Angular temperature variations in a wall‐cooled packed‐bed reactor

Abstract

The signijkance of the statistical character of wall-cooled packed-bed reactors was studied by measuring angular temperature variations, which result @om the random nature of the packing. These are neglected in present-day mathematical models designed to describe the reactor behavior. The amplitude of these variations was determined experimentally as a function of the mass flux and the position in the tube, under conditions of heat transfer as well as of reaction. Angular variations are significant whenever radial temperature gradients are large.Different methods used to average observed variations were surveyed. For the system presented, the angular variations have only a limited influence on the reaction rates if the angular averaged temperature is used. Thus, a two-dimensional deterministic continuum model can be used, notwithstanding the statistical character of the packed bed.

Mass Dispersion in Liquid Flow through Packed Beds

“…Ziolkowski and Szustek found a large scatter for different beds of the values of the local tracer concentrations at the same position in the bed when the bed was repacked after each concentration distribution measurement. Furthermore, the results coincided qualitatively with temperature variations in point measurements of the temperature in packed beds. , …”

“…Furthermore, the results coincided qualitatively with temperature variations in point measurements of the temperature in packed beds. 22,23 The observations mentioned previously are characteristic for the mechanism responsible for hydrodynamic dispersion in packed beds. The longitudinal and transverse dispersion originates from the tortuous flow of the liquid in the form of blending and separating streams in the voids between the particles.…”

Nonequilibrium effects in fixed-bed interstitial fluid dispersion

“…Further it predicts that the variations increase in the neighborhood of the wall, that they grow when d R /d . decreases and other results on temperature scatter as found experimentally by Dixon et al (1978), and Schouten and Westerterp (1996). The measured temperature scatter ¹ should be considered as a measure of the heat #ux, as Eq.…”

Experimental Analysis of Heat Transfer in Packed Beds with Air Flow

“…Ladder frame. This is the preferred technique of the Westerterp group. ,− A ladder frame holds several thermocouples, with the ladder placed inside the bed. The sensor tips are positioned at many axial, radial, and angular positions, allowing complete temperature profiles to be maeasured in a single experiment.…”