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Performance Evaluation of Solar Chimney Draft: Application to Ventilation

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Smart Grid and Renewable Energy 2024年第4期15卷 107-122页

作者： Boukaré Ouedraogo Adama Ouedraogo Arouna Kabore Kalifa Palm Dieudonné Joseph Bahiebo Laboratoire dEnergies Thermiques Renouvelables (LETRE) Universit Joseph KI-ZERBO: UFR/SEA Ouagadougou Burkina Faso Laboratoire de Chimie Analytique Physique Spatiale et Energtique (LACAPSE) Universit Norbert ZONGO Koudougou Burkina Faso Centre Universitaire Polytechnique de Kaya (CUP-Kaya) Universit Joseph KI-ZERBO Ouagadougou Burkina Faso Laboratoire des Systmes dEnergie Renouvelable et Environnement Institut de Recherche en Sciences Appliques et Technologies (IRSAT) Centre National de la Recherche Scientifique et Technologique (CNRST) Ouagadougou Burkina Faso

Ventilation is one of the factors contributing to energy consumption in buildings and food preservation. The solar chimney proves to be an alternative for reducing conventional energy consumption. Thus, in this study, the performance of a solar chimney with two active faces for thermally drawing air from a chamber for preserving agri-food products was evaluated. These performances were experimentally assessed through data measurements: temperatures and velocities within the chimney, and their analysis using Excel and MATLAB. The obtained results were compared with those from literature to verify their validity. From this study, it is found that the maximum temperature at the chimney outlet reaches 49.4˚C with an average value of 43.7˚C. Additionally, the heating evolution of the chimney air presents four (04) identical phases in pairs, reflecting the chimney’s operation throughout day. The temperature difference between the outlet and inlet of the chimney reaches a maximum of 17˚C with an average of 12.6˚C. Regarding airflow, the maximum air velocity at the chimney outlet is 0.8 m/s, and the average velocities have consistently been greater than or equal to 0.46 m/s. Thus, it can be concluded that the solar chimney is capable of providing ventilation for the preservation chamber through thermal draft.

关键词： Solar Chimney Natural Ventilation Thermal Draft airflow Chimney Effect

Evaluating the different boundary conditions to simulate airflow and heat transfer in Double-Skin Facade

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Building Simulation 2022年第5期15卷 799-815页

作者： Javad Ahmadi Mohammadjavad Mahdavinejad Olena Kalyanova Larsen Chen Zhang Afsaneh Zarkesh Somayeh Asadi Highperformance Architecture Laboratory Department of ArchitectureTarbiat Modares UniversityJalal-e Al Ahmad HighwayNasr bridgeTehranIran Department of Built Environment Faculty of Engineering and ScienceDivision of Architectural EngineeringAalborg UniversityAalborgDenmark Department of Architectural Engineering Pennsylvania State UniversityPA 16801USA

The CFD simulation accuracy mostly depends on the appropriate setting of boundary conditions and numerical simulation parameters.This study shows the influence of two types of boundary condition settings on the CFD simulation results of Double-Skin Facade(DSF)for a specific problem.These two boundary settings are the constant temperature on the DSF surfaces called Boundary A,and Boundary B is defined via solar radiation using the Discrete Ordinate radiation Model(DOM).The paper verified both the numerical simulations using the experimental data.Comparing the numerical results of two types of boundaries with experimental data shows that both cases underestimated the values lower than 5.2 K and 0.1 m/s for the temperature and velocity respectively at the regarded measured points.Boundary A gives more accurate temperature prediction results,while Boundary B shows velocity magnitude closer to the measurements in the middle height of the cavity;the average temperature and velocity differences between the two boundary types are 0.6 K and 0.003 m/s respectively which are negligible.Finally,the selection of boundary conditions depends on study purposes,however,when the DSF is equipped with blinds and if there is not enough data in hand but the exact value of solar irradiation,using the Boundary B approach is suggested;it can provide reasonable results associated with multi-type of thermal boundary conditions at the same time.Furthermore,if the goal is to investigate the flow pattern in the DSF,Boundary B is argued to perform better than the constant temperature boundary condition.

