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Study on the discharge coefficient of wind-driven naturally ventilated Chinese solar greenhouses

Building Simulation 2024年第9期17卷 1541-1556页

作者： Jingfu Zhang Shumei Zhao Zhiwei Liu Yanfeng Li Youyu Li Zilong Fan Tao Ding College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100080China Infrastructure Construction Department China Agricultural UniversityBeijing100080China Tibet Academy of Agricultural and Animal Husbandry Sciences Lhasa851418China

The Chinese solar greenhouse(CSG)is a prevalent feature in agricultural practices within ***,the regulation of natural ventilation within this architectural structure remains ***,the development of a natural ventilation model becomes imperative for the effective management of the greenhouse *** particular significance within these models is the consideration of the discharge coefficient as a pivotal *** a multi-case investigation into the variable-dependent discharge coefficient is crucial for both practical application and model *** research delved into the impact of various factors,including the upper-lower vents area ratio(A_(up)/A_(low)),vent-greenhouse area ratio(A_(low)/A_(greenhouse)),lower vent position height(h/H),the incident angle of the external wind,and altitude,on the discharge coefficient(C_(d))of CSG.A CFD model was developed for a scaled CSG with validation conducted through field experiments and wind tunnel *** indicated a 61.6%reduction in C_(d)on average corresponding to an 80%decrease in A_(up)/A_(low).C_(d)levels remained consistent following the attainment of an A_(up)/A_(low)ratio of ***,there was an average increase of 52.5%in C_(d)levels for every 0.09 decline in h/H,attributed to the blocking effect of the ***,the ventilation rate and the pressure coefficient difference were utilized to construct a model of C_(d)pertaining to greenhouse design and ventilation operation,exhibiting a notable accuracy level of R^(2)=***,the blocking effect of higher h/H was relieved as the incident angleθdecreased under the windward *** increase in A_(up)/A_(low)and the decrease in A_(low)/A_(greenhouse)were identified as crucial factors contributing to the growth of C_(d)under leeward ***,the high-altitude environment led to a rise in C_(d)levels in contrast to the low-altitude *** increasing rate of C_(d)c

关键词： Chinese solar greenhouse discharge coefficient area ratio position height wind direction altitude

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The Effect of Diffuser Angle on the discharge coefficient of a Miniature Critical Nozzle

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Journal of Thermal Science 2010年第3期19卷 222-227页

作者： Jae Hyung Kim Heuy Dong Kim Toshiaki Setoguchi School of Mechanical Engineering Andong National UniversityAndong760-749Korea Department of Mechanical Engineering Saga University1HonjoSagaJapan

Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow ***,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS ***,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are *** the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical *** computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 *** computational results are validated with some experimental data *** results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical *** is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain *** implies that the miniature critical nozzles should be carefully designed.

关键词： Compressible Flow Critical Nozzle Compressible Flow discharge coefficient Diffuser Configuration Reynolds Number

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discharge coefficient of 3-in-1 Hole with Various Inclination Angle and Hole Pitch

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Chinese Journal of Aeronautics 2008年第5期21卷 385-392页

作者：李广超朱惠人樊慧明西北工业大学动量与能源学院西安710072

discharge coefficients of 3-in-1 hole of three inclination angles and three spacing between holes are presented which described the discharge behavior of a row of holes. The inlet and outlet of the 3-in-1 hole both have a 15° lateral expansion. The flow conditions considered are mainstream turbulence intensities and density ratios of secondary flow to mainstream. The momentum flux ratios varied in the range from 1 to 4. The comparison is made of the discharge coefficients of three shaped holes to find an optimal hole with low flow loss. The results show that the discharge coefficients of 3-in- 1 hole are highest in three shaped holes and therefore this article is focused on the measurements of discharge coefficients of 3-in-1 hole for various geometries and aerodynamic parameters. The measured results of 3-in-1 hole indicate that turbulence intensities, density ratios and momentum flux ratios have weak influence on discharge coefficients for inclination angle of 20°. The high turbulence intensity yields the small discharge coefficients for inclination angle of 45° and 90°. The increased both momentum flux ratios and density ratios lead to the increased discharge coefficients for inclination angle of 45° and 90°. The increased inclination angle causes the rapidly increased discharge coefficients. There is a weak dependence of discharge coefficients on hole pitches.

