Dry Pressure Drop Research Articles

Experimental and numerical investigation of dry pressure drop of 3D-printed structured packings for gas/liquid contactors

Separation units, such as distillation and absorption columns, are used widely in the chemical industry. Their efficiency depends on the performance of their packing, determined by their pressure drop, capacity, and mass transfer efficiency. Combining CFD and additive manufacturing allows the design/production of efficient and high capacity packing. In this paper, the dry pressure drops of newly developed wire-based structured packings are evaluated numerically via a single-phase CFD model. The k-ω-SST turbulence model in Ansys Fluent was used. The experimental and numerical dry pressure drops of three Tetraspline (TS) packings are compared. The numerical model is validated with average errors of 13% and 20% compared with experimental data for TS made in stainless steel and polyamide, respectively, over a capacity factor range of 0.9 to 3.1 Pa0.5. A Kelvin-cell-based packing is also studied to confirm the robustness of the model. This study allows the rapid optimisation of the different TS with different geometric parameters, such as wire diameter and length, based on the pressure drop. Indeed, the experimental values of the dry pressure drop of a column of packing that measures 16,500 cm3 have been reproduced numerically with only a small deviation using a periodic domain of 42 cm3.

Pressure drops and mass transfer of a 3D printed tridimensional rotational flow sieve tray in a concurrent gas–liquid column

In this study, the pressure drops and mass transfer performance of a improved tridimensional rotational flow sieve tray (TRST) manufactured by 3D printing under the condition of gas–liquid concurrent flow were investigated experimentally. Results suggest that the pressure drops of the improved TRST are much lower than that of the original TRST due to the transition of the arc surface of the blades is smoother. Dry pressure drop of the TRST is within 12 Pa, and wet pressure drop is within 80 Pa. A volumetric overall mass transfer coefficient of the tray section was proposed, which increased first and then decreased with increased superficial flow factor and concentrations of NaOH solution, increased with the increasing spray density and decreased with the increasing partial pressure of CO2. For tray geometric parameters, the influence of blade numbers is strongest, twist angle of the blades is weakest, and tray heights and sieve hole diameters are the middling. We also designed an energy efficiency factor to reasonably evaluate the comprehensive performance of TRST. Through comparative analysis, TRST with 8 blades, a 60° or 90° twist angle of the blades, a tray height of 15 mm, and sieve holes of 2 mm diameter were found to has the optimal geometry.

Development of a Continuous Photo-catalytic/Ozonation System: Application on Amido Black Removal from Water

ABSTRACT A continuous system for photo-catalytic/ozonation was designed at laboratory scale and evaluated for water treatment using Amido Black 10B dye (AB) as a pollutant model. The effect of single ozonation (O3), photolytic ozonation (UV/O3) and combined photocatalytic/ozonation treatment (UV/O3/TiO2) were investigated. TiO2 nanocatalysts films were coated on stainless steel grids (AISI 304) by Atomic Layer Deposition technique (ALD) at 350 °C. An experimental hydrodynamic study of the designed reactor was conducted based on dry and total pressure drop. Three flow regimes were observed by increasing the total pressure drop against gas load factor (Fs). Depollution experiments conducted on the developed reactor showed that reaction rates and efficiency of studied processes were dependent on the studied operational parameters (initial dye concentration, ozone dose, pH). The maximum AB dye ([AB]0 = 100 mg. L−1) conversion efficiency, using the designed (UV/O3/TiO2) system, was about 40.3% of initial TOC and 100% AB color removal was achieved within 10 min at an optimal ozone dose of 132 mg. L−1. A significant improvement in AB removal using UV/TiO2/O3 process (koverall = 0.056 min−1, 40.3%) compared to O3 alone (koverall = 0.032 min−1, 26.87). Results shows also that the addition of tert-butanol (TB), as radical scavenger ([TB] = 0.2 M and 0.4 M), greatly affects the reaction mechanisms of a photocatalytic ozonation process within 5 min of reaction, by decreasing the Amido Black conversion from 99.67% ([TB] = 0 M) to 74.63% and 31.35%, respectively, in presence of 0.2 M and 0.4 M of tert-butanol. The remarkable decrease in AB removal rate observed in the presence of a radical scavenger expresses that there was an obvious enhancement of hydroxyl radical OH• generation due to the synergetic effect between ozone and photocatalytic processes.

