NATURAL CONVECTIVE HEAT AND MASS TRANSFER BY THE COUPLING OF TEMPERATURE CRADIENT AND CONCENTRATION GRADIENT IN A POROUS MEDIUM

ＮＡＴＵＲＡＬＣＯＮＶＥＣＴＩＶＥＨＥＡＴＡＮＤＭＡＳＳＴＲＡＮＳＦＥＲＢＹＴＨＥＣＯＵＰＬＩＮＧＯＦＴＥＭＰＥＲＡＴＵＲＥＣＲＡＤＩＥＮＴ　ＡＮＤＣＯＮＣＥＮＴＲＡＴＩＯＮＧＲＡＤＩＥＮＴＩＮＡＰＯＲＯＵＳＭＥＤＩＵＭ￥ＣｈｅｎＢａＯ－Ｍｉｎｇ；Ｆ...     

A MATHEMATICAL MODEL FOR HEAT AND MASS TRANSFER IN UNSATURATED WET POROUS MEDIA CONSIDERING EFFECT OF CAPILLARY HYSTERESIS

Based on the transport mechanism of heat and mass transfer and by using the minimum gradient theory for unsaturated flow in capillary porous media, a mathematical model is developed for heat and mass transfer in unsaturated wet porous media considering the effect of capillary hysteresis. The heat and mass transport properties in the derived differential equations are analyzed in detail. which opens new way to further develop practical methods for determining heat and mass transport properties in wet porous media.     

NUMERICAL STUDY ON SORET-EFFECT AND DUFOUR-EFFECT FOR DOUBLE-DIFFUSIVE NATURAL CONVECTION IN POROUS ENCLOSURE

The influences of Soret effect and Dufour effect on the natural convection and heat and mass transfer for a porous enclosure were investigated by means of the penalty finite element method. Numerical results indicate that the Soret and Dufour effects have significant influences on heat and mass transfer in the presence of large temperature gradient and concentration gradient.     

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.     

THEORETICAL STUDY OF HEAT TRANSFER ENHANCEMENT IN PIPE WITH POROUS BODY

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＨｅａｔｔｒａｎｓｆｅｒｅｎｈａｎｃｅｍｅｎｔｂｙｐｏｒｏｕｓｂｏｄｙｈａｓｂｅｅｎｗｉｄｅｌｙｓｔｕｄｉｅｄｉｎｒｅｃｅｎｔｄｅｃａｄｅｓ .Ｔｈｅｐｏｒｏｕｓｂｏｄｙｓｔｕｄｉｅｄ ｐｒｅｖｉｏｕｓｌｙ ,ｗｉｔｈｔｈｅｐｏｒｏｓｉｔｙｌｅｓｓｔｈａｎ80 % [1] ｃａｎｅｎｈａｎｃｅｔｈｅｈｅａｔｔｒａｎｓｆｅｒ ,ｂｕｔｔｈｅｆｌｏｗｒｅｓｉｓｔａｎｃｅｉｎｃｒｅａｓｅｓｑｕｉｌｅｆａｓｔｅｒ .Ｉｔａｆｆｅｃｔｓｉｔｓｕｓｅｉｎｐｒａｃｔｉｃｅ.Ｔｈｅ ｐｒｅｓｅｎｔｓｔ…     

A NEW INSTRUMENT FOR MEASURING LOCAL MOISTURE CONTENTS IN MOIST POROUS MEDIA

A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.     

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...     

NUMERICAL SIMULATIONS OF A CENTERED CONDUCTING BODY ON NATURAL CONVECTION AND HEAT TRANSFER IN AN ENCLOSURE

1.INTRODUCTIONA heat-conducting body is located somewherewithinthe enclosure,thereby affecting the naturalconvection flowand heat transfer.Soit is veryi m-portant in theory and used widely in many engi-neering systems.For example in a metal castingprocess,a solid may be placedinthe mold to forma holeinthe casting,another examplein electronicpackages with windows or walls.Natural convection and heat transfer of a cen-tered conducting body in an enclosure are complexproblems in the fluid me…     

