a few annotation efforts (just one click near the nucleus center). Experiment results on Neuroendocrine Tumor (NET) microscopy images proves the proposed method to be state-of-the-art.
Extreme learning machine (ELM) for single-hidden-layer feedforward neural networks (SLFN) is a powerful machine learning technique, and has been attracting attentions for its fast learning speed and ...good generalization performance. Recently, a weighted ELM is proposed to deal with data with imbalanced class distribution. The key essence of weighted ELM is that each training sample is assigned with an extra weight. Although some empirical weighting schemes were provided, how to determine better sample weights remains an open problem. In this paper, we proposed a Boosting weighted ELM, which embedded weighted ELM seamlessly into a modified AdaBoost framework, to solve the above problem. Intuitively, the distribution weights in AdaBoost framework, which reflect importance of training samples, are input into weighted ELM as training sample weights. Furthermore, AdaBoost is modified in two aspects to be more effective for imbalanced learning: (i) the initial distribution weights are set to be asymmetric so that AdaBoost converges at a faster speed; (ii) the distribution weights are updated separately for different classes to avoid destroying the distribution weights asymmetry. Experimental results on 16 binary datasets and 5 multiclass datasets from KEEL repository show that the proposed method could achieve more balanced results than weighted ELM.
The relative location of inlets and outlets plays an important role in thermal comfort and energy conservation under ventilation modes for the building non-uniform indoor environment. Hence, a ...comparison study of thermal comfort and energy efficiency of eight widely-used ventilation modes for space heating was conducted in this study. Both subjective experiments and verified computational fluid dynamics (CFD) models were carried out. In the subjective experiments, the vote of local thermal sensation (LTS), overall thermal sensation (OTS) and draft sensation were collected. In the CFD simulations, RNG
k-ε
model was applied to compare and analyze the air temperature field, turbulence intensity, ventilation effectiveness and air diffusion performance index (ADPI). The thermal comfort results showed that the air inlets are better located at the mid-height level of a wall, and the outlets are located at the same or higher height. While the results of the energy efficiency suggested that the inlets are better installed at the lower level of a wall, and the outlets should be placed far from the inlets. Since the results were conflict, the economic-comfort ratio was introduced to calculate and compare the thermal comfort and energy efficiency simultaneously. The final results concluded that it can achieve excellent thermal comfort performance without sacrificing energy efficiency when the inlets are at the height of 1.2 m of the front wall, and the outlets are at 1.2 m height of the back wall. Hence it is the best choice for the winter air distribution in northern China. This study can offer a guideline for the air terminal arrangements in non-uniform ventilation under heating mode.
With the increasing building energy consumption, the improvement of building energy efficiency (BEE) becomes a key part of the reduction of energy intensity in the “Eleventh Five-Year Plan” period ...(during 2006 and 2010) in China. For this reason, the China central government has enforced and implemented a series of policies to promote BEE. Based on the analysis of main characteristics of BEE development in China and developmental routes of BEE, this paper systematically explored six fiscal incentive policies. Meanwhile, four specific programs involving new building, existing residential building, government office building and large-scale public building, and applications of renewable energy in building were investigated. Besides, the key factors of BEE development and BEE developmental stages were analyzed. The research revealed the present progress of implementation on BEE policies, and identified the drawbacks of the present BEE mechanism. Moreover, four proposals were recommended to enhance the development of BEE in the next “Five-Year Plan” period.
▶ Characteristics of China's building energy efficiency (BEE) are analyzed. ▶ Explores developmental routes, policies and programs for BEE. ▶ Implementing and developing progresses of BEE policy are revealed. ▶ Drawbacks and proposals concerning BEE are pointed out.