Nye Tray Versus Sieve Tray: Experimental Study on Hydrodynamic Parameters

AbstractThe hydrodynamic parameters of a Nye tray were investigated by performing experiments in a tower with a diameter of 1.22 m. Air was used as the gas phase and water was used as the liquid phase. A number of parameters such as the dry pressure drop, the total pressure drop, the clear liquid height, the froth height, and the entrainment were measured. A tray stability factor was obtained using the amount of weeping, the clear liquid height, the dry pressure drop, and the Froude number. All experiments were repeated for the matching sieve tray under the same conditions. Ultimately, advantages and disadvantages were compared, and the results demonstrated that the Nye tray has a couple of advantages over the sieve tray, except that the sieve tray is slightly more stable.

Experimental Study of the Influence of Gas Flow Rate on Hydrodynamic Characteristics of Sieve Trays and Their Effect on CO2 Absorption

An experimental study was conducted in the sieve tray column to investigate the influence of gas flow rate on the hydrodynamic characteristics of the sieve tray, such as total tray pressure drop, wet tray pressure drop, dry tray pressure drop, clear liquid height, liquid holdup, and froth height. The hydrodynamic characteristics of the sieve tray were investigated for the gas/water system at different gas flow rates from 12 to 24 Nm3/h and at different pressures of 0.22, 0.24, and 0.26 MPa. In this study, a simulated waste gas was used that consisted of 30% CO2 and 70% air. The inlet volumetric flow rate of the water was 0.148 m3/h. The temperature of the inlet water was 19.5 °C. The results showed that the gas flow rate has a significant effect on the hydrodynamic characteristics of the tray. The authors investigated the effect of changing these hydrodynamic characteristics on the performance of a tray column used for CO2 capture.

CFD Simulation of Dry Pressure Drop in a Cross-Flow Rotating Packed Bed

The cross-flow rotating packed bed (RPB) has attracted wide attention in recent years because of its advantages of large gas capacity, low pressure drop and lack of flooding limitation. However, the complex structure of the packing makes it difficult to obtain the gas flow characteristics in the cross-flow RPB by experiments. In this study, the dry pressure drop in the cross-flow RPB was investigated by computational fluid dynamics (CFD). The packing was modeled by the porous media model and the rotation of the packing was simulated by the sliding mesh model. The simulation results obtained by three turbulence models were compared with experimental results, and the RNG k-ε model was found to best describe the turbulence behaviors in the cross-flow RPB. Then, the effects of gas flow rate and rotating speed on dry pressure drop in different parts of the cross-flow RPB were analyzed. The results of this study can provide important insights into the design and scale-up of cross-flow RPB.

Hydrodynamics of a novel 3D printed structured packing–SpiroPak

Hydrodynamic performance of an ultra low-pressure drop and high surface area, 3D printed structured packing (SpiroPak) was investigated in this study. Computational fluid dynamics (CFD) modelling combined with single-phase (dry) and irrigated (multiphase) experiments were carried out to validate the CFD modelling results. Experiments were conducted to measure the dry and wet pressure drop at a range of liquid load (0–38.2 m3/m2∙h) and F-factor (0–1.2 Pa0.5). Liquid distribution was measured using Wire Mesh Sensor (WMS) for SpiroPak and compared with a commercial and 3D printed replica of Mellpak 250X and Montzpak B1–500. The topology of the packing was analysed to calculate the specific surface area that could be available for mass transfer. It was found that the SpiroPak can have up to 50~200% more surface area per unit volume when compared with commercial packing. Experimental and modelling results showed that SpiroPak could reduce the dry pressure drop by approximately 50%. Parametric study found that reducing corrugation size to increase surface area and increasing the gap size to reduce the pressure drop were key design parameters of SpiroPak. Finally, scale-up and scale-out (tessellation) techniques were compared to determine the optimum element size for the application of SpiroPak on a large scale.

