摘要:

To study unsteady state problems of heat and mass transfer in concrete pavements, which are generally considered to be fine porous media, both relevant material characteristics and transport properties must be considered simultaneously. A system of nondimensional differential equations for heat and mass transfer in porous media is derived and used to investigate the drying history of moisture content in a particular light-weight concrete slab. An implicit finite difference numerical scheme is employed for obtaining the numerical results. The results show that the Lewis numberLe,BihnumberBimplay an essential role in the simultaneous mass and heat transfer.

ISSN:0098-6445    

DOI:10.1080/00986448608911789

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An analysis is presented to study the effects of buoyancy-induced streamwise pressure gradients on laminar forced convection heat transfer to non-Newtonian fluids from a horizontal plate. Numerical solution of the transformed boundary layer equations has been carried out for different values of the flow behavior index and the buoyancy parameter by means of the local nonsimilarity method. A discussion is provided for the effect of the buoyancy force on the friction factor, the dimensionless heat transfer rate and the details of the velocity as well as temperature fields.

ISSN:0098-6445    

DOI:10.1080/00986448608911790

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The behavior of a relief valve with a short throat has been studied. Measurements of discharge rates when the unit was fed with a two-phase mixture have been made at moderate pressure differentials. These experiments show that the valve behavior is similar to that of an orifice and that flashing does not occur until downstream of the flow restriction. Design techniques which enable valve discharge rates to be computed under these conditions are developed

ISSN:0098-6445    

DOI:10.1080/00986448608911791

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A mathematical model for the dynamic behavior of a countercurrent rotary dryer has been developed and solved. The model consists of four hyperbolic partial differential equations with split boundary conditions. The equations are solved numerically using an algorithm based on the method of characteristics. The solution is stable and rapid. Sample results of a dryer simulation are presented.

ISSN:0098-6445    

DOI:10.1080/00986448608911792

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Equations for the liquid velocity profile and the average gas hold-up in bubble columns including cocurrent flow are proposed. It is shown that the inversion point of liquid flow can be used as the characteristic parameter for calculating the liquid flow profiles and gas hold-up. A tracer method was developed to measure the inversion point of liquid flow in bubble column reactors. For water as the liquid phase this inversion point was found at a distance from the column axis of 0·70 0·73 times the column radius. Besides, bubble velocities and bubble diameters in water and methanol-water solutions were determined, using a 5-point conductivity microprobe. It was found that in dilute solutions of methanol the bubble velocity is lower than in pure water. With increasing superficial gas velocity, the bubble velocity steadily increases in pure water, whereas in methanol-water solution it first decreases and, after reaching a minimum, increases too.

ISSN:0098-6445    

DOI:10.1080/00986448608911793

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A generalized corresponding states principle (GCSP) based on the known properties of two reference fluids has been used to correlate the viscosities of fluid mixtures over a wide range of pressure and temperature. It is shown that good predictions of the viscosities for a variety of mixtures can be obtained with this method. Asymmetric mixtures, however, require the use of one adjustable constant. Comparisons with the TRAPP method are shown and the advantages and limitations of the two methods are discussed.

ISSN:0098-6445    

DOI:10.1080/00986448608911794

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Deep drying of inherent moisture from subbituminous coal produces a dried product which is friable and very reactive to oxygen in air. The major problems in handling dried coal, which are unique to deep drying of low-rank coal, are: (1) avoidance of spontaneous combustion, (2) prevention of moisture reabsorption, and (3) control of dust. Atlantic Richfield has developed, and successfully demonstrated, technologies which solve all three problems. However, this paper will be confined to the spontaneous combustion problem

ISSN:0098-6445    

DOI:10.1080/00986448608911795

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Drying subbituminous coal has never been practiced commercially. The commercial dryers built to date have been designed for drying surface moisture in conjunction with upstream coal preparation facilities. This type of drying is mainly controlled by input energy and the basis of the design is an energy balance. In drying inherent moisture from subbituminous coal, the thermal conductivity of the coal and the diffusion of molecular water within coal particles impose limitations on the process conditions. Energy input and solids residence time in the dryer have to be controlled properly for simultaneously balancing the heat and mass transfer within the coal particles. Improper control of either parameter can cause fires and explosions during the key steps of the drying process—drying and cooling

ISSN:0098-6445    

DOI:10.1080/00986448608911796

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A characteristic length, defined by the volume, surface area, and a dimensionality parameter, is proposed for internal natural convection. For geometries (such as bodies in enclosures) without simple and/or fundamental characteristic lengths, heat transfer correlations using the proposed characteristic dimension are much better than those using simple, but somewhat arbitrary, lengths. Also, for complex geometries, the Rayleigh number based on this parameter is a better measure of the intensity of convection than is that based on some simple length such as height or diameter. The proposed dimension usually is the same as the fundamental (and obvious) dimension if one exists for the system. Thus for simple geometries it is the same as that normally used, but for more complex geometries it provides a better measure of the characteristic length scale.

ISSN:0098-6445    

DOI:10.1080/00986448608911797

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A correlation has been tested for the determination of the acceleration length of fine particles in vertical, two phase, upward flow. This correlation is based upon data obtained in different studies. The dimensionless acceleration length is correlated with the Froude number, the particle to tube diameter ratio, the particle to fluid density ratio, the gas Reynolds number and loading.

ISSN:0098-6445    

DOI:10.1080/00986448608911798

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor