Since the Ergun equation is applicable for calculation of gas-liquid pressure drop in the cases without interphase interaction

and the pressure drop ratio of single gas phase to gas-liquid concurrent flow can be accounted for as the relative permeability of the gas phase

the Ergun equation is proposed to characterize the flow regime transition based on the gas-liquid interaction in a trickle bed. To check the validity of this methodology

experimental work was conducted in a plexiglass column of 140 mm ID packed with glass beads of different diameters (1.9

3.6

5.2 and 9.3 mm) by applying air and water as the working media. The transient data under pulsing flow were obtained by applying pressure transducers and electrical capacitance tomography (ECT).The comparison of pressure drops from experiment and prediction showed that the Ergun equation was inappropriate to the pulsing flow

in which the gas-liquid interaction is significant. Therefore

the experimental two-phase pressure drop was used instead of the theoretical one for the calculation of gas relative permeability. It was found that the permeability of gas under various gas and liquid flow rates as well as different particle diameters was lower than 0.08 if pulsing flow was reached.