In light of carbon peak and carbon neutrality goals, China has attached great importance to energy savings and carbon reduction. Carbon reduction in the transport sector is critical to achieving the ...two-carbon target, as it accounts for 9.41% of total carbon emissions. As the sharing economy grows, car sharing is considered to present excellent carbon reduction potential in the transportation sector. However, the current research is focused on car sharing usage, with a lack of research on the carbon reduction capability of car sharing in China. Hence, this study aims to investigate the carbon reduction capacity of car sharing, including usage rates of car-share services and changes in travel behavior, through an online questionnaire combined with carbon emission data from the transportation sector. The study aims to analyze the contribution of car-share services to carbon reduction in the transportation sector under the current model. The well-to-wheel (WTW) approach is employed, including the energy consumption of vehicles and carbon emissions in the production process. The research results indicate that the introduction of car-sharing services increases driving energy consumption; however, this increase is offset by the decrease in carbon emissions as a result of the production process. Therefore, the overall effect is a reduction in carbon emissions of 1.058971 million tons in 2021, accounting for 1.95 percent of total transport carbon emissions. In addition, the impact on different modes on carbon emission reduction is also explored in this study. The results demonstrate that the private car disposal rate shows the most significant influence on traffic carbon emissions; a 10% reduction in the number of private cars can lead to a 2.48% carbon reduction. The relevant conclusions of this study can provide support for the future development of car sharing in China and the reduction of carbon emissions in the transportation sector.
The couple of radiation with convection heating owned advantages of less energy utilization, healthier and more comfortable indoor environment. However, local thermal discomfort was often induced by ...large vertical temperature difference and radiation asymmetry temperature. This work studied indoor thermal environment characteristics under different coupling ways of radiation and convection heating terminals through experiments and CFD simulation. The studied five scenarios were denoted as: (I) lateral air supply + adjacent side wall radiation, (II) lateral air supply + opposite side wall radiation, (III) lateral air supply + floor radiation, (IV) lateral air supply + adjacent side wall radiation + floor radiation, and (V) lateral air supply + opposite side wall radiation + floor radiation. The overall thermal comfort indices (including air diffusion performance index (ADPI), predicted mean vote (PMV), and predicted percent of dissatisfaction (PPD)) and local thermal comfort indices under different scenarios were investigated. For Scenarios I–III, the local dissatisfaction rates caused by vertical air temperature difference were 0.4%, 0.1%, and 0.2%, respectively, which belonged to “A” class according to the ISO-7730 Standard. While the vertical asymmetric radiation temperature of Scenario I/II was about 6.5 °C lower than that of Scenario III/IV/V. The ADPI for Scenarios III–V were about respectively 5.7%, 16.7%, and 21.0% higher than that of Scenarios I–II, indicating that a large radiation area and radiation angle coefficient could reduce the discomfort caused by radiant temperature asymmetry. The coupling mode improved local discomfort by decreasing vertical temperature difference and radiation asymmetry temperature wherefore improving the PMV from −1.6 to −1. The lateral air supply coupled with asymmetric radiation heating could potentially improve the thermal comfort of occupied area, while the comprehensive effect of thermal environmental improvement, energy-saving, and cost-effectiveness needes to be further investigated.
This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle ...(PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.
This paper reviews the heat transfer model for geothermal reservoirs, the fracture network in reservoirs, and the numerical model of hydraulic fracturing. The first section reviews the heat transfer ...models, which contain the single-porosity model, the dual-porosity model, and the multi-porosity model; meanwhile the mathematical equations of the porosity model are summarized. Then, this paper introduces the fracture network model in reservoirs and the numerical method of computational heat transfer. In the second section, on the basis of the conventional fracture theory, the PKN (Perkins–Kern–Nordgren) model and KGD (Khristianovic–Geertsma–De Klerk) model are reviewed. Meanwhile, the DFN (discrete fracture network) model, P3D (pseudo-3D) model, and PL3D (planar 3D) model are reviewed. The results show that the stimulated reservoir volume method has advantages in describing the fracture network. However, stimulated reservoir volume methods need more computational resources than conventional fracture methods. The third section reviews the numerical models of hydraulic fracturing, which contains the finite element method (FEM), the discrete element method (DEM), and the boundary element method (BEM). The comparison of these methods shows that the FEM can reduce the computational resources when calculating the fluid flow, heat transfer and fracture propagations in a reservoir. Thus, a mature model for geothermal reservoirs can be developed by coupling the processes of heat transfer, fluid flow and fracture propagation.
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