INVESTIGATION ON FLOW AND HEAT TRANSFER CHARACTERISTICS OF ANNULAR TWO-PHASE FLOW THROUGH THE VENTURITUBE

A model that incorporates the important phenomena in the annular gas-water flow through the Venturi tube is presented. A series of experiments are carried out to measure the flow and heat transfer characteristics in cold and hot conditions. Comparison between numerical and experimental results shows good agreement.     

FLOW AND HEAT TRANSFER OF OLDROYD-B FLUIDS IN A ROTATING CURVED PIPE

The flow and convected heat transfer of the Oldroyd-B fluids in a rotating curved pipe with circular cross-section were investigated by employing a perturbation method. A perturbation solution up to the second order was obtained for a small curvature ratio, κ. The variations of axial velocity distribution and secondary flow structure with F, Re and We were discussed in detail in order to investigate the combined effects of the three parameters on flow structure. The combined effects of the Coriolis force, inertia force and elastic force on the temperature distribution were also analyzed, which are greater than the adding independent effects of the three forces. The variations of the flow rate and Nusselt number with the rotation, inertia and elasticity were examined as well. The results show the characteristics of the heat and mass transfer of the Oldroyd-B fluids in a rotating curved pipe.     

EXPERIMENTAL AND NUMERICAL ANALYSIS OF LAMINAR AND LOW TURBULENT FLOW DISTRIBUTIONS IN INLET DIVIDING HEADER OF SHELL AND TUBE HEAT EXCHANGER

Flow distribution headers play a major role in heat exchangers. The selection of header diameter, branch pipe diameter, branch pipe spacing etc. is based on the designer's experience and general guide lines. The proper selection of the header dimensions will yield uniform flow distribution in heat exchangers, which in turn will enhance the heat exchanger efficiency. In this work, the flow distribution in branch pipes and the pressure variation across the branch pipes in laminar and low turbulence region is studied with two models of the inlet dividing headers. When the numerical analysis has been applied, its inability to predict the no flow condition through the branch pipes is revealed. The results are presented in the form of flow rate ratio through branch pipes and nondimensional coefficients across branch pipes which are useful to apply the existing mathematical models for the present experimental setup.     

LAMINAR FLOW AND HEAT TRANSFER IN THE DEVELOPING REGION OF HELICAL SQUARE DUCTS

Simultaneous development of the laminar flow and heat transfer in helical square ducts was numerically studied. The governing equations were written in an orthogonal helical coordinate system and fully parabolized in the axial direction. Results were found out over a wide range of the governing parameters. Two axial velocity entries were taken into account. The development of secondary flow, axial velocity and temperature distribution for the large Dean number were examined in detail and the effects of different governing parameters on the friction factor and the Nusselt number were annlyzee. Many new and interesting conclusions were reached. The present results reveal the nature of fluid flow and heat transfer in the developing region of helical square ducts.     

COMPUTATION OF TURBULENT FLOW AND HEAT TRANSFER IN LARGE RADIUS 90－DEGREE CIRCULAR BENDS

ＣＯＭＰＵＴＡＴＩＯＮＯＦＴＵＲＢＵＬＥＮＴＦＬＯＷＡＮＤＨＥＡＴＴＲＡＮＳＦＥＲＩＮＬＡＲＧＥＲＡＤＩＵＳ９０－ＤＥＧＲＥＥＣＩＲＣＵＬＡＲＢＥＮＤＳＭ．Ｊ．Ｗａｎｇ（ＴｅｃｈｎｉｓｃｈｅＵｎｉｖｅｒｓｉｔａｔＭｕｎｃｈｅｎ，ＢＲＤ）ＳｕＭｉｎｇ－...     

FINITE ELEMENT ANALYSIS OF LAMINAR FLOW AND HEAT TRANSFER IN A BUNDLE OF CYLINDERS

In this paper two-dimensional Navier-Stokes equations and energy equation governing incompressible laminar flow past a bundle of cylinders were numerically solved by using the finite element method.The velocity correction method was used for time advancement, and spatial discretization was carried out with the Galerkin weighted residual method.Viscous flows past the cylinder banks arranged in in-line cylinder bundles and staggered cylinder bundles, coupled with heat transfer, were investigated for pitch-diameter ratios of 1.5 and 2.0 and the Reynolds numbers from 50 to 500.Flow structures and heat transfer behavior were discussed.The results obtained agree well with available numerical data.     

NUMERICAL SIMULATION OF FLOW AND HEAT TRANSFER CHARA-CTERISTICS OUTSIDE A PERIODICALLY VIBRATING TUBE

Fluid flow and heat transfer characteristics outside a vibrating tube were numerically simulated by the dynamic mesh method. The mechanism of heat transfer enhancement via periodic vibration of the tube was explored by using the field synergy principle. It is found that the field synergy angle between fluid velocity vector and temperature gradient vector for a periodically vibrating tube is significantly smaller than that for a stationary tube, and it changes approximately according to the sinusoidal law in a vibration period. The effect of time phase of the vibration on the field synergy angle and convective heat transfer coefficient were also discussed. Results indicate that the vibration can enhance heat transfer and this effect is more remarkable when time phase angle ranges between 50° and 1400 in a half period. Especially when the time phase angle is 90°, the average field synergy angle outside the tube reaches the minimum, which leads to the best heat transfer performance.     

DIRECT NUMERICAL SIMULATION OF TURBULENT HEAT TRANSFER IN A WALL-NORMAL ROTATING CHANNEL FLOW

1. INTRODUCTIONTurbulent flows with heat transfer in rotatingframe exist in a variety of industrial , geophysicaland astrophysical applications . The rotation in-duces additional body forces ,i .e .,centrifugal andCoriolis forces , acting on the turbulent…     

EXPERIMENTAL STUDY OF ENHANCED HEAT TRANSFER BY FLOW-INDUCED VIBRATION OF ELASTIC TUBE BUNDLES

1.　INTRODUCTIONThe flow-induced vibration isa general phenomenon in heatexchangers.Its mechanismconsists of vortex shedding,turbulentbuffeting,fluid elastic excitation,acoustic excitation,static pressure pulsation oftwo-phase-flow,etc.In thisaspect,a large quantity ofwork wasconducted,and many theoretical models and experiential discriminantswere putforward bylots of researchers(see Ref.[1 ] ) .The previous study mostly laid emphasis on the avoidanceof flow-induced vibration,however,its …     

EXPERIMENTAL STUDY OF CONDENSATION HEAT TRANSFER CHARACTERISTICS OF HORIZONTAL TUBE BUNDLES IN VACUUM STATES

To develop an excellent heat transfer element under the vacuum condition,experiments about the heat transfer performance of horizontal tube bundles of different materials under various vacuum condition...     

THE INFLUENCE OF DIFFERENT DESIGN PARAMETERS AND WORKING CONDITIONS ON CHARACTERISTICS OF HEAT METERS

In this article,the UDF technology in Fluent software is used to simulate three-dimensional flow fields and to obtain various flow parameters. The standard k-ε model and the RNG k-ε model are both used to calculate the inner flow field of the basal meter,and a comparison of the calculated results between two models shows that RNG k-ε model is more effective for calculations of the inner flow of rotary wing mechanism. The influence of tip clearance on the characteristics of the basal meter is studied. The in...     

FLUID CHARACTERISTICS OF ROTARY WING HEAT METER WITH SINGLE-CHANNEL

Fluid characteristics of a rotary wing heat meter with single-channel were studied through theretical analysis, numerical simulation and experiments. The obtained results show that the number of vanes can obviously influence the heat meter, but the water temperature seldom influence the meter , and the optimal number of vane is 6-8.     

HEAT AND MASS TRANSFER CHARACTERISTICS IN UNDERGROUND COOLING POOL AND EXPERIMENTAL INVESTIGATION

ABSTRACT: To dear with the problems perplexed by energy consumption, noise and earth sink in the refrigeration and air conditioning, this paper puts forward a new technology-refrigeration using geothermic energy. The heat and mass transfer characteristics of the underground cooling pool are analyzed and numerical model is given. The experimental results show that refrigeration using geothermie energy applies well in all kinds of environmental conditions.     

