Advancing performance of a predictive model for pressure drop of wire gauze corrugated sheet structured packings in deep vacuum applications

Abstract

A specific fluid dynamics related feature associated with application of corrugated sheet structured packings in distillation columns operated under deep vacuum conditions is that the vapour ascends through a sparsely irrigated packed bed under laminar flow conditions. In the present paper the well-known Delft Model (DM) and two ad-hoc arranged fully appropriate predictive models have been evaluated in this respect using experimental evidence obtained in total reflux vacuum distillation tests carried out with conventional and advanced geometries of a well-established wire-gauze corrugated sheet structured packing. Shortcomings and strong points of compared predictive models, which have exhibited large discrepancies with respect to relative magnitude of governing flow resistances, have been addressed, and upon a tedious elaboration the way paved for upgrading DM accordingly. As shown in present paper, a simple fundamentally sound correction of existing expressions for gas-gas interaction under laminar and turbulent flow conditions, and implementation of empirically founded expressions to account for previously unrecognized form drag related losses, occurring in case of conventional packing due to a rather sharp disrupted change in gas flow direction at transitions between packing layers, resulted in a remarkable advancement in performance of the upgraded Delft model (DM) in all cases. Yet, a further in-depth research effort is necessary to unravel true nature and scale of governing flow resistances.