A new tomography-based approach for the fluid dynamic description of conventional structured packings and sandwich packings

Pressure drop, holdup and flooding points are essential factors for the hydraulic design of columns equipped with structured packings. This is also true for sandwich packings representing a combination of two alternating layers of conventional structured packings with different geometric surface areas. Such a combination results in a heterogeneous flow pattern evolving within certain operating ranges. In order to describe accurately the fluid dynamics over the entire operating range of both common structured packings and sandwich packings, a modelling approach is proposed based on conventional measurements and tomographic investigations. The approach distinguishes film-like flow patterns and froth regimes. For film-like flow patterns, packing-typical descriptions are used, whereas the froth in packings is described using an analogy to trays. Correlations were derived to determine the liquid holdup for film and froth flow, the dry and irrigated pressure drop as well as the gas velocities at the loading limits. The fluid dynamic model was verified with 1595 measurements for pressure drop and 510 measurements for holdup for the test system water/air.

Design and conception of an innovative packing for separation column — Part III: Development of new hydrodynamic and mass transfer correlations for a wire-based lattice packing

This paper presents accurate models evaluating the hydrodynamic and separation behavior of an innovative packing structure called Tetra Spline (TS) packing. The newly designed internal is a wire-based lattice packing fabricated via additive manufacturing for gas-liquid contact systems, such as distillation and absorption columns. Using dimensional analysis, four correlations are developed for the prediction of dry and wet pressure drops, flooding velocity, and HETP of the TS internals in a two-phase system, regardless of its physicochemical properties. The performances are modeled based on extensive experimental data described in a previous work. These data are obtained by performing hydrodynamic and mass transfer characterizations on fifteen different TS configurations. Then, some of the proposed correlations are compared to other models available in literature. The final step will highlight that after optimization of the geometrical parameters the TS packing can reach high performances.

Influence of Surface Modification on the Transient Dehumidification Performance of Fin-and-tube Heat Exchanger

In this study, surface modifications subject to hydrophilic and hydrophobic conditions are made for copper fin-and-tube heat exchanger to examine the dehumidification performance. Polydimethylsiloxane was used to coat on the surface of heat exchangers to increase the hydrophobicity with a contact angle of 105° while the uncoated copper surface is 76°. The effects of fin spacing and relative humidity on the transient dehumidifying performance are examined in details. The experimental results indicate that surface modification imposes negligible influence on the heat transfer performance. Hydrophobic surface promotes dropwise condensation and may form water bridging which may impede the droplets from falling, thereby showing some 3.4 times higher pressure drop than the hydrophilic one. Upon condensation on the hydrophilic surface, the size of the droplets plays pivotal influence on the transient pressure drop of the heat exchangers. The flow visualization indicates that liquid films prevails on the fin surfaces due to high surface wettability. However, the behavior of transient pressure drop depends on the relative humidity (RH) considerably. For RH = 50%, the required time to reach steady state is much longer than that of RH = 80%. Interestingly, an overshoot of pressure drop vs. time before reaching the steady state is clearly seen for RH = 65%. This phenomenon is associated with the dynamic condensate removal from the fin surface. The droplet distribution density is comparatively uniform at a low frontal velocity (i.e. 0.5 m s−1). Upon raising frontal velocity, the droplet distribution density becomes less uniform with fewer droplets adhering on the fin surfaces. Hence, the wet and dry pressure drop ratio exhibits a decreasing trend at a higher frontal velocity.

Airside heat transfer and pressure drop of an aluminum heat exchanger having a new louver fin with leading edge extension

Conventional louver fins have an inherent problem of condensate drainage. In this study, a newly developed louver fin is introduced. The louver fin has an extension at leading edge. Dry and wet surface heat transfer and pressure drop characteristics of the heat exchanger made of the new fins were investigated, and results are compared with those having trailing edge extension fins or conventional fins. For conventional sample, significant differences between dry and wet j and f factors were observed. Dry j factors were 166% larger than wet j factors, and wet f factors were 68% larger than dry f factors. The discrepancies were significantly reduced for the samples having extensions, which suggests that extensions are effective in condensate control. The present sample having leading edge extension yielded higher dry j factors than the sample having trailing edge extension, probably due to proper allocation of louvers. Wet j factors of the two extended samples were approximately the same, which means that the condensate drainage is better for trailing edge extension than leading edge extension. Under dry condition, j/f1/3 of leading edge sample were 132 % and 59% higher than those of trailing edge extension and conventional sample respectively. However, under wet condition, j/f1/3 of leading edge extension sample were 87% and 205% higher than those of trailing edge extension and conventional sample. This confirms that the present leading edge extension sample shows better performance than trailing edge extension sample, both under dry and wet condition.