关键词： Double-Skin Facade boundary conditions thermal performance airflow irradiation

Active Absorption of Perforated Plate Based on airflow

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Journal of Donghua University(English Edition) 2022年第6期39卷 590-596页

作者：张仁琪朱从云丁国芳黄其柏 School of Mechatronics Engineering Zhongyuan University of TechnologyZhengzhou 450007China School of Mechanical Science&Engineering Huazhong University of Science and TechnologyWuhan 430074China

The theory of active absorption of the perforated plate is proposed in this paper.The perforated plate is used as the material of active absorption and the depth of the cavity behind the perforated plate is changed according to the resonant frequency of the perforated plate.The rigid wall is moved to produce resonance so that the absorption coefficient can reach the maximal level.It is shown from the numerical calculation that when the perforated plate resonates,the moving distance is large at low frequencies,and the absorption coefficient is low under certain conditions.Perforated plate resonance is effective for single frequency of incident sound wave,which is difficult for the wide frequency,so active absorption based on airflow is posed,and the numerical calculation and experiment are carried out.The results denote that this method of active absorption is practical.

关键词： airflow perforated plate resonance absorption coefficient active absorption

Influence of gas ventilation pressure on the stability of airways airflow

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International Journal of Mining Science and Technology 2018年第2期28卷 297-301页

作者： Zhou Aitao Wang Kai Wu Longgang Xiao Yiwen Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining & Technology School of Resource and Safety Engineering China University of Mining & Technology

Coal mine ventilation is an extremely complicated system that can be affected by many factors. Gas ventilation pressure is one of important factors that can disturb the stabilization of airflow in airways.The formation and characteristics of gas ventilation pressure were further elaborated, and numerical simulations were conducted to verify the role of gas ventilation pressure in the stability of airway airflow.Then a case study of airflow stagnation accident that occurred in the Tangshan Coal Mine was performed.The results show that under the condition of upward ventilation, the direction of gas ventilation pressure in the branch is the same to that of the main fan, airflow of the branches beside the branch may be reversed. The greater the gas ventilation pressure is, the more obvious the reversion is. Moreover, reversion sequence of paralleled branches is related to the airflow velocity and length of the branch. Under the condition of downward ventilation, the airflow in the branch filled with gas may be reversed. Methane in downward ventilation is hard to discharge; therefore, accumulation in downward ventilation is more harmful than that in upward ventilation.

关键词： Gas accumulation Gas ventilation pressure airflow stability Underground ventilation

Effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge in atmospheric airflow

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Plasma Science and Technology 2020年第5期22卷 52-62页

作者：徐永锋郭宏飞王玉英樊智慧任春生 Key Laboratory of Materials Modification by Laser Ionand Electron BeamsDalian University of TechnologyDalian 116024People's Republic of China School of Science Hebei University of EngineeringHandan 056038People's Republic of China

In this paper,an asymmetric electrode geometry(the misalignment between the ends of highvoltage and grounded electrodes)is proposed in order to investigate the effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge(DBD).The results show that diffuse discharge manifests in the misaligned region and the micro-discharge channel in the aligned region moves directionally.Moreover,the diffuse discharge area increases with the decrease of the discharge gap and pulse repetition frequency,which is consistent with the variation of the moving velocity of the micro-discharge channel.When airflow is introduced into the discharge gap in the same direction as the transverse electric field,the dense filamentary discharge region at the airflow inlet of asymmetric electrode geometry is larger than that of symmetric electrode geometry.However,when the direction of the airflow is opposite to that of the transverse electric field,the dense filamentary discharge region of asymmetric electrode geometry is reduced.The above phenomena are mainly attributed to the redistribution of the space charges induced by the transverse electric field.

