摘要:

Drying curves obtained in a pilot-scale fluidized bed dryer using biological source solids (sawdust, soya and fish meal) were used to estimate the parameters involved in heat and mass transfer phenomenas: heat transfer coefficient and moisture diffusivity coefficient. Parameters involved in mass transfer were estimated from drying models based on diffusional mechanisms and others that in addition consider internal and external resistance to the mass transfer. The estimate ef ective diffusivity coefficient was between 2x10-11 to lx10 (m2/s) for the considered products. Heat transfer coefficient was estimated from drying data points in the constant drying rate period when the external resistance to the mass transfer controls the process.

ISSN:0737-3937    

DOI:10.1080/07373939608917121

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An expenmental and theoretical study of heat and mass transfer analogy and a comparison of that to a binary liquid mixture evaporation is presented. Common organic solvents, ethanol and n-heptane, were used to form an alcohol - hydrocarbon mixture. Studies were carried out in a horizontal rectangular channel having air flow velocities of 0.2 – 0.9 m/s. Heat transfer coefficients were measured with a copper plate resistor and mass transfer coefficients with a square pool. The heat and mass transfer analogy is presented for a system having two evaporating compounds with a fixed value of air flow and verified by measuring and comparing mass transfer coefficients for distilled water with air flow velocities of 0.2 - 0.9 mls. An illustrative example of the use of the theory for industrial ventilation is presented.

ISSN:0737-3937    

DOI:10.1080/07373939608917122

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this work a quasi-steady-state analysis is used to describe the evolution of the sublimation front temperature in freeze-drying of a food model (aqueous solution of Tylose. 3%). From the water loss data obtained in a freeze-drying experiment, in which the upper dried surface temperature and that of the frozen zone of the food model are conmlled to a cenain heating sttategy, several values of the transport coefficients in the dried layer are calculated under different operational conditions (i.e. chamber pressure and average product temperature). These values are correlated by non linear regression and expressions for the effective thermal conductivity and water vapour diffusivity in the dried layer of the material are

ISSN:0737-3937    

DOI:10.1080/07373939608917123

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A diffusion-bared mathdcal model is prswmed for batch drying of corn in a novel rotating jn spouted bcd device under constant as well as intermitted drying conditions. Such a device is suited for drying of large partides (e.g. grains, beam, seed, etc) for which internal heat and mass tranfer rates control the drying kinetics. Based on literature data for moisture diffusivities the model predictions are compared with experimental data for both continous and time-dependend air supply and/or heat input. Effects of dcvant parameter are evaluated and discussed in the light of potential pnrctieal applications.

ISSN:0737-3937    

DOI:10.1080/07373939608917124

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Luikov's system of partial differential equations for heat, mass and pressure transfer war applied to describe the drying process in a capillary porous body. A two dimensional finite element model were formulated to solve the system of equations. The simulated results agreed

ISSN:0737-3937    

DOI:10.1080/07373939608917125

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The internal insulation in shell type power transforms is usually ensured by the stacking of plates of board impregnated with oil. A board is in equilibrium with the atmosphere at a moisture content varying from seven to eight percent by weight, but, when the insulating function is required, the water content must be lower than 0.5 %. The aim of the present work is the understanding and the modelling of transformer boards drying.

ISSN:0737-3937    

DOI:10.1080/07373939608917126

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new jam technology was developed in which osmotically dehydrated fruits were used directly in jam processing. Since the fruits undergo a process at lower temperature (35-40°C) for short time during osmotic dehydration, the new jam product exhibits surperior natural colour, good flavour and overall quality. Sugar solution spent in osmotic dehydration treatment can be used in jam.

ISSN:0737-3937    

DOI:10.1080/07373939608917127

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Comlations are derived relating the heat-transfer coefficient to the mass- transfer coefficient in kiln drying of timber boards by using the Chilton-Colbum analogy. Existing experimental data for the mass-transfer coefficient of naphthalene vapour in the airstream at low temperature are convened to coefficients under commercial timber drying conditions. The calculated results from this analysis are compared with the values employed by wood drying modellers in their models and it appears that the external transfer coefficients used by the drying mcdellers are generally below the values calculated from thelaboratoly data.

ISSN:0737-3937    

DOI:10.1080/07373939608917128

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The modelisation of cereal drying kinetics is more, and more often performed by the diffusion equation (Fick's law) Eor homogeneous materials rather than lumped or semi-empirical equations. The heterogeneity of the material is accounted for by the use of an effective diffusivity the prediction of which is essential for the determination of the functional relationship between diffusion coefficient and arain moisture content and temperature. For this dependence, the method of resolution may be analytical or numerical. In this study, the estimation of diffusion coefficient is based on drying curves obtained with arains in the ranae of initial moisture content of 18-509 and a temperature of 50:120˜˜. The important result corresponds to the finding that the moisture diffusivity is a function not only of variabies of the state i.e. moisture content and temperature, but also of the initial moisture content as in the following : 'D = P4g X, exp(8 X ). AD and B are both dependent on temperature

ISSN:0737-3937    

DOI:10.1080/07373939608917129

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Continuous- and cyclic-dryins experiments have been carried out on an Australian hardwood timber; tuipentine. to compare the drying timesand the final quality of the timberproduced by these techniques. More severe drying conditions have been used in the the active drying Periods for cvclic drvins than for continuous drvins in order to hchieve similar drying Cimis. Fourteen boards of approximate original dimension 45 mm wide by 25 mm thick by 750 mm long, sealed at each end using an epoxy mastic coating, have been dried in each experiment. with end-matched samples being used to reduce the effect of different growing locations. The two cyclic-drying experiments differed in the use of high-humidity conditions in the relaxation period for the first experiment and ambient conditions in the relaxation period for the second experiment.

ISSN:0737-3937    

DOI:10.1080/07373939608917130

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor