Very small particles of catalyst have been used in industry te enhance the effectiveness of catalyst. In such case

the capillary force caused by surface tension of liquid phase rapidly increases and a great number of liquid-phase bridges between particles is built. It is considered that hydro-dynamic performance and mass transfer for small particles greatly differ from those for large particles. This investigation studies the effect of flow condition and physical properties of liquid on gas-liquid interfacial area"a"

when gas and liquid flow cocurrently downward through trickle bed of small particles. Correlations of"a"in trickle-flow and pulse-flow regimes were obtained by regression analysis.