Wet gas pressure drop across multi-orifice plate in horizontal pipe in low gas-phase Froude number region

Abstract

In comparison with the traditional single-orifice plate, as a throttling element, multi-orifice plates exhibit a low pressure loss, low flow-induced noise, and stable pressure difference response, which are advantageous in wet gas measurements. In this study, the pressure drop of wet gas across two multi-orifice plates (one with circular holes and another with slotted holes) in a horizontal pipe was experimentally investigated in the stratified flow region and intermittent flow region. The two regions are different from the flow pattern but can be collectively referred to as a low gas-phase Froude number (FrG) region. At the same porosity, there is no significant difference between circular and slotted multi-orifice plates in pressure drop characteristics. As the flow pattern transitions from stratified to intermittent, ΦG increases considerably with a decrease in FrG and an increase in liquid-phase Froude number (FrL); this differs from the well-known wet gas pressure drop characteristics of orifice plates as obtained from common wet gas with annular-mist flow. The prediction accuracies of the available pressure drop models for the gas–liquid flow across the orifice plate were analyzed based on the experimental results. The findings indicate that none of the models can provide accurate predictions in the two low-FrG subregions simultaneously. With the modified models, in which FrG and FrL are correlated simultaneously, new correlations are proposed for the low-FrG region. Among these models, the modified Murdock model exhibits the best prediction accuracies, i.e., 15% and 6%, when the upstream is in the flow pattern transition region and stratified flow region, respectively. These results elucidate the mechanism and prediction methods for the application of multi-orifice plates to wet gases as a measuring sensor.