共查询到20条相似文献,搜索用时 78 毫秒
1.
Movable Electrical Conducting Probe (MECP), a kind of simple and reliable measuring transducer, used for predicting full-flow-path flow pattern in a boiling vapor/liquid two-phase flow is introduced in this paper. When the test pipe is set at different inclination angles, several kinds of flow patterns, such as bubble, slug, churn, intermittent, and annular flows, may be observed in accordance with the locations of MECP. By means of flow pattern analysis, flow field numerical calculations have been carried out, and heat transfer coefficient correlations along full-flow-path derived. The results show that heat transfer performance of boiling two-phase flow could be significantly augmented as expected in some flow pattern zones.The results of the investigation, measuring techniques and conclusions contained in this paper would be a useful reference in foundational research for prediction of flow pattern and heat transfer behavior in boiling two-phase flow, as well as for turbine vane liquid-cooling design. 相似文献
2.
Im~ctionConfined swirling tWo-e flows are widelyutilized in engineering aPPlications, such as combushonsystems, cyclone separators etc. So they are a tOPic ofgreat interest to the engineering cOInlnunity. Incombushon systems they are used tO enhance the flamestability and tO box the foel and the ondzer well. Incyclone separators they are used to separate the Pridesby the centrifugal force. In all of those engineeringsystems, the behavior of both the particles and the air isof great ~e.St… 相似文献
3.
Study on Characteristics of Steady Flow Condensation Heat Transfer in a Fube Under Zero—Gravitation 总被引:2,自引:0,他引:2
StudyonCharacteristicsofSteadyFlowCondensationHeatTransferinaTubeunderZero-GravitationQnWei(HarbinInstituteofTechnology,Harbi... 相似文献
4.
To meet the need of real-time simulation for two-phase flow network in power plants, this paper presents a mathematical model
based on basic principles and a numerical solution method. This model can be used to describe nonhomogeneous two-phase flow
networks. The algorithm presented in this paper makes use of the sparsity, the symmetry and the diagonal dominancy of the
coefficient matrix to save storage space, reduce computational time and meet the requirements of real-time simulations. 相似文献
5.
Heat and Mass Transfer Enforcement of Vibrating Fluidized Bed 总被引:1,自引:0,他引:1
HeatandMassTransferEnforcementofVibratingFluidizedBed¥ChuZhide;YangJunhong;LiXuhui;SongYang(DepartmentofThermalEnergyEngineer... 相似文献
6.
Chyi-YeouSoong 《热科学学报(英文版)》2003,12(1):62-76
In the present paper, fluid flow and convective heat transfer between two co-axial disks rotating independently are dealt with mainly based on the author's recent research on that topic. Three rotational modes, i.e. co-rotation, rotor-stator, and counter-rotation, are considered. Theory of rotating non-isothermal fluids with the presence of disk rotation and thermal effects is addressed. Rotational buoyancy effects on the flow structure development are highlighted. Results of flow visualization and heat transfer measurements are discussed to explore the thermal flow mechanisms involved in the two-disk flows at various rotational and geometric conditions. Potential issues open to the future investigation are also proposed. 相似文献
7.
S.C. Saxena 《热科学学报(英文版)》1994,3(3):211-215
HydrodynamicandHeatTransferCharacteristicsofMagnetofluidizedBedsS.C.Saxena(DepartmentofChemicalEngineering,TheUniversityofIll... 相似文献
8.
A κ-ε-PDF model based on statistical theory for turbulent gas-particle flows is proposed.and a numerical procedure combining the finite difference and finite fluctuaing-velocity-group methods is used.The obtained statistically averaged equations have the same form as those obtained by using the Reynolds averaging.Using the κ-ε-PDF model(PDF particle turbulence model combined with the κ-ε- gas turbulence model),amny terms,such as the diffusion term in particle Reynolds Stress equations,can be accurately calcuated for verifying the second-moment-closure model,the κ-ε-PDF model is used to simulate sudden-expansion particle-laden flow.comparison of the predictions using both κ-ε-PDF and the κ-ε- models with experimental results shows that the κ-ε-PDF model give more reasonable non-siotropic features of particle turbulence. 相似文献
9.
IntrotctiouAImular chrDmatography Provides the POssibility ofseparating multicomponent fixtures continuously inone single unit. The rotating annulus of thechromatotw can be filled with arbitw stationalsPhases depending on the existing separation Problem.The feed is introduced at a fixed and stationary sechonat the top of the unit, while the eluent is distributedeverywhere else around the upper circumference. At thebottom the separated Products can be collected atcendn stationals exit angle… 相似文献
10.
Maunu KUOSA Petri SALLINEN Arttu REUNANEN Jari BACKMAN Jaakko LARJOLA Lasse KOSKELAINEN 《热科学学报(英文版)》2005,14(1):48-55
The study deals with the cooling of a high-speed electric machine through an air gap with numerical and experimental methods. The rotation speed of the test machine is between 5000-40000 r/min and the machine is cooled by a forced gas flow through the air gap. In the previous part of the research the friction coefficient was measured for smooth and grooved stator cases with a smooth rotor. The heat transfer coefficient was recently calculated by a numerical method and measured for a smooth stator-rotor combination. In this report the cases with axial groove slots at the stator and/or rotor surfaces are studied. Numerical flow simulations and measurements have been done for the test machine dimensions at a large velocity range. At constant mass flow rate the heat transfer coefficients by the numerical method attain bigger values with groove slots on the stator or rotor surfaces. The results by the numerical method have been confirmed with measurements. The RdF-sensor was glued to the stator and rotor surfaces to measure the heat flux through the surface, as well as the temperature. 相似文献
11.
Local instantaneous temperature signal and time‐averaged heat transfer coefficient were measured using a miniature heat transfer probe. The experiments were carried out in the bottom zone of a 5.8m high, 0.3m×0.5m rectangular cross‐section circulating fluidized bed. The results show that the heat transfer coefficient was higher near the walls, and became lower near the central region, and that the heat transfer coefficient decreases with increment of the air velocity due to the associated reduction of solids holdup in the bottom zone. In addition, the power spectrum density functions of the local instantaneous temperature signal can be characterized by the 1/f‐like distribution. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
The radial variation of the heat transfer coefficient across the bed width, including the effect of fins and fin shapes (surface roughness), on the heat transfer characteristics in the lean phase region of a circulating fluidized bed riser column are investigated. Three test sections (bare horizontal tube, V-fin tube and square fin tube) are employed for the investigation. The experimental unit consists of a riser column of 102×102 mm in bed cross-section, 5·25 m in height with a return leg of the same dimensions, and both made up of plexiglas columns. For the same operating conditions, the provision of fins results in a drop in heat transfer coefficient, but increases total heat transfer owing to increased surface area. The present experimental data are compared with published literature and good agreement has been observed. The experimental data also corresponds to the two-zone hydrodynamics (i.e. the core–annulus structure) of a circulating fluidized bed. © 1997 John Wiley & Sons, Ltd. 相似文献
13.
Xiaoguang Ren Jiangdong Zheng Sefiane Khellil Arumemi-Ikhide Michael 《Frontiers of Energy and Power Engineering in China》2009,3(1):85-89
In order to enhance heat transfer and mitigate contamination in the boiling processes, a new type of vapor-liquid-solid (3-phase)
circulating fluidized bed boiling system has been designed, combining a circulating fluidized bed with boiling heat transfer.
Experimental results show an enhancement of the boiling curve. Flow visualization studies concerning flow hydrodynamics within
the riser column are also conducted whose results are presented and discussed. 相似文献
14.
Xiaoguang REN Jiangdong ZHENG Sefiane KHELLIl Arumemi-Ikhide MICHAEL 《Frontiers in Energy》2009,3(1):85
In order to enhance heat transfer and mitigate contamination in the boiling processes, a new type of vapor-liquid-solid (3-phase) circulating fluidized bed boiling system has been designed, combining a circulating fluidized bed with boiling heat transfer. Experimental results show an enhancement of the boiling curve. Flow visualization studies concerning flow hydrodynamics within the riser column are also conducted whose results are presented and discussed. 相似文献
15.
J.F. Lu J.S. Zhang G.X. Yue Q. Liu L. Yu X.D. Lin W.J. Li Y. Tang T.Y. Luo R.S. Ge 《亚洲传热研究》2002,31(7):540-550
Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540–550, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10056 相似文献
16.
17.
18.
Heat transfer improvement in a water wall tube with fins was investigated in a circulating fluidized bed (CFB) boiler. Experiments were first conducted in a 6 MWth CFB boiler then a model was developed to analyse and interpolate the results. Temperatures at some discrete points within the wall cross‐section of the tube were measured by burying 0.8 mm thermocouples within a tube. Experimental data showed an increase in heat absorption up to 45 per cent. A good agreement between measured and predicted values was noted. The distribution of temperature in the metal wall and of heat flux around the outer wall of a tube with longitudinal and lateral fins was analysed by numerical solution of a two‐dimensional heat conduction equation. Effects of bed‐to‐wall heat transfer coefficient, water‐to‐tube inside heat transfer coefficient, bed temperature, water temperature and thermal conductivity of the tube material on the heat flux around the water tube are discussed. The present work also examines the influence of the length of the longitudinal fin and the water tube thickness. Heat flux was highest at the tip of the longitudinal fin. It dropped, but increased again near the root of the lateral fin. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
19.
In this study, the forces affecting the motion of particle clusters near the wall of a CFB were theoretically analysed. The motion trajectory and the contact time of clusters were determined from the proposed model for two cases, steel ball having density of 6980 kg m?3 and sand having density of 2500 kg m?3. Computational results showed that the construction and operational parameters such as the bed equivalent diameter, the gas velocity and the bed temperature have great influence on the contact time of clusters. Based on analysis of the contact time of clusters, a theoretical model was developed for predicting the particle–gas convection heat transfer coefficient. The results were compared with experiments and were a quite agreement with the measured data in the open literature which suggests that the theoretical analysis conducted in this work can very well describe the convection heat transfer in a CFB. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
The axial and radial variation of the heat transfer coefficient in a circulating fluidized bed riser column, and the effect of operating parameters thereon, are investigated. The experimental set-up consists of a riser column of 102 mm×102 mm in bed cross-section, 5·25 m in height with a return leg of the same dimensions. The unit is fabricated with plexiglass columns of 0·6 m in length which are interchangeable with one another. Two axial heat transfer test sections of 102 mm×102 mm in cross-section, 500 mm in height, and made of mild steel, are employed for the axial heat transfer study and one horizontal tube section of 22·5 mm OD made of mild steel is employed for the radial heat transfer study. The primary air velocity is varied between 4·21 and 7·30 m s−1. Local sand of mean size (dp) 248 μm is used as the bed material. One empirical model with the help of dimensional analysis has been proposed to predict the heat transfer coefficient to a bare horizontal tube in a CFB riser column and the model results are validated with the experimental data; good agreement has been observed. © 1997 John Wiley & Sons, Ltd. 相似文献