Characterization Study of the Impact of Non-Dimensional Parameters on Radial Heat Transfer in Packed Beds

Abstract

The simulation of packed beds packed with long tubes through choice of suitable packing materials and the size of particles to be used to achieve maximum heating efficiencies is one major problem in most industrial applications. This work proposes the development of a computer simulation model to analyze the impact of the most important nondimensional parameters on the radial heat transfer efficiency in a packed bed. Experiments are conducted considering the impact of the particle diameter, properties, as well as bed arrangement on the radial heat transfer in a packed bed as a function of the Reynolds number. The experimental work is performed on a plain annulus filled with circular two-dimensional objects in the two-dimensional simulation model. This is followed by spherical objects in the three-dimensional simulation model. Effective Thermal Conductivity is taken as the criterion in the analysis.
The study focuses on steady-state, laminar flow (ReP < 10) which is common in the case of Fischer-Tropsch to reduce pressure drop by slow moving fluid. For better insight into the impact of the effects of porosity and the aspects ratios of the particulates (tube diameter-to-particulates of 1.2 to 10), preliminary two-dimensional simulations were performed using two packing styles: organized and staggered. The 2D analysis provided an insight into the design of 3D simulations, which are 15-20 times more computationally intensive.
Cylindrical packed beds comprising of a ball that has different aspect ratios and constant porosity (ranging from 2 to 10) were tested at radial packing and hollow packing configuration in 3D analyses. It shows that the radial packing is the best in terms of getting the optimal ETC compared to the other configurations whereas the brick particle always gives lower ETCs with no affectedness on the packing arrangement or the aspect ratio. Remarkably, changes in Reynolds numbers did not play a significant role in ETC with air as a fluid, showing that packing geometry and material properties play a predominant role in the case of laminar flows.