Comprehensive Evaluation Factor Research Articles

Heat transfer enhancement of air flow through new types of perforated dimple/protrusion fins

Heat transfer enhancement technologies of air flow are critical to energy conservation and emission reduction in industrial applications. This paper explores the numerical simulation analysis of 18 kinds of perforated dimple/protrusion fins. The wind speed varies within the range of 2 ∼ 6 m/s, and the investigation delves into the impact of different structural parameters on strengthening factor Nu/Nu0, resistance factor f/f0 and other comprehensive evaluation factor performance evaluation criteria (PEC) of perforated dimple/protrusion fins. The study specifically explores the influence of structural parameters, including intercepting perforated dimple/protrusion height (S0), hole diameter (D), hole structure offset (a), and the arrangement of perforated dimple/protrusion structure, on heat transfer performance. The comprehensive evaluation factor PEC of the new fin increased by 23.7 % compared with the porous fin. The overall heat transfer performance of the perforated dimple/protrusion fins rises with height under the same operating conditions. It first increases and then declines with the increasing hole diameter, and first drops and then increases with the increasing offset. The perforated protrusion/dimple fins obtain the best enhancement factor when the hole diameter is 3.4 mm. The hole structure offset is better on the inflowing leeward side than on the inflowing side. The fins with both perforated dimple and perforated protrusion structures have advantages over the one with either of two structures, and the alignment arrangements are identified as the optimal configuration. The new structural characteristics of perforated dimple/protrusion fins in heat exchangers can be utilized to create new designs that potentially outperform conventional models.

Application and characterization of digital Sallen–Key filter in nuclear spectrum smoothing

In the nuclear spectrum analysis processing, spectrum smoothing can remove the statistical fluctuation in the spectrum, which is beneficial for peak detection and peak area calculation. In this work, a spectrum smoothing algorithm is proposed based on digital Sallen–Key filter, which contains four parameters (m, n, k, D). The amplitude–frequency response curve of Sallen–Key filter is deduced and the filtering performance is analyzed. Meanwhile, the effects of the four parameters on the shape of the smoothed spectrum are explored: D affects the counts and peak areas of the spectrum, and the peak area can be corrected by the peak area correction function S’. The parameters of m, n and k affect the peak position after smoothing, making the peak position shift to the right, and the peak position correction function P’ can be used to correct the peak position, when n¿2, the spectrum data appear negative after smoothing, when k¿2, the smoothed spectrum broadening degree is greater than 20%. Smoothness (R), noise smoothing factor (NSF), spectrum count ratio before and after smoothing (PER), and comprehensive evaluation factor (Q) are used to evaluate the smoothing effect of the algorithm. The parameters of the algorithm are optimally selected: about the gamma spectrum of 137Cs and 60Co, the optimal parameters are m=1.5 n=2 k=2 D=1, about the characteristic X-ray spectrum of Fe and quasi-geological sample (TiMnFeNiCuZn), the optimal parameters are m=1.1 n=1.1 k=1.3 D=1. Based on Sallen–Key smoothing method, Fourier transform method, Gaussian function method, wavelet transformation method, center of gravity method and least squares method, the gamma spectrum of 137Cs is smoothed and denoised in this paper. The results show that the Sallen–Key method has better spectrum denoising effect (R=0.6056) and comprehensive performance indicators (Q=0.6104), which can be further applied for the smoothing of nuclear spectrum data.

Optimization Study of Injection-Production Parameters for CO2 Enhanced Oil Recovery and Storage in Low Permeability Oil Reservoirs

To address the difficulty of water injection in the late stage of developing a certain low-permeability reservoir, CO2 injection and fracturing parameter optimization were conducted. The Latin hypercube sampling and numerical simulation methods were used to study the five-spot well network model established, and evaluate the impact of injection and fracturing parameters on oil recovery and CO2 storage using a comprehensive evaluation factor of oil displacement and storage. The results show that the injection rate is the main controlling factor affecting the oil recovery and storage effect, and the optimal injection rate is 6000m3/d. There is a certain contradiction between the oil recovery and storage objectives at different stages of injection development, but after ten years of injection development, the objectives of oil recovery and storage are consistent. The optimal combination of ijection and fracturing parameters yields a recovery rate of 72.54% and a CO2 storage amount of 101635.81 tons. This paper proposes that there is a certain contradiction between the oil recovery and storage objectives at different stages and evaluates schemes with different injection development periods by constructing a comprehensive evaluation factor for oil displacement and storage, which has certain reference value for optimizing parameters in the CO2 injection development of low-permeability reservoirs.