关键词： aerospace propulsion system gas turbine film cooling hole discharge coefficient

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Estimation of debris flow discharge coefficient considering sediment concentration

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International Journal of Sediment Research 2019年第1期34卷 1-7页

作者： Namgyun Kim Hajime Nakagawa Kenji Kawaike Hao Zhang Department of Civil and Earth Resource Engineering Kyoto University 2. Disaster Prevention Research CenterKyoto University Disaster Prevention Section Science Research CenterKochi University

A sabo dam has a purpose to block the path of debris flow. However, when overflow occurs, a sabo dam works as a weir, a vertical obstruction, where the fluid must flow over. Many empirical formulas and discharge coefficients for weirs relating flow depth to discharge have been proposed to calculate overflow discharges. However, only a few studies about overflow discharge coefficients are available in the case of debris flow. In this paper, experiments and numerical simulations were done to estimate debris flow discharge coefficients by considering the sediment concentration. In the numerical simulation, a complete overflow equation and a free overfall equation were implemented to calculate debris overflow discharges at a sabo dam. To determine the discharge coefficients for each equation, single factor regression analysis was used. Laboratory experiments were done to calibrate and to compare with the simulation. Study results showed that the discharge coefficients increase as the sediment concentration increases. This finding suggests debris flow discharge coefficients are derived to calculate the debris overflow discharges at a sabo dam.

关键词： Numerical simulation Debris flow Sabo dam discharge coefficient

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Investigation of Interacting Mechanism between Film Cooling and Internal Cooling Structures of Turbine Blade

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Journal of Thermal Science 2023年第1期32卷 330-350页

作者： ZHANG Guohua XIE Gongnan BENGT Sundén School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072China School of Mechanical Engineering Northwestern Polytechnical UniversityXi'an 710072China Department of Energy Sciences Lund UniversityLund SE-22100Sweden Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China

This paper presents three-dimensional numerical simulations with the established realizable k-εmodel to clarify the underlying and interacting mechanisms between the film cooling and the internal *** the one hand,the effects of three different internal cooling channels,i.e.,smooth channel,continuous ribbed channel,and truncated ribbed channel,on the film cooling effectiveness and the discharge coefficients are *** the other hand,the influences of three different film cooling holes,i.e.,cylindrical hole,two elliptical holes and two circular-to-elliptical holes,on the heat transfer performances and pressure loss of the internal cooling channel are ***,the suction effects of the film cooling holes are analyzed through setting up baselines with only internal cooling *** show that the placement of ribs in the internal channel has different influences on the film cooling effectiveness with respect to different hole shapes depending on the blowing *** discharge coefficient of the film hole can be improved by introducing ribs to the internal *** of film hole is helpful for enhancing the heat transfer performance and reducing the pressure loss of the internal ***,ribs instead of the suction effect of film hole play a major role to enhance the heat transfer performance in the internal cooling channel.

关键词： interacting mechanism film cooling effectiveness discharge coefficient heat transfer performance pressure drop

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Fluid dynamic modeling of junctions in internal combustion engine inlet and exhaust systems

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Journal of Thermal Science 2010年第5期19卷 410-418页

作者： David Chalet Pascal Chesse Internal Combustion Engine Team Laboratory of Fluid Mechanics-UMR CNRS 6598 Ecole Centrale de NantesBP 92101 44321 NantesFrance

The modeling of inlet and exhaust systems of internal combustion engine is very important in order to evaluate the engine *** paper presents new pressure losses models which can be included in a one dimensional engine simulation *** a first part,a CFD analysis is made in order to show the importance of the density in the modeling ***,the CFD code is used,as a numerical test bench,for the pressure losses models *** coefficients depend on the geometrical characteristics of the junction and an experimental validation is made with the use of a shock tube test *** the models are then included in the engine simulation code of the *** numerical calculation of unsteady compressible flow,in each pipe of the inlet and exhaust systems,is made and the calculated engine torque is compared with experimental measurements.

关键词： compressible flow gas dynamics pressure wave propagation discharge coefficient internal combustion engine CFD simulation

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Numerical simulation on a film-cooled rotating model with 30° injection holes

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航空动力学报 2010年第7期25卷 1443-1453页

作者： YANG Bin XU Guo-qiang TAO Zhi DING Shui-ting WU Hong-wei National Key Laboratory of Science and Technology on Aero-Engines School of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing 100191 China

The flow and heat transfer characteristics were numerically investigated on a film cooling model under different rotating operating *** computational model was originated from the mid-span section of a typical turbine rotor with two rows of 14 staggered injection holes angled 30° both on the suction surface and pressure surface,and the flow through the coolant plenum and all the hole-pipes were resolved as a part of the computational domain by specifying the coolant mass flux in the *** computations primarily focus on under-standing the rotational effect on film cooling performance in mechanism research *** the present study,the Reynolds number(Re) based on mainstream velocity and injection hole diameter varied from 1835.5 to 5507.4,and the averaged blowing ratio(M) ranges of 0.5 to *** show that the coolant will move on to the high-radius locations near the suction and pressure surfaces due to the strong centrifugal effect,which leads to the decrease in adiabatic effectiveness *** discharge coefficients(Cd),on the pressure surface,are much higher than that on the suction surface under a given operating *** addition,the critical values of angular speed which represent the equilibrium of centrifugal force and Coriolis force near the pressure surface are also presented.

