Experimental observation of pressure and holdup overshoot following a sudden increase of liquid flow

This paper presents the results of an experimental investigation of the hyd rodynamics of a countercurrent packed-bed column exposed to a step change i n the liquid flow rate. For the first time in the literature, this paper re ports observations of the overshoots of the transient curves of pressure as well as liquid holdup when the change in the liquid rate brings the hydrod ynamic regime of the bed close to the flooding line. The experimental techn ique indicated that column flooding did not appear to occur, even temporari ly. The experimental. transient curves for the pressure along the packed se ction, the total pressure drop across the column, and the liquid holdup are interpreted in terms of a simple three-parameter transfer function. Plots of the magnitude of the overshoot and the instant of its appearance as func tions of the gas-to-liquid mass now rate ratio are presented and analyzed. On the basis of these results, the existence of a pressure overshoot is att ributed to the extra energy required for redistribution of the gas and liqu id flow according to the new prevailing flow regime.