الفهرس 
CHAPTER ONE : INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Heat transfer parameters are very important for design a new heat transfer unit or to control the heat flow in an existing lmit. Due to importance of fixed bed systems in the industrial applications and because the most of processes which carried out in these systems are usually associated with energy transport, the present study is directed to determine parameters of heat transfer in fixed packed bed systems. The radial temperahlre profiles measurements are more common from which nearly all heat transfer data has been obtained. Both effective radial thermal conductivity ”Ae•r” and wall heat transfer coefficient ”aw” for three different kinds of packing materials alumina spheres, wood chips and charcoal, with different sizes were determined. Such parameters for wood chips and charcoal are very important in field of energy production by pyrolysis and gasification processes and had not been detennined before.
A cylindrical steel tube of 82.5 Iron irmer diameter ”d/’ at constant wall temperahlre packed with a material was used for experimental measurements of temperature profiles at different conditions. A down ward flow of cold fluid (air or nitrogen), approximately at room temperature, is heated up in this hIbe. The measurement are carried out over a wide range of wall temperahlre ( 100 DC ::s T ::s 950 DC ) and for a different gas flow to achieve particle Reynolds number up to 550. The packing materials are, alumina spheres with 4.8 mm particle diameter (dldp=17.2), wood chips and charcoal with two different sizes distribution ( dp = 8 : 11.2 mm & 4 : 6.3 mm ) to achieve two aspect ratios ( dldp = 16 & 8.6 ). Measurements of temperature profiles were carried out in the packed hlbe at three different bed levels and its values at steady state were used in the calculation.
The experimental data of temperature measurements was analysed according to pseudo homogenous two dimensional non plug flow model without axial dispersion, where the model was solved numerically using fmite difference approximation method, the results were fitted with the experimental data.
Effective radial thermal conductivity ’”Ae.r” for bed of alumina spheres was correlated in an empirical correlation as two terms, one depends on stagnant thermal conductivity of the bed, ”Ae 0” ( conduction term ) and the other depends on particle Reynolds number ”Rep” (Convection tenn ).
Also wall heat transfer coefficient, aw was calculated and finally correlated in dimensionless fonn as a wall Nllsselt number ”Nuw” .
O 0.75 0.33 Nu w = Nu wo + .IIRe p .Pr
The second part of the research was extended to bed packed with wood chips and charcoal. Shldying of these materials is very important, where charcoal is produced during heating of wood to 500°C in absence of air ( pyrolysis) and the heating of charcoal to elevated temperature, 850°C in presence of water vapor ( gasification) produce H2 and CO gases. The tWo heat transfer parameters were obtained for wood and charcoal at different conditions of bed temperahlres and gas flow and finally the design equation was obtained for the both packed materials as,
O 06 R 0.75 P 033 Nu w = Nu wO + . 75 e p . r’ . h N 20.36 WIt, Uwo = --- d( /dp