New Liquid Holdup and Load Point Models in the Loading Region for Sheet Metal-Structured Packings and Performance Comparisons with Literature Models

Abstract

Regarding sheet metal-structured packings, model development for the loading region is a difficult process because of complex vapor and liquid flow behaviors compared to the preloading and flooding regions. Therefore, only a few loading region models are available in the literature to estimate liquid holdups and load points. Also, the available models were developed with few experimental data points and with limited operating conditions. In the present study, the performances of the literature models were evaluated using 181 experimental liquid holdup and load point data points obtained from the open literature over a wide range of operating conditions. The results showed that the existing literature models are not properly accounting for the effects of different thermodynamic and geometrical properties on liquid holdups and load points. Therefore, new models were developed. The new models were verified using a wide range of experimental data gathered for different packings and different systems. The mean absolute relative error of model predictions for liquid holdups and load points are less than 10 and 20%, respectively. In addition, the new models only require readily available packing geometrical areas, void fractions, and crimp angles instead of confidential packing-specific constants or confidential packing crimp dimensions. Therefore, the new models are easy to use.

New Liquid Holdup Models in Both Preloading and Flooding Regions and a Flood Velocity Model to Identify Flooding for Sheet Metal Structured Packings

“…As discussed in our previous article, the liquid holdup and film thickness in a structured packing column increase with increasing vapor flow rate, after the load point. When the column is close to the flood point, the liquid film thickness reaches a critical value.…”

“…A more detailed discussion of the hydrodynamic behavior of the packed columns in the preloading and flooding regions is summarized below. In addition, please refer to Jammula article for discussion on the loading region (Figure ).…”

“…Region 2 is the loading region and region 3 is the flooding region. Regions 2 and 3 data were omitted intentionally from the present preloading region database (region 3 data was used in Section flooding region data and region 2 data was presented in our loading region article). A summary of the literature data of the preloading region is presented in Table .…”

“…A database of the experimental liquid holdup flood point data was assembled from the open literature. ,, A detailed discussion of this database is presented in a previous article . Regarding that literature data, when the liquid holdup started increasing exponentially with increasing vapor flow rate, that liquid holdup was regarded as the “liquid holdup at the flood point.” Regarding that database, the test systems are limited to air/water, air/water/sucrose, and air/water/MEA.…”

“…A liquid holdup model needs to estimate the total liquid holdup during the operation of the column, and this will help in the packing and column support estimation calculations associated with the column at the desired operating conditions . A number of researchers used liquid holdup as a key parameter in pressure drop and mass transfer models. − A good liquid holdup model not only improves the understanding of packing hydraulics but it also improves the performance of other models. A brief discussion of the literature liquid holdup models is presented below.…”