THE EXPERIMENTAL STUDY FOR NATURAL CONVECTIVE HEAT AND MASS TRANSFER IN POROUS MEDIA

An electrochemical method is employed to study experimentally natural convection driven by combined thermal and solutal buoyant forces in a fluid-saturated porous enclosure. The horizontal temperature and concentration gradients are imposed in such a way that their effects on the flow are either opposing or augmenting. The inside temperature profiles and heat and mass transfer characteristics on the vertical walls are experimentally determined. The effects of dimensionless parameter Ra, Le, N on flow, heat and mass transfer are discussed in details.     

EFFECTS OF TRANSVERSE OSCILLATIONS ON NATURAL CONVECTIVE FLOW INDUCED BY COMBINED THERMAL AND MASS DIFFUSIONS IN POROUS MEDIA

This paper studies the unsteady heat and mass natural convection in a highlyporous medium bounded by an infinite vertical porous wall. The unsteady sourceof the problem arises from the transverse oscillations in suction velocity offluids, The analytical results for the problem are obtained based on the methodof small parameter, and show that the natural circulation in the porous mediumis affected by this kind of oscillation.     

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.     

THEORETICAL STUDY OF HEAT TRANSFER ENHANCEMENT IN PIPE WITH POROUS BODY

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

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.     

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

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

COUPLING DISTINCT AND CONTINUOUS MEDIUM MODEL FOR FLOW ANALYSIS IN A FRACTURED ROCK MASS AND ITS APPLICATION

Fractures in a rock mass can be divided into dominant fracture system and network fracture system. An approach for the analysis of three dimensional ground water flow in a fractured rock mass is presented, in which flow in the dominant fracture system is described by a distinct medium model while flow in the network fracture system plus rock matrices (if considered) is described by a continuous medium model, and the two models are coupled by hydraulic head and flux. The coupling model facilitates to calculate one-by-one the fluid flow in the dominant fractures which are functioned as the major water transmission conduits, and it avoids unnecessary calculating fluid flow in individual network fractures which are numerous in number. In this way, the method can be applied to a large-sized calculation domain. In addition, a method of using network geometry data to calculate its equivalent porous permeability is presented in the paper, and the model implementation of water source and sink such as the pumping     

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.     

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.     

CHARACTERISTICS OF MICROBIAL TRANSFUSION IN POROUS MEDIUM AND ITS THEORETICAL INVESTIGATION

ＮＯＭＥＮＣＬＡＴＵＲＥＣｍｍ ——ｔｈｅｃｏｎｃｅｎｔｒａｔｉｏｎａｔａｃｅｒｔａｉｎｔｉｍｅ ,Ｃｅｌｌ/ｍＬＣｍｆ ——ｔｈｅｃｈａｎｇｅｏｆｔｈｅｃｏｎｃｅｎｔｒａｔｉｏｎａｆｔｅｒｍｉｃｒｏｂｅｓａｒｅａｄｓｏｒｂｅｄＤ′——ｔｈｅｃｏｎｖｅｃｔｉｏｎ ｄｉｆｆｕｓｉｏｎｃｏｅｆｆｉｃｉｅｎｔ,ｃｍ2 /ｓＶ——ｔｈｅｆｌｕｉｄ’ｓａｃｔｕａｌｖｉｓｃｏｓｉｔｙ ,ｃｍ/ｓＣｚｍ ———ｔｈｅｃｏｎｃｅｎｔｒａｔｉｏｎｏｆｔｈｅｉｎｊｅｃｔｅｄｍｉｃｒｏ ｂｉａｌＣｏ ———ｔｈｅｃｏｎｃｎｅｔｒａｔ…     

THE NATURAL CONVECTION OF AQUIFERS WITH CONSTANT HEAT SOURCES AND ITS INFLUENCE ON TEMPERATURE FIELDS

By combining sand tank tests with numerical simulations, this paper studies the temperature fields around constant heat sources to reveal the mechanism of the natural convection and its influence on the temperature fields in the process of energy storage. Using the "24-channel temperature auto acquisition system" developed by our research group in the tests, the temperatures are recorded at measuring points within the research area in the tests, the revised Brinkman equation and a transfer-convection balance model are used for solving the aquifer water-thermal coupling problems, and through comparison of the test results with the calcula- tion results, it is discovered that the influence ranges and the variations of the two temperature fields are consistent, which validates the mathematical model. On the basis of this, we also study the influences of the heat source positions and the boundary conditions on the temperature fields, and the results show that, under the natural convection, the heat source positions may influence the distri- bution of the temperature fields, thus affect the energy storage. For the same energy storage layer, the temperature field for the top energy storage is characterized by a smaller heat influence range and a relatively concentrated temperature distribution. However, when the heat source is at the bottom, the range of a temperature field, and the temperature is relatively dispersed, which is not favorable to heat recycle, with the same heat source position, the boundary conditions determine the size of the critical Rayleigh number, and thus have an influence on the occurrence and the strength of the natural convection, and accordingly, on the temperature fields.     

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.     

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

1.INTRODUCTIONtheheatandmoisturetransportpropertiesinwetporousmediaareessentialdatatodealwithmanyengineeringproblemsandarealsooneofthemostimportantresearchobjectivesinthefieldofheatandmasstransferinwetporousmedia.Althoughmanymethodshavebeendevelopedtoanalyzetheheatandmoisturetransportpropertiesinwetporousmedia,theexistingdataoftheheatandmoisturetransportpropertiesaresodeficientthatthedatacannotmeettheneedsfortheoreticalresearchandengineeringapplicationsbecauseofthecomplexityintheheatandmas…     

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…     

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.     

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.