Validity of Darcy's law at low flow-rates in liquid chromatography

The applicability of Darcy's law at extremely low flow velocities has been questioned in the scientific literature. It was investigated using a simple chromatographic system. Ethylene glycol (viscosity, 19.9 cP at 20 degrees C) was pumped through 10 to 25 cm long chromatographic columns packed with small porous spherical particles (size, 5 to 10 mu m) The dependence of the linear velocity of this liquid on the inlet pressure was found to be linear in the range of Reynolds numbers (based on particle diameter) between Re=1.10(-6) and 1.10(-4). These results contradict earlier reports by Fand et al. and more recent findings by Kececioglu and Jiang that suggest a limited applicability of Darcy's law to the range Re=0.3 to 0.7. (C) 1999 Elsevier Science B.V. All rights reserved.