Wet Pressure Drop Research Articles

Hydrodynamics and wet pressure drop model based on flow regimes of the novel Flow-Divided Baffle-Bridge Tray

This study introduces the Flow-Divided Baffle-Bridge Tray (FDBBT), an innovative tray design featuring hole-bridge structures at the caps’ base for pre-distribution of gas and liquid, and stepped baffles configuration at the caps’ top to minimize entrainment. The pressure drop, weep and entrainment of FDBBT were evaluated in a Φ796 mm experimental setup. Compared to the sieve tray and Glitsch V-1 valve tray, FDBBT demonstrated lower pressure drops and significantly reduced entrainment, suggesting a higher operational ceiling. Furthermore, a specialized single-cap experimental apparatus was designed to assess the lifted liquid rate and uncover gas-liquid flow regimes within the cap, namely churn flow, free-surface flow, and periodic-free-surface flow. Employing data from the single-cap experiments, complemented by CFD-assisted analysis, FDBBT's pressure drop model was established and then validated by the Φ796 mm experiments, with most deviations falling within a 5 % threshold.

Experimental study on the influencing factors of coalescer and liquid film interception theory

Coalescer are commonly utilized in the realm of deep gas drying field, and its performance is contingent upon the filter. The filter consists of a support structure, a coalescing layer, and a drainage layer. However, research focuses more on the impact of coalescing and drainage layers on coalescence performance. The impact of the support structure and the interlayer gap of the coalescing layer on coalescence performance during the production process remains unknown. To address the issue, the experiments were performed under 0.30 m/s surface velocity and 2.50 g/min liquid loading rate with coalescing layer ranging from 1 to 6 layers. Variation of pressure drop under different supports identified a statistically significant advantage for diamond mesh over orifice. The three placement methods' specific order of pressure drop is both-sided > front-side> no-support > back-side placement. Based on experimental evidence showing that liquid film interception of droplets dominates in the coalescence process, the liquid film interception theory was proposed. Further, based on the "liquid film interception theory", the effect of interlayer gaps on coalescence performance was researched. The results show that setting interlayer gaps corresponds to an increase in separation efficiency by 1–4 %, an increase in wet pressure drop by 34.63–63.86 %, and a decrease in quality factor by 208.76 %. Therefore, to achieve high-performance filter media, interlayer gaps should be avoided during the manufacturing process.

Prototyping of rotating packed bed structural internals

A rapid prototyping method was developed for quick and inexpensive design of various geometrical solutions for rotating packed bed internals. Sixteen geometries were designed with the use of 3D modeling software and subsequently 3D-printed, if possible. The printed packings were tested for dry pressure drop to reject the ones generating too high air flow resistance. Eventually, the packings were tested for wet pressure drop and effective mass transfer area generated in specified conditions. An evaluation method was designed to compare the results from the different packings and determine the geometry most suited for the absorption process.

Multi-scale CFD study of multiphase flow in structured sinusoidal corrugated sheets packings

Structured packing is an important equipment and has wide applications in chemical separation process. In this study, the complex hydrodynamics characteristics of structured sinusoidal corrugated sheets packings were investigated by 2D liquid film model and 3D Representative Element Unit model. Volume of Fluid method was employed to investigate the effect of eleven different structures of sinusoidal corrugated sheets packings (i.e. wavelength, amplitude, and corrugated angle) on liquid holdup, wet pressure drop, and interfacial area. In addition, a shape factor was proposed to characterize the effect of flow regime on packing hydrodynamics characteristics and wetting performance. The packing shape factor analysis method proposed in this study could provide a reference for the structural optimization and evaluation of structured packing in the future.

CFD simulation of the PACK-860X

This study recommends a novel structured packing (SP) PACK-860X with a specific surface area of 860[Formula: see text]m2/m3, which is defined utilizing a numerical method. We attempt to investigate the main properties of PACK-860X for illustration, height equal to a theoretical plate (HETP), dry pressure drop (DPD) and wet pressure drop (WPD). In addition, the flow pattern is expressed for packing through computational simulation. To assess the amounts of HETP, WPD and DPD, the 3D CFD simulation with the Eulerian–Eulerian multi-phase technique is employed in this work. Based on the results of this work, WPD and DPD are improved. According to the data, numerical outcomes are in good agreement with the theoretical results, which shows the reliability of CFD methods for modeling the separation processes.

Will laboratory and pilot plant columns soon become superfluous? – A concept for the determination of structured packing characteristics in a measuring cell under distillation conditions

A new approach to carry out separation performance tests for structured packings is introduced through a newly designed measuring cell. To characterize this measuring cell, a suitable test system was identified and measurements regarding the separation performance as well as the dry and wet pressure drop were conducted. Furthermore, experiments were carried out with similar boundary conditions in columns of varying diameters (DN 50, DN 80, DN 250). The paper presents a comparison of the results gained to demonstrate the transferability and information value of the new measuring cell in comparison to conventional lab and pilot-plant columns. To our knowledge, these are the first investigations evaluating the separation performance of distillation processes in small measuring cells of this kind.

Numerical simulation of binary component separation with perforated-on sheets of the structured packing

In this research work, we proposed a modern structured packing (SP) with perforated sheets with a specific surface area of 860[Formula: see text][Formula: see text]/[Formula: see text], which was determined using numerical techniques. This work aims to evaluate the major characteristics of PACK-860 for instance, height equivalent to a theoretical plate (HETP), dry pressure drop (DPD) and wet pressure drop (WPD). Additionally, the flow construction was defined for specific packing via computational simulation. To evaluate the value of HETP, DPD and WPD, the three-dimensional (3D) computational fluid dynamics (CFD) simulation with the Eulerian–Eulerian (EE) multi-phase method applied in this paper. According to the findings of this research, the performance of the mass transfer (MT), WPD and DPD was enhanced with the perforated-on sheets of packing. Based on the observation, numerical results are consistent well with the theoretical data which reveals