Characterization of a New Structured Packing by Computational Fluid Dynamics

AbstractThe novel wire gauze structured packing PACK‐1300Y with high specific surface area was characterized by computational fluid dynamics. The main features of PACK‐1300Y were investigated including the dry and wet pressure drop as well as the height equivalent to a theoretical plate (HETP). Moreover, the flow structure of this packing was described via numerical simulations. To evaluate the amount of HETP and dry and wet pressure drop, 3D computational fluid dynamic modeling with respect to the Eulerian‐Eulerian multiphase approach was applied. The average relative errors were determined between the findings achieved from computational fluid dynamic simulation and experimental findings for mass transfer efficiency and wet and dry pressure drop, respectively.

New Column Design to Enhance Flexibility: Concept for Hydrodynamic Characterization

AbstractThis study presents a new and innovative sieve tray design for a more flexible operation of separation columns in terms of possible throughput. The advantage of this new tray design is to ensure an optimal operation for varying feed flow rates and constant separation efficiencies for different load ranges. The aim of this work is to give a short introduction and an outlook to the investigation of the functionality of the designed trays. Moreover, the general design of the new trays, first results for CFD simulations of the dry pressure drop and the experimental setup are presented.

Dry bed gas pressure drop across the concentric-ring rotating bed

Dry bed gas pressure drop across the concentric-ring rotating bed

Prediction of residual saturation and pressure drop during coalescence filtration using dynamic pore network model

Microstructure optimization of mist and dust filter media used in many applications including respirators, lubricated machining, compressors and engine crankcases is increasingly becoming reliant on computational simulations of dry and wet filtration processes. Computational fluid dynamics (CFD) based full-morphology simulations with advanced interface capturing techniques offer unique advantages in enabling accurate characterization of the pore-scale transport processes, yet demand substantial computational effort especially for fine filters. In this work, a dynamic pore network modeling (DPNM) framework is developed and evaluated for the prediction of residual saturation and pressure drop during mist filtration, and applied to an oil-air system. Two nonwoven filters (stainless steel and polyester) with different fibre diameters and packing densities are considered. The pore network is extracted using a watershed-based algorithm, from realistic virtual filter geometries (Abishek et al., 2017), and validated for macroscopic properties such as packing density. The validity of the steady PNM model is assessed by comparison of the dry (air) pressure drop against CFD and experimental data in the literature. The validity of the DPNM model is assessed by comparison of multiphase pressure drops and residual saturation against micro-CT and gravimetric experiments carried out in this work, as well as pore-scale CFD simulations using the volume-of-fluid model. It is found that the dynamic pore network model is able to successfully predict the critical properties of the filtration process such as saturation (local and total) and pressure drop to within 15% of experiment and CFD. Considering that the overall computational cost of DPNM is about 2–3 orders of magnitude lower than fully resolved CFD, DPNM stands as a potential tool for the early-stage design and optimization of mist filtration media.

Computational Fluid Dynamics Characterization of High‐Capacity Structured Packing

AbstractThe novel wire gauze structured packing, PACK‐860, was characterized by means of numerical methods. The main features of PACK‐860 such as height equivalent to a theoretical plate (HETP) and dry/wet pressure drop were evaluated. The flow structure in this packing was described by numerical simulation. To estimate the amount of HETP and dry/wet pressure drop, three‐dimensional computational fluid dynamics (3D CFD) modeling with the Eulerian‐Eulerian multiphase approach was applied. The average relative errors between the results obtained from CFD simulation and experimental findings for mass transfer efficiency and wet and dry pressure drop were assessed. Numerical observations were found to agree well with the empirical results, proving the reliability of CFD simulations for modeling separation processes.