Identifying the Internal Coupling Coordination Relationship of Forest Ecological Security and Its Spatial Influencing Factors

Forest ecological security is an important guarantee for national security and the healthy development of forestry. Existing research has been limited to the comprehensive evaluation and obstruction factors of forest ecological security, and this study innovatively analyzes internal coordination of forest ecological security and its spatial influencing factors in order to enhance the internal coordination of the forest ecosystem and promote the coordinated improvement of regional forest ecological security. Firstly, the forest ecological security in China from 2006 to 2020 was evaluated. On this basis, the coupling coordination degree of forest ecological security (FESD) was calculated, and its influencing factors and spatial spillover effects were analyzed using the spatial econometric model. The results show that: (1) most of China’s provincial forest ecological security is at a critical and relatively safe level, and shows a trend of gradual improvement; (2) FESD in 25 provinces, represented by Guangxi, is in the acceptable range and is constantly improving; and (3) annual mean temperature, urbanization rate, completed forestry investment, and forest pest control have been positive influences on FESD. Forest population density, per capita GDP, and investment in environmental governance have significant negative influences. In addition, completed forestry investment, annual mean temperature, urbanization rate, forest population density, and forest pest control have significant spillover effects on FESD. Therefore, in the process of forest ecological management, it is necessary to further strengthen investments in forestry and pest control, and to pay more attention to the interaction between regions.

Sustainable energy transition in Southeast Asia: Energy status analysis, comprehensive evaluation and influential factor identification

Southeast Asia, one of the world's most vibrant economies, faces significant challenges in enhancing energy security and mitigating carbon emissions. This study provides a holistic view of the energy security status in Southeast Asia by presenting energy facts from six aspects and identify the critical factors affecting sustainable energy transition in this region with the techniques of political, economic, social, technological, environmental, and legal (PESTEL) Analysis and fuzzy Multi Criteria Decision Making (MCDM) methods. It indicates that: (1) Southeast Asia performs well in enhancing energy supply but awkwardly in sustainable energy transition, and great divergence exists among different countries; (2) The economic aspect is the most important in sustainable energy transition, followed by the technological, environmental and political aspects; (3) Important factors influencing sustainable energy transition in Southeast Asia include political instability, backward economy, uncertain social acceptance, insufficient energy infrastructure, restrictions of geographical conditions, and limited government efforts.

Convective thermal-hydraulic performance in twisted tubes: From the perspective of symmetrical cross-sectional shapes

To explore the impact of intersecting surface shape on the thermal-fluid behaviors in the twisted tube (TT) under the two conditions of equal area and equal perimeter of intersecting surfaces, a 3D simulation method is used to examine the convection heat transfer characteristics of fluids with different viscosities in TTs with typical symmetrical cross sections at low Reynolds number (Re) according to experimental verification. The results manifest that the regularly helical deformation of the TTs induces secondary flows in the perpendicular direction of the main flow, leading to a better convection heat transfer performance. In the Re range of 650– 1550 with water, the twisted triangular tube produced with equal cross-sectional perimeter exhibits the topmost convection heat transfer performance, with a comprehensive performance evaluation factor of heat transfer (PEF) of 1.85– 1.87. As for the equal cross-sectional perimeters with engine oil, the twisted elliptical tube shows the highest PEF of 1.39– 1.40 as the Re is below 1100. When the Re exceeds 1100, the twisted triangular tube displays the supreme PEF of 1.33– 1.37. For the equal cross-sectional areas with water and engine oil, the twisted elliptical tube presents the utmost PEF of 1.32– 1.47.