关键词： film cooling rotating adiabatic effectiveness heat transfer discharge coefficient

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Towards high-efficiency of hydrogen purification in metal hydride

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Progress in Natural Science:Materials International 2023年第3期33卷 301-308页

作者： Koua Alain Jesus Koua Jiahe Peng Arramel Arramel Neng Li State Key Laboratory of Silicate Materials for Architectures School of Materials Science and Engineering Wuhan University of Technology Shenzhen Research Institute of Wuhan University of Technology Nano Center Indonesia Jalen Raya PUSPIPTEK South Tangerang School of Chemistry and Environmental Engineering School of Environmental Ecology and Biological Engineering Novel Catalytic Materials of Hubei Engineering Research Center Wuhan Institute of Technology

Recent advancement on hydrogen（H2） retrieval in a mixture gas of H2/CO2based on the metal hydride（MH）technique has attracted numerous interests. In this work, we implement the lumped element model simulation to conduct a theoretical approach on the hydrogen purification process. The influence of orifice geometry and temperature of the tank, and inflow gas rate(fin) is investigated. The results show that the discharge coefficient（DC） is affected by the tank's orifice geometry. The orifice shape is increasing the value of DC, as a result, the CO2（impurity） outflow rate heightens during the venting process and thereby promoting to obtain a high hydrogen purity. By overcoming the exothermic/endothermic effect in the absorption/desorption step and a proper finselection, we find an improvement in the hydrogen storage capacity（wt%） into MH and consequently the hydrogen recovery rate increases. A sharp improvement in orifice geometry and thermal conditions of the tank,and finenhances the main targeted results（hydrogen purity and recovery rate） and ensures the proper operation of the MH technique.

关键词： Hydrogen purification Metal hydride discharge coefficient Lumped model simulation Carbon dioxide

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Drag prediction method of powered-on civil aircraft based on thrust drag bookkeeping

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Chinese Journal of Aeronautics 2015年第4期28卷 1023-1033页

作者： Zhang Yufei Chen Haixin Fu Song Zhang Miao Zhang Meihong School of Aerospace Engineering Tsinghua University Shanghai Aircraft Design and Research Institute

A drag prediction method based on thrust drag bookkeeping（TDB） is introduced for civil jet propulsion/airframe integration performance *** method is derived from the control volume theory of a powered-on *** problem of the TDB is identified to be accurate prediction of velocity coefficient of the powered-on *** of CFD solver is validated by test cases of the first AIAA Propulsion Aerodynamics *** the TDB method is applied to thrust and drag decomposing of a realistic aircraft.A linear relation between the computations assumed free stream Mach number and the velocity coefficient result is *** thrust losses caused by nozzle internal drag and pylon scrubbing are obtained by the isolated nacelle and mapped on to the in-flight whole configuration *** of the powered-on condition are investigated by comparing through-flow configuration with powered-on *** variance on aerodynamic coefficients and pressure distribution is numerically studied.

关键词： discharge coefficient Drag prediction Powered-on configuration Thrust drag bookkeeping Velocity coefficient

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Numerical Investigation of Flow and Heat Transfer in Vane Impingement/Effusion Cooling with Various Rib/Dimple Structure

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Journal of Thermal Science 2023年第4期32卷 1357-1377页

作者： WANG Mingrui ZHU Huiren LIU Cunliang WANG Rui WU Zhuang YAO Chunyi School of Power and Energy Northwestern Polytechnical UniversityXi’an710129China

By investigating heat transfer and flow structures of dimples,orthogonal ribs,and V-shaped ribs in the impingement/effusion cooling,the article is dedicated to selecting a best-performing internal cooling structure for a turbine *** overall cooling effectiveness and coolant consumption are adopted to evaluate the cooling *** analyze the influence of structural modification,the flow field is investigated on chordwise/spanwise sections and the target *** blockage effect on crossflow can protect jet flow,resulting in higher heat transfer performance of the target *** own a stronger blockage effect than *** with the blockage effect,the influence of the rib shape is *** installing dimples between ribs,heat transfer is augmented *** introduction of ribs/dimples leads to higher discharge coefficients of jet nozzles but lower discharge coefficients of film ***,the film cooling ***,the installation of the ribs and dimples decreases total coolant *** effect of ribs/dimples on heat transfer and effusion condition of internal and external cooling is *** best-performing cooling structure is the target surface with dimples and orthogonal ribs,which decreases the wall temperature and coolant consumption by 14.57-28.03 K and 1.19%-1.81%*** article concludes the flow mechanism for dimples and influence factors on the cooling performance,which may serve as guidance for the turbine vane design.

关键词： conjugate heat transfer impingement cooling dimple V-shape rib discharge coefficient

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