关键词： dielectric barrier discharge high-voltage atmospheric pressure air airflow lowtemperature plasma nanosecond pulsed discharge

Chaotic Motion Analysis for a Coupled Magnetic-Flow-Mechanical Model of the Rectangular Conductive Thin Plate

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Computer Modeling in Engineering & Sciences 2023年第11期137卷 1749-1771页

作者： Xinzong Wang Xiaofang Kang Qingguan Lei School of Civil Engineering Anhui Jianzhu UniversityHefei230601China Key Laboratory of Intelligent Underground Detection Technology Anhui Jianzhu UniversityHefei230601China

The chaotic motion behavior of the rectangular conductive thin plate that is simply supported on four sides by airflow andmechanical external excitation in a magnetic field is studied.According to Kirchhoff’s thin plate theory,considering geometric nonlinearity and using the principle of virtualwork,the nonlinearmotion partial differential equation of the rectangular conductive thin plate is deduced.Using the separate variable method and Galerkin’s method,the system motion partial differential equation is converted into the general equation of the Duffing equation;the Hamilton system is introduced,and the Melnikov function is used to analyze the Hamilton system,and obtain the critical surface for the existence of chaos.The bifurcation diagram,phase portrait,time history response and Poincarémap of the vibration system are obtained by numerical simulation,and the correctness is demonstrated.The results showthatwhen the ratio of external excitation amplitude to damping coefficient is higher than the critical surface,the system will enter chaotic state.The chaotic motion of the rectangular conductive thin plate is affected by different magnetic field distributions and airflow.

关键词： Rectangular conductive thin plate chaotic airflow magnetic field Melnikov function Galerkin’s method

EXPERIMENTAL STUDY OF airflow INDUCED BY PUMPING TESTS IN UNCONFINED AQUIFER WITH LOW-PERMEABILITY CAP

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Journal of Hydrodynamics 2012年第4期24卷 605-608页

作者： HUANG Hui QIAN Jia-zhong KUANG Xing-xing CHEN Zhou LI Ru-zhong School of Resources and Environmental Engineering Hefei University of Technology Hefei 230009 China Department of Earth Sciences The University of Hong Kong Hong Kong China

The airflow in unsaturated soils is an issue of great importance in various fields such as in agricultural, nuclear, environmental engineering. However, up to now, little attention was paid to the generation of the airflow induced by a pumping test in an unconfined aquifer with a low-permeability cap and its influence on the pumping test. In this paper, pumping tests were carried out experimentally in the aquifer with a low-permeability cap in order to study the influence of the airflow induced by the pumping on the drawdown of the tests. It is shown that：（1） there is an airflow with negative pressure generated by the pumping tests, （2） the Negative air Pressure （NP） is increased with the pumping rate but decreased with the radial distance, and （3） the NP also changes with the initial water table. The results provide a good basis for further theoretical study of the airflow induced by pumping.

关键词： low-permeability cap pumping tests airflow unconfined aquifer drawdown

Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in airflow

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Plasma Science and Technology 2016年第5期18卷 520-524页

作者：齐海成高巍樊智慧刘一荻任春生 School of Physics and Optoelectronic Technology Dalian University of Technology Dalian 116024 China School of Physics Science and Technology Anshan Normal University Anshan 114005 China AVIC Shenyang Aircraft Design & Research Institute Shenyang 110035 China

Volume diffuse dielectric barrier discharge （DBD） plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra （OES）, the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap.

关键词： diffuse DBD OES airflow atmospheric pressure nanosecond pulse

THE ANALYSIS FOR THE airflow EXCITING-VIBRATION FORCE OF CONTROL STAGE OF STEAM TURBINE

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Applied Mathematics and Mechanics(English Edition) 2001年第7期22卷 794-801页

作者：柴山张耀明马浩曲庆文赵又群 Research Institute for Science and Technology Shandong Institute of Technology Zibo P R China

Based on the hydrodynamics, the airflow exciting-vibration force of control stage of steam turbine is studied by using the momentum theorem. A formulation for calculating the air exciting-vibration force of the control stage of steam turbine is deduced first by using theoretical analysis method and taking all the design factors of vane and nozzles into consideration. Moreover, the exciting-vibration forces in different load cases are discussed respectively.

关键词： rotor dynamics exciting-vibration force airflow