EXPERIMENTAL STUDY ON ENHANCED HEAT TRANSFER WITH NI-BASED IMPLANTED SPIRAL FINNED TUBES

1 .　INTRODUCTIONHeatexchangershavebeenwidelyusedinvar iousfields ,andhigherefficiencyandreliabilityareneededinapplications.Higherefficiencymaydeattainedwithdifferentenhancementmethodsofheattransferpresentedbymanyresearchers .Butthestudyonimprovingreliabilityhasproceededalittle .Thenewtypeofheatexchangerelements Ni basedImplantedSpiralFinnedTurbes (NISFT)arestudiedandtestedinthis paper ,whichcancontributetoincreasetheefficiencyandreliabili ty[1] .Itistheeffectivewayofenhancedheattrans…     

EXPERIMENTAL RESEARCH OF CYLINDER TO BED HEAT TRANSFER IN AGITATED FLUIDIZED BEDS

NOMENCLATUREAc　　 cylinder surface area,m2dc cylinder diameter,mdp mean diameter of solid particles,mD cylinder vessel diameter,mH static bed height,mh average surface-to-bed heattransfer coeffcient,Wm- 2 K- 1hmax maximum average surface-to-bed heattransfer coefficient,Wm- 2 K- 1n rotary speed of agitating mechanism,r/ minL cylinder length,mQ heattransfer rate,WTs heater surface temperature,KTb bed temperature,KU overall superficial gas velocity,ms- 1Umf superficial minimum fluidiza…     

THE FRICTIONAL RESISTANCE CHARACTERISTICS OF GAS LIQUID TWO PHASE FLOW IN HELICAL COILED TUBES

1.　INTRODUCTIONThe equipments with helical-coiled tubes have been widely applied in industry,such asnylon production,boiler,special heat exchangers,nuclear power station and so on.Manyauthors have been done lots of experimental studies on frictional resistance characteristics ofgas liquid two-phase flow in helical-coiled tubes[1 ] [2 ] .But,there has been rate related treat-mentby means of dimension analysis andπtheorem.The experimentof frictional resistance characteristics of gas-liqui…     

LARGE EDDY SIMULATION OF FREE SURFACE TURBULENT CHANNEL FLOW WITH HEAT TRANSFER

1. INTRODUCTIONFreesurface turbulent flow exists widely in engineering. Due to difficulties in measurement and simulation, very little has been understood about the structures and transport mechanism of turbulence near the freesurface. Komori and Ueda…     

NUMERICAL SIMULATION OF TURBULENT FLOW CHARACTERISTICS IN A CURVED PIPE WITH A BAFFLE

A numerical study on the characteristics of developing turbulent flow in a curved pipe with a baffle was carried out in body-fitted coordinates with the k-ε model turbulence. A curved duct of square cross-section was examined first, and the results agree very well with the experimental data. Then two kinds of pipes, a normal curved pipe and that with a baffle were studied. The computational results are presented and compared with each other to illustrate the changes of the flow after adding the baffle. The longitudinal velocity in the pipe with a baffle was characterized by outer velocity bigger than the inner one. The secondary flow was characterized by four-vortex structure with the intensity reduced, which results in the equability of the flow field of the cross-section compared with that without a baffle, and has much more significant meaning in engineering.     

NUMERICAL SIMULATION OF STREAMBED HEAT TRANSFER

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PREDICTION OF TURBULENT FLOW CHARACTERISTICS IN THE CURVED DUCT WITH A BAFFLE

The changes of the developing turbulent flow characteristics in curved duct after adding a baffle are studied numerically at the body-fitted coordinates.a k-εmodel is used to represent the turbulence.a curved duct of rectangular cross-section is computed firstly, it has been observed that the predictions using the procedure agree very satisfactory with the experimental data.Then,two kinds of square ducts are studied,one is normal curved duct,the other is a duct with a baffle.The computational results are presented and compared to each other,in order to display the changes of the flow after adding a baffle in curved ducts.The secondary flow in a duct with a baffle is characterized by four-vortices structure with the outer two bigger than the inner two.Besides,compared with the duct without a baffle,the intensity of the secondary flows is reduced,which results in the flow field of the cross-section much more equable and has much more significant meaning in the engineering.