A SIMPLIFIED MODEL FOR DETERMINATION OF MOISTURE DIFFUSIVITY OF DATE FROM EXPERIMENTAL DRYING CURVES

Experimental drying curves for Tunisia Deglet Nour dates were obtained in a laboratory dryer under different drying conditions The air temperature was varied from 30 to 69^°C, relative humidity from 11.6 to 47.1 % and air velocity from 0.9 to 2.7 m/s. A numerical method to obtain a solution of a diffusion equation in which the diffusivity depends upon temperature and moisture content has been proposed to investigate the moisture movement in a date by assuming the sample to be a homogenous infinite cylinder. To rind the fitting moisture and temperature dependent diffusivity, the calculated drying curves are compared with the observed drying curves and an empirical equation for the moisture diffusivity of the date has presented as a function of temperature and moisture. It has been shown that the moisture distribution in the date during drying can be obtained by using the empirical equation presented.     

Heat conduction in multilayer spherical products by transfer functions

The development of a computer program is presented in order to determine the heat conduction transfer in multilayer spherical products, hollow or solid, by means of the transfer function method. We can establish a methodology in order to determine heat flux and inner and/or outer temperatures for spherical solid multilayer products, and heat flux and temperatures in any intermediate point of the spherical multilayer products both hollow and solid. The program developed is designed for variable intervals and it allows for the inclusion of the superficial convection coefficient in the cases where it remains constant, or its exclusion from the mathematical model in the cases where it does not remain constant, as well as in the cases in which it does not exist (heating or cooling by superficial contact). The method was validated with oranges of average diameters between 7.73 and 7.89 cm and thickness of rind between 4.7 and 6.8 mm, and these showed good results.     

Modelisation of Ni-P electroless deposition in ammoniacal solutions

A reaction path for the electroless deposition of Ni-P layers is developed. The steady-state polarisation and impedance responses are calculated. The comparison between the experimental results and the calculation shows the adequacy of the model. The mechanism accounts for most of the experimental features observed for the steady-state and the impedance behaviours and their dependencies with pH, hypophosphite and nickel sulphate concentrations.     

A SIMPLIFIED MODEL FOR DETERMINATION OF MOISTURE DIFFUSIVITY OF DATE FROM EXPERIMENTAL DRYING CURVES

ABSTRACT

Experimental drying curves for Tunisia Deglet Nour dates were obtained in a laboratory dryer under different drying conditions The air temperature was varied from 30 to 69^°C, relative humidity from 11.6 to 47.1 % and air velocity from 0.9 to 2.7 m/s. A numerical method to obtain a solution of a diffusion equation in which the diffusivity depends upon temperature and moisture content has been proposed to investigate the moisture movement in a date by assuming the sample to be a homogenous infinite cylinder. To rind the fitting moisture and temperature dependent diffusivity, the calculated drying curves are compared with the observed drying curves and an empirical equation for the moisture diffusivity of the date has presented as a function of temperature and moisture. It has been shown that the moisture distribution in the date during drying can be obtained by using the empirical equation presented.     

一维河流数值模拟算法的概述

本文仅对一维河流数值模拟算法的近期发展作一简短报道，内容有当今数值模拟对算法提出的具体要求，动床一维非恒定流算法，泥沙模型中的饱和和非饱和输沙模式嵌套算法，一、二维泥沙模型嵌套算法等，并指出交叉边缘学科的渗透和多学科的结合以及应用是今后河道数学模型研究和发展的重要方向．