Cyclic behavior of unbonded post-tensioned precast segmental concrete columns fabricated by 3D printed concrete permanent formwork

A 3D printed concrete permanent formwork of composite unbonded post-tensioned precast segmental concrete (3DPCPSC) column is proposed in this research. Its hysteresis performance and the failure mode are researched by quasi-static experiment and compared with the precast segmental reinforced concrete (PSRC) columns. Two interface enhancement methods, stainless-steel-nails internal shear bonds and prestressed steel-hoops external active confinement are proposed, and the enhancement effect and mechanism of 3DPCPSC columns with two interface enhancement methods are studied. Furthermore, the pouring and vibration load of 3D printing concrete formwork is analyzed using a three-dimensional solid finite element model finite element model. The results indicate that the energy dissipation capacity of 3DPCPSC columns is better than that of the PSRC column when the 3DPC formwork does not spall. The largest accumulated energy dissipation of the 3DPCPSC specimen is 1.14 times of the PSRC column. The 3DPCPSC column without interface enhancement has the phenomenon of formwork spalling, the bearing capacity is lower than the PSRC column, and the bearing capacity of the 3DPCPSC columns with two interface enhancement methods is close to or higher than the PSRC column. The initial stiffness of all the 3DPCPSC specimens is larger than the PSRC column. A comprehensive evaluation factor η is proposed to evaluate the hysteretic performance of precast segmental concrete columns. The comprehensive performance of the 3DPCPSC and PSRC is compared by the comprehensive evaluation factor η.

Comprehensive evaluation and obstacle factors of coordinated development of regional water–ecology–energy–food nexus

Comprehensive evaluation and obstacle factors of coordinated development of regional water–ecology–energy–food nexus

The risk evaluation and management of the sports service supply chain by introducing fuzzy comprehensive appraisal and artificial intelligence technology

AbstractThis article aims to improve the inefficiency of the sports service supply chain (SC) caused by the unscientific management of stakeholders in the sports service SC. First, combined with the literature, the identification and management of the service SC domestically and internationally are explained, providing a meaningful reference for improving sports service bases. Second, fuzzy comprehensive appraisal (FCA) algorithm process and artificial intelligence (AI) technology are used to evaluate and manage the risk of sports service SC. The FCA algorithm provides a comprehensive evaluation factor set for the sports service SC risk evaluation. Then, the complete evaluation set is established. To obtain the evaluation matrix, the ‘expert’ carries out fuzzy evaluation on each single factor. AI provides a data analysis platform for integrated SC risk management. The platform can realize the logical hierarchical relationship between indicators and rules, systematically standardize the sports service SC and rules, and conduct unified display, monitoring, and trend analysis. Finally, the FCA method is used to evaluate the risks of the sports service SC, and the results of the comprehensive management of the dangers of the SC are analysed. The results show that the evaluation indicators of sports service venues' SC service capabilities have a good consistency. The highest weight score of government service capability in the sports service SC is 0.2413, and the lowest weight score of the service capability index of the sports operation platform is 0.1708. Sports service venues' SC capacity in NANCHANG City is relatively average. This article deeply understands the structure of the sports service SC. It provides relevant basis and guidance for sports service integrators, service providers, and other market entities to adjust management strategies and improve market competitiveness. It also clarifies the risks and management results of the sports service SC, provides academic help for the researchers and enriches and develops the theory of the reform and construction of the Chinese sports service SC.

General performance evaluation method of the heat aided liquid air energy storge system with waste heat utilization

As a large-scale energy storage technology, liquid air energy storge (LAES) system is considered as a promising route to solve the instability of renewable energy. The heat aided LAES system with waste heat utilization (WHU) has been widely concerned for the high electrical efficiency. However, there is no unified theoretical evaluation method for such systems. In this study, the WHU-LAES systems are generalized and unified, and a comprehensive evaluation factor (efficiency improving ability) is proposed. The specific influence modes of the added heat energy on the WHU-LAES system are analyzed: the “allocation effect” shows the heat energy redistribution in the air expansion (AE) subsystem and the follower waste heat utilization system due to the heat integration in the AE subsystem; the “gain effect” is brought by the simultaneous heat integration of the “power increase” subsystems and “consumption reduction” subsystems; the “superposition effect” is revealed and shows the efficiency improving ability is comprehensively determined by the direct benefit, the explicit influence, the “allocation effect” and the “gain effect”. In the end, the efficiency improving ability is applied to the supplementary heat characteristic analysis and the comprehensive evaluation of 8 cases of WHU-LAES systems, which proves the effectiveness of the comprehensive evaluation factor.

Comprehensive efficiency analysis of air-cooled vs water-cooled electric motor for unmanned aerial vehicle

The efficiency of an electric motor for an unmanned aerial vehicle can reduce when its temperature exceeds the working temperature. In this paper, air- and water-cooling methods for electric motors in unmanned aerial vehicles are proposed and comprehensively compared. The effects of fan speed, water flow speed, and convection heat transfer coefficient on the outer surface of the electric motor on the cooling capacity of the electric motor are discussed. A comprehensive performance evaluation factor for the cooling method of the motor is proposed. Results show that when the fan speed increased from 800 to 2000 rpm, the cooling efficiency increased by 27.78% for the air-cooled motor, whereas when the inlet flow rate of cooling water increased from 0.1 to 0.9 m/s, the cooling efficiency increased by 67.47% for the water-cooled motor. The comprehensive performance of the water-cooled motor reached the highest level with a velocity of 0.7 m/s. The convection heat transfer coefficient increased from 5 to 25 W/(m2·K), and the cooling efficiency increased by 22.93% and only 2.77% for the air- and water-cooled motors, respectively. These findings can provide guidance for designing highly efficient electric motor cooling equipment for unmanned aerial vehicles.

Rotor Fault Diagnosis Method Based on VMD Symmetrical Polar Image and Fuzzy Neural Network

Rotor fault diagnosis has attracted much attention due to its difficulties such as non-stationarity of fault signals, difficulty in fault feature extraction and low diagnostic accuracy of small samples. In order to extract fault feature information of rotors more effectively and to improve fault diagnosis precision, this paper proposed a fault diagnosis method based on variational mode decomposition (VMD) symmetrical polar image and fuzzy neural network. Firstly, the original rotor vibration signal is decomposed by using the VMD method and the relevant parameter selection algorithm of the VMD method is also proposed. Secondly, the intrinsic mode functions (IMF), which are sensitive to the signal characteristics, are selected for signal reconstruction based on a comprehensive evaluation factor method. As well, the reconstructed signal is transformed into a two-dimensional snowflake image through using the symmetrical polar coordinate method. Finally, the image features are extracted by the gray level co-occurrence matrix to form the state feature vector, which is input into the fuzzy neural network to realize the rotor fault diagnosis. Through the analysis of measured signals, the experimental results show that the proposed method can reach a higher recognition rate of 98% and the k-cross-validation experiment is used to demonstrate the robustness of the fuzzy neural network, and the average recognition accuracy of this experiment is 99.2%. Compared with some similar methods, the proposed method still has the highest fault recognition precision 98.4%, and the smallest standard deviation 0.5477.

Influence of nanoparticle and channel arc structure on comprehensive performance of nanofluids in curved tiered microchannel heat sinks

AbstractIn order to improve the heat dissipation of the electrical components, a curved tiered microchannel heat sink (TMCHS) was proposed and optimized and applied to cool the electrical components together with nanofluids. Influence of channel radian (φ = 0°, 75°, 135°, 180°), arc number (n = 0, 2, 3, 4), and nanoparticle concentration (w = 0.0%, 0.1%, 0.3%, 0.5%) on flow and heat transfer characteristics of nanofluids in curved TMCHS was numerically investigated. Comprehensive evaluation coefficient comprehensive evaluation factor (PEC) was used to evaluate the thermo‐hydraulic performance of TMCHS and nanofluids. Results indicated that the greater the radian and arc number, the better the thermal performance of TMCHS. The overall performance of TMCHS is the best when the radian is 180° and the arc number is 4. Results in this paper provide important technical guidance for the application of curved tiered microchannel heat sinks and nanofluids to the field of thermal management of electronic components.