DETERMINATION OF HEAT AND MOISTURE TRANSPORT PROPERTIES IN WET POROUS MEDIA USING THEPARAMETER ESTIMATION METHOD

1.INTRODUCTIONtheheatandmoisturetransportpropertiesinwetporousmediaareessentialdatatodealwithmanyengineeringproblemsandarealsooneofthemostimportantresearchobjectivesinthefieldofheatandmasstransferinwetporousmedia.Althoughmanymethodshavebeendevelopedtoanalyzetheheatandmoisturetransportpropertiesinwetporousmedia,theexistingdataoftheheatandmoisturetransportpropertiesaresodeficientthatthedatacannotmeettheneedsfortheoreticalresearchandengineeringapplicationsbecauseofthecomplexityintheheatandmas…     

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 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 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…     

SIMULTANEOUS MEASUREMENT OF THE HEAT AND MASS DIFFUSIVITIES IN UNSATURATED MOIST SOILS USING CONSTANT HEAT FLUX METHOD

The simultaneous measurement of the heat and mass diffusivities in unsa-turated moist soils is presented by use of constant heat flux method. By integrating the analytical solutions of the equations governing the heat and mass transfer process in a one-dimensional semi-infinite moist soil sample under condition of constant heat flux with the measurement data of the temperature and the moisture content fields in the soil sample, the heat and mass diffutivities of the soil sample are obtained. The experimental results show that the developed method is timesaving and can determine the heat and mass diffusivities in a moist soil through only one test, resulting in significant advantages in practical applications. This method has potential applications to the determination of heat and mass diffusivities in moist soils and may provide a new way for the fast and accurate measure-ment of the heat and mass diffusivities in moist soils and other unsaturated wet porous media.     

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

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

WAVE EQUATION MODEL FOR NUMERICAL SOLUTIONS OF ADVECTION－DOMINANT HEAT TRANSFER

ＷＡＶＥ　ＥＱＵＡＴＩＯＮ　ＭＯＤＥＬ　ＦＯＲ　ＮＵＭＥＲＩＣＡＬ　ＳＯＬＵＴＩＯＮＳ　ＯＦ　ＡＤＶＥＣＴＩＯＮ－ＤＯＭＩＮＡＮＴ　ＨＥＡＴ　ＴＲＡＮＳＦＥＲＷＡＶＥＥＱＵＡＴＩＯＮＭＯＤＥＬＦＯＲＮＵＭＥＲＩＣＡＬＳＯＬＵＴＩＯＮＳＯＦＡＤＶＥＣＴ...     

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.     

NUMERICAL STUDY ON MIXED CONVECTIVE FLOW IN A SOLAR COLLECTOR

In a solar energy heat collector forced convection and free convection will occur concurrently. In this paper, the mixed convective flow was investigated. The dimensionless equation was derived and the results was verified by experiments. The numerical solution shows that error is less than 5% if the effect of free convection is ignored.     

A MODEL OF WATER, VAPOR AND HEAT FLOW IN POROUS MEDIA

ＡＭＯＤＥＬＯＦＷＡＴＥＲ，ＶＡＰＯＲＡＮＤＨＥＡＴＦＬＯＷＩＮＰＯＲＯＵＳＭＥＤＩＡ￥ＹａｎｇＪｉｎ－ｚｈｏｎｇ；ＣａＩＳｈｕ－ｙｉｎｇ（ＷｕｈａｎＵｎｉｖｅｒｓｉｔｙｏｆＨｙｄｒａｕｌｉｃａｎｄＥｌｅｃｔｒｉｃＥｎｇｉｎｅｅｒｉｎｇ，Ｗｕｈａｎ４...     

FLOW RESISTANCE AND HEAT TRANSFER CHARACTERISTICS OF A NEW-TYPE PLATE HEAT EXCHANGER

A new-type corrugation Plate Heat Exchanger （PHE） was designed. Results from both numerical simulations and experiments showed that the flow resistance of the working fluid in this new corrugation PHE, compared with the traditional chevron-type one, was decreased by more than 50%, and corresponding heat transfer performance was decreased by about 25%. The flow field of the working fluid in the corrugation PHE was transformed and hence performance difference in both flow resistance and heat transfer was generated. Such a novel plate, consisting of longitudinal and transverse corrugations, can effectively avoid the problem of flow path blockage, which will help to extend the application of PHEs to the situation with unclean working fluids.     

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.