Hydrodynamics experiments with respect to supercritical and subcritical fluids were conducted in a laboratory-scale trickle bed reactor filled with relatively small particles of 0.67-1.32 mm in diameter. Residence time distribution was measured with tracer injection, and the results indicated that the supercritical fluids (SCF) have non-liquid-like features. From the pressure drop fluctuations, the pulsing flow was observed with the increase of the supercritical fluid mass flux; clearly, it shows that SCFs possess liquid-like property. Based on the empirical relationship proposed by Al-Naimi et al. (2011), the experimental data for subcritical fluids could be well correlated, which results in a new correlation in the predication of the pressure drop for fluids at subcritical conditions. (C) 2013 Elsevier Ltd. All rights reserved.