摘要:

An attempt is made to elucidate the electrochemical aspects of the electroosmotic dewatering (EOD) of clays as reported in some recent work, especially that on interrupted DC power electroosmotic dewatering published by Rabie, Mujumdar and Weber (2). These authors showed that the dewatering by EOD stops after the DC power has been on for several minutes or hours; on interruption of their power and on short-circuiting of the electrodes, conditions can be created again for some further dewatering by DC power EOD. This discovery, of Rabie et al. is interpreted as a fuel cell effect and it is shown that it affords clues to several other electrochemical strategies for the possible enhancement of the efficiency of the EOD by DC power.

ISSN:0737-3937    

DOI:10.1080/07373939508916950

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effect of heat input, mixing at regular intervals, airflov over the surface and the relative humidity were investigated within a radiation chamber. Likening to sun drying as practiced in the tropics, the chamber was constructed to study the direct radiant heat drying of rough rice under various bed thicknesses. Graphic results showing the variations of rough rice surface temperature during the experiments are presented. Comparisons are also made between the relative contributions of bed depth and mixing on the drying rate. A non-mixed bed of 3 cm dried just as fast as a 6 cm mixed bed although moisture content was nonuniform in the former case. After drying, the grains were dehusked by hand and examined for physical defects like cracks. Possible constraints involved in drying thick beds of rough rice under direct radiation were investigated with the aim of defining suitable strategies for improving actual sun drying.

ISSN:0737-3937    

DOI:10.1080/07373939508916951

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Drying of textile bobbins was carried out on two kinds of laboratory-scale dryers: in a cross circulation drying rig, atmospheric pressure heating air is used, while in the through circulation drying apparatus, the heating air is pressurized before the drying process takes place. In both cases, a bobbin was fitted with seven thermocouples, placed in a plane normal to the bobbin axis but at different radial distances, in order to provide temperature data during the drying process. In cross circulation drying, plots of temperature against time indicated the presence of two moving fronts, one starting from inside the bobbin, another from the outside, while in through circulation drying, similar plots showed the presence of an evaporation front, moving from inside the bobbin to the outside. In both canes, numerical models were developed to simulate the drying processes.

ISSN:0737-3937    

DOI:10.1080/07373939508916952

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate.

ISSN:0737-3937    

DOI:10.1080/07373939508916953

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The proximate composition of garlic (cv. Early Californian) was determined and compared to values reported in the literature. The specific heat and thermal conductivity were determined using the method of mixtures and a modified Fitch apparatus, respectively and both approaches proved sufficiently accurate for such purposes. An analysis of variance revealed that moisture content had a highly significant effect on both specific heat and thermal conductivity of garlic. A linear empirical model was developed to characterise the specific heat as a function of moisture content. The model predictions were very close to values predicted on the basis of the proximate analysis. The measured thermal conductivity data were fitted to parallel, perpendicular and random structural models as weU as empirical mathematical expressions. The parallel and exponential models gave satisfactory agreement with the data.

ISSN:0737-3937    

DOI:10.1080/07373939508916954

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A complete mathematicalhumerical model is proposed, in order to simulate the performance characteristics of a novel concept of a drying heat pump based on the theory of minimum energy cyclcs. The drying heat pump involvcs vapour condensation in a Lava1 nozzle. removal of the liquid phase in a supersonic separator as well as compression of the working medium. which is superheared vapour.

ISSN:0737-3937    

DOI:10.1080/07373939508916955

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Yellow dented corn samples were dryed i n the laboratory with heated air i n a batch fluidized bed dryer at three different operation conditions. The evolution o f the temperature nnd moisture content were predicted with both, a model proposed in the literature that neglects the position dependence o f the diffusion coefficient and a modified version o f i t that takes into account the above mentioned functionality. Both models were solved by means of collocation i n finite elements. The consideration o f the diffusivity as a position function leads to better agreement with the experimental results.

ISSN:0737-3937    

DOI:10.1080/07373939508916956

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An experimental study has been canied out on the characteristics of water adsorption isotherms for typical materials used in a box of tobacco products or cigarettes. Equilibrium moisture contents for different varieties of tobacco, papers, filters and activated carbons were measured with a flow-type adsorption system under the conditions of a constanttemperature a t 303 K and relative humidities ranging from 5 % to 80 92. A modified Dubinin-Astakhov equation was accurately applied to represent the water adsorption isotherms for all materials. These isotherms were characterized by three parameters contained in the equation and divided into three groups; i.e. 1)tobacco, 2)papers a s well a s filters, and 3)activated carbons, depending mainly on pore sizes a s well a s the degree of swelling of the materials used. Under a relative humidity of around 60 %, the main water migration was found to take place in the tobacco and the percentage of migrated water to the total was assessed to be more than 80 %. The results suggested that the

ISSN:0737-3937    

DOI:10.1080/07373939508916957

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A mathematical model is developed to simulate the drying of a hygroscopic porous solid. The model, based on the gradient of moisture concentration per unit volume as driving force, takes into account the migration of water within the solid by diffusion and the evaporation at the interface. A mathematical equation for diffusion in a slab with three dimensional shrinkage has been derived, assuming that the magnitude of shrinkage is equal to the volume of water evaporated. The resulting diffusion equation and the heat balance eauation for infinite thermal conductivitv were solved n;merically with temperature dependent diffusion coefficient and convective boundary conditions. The deDendence of the desorption isotherm with temperature is-also considered. corndination of all these factors in a single model provides a tool that is effective in predictinq dryinq behavior and also useful in exploring and understanding the impact of important variables on the drying process.

ISSN:0737-3937    

DOI:10.1080/07373939508916958

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A highly heat-sensitive and xerolabile suspension of photosynthetic bacteria was dried in batch and continuous vibrofluidized beds of porous and nonporous solid carriers. Experimental drying rate and particle temperature curves as well as growth tests for fresh and dried bacteria show that this is a technically feasible process, and product obtained is of required quality.

ISSN:0737-3937    

DOI:10.1080/07373939508916959

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor