Numerical determination of fluid‐to‐particle mass and heat transfer coefficients in packed bed reactors

Abstract

A method based on particle‐resolved CFD is built and validated, to calculate the fluid‐to‐particle mass and heat transfer coefficients in packed beds of spheres with different tube‐to‐particle diameter ratios (N) and of various particle shapes with N = 5.23. This method is characterized by considering axial dispersion. The mass and heat transfer coefficients increase by 5%–57% and 9%–63% after considering axial dispersion, indicating axial dispersion should be included in the method. The mass and heat transfer coefficients are reduced as N decreases. The catalyst particles without inner holes show higher mass and heat transfer coefficients than the ones with inner holes, because of unfavorable fluid flow in inner holes. The bed of trilobes has the highest mass and heat transfer coefficients, being 85% and 95% higher than the one of spheres. This work provides a versatile method and some useful guidance for the design of packed bed reactors.

Pore‐to‐mesoscale network modeling of heat transfer and fluid flow in packed beds with application to process design

“…We assume an initial water temperature of 300 K and solve Equation (4). We then use the pressure field to determine the temperature, Equations (12) and (13). This was then used to update the viscosity, Equation ( 6), and the process is iterated.…”

“…Conversely, direct numerical simulations (DNS), including particle resolved computational fluid dynamics (CFD) 8,9 and the lattice Boltzmann method (LBM), 10,11 are capable of simulating microscopic processes in porous media. Weng et al 12 presented a particle resolved CFD simulation to calculate the mass-and heat-transfer coefficients in packed beds of spheres with different tube-to-particle diameter ratios. This approach required a fine computational mesh (over 7.6 million grid blocks) and yet could only consider rather small samples (the diameter of the container was less than 31 mm) with a constant viscosity.…”