Comparative study of dry pressure drop and flow behaviour of gas flow through sieve plate packing

AbstractSieve plate packing is a newly developed packing that has been used in several industries due to its simple structure and operating flexibility, and no liquid flooding. In this work, first, systematic experiments were conducted to measure the pressure drop of gas flow through six sieve plate packings. The results indicated that the geometric characteristics of the packing have complicated effects on the pressure drops. Based on this, CFD simulations on the gas flow field were conducted using the realizable k‐ε model, and flow behaviours such as the pressure drop, pressure nephogram, and velocity distributions within different packings were obtained. The simulation results clearly showed interesting flow patterns, including the contraction and expansion of the gas stream through the sieve hole, the flow separation on the sharp edge of the hole, and the vortexes formed when gas impacts the downstream plate. By comparing the flow patterns and the pressure drop under different packings operating at different conditions, the effects of the geometric characteristics of the packing on the pressure drop could be clearly distinguished from the flow behaviours, so that the variations in pressure drop with various packing structures were clearly indicated. Finally, based on the experimental data and the simulated results, correlations for the prediction of the pressure drops were proposed. This work will provide a useful basis for understanding the flow behaviour of gas and liquid two‐phase flow in sieve plate packing.

Full-Scale CFD Modeling of Multiphase Flow Distribution in a Packed-bed Absorber with Structured Packing Mellapak 250Y

AbstractA full-scale multi-environment Eulerian CFD model for a countercurrent packed-bed absorber with structured packing Mellapak 250Y was built in ANSYS Fluent 2019 R1 in order to model CO2 capture using physical solvents. The objective of the model is to predict the overall absorber gas-liquid internal flow profiles within the complex packing geometry, while accurately predicting the hydrodynamic parameters, such as liquid holdup and pressure drop. The gas-solid and gas-liquid drag coefficients were fitted and validated using the following experimental data by Green et al. (2006. “Hydraulic Characterization of Structured Packing via X-ray Computed Tomography”; 2007. “Novel Application of X-ray Computed Tomography: Determination of Gas/liquid Contact Area and Liquid Holdup in Structured Packing.” Industrial & Engineering Chemistry Research 46: 5734–53.): dry pressure drop, irrigated pressure drop, and liquid holdup. The validated CFD model was used to study the effect of liquid distributor design on the liquid distribution in the absorber using three distributors provided with seven, thirteen, and twenty orifices of 0.2 mm diameter. The CFD model predictions revealed that the distributor with the largest number of orifices resulted in the least liquid maldistribution in the absorber, which led to increasing the overall CO2 absorption efficiency in Selexol as a physical solvent. Also, the overall CO2 absorption efficiency decreased with increasing the superficial liquid velocity due to the shorter contact times between CO2 and Selexol in the absorber at higher superficial liquid velocities.

Experimental and Computational Fluid Dynamics Validation of Correlations for Dry Pressure Drop in Trays without Downcomer

AbstractThe dry tray pressure drop (ΔPd) is a design parameter that provides preliminary information about the total pressure drop. This work aimed to assess correlations for ΔPd prediction for different types of trays without downcomer and to evaluate the effects of the free area ratio (φ) and the hole diameter (d) on ΔPd. Assessment was performed by comparing results of several correlations with those from an experimentally validated computational fluid dynamics simulation. The study shows that the correlations of Červenka and Kolář, Bennett, Agrawal and Cook, and Stichlmair and Mersmann predicted the dry pressure drop satisfactorily. The correlation of Bennett, Agrawal and Cook can be recommended for the prediction of ΔPd for a wide range of geometries and operation conditions. Also, φ has a higher influence on ΔPd than d.

CFD analysis of gas flow characteristics in a rotating packed bed with randomly arranged spherical packing

In recent years, some unit operations such as absorption and rectification in rotating packed beds (RPBs) have drawn great attention, and single-phase hydrodynamics characteristics became the basis to understand the multiphase flow and mass transfer process. In this work, the 3D steady-state gas flow in the RPB with randomly arranged spherical packing was investigated by computational fluid dynamics (CFD). The gas flow field and the effects of operational parameters were analyzed. Results showed that the errors between the simulated and the experimental data of the total pressure drop were within ±20%. The pressure drop of packing zone and tangential velocity increased with the increase of rotational speed, while the rising of the gas flow rate could result in the increase in the radial velocity, the pressure drop of the inner or outer cavity. The turbulent kinetic energy was predominantly affected by the tangential slip velocity, and the higher values of turbulent kinetic energy were illustrated near the outer edge of the rotor. Furthermore, a semi-empirical correlation based on the numerical simulation was proposed to predict the dry pressure drop of the packing zone combining the wall effect.