Determination of flow profiles in porous media using shifts in gamma spectra

Abstract

A new technique was developed to determine the tracer location and fluid velocity in porous media nonintrusively. This technique exploits the competitive effects between the photoelectric interaction and the Compton scattering phenomenon to determine the distance between a radioactive tracer in a porous medium and an externally positioned detector. The photon energy distribution shifts toward lower photon energies as the tracer moves away from the detector. The shift in the energy distribution can be quantified by the ratio of the scattered photon intensity to the full energy photon intensity. A convective-dispersion model was used to determine the spatial distribution of the radioactive tracer. An analog Monte Carlo method was developed to simulate photon transport in porous media. Comparison between experimental data and the model shows that in-situ tracer velocities can be accurately predicted.

Heat-Transfer Studies in Packed-Bed Catalytic Reactors of Low Tube/Particle Diameter Ratio

“…[32][33][34][35][36][37] Several theoretical and experimental studies on the velocity profiles within packed beds have been published since early 1950. 9,14,32,[38][39][40][41][42][43][44][45][46][47] The use of anemometry techniques allowed the measurement of distortions in the velocity profiles due to voidage profiles in the packed bed, which become larger as the ratio of tube/particle diameter decreases. The zones with larger velocities corresponds to those with high void fraction, which are normally located near the wall.…”

“…Several theoretical and experimental studies on the velocity profiles within packed beds have been published since early 1950. ,,,− The use of anemometry techniques allowed the measurement of distortions in the velocity profiles due to voidage profiles in the packed bed, which become larger as the ratio of tube/particle diameter decreases. The zones with larger velocities corresponds to those with high void fraction, which are normally located near the wall. ,,− An exact representation of the spatial distribution of the interstitial fluid velocity in packed beds seems to be a very difficult task, and it requires the proper three-dimensional description of the void fraction distribution into the bed at typical values of interest, which, for low tube/particle diameter ratios, are in the range of 0.4−0.5.…”