Comprehensive Evaluation and Obstacle Factor Analysis of High-Quality Development of Rural E-Commerce in China

The high-quality development of rural e-commerce is not only one of the important tasks to solve the “three rural” problems and comprehensively promote rural revitalization, but also the internal requirement to implement the new concept of high-quality development and promote the quality and efficiency of rural industries. On the basis of clearly defining the connotation of high-quality development of rural e-commerce in China, this paper established an evaluation index system of high-quality development of rural e-commerce and analyzes the high-quality development level and main restrictive factors of rural e-commerce in China under the new development concept by using the entropy method and an obstacle factor diagnosis model. The results showed that from 2015 to 2020, the overall development quality of rural e-commerce in China showed an upward trend, but it still needs to be improved. The five dimensions of innovation, coordination, openness, green and sharing have different degrees of impact on the development quality of rural e-commerce in China at the present stage, which are as follows: coordination, innovation, sharing, green and opening. The main obstacles to the high-quality development of rural e-commerce in China are coordination and innovation. Researchers; the difference in Internet penetration between urban and rural areas; the upward proportion of agricultural products; regional difference; and industrial agglomeration are the main obstacles to the high-quality development of rural e-commerce in China. Finally, aiming at the main restrictive factors, this paper puts forward the corresponding development countermeasures from five aspects: innovation, coordination, openness, green and sharing.

Numerical Study of Thermal Enhancement in a Single- and Double-Layer Microchannel Heat Sink with Different Ribs.

In this paper, a microchannel heat sink model was proposed to realize single- and double- layer flow through built-in ribs. The finite element volume method was used to analyze the influence of the length, thickness and angle of the inner rib on the flow and heat transfer characteristics of the microchannel heat sink. The pressure drop, temperature field, flow field, and thermal characteristics are given. The numerical simulation results show that the rectangular rib plate makes the fluid in the microchannel heat sink flow alternately in the upper and lower layers, which can effectively enhance heat transfer. However, with the increase in rib length, the comprehensive evaluation factor decreases. The change of the angle of the rectangular rib plate has little influence on the Nusselt number. The change rate of the comprehensive evaluation factor of the thickness of the rectangular rib plate is the largest. When the Reynolds number is 1724, the comprehensive evaluation factor of Case 9 is 4.7% higher than that of Case 2. According to the parameter study of the built-in rib plate, the optimal parameter combination is given, in which the angle is 0°, the length is 7.5 mm, and the thickness is 0.2-0.3 mm.

Construction of the Mathematical Model for Teaching Classroom Evaluation in Colleges and Universities Using an Optimized Apriori Algorithm

In order to increase the effectiveness and teaching quality of numerous classroom activities in colleges and universities, this paper puts forward the effectiveness assessment technique of teaching activities in colleges, universities, and institutions of higher education based on the optimized Apriori algorithm. A mathematical model for assessing the efficacy and usefulness of classroom activities in colleges and universities is constructed. Teaching contents, teaching attitudes, teaching methods, teaching effects, test results, and students’ performance are introduced as comprehensive evaluation factors, and a decision-making model for assessing the success and efficiency of classroom activities in colleges and universities is established by adopting scientific, reasonable, and systematic teaching methods. Through the grey correlation analysis of classroom teaching quality, the delay characteristic analysis and the adaptive parameter adjustment method are adopted. This paper constructs the optimal Apriori algorithm model of college teaching classroom activities, constructs the optimal evaluation function model of college teaching classroom activities effectiveness evaluation by the method of support-confidence joint estimation, extracts the optimal quality parameter set of college teaching classroom activities by the optimization detection method and association rule mining, and realizes the effectiveness evaluation and multi-dimensional parameter estimation of college teaching classroom activities by the optimized Apriori algorithm. The test outcomes confirm that this technique is reliable in evaluating the effectiveness of classroom activities in colleges and universities, and the directional distribution of association rules of classroom quality in colleges and universities is significant, which meaningfully advances the classroom teaching levels and quantitative evaluation abilities.

Integrated Battery Thermal Management System Coupling Phase Change Material Cooling and Direct Heating Strategies

The current battery thermal management (BTM) system integrating indirect heating and PCM cooling structures still suffers from relatively low heating efficiency and high energy consumption. In this work, we develop a BTM structure, which possesses both heating and cooling functionalities, by directly wrapping thin heating films around the cells inserted in a phase change material cooling module. Compared to the indirect heating structure, this novel direct contact structure allows direct heat transfer from the heating film to the batteries and thereby presents a more effective heating performance and lower energy consumption. For example, under the ambient temperature of 0 °C, the direct heating strategy with a heating power of 80 W delivers the shortest heating time of 78 s along with a temperature difference (ΔT) of 3.07 °C, thereby demonstrating the highest comprehensive evaluation factor of 0.645 and lowest energy consumption of 3.9%. Under the more severe ambient temperature of −20 °C, a heating time of 384 s with a ΔT of 3.77 °C can be achieved at a direct heating power of 60 W, suggesting the highest comprehensive evaluation factor of 0.503 and a lower energy consumption of 14.5%.

Development and performance research of a helical longitudinal-groove tube with secondary flow reinforcement for heat transfer

The secondary flow has a strong promotion effect on heat transfer in the tube. In order to further utilize the secondary flow phenomenon to strengthen heat transfer of the helical tube, in this paper, a secondary flow enhanced heat transfer helical tube is developed, and stable secondary flow with high strength is obtained. The structure parameters are optimized with the highest comprehensive evaluation factor as the goal. The results show that compared with helical transverse-groove tube and helical grooved tube, helical longitudinal-groove tube has the best heat transfer performance. The new structure's enhanced heat transfer effect for high-Pr number fluid is better than that of low-Pr number fluid, and the enhanced heat transfer effect is not affected by the inlet Reynolds number. The helical angle of helical groove has a greater influence on the comprehensive evaluation factor, while the groove depth and the number of heads have a smaller influence on the comprehensive evaluation factor. The optimal parameter scheme is: The groove depth is 0.5 mm, the helical angle of helical groove is 82°, the head number of helical groove is 1, the comprehensive evaluation factor of helical longitudinal-groove tube compared with ordinary helical tube is 1.173

Research on Comprehensive Evaluation Model of a Truck Dispatching System in Open-Pit Mine

In this paper, a comprehensive evaluation factor model of a truck dispatching system in open-pit mines is constructed from the three dimensions of optimal route, traffic flow planning, and real-time dispatching, and the final combined weight of the factor is determined according to game theory. On this basis, a comprehensive evaluation model of a truck dispatching system in open-pit mines based on gray relational analysis—technology for order preference by similarity to an ideal solution (GRA-TOPSIS) is established. Taking the truck dispatching system in five open-pit mines as the research background, the advantages and disadvantages of the dispatching system were comprehensively evaluated, and the differences between the dispatching systems were analyzed using the radar chart method. The research shows that the evaluation results of the comprehensive evaluation model of the truck dispatching system in open-pit mines based on GRA-TOPSIS are in line with the reality, which is more conducive to analyzing and comparing the advantages and disadvantages of the systems, effectively identifying the differences of various systems, and making the evaluation of truck dispatching systems more scientific. The research results of this paper broaden the evaluation of truck dispatching systems and provide a theoretical basis for the optimization of truck dispatching systems.

Numerical Study and Structural Optimization of Vehicular Oil Cooler Based on 3D Impermeable Flow Model

A non-uniform permeable flow numerical model of vehicular oil cooler was proposed to simulate the thermal performance of oil cooler, due to the complex internal structure of cooler and the anisotropy of coolant flow and heat transfer. By comparing the numerical simulation results with the experimental results, the maximum error of the simulation results under different working conditions is 9.2%, which indicates that the modelling method is reliable and can improve the development efficiency. On this basis, through the three-dimensional numerical simulation to establish and optimize the oil cooler’s parameters. The thermal performance under different structural oil cooler were compared using the comprehensive evaluation factor j/f. The results and the experimental data show that under the impermeable flow model can obtain good heat transfer efficiency with low flow resistance at the same time. When the cross-sectional area is 3 mm2, length of 90 mm, layer number of 11, the model accuracy was 0.6%, as the optimal structure parameters, the heat transfer increase by 47% and with the total pressure drop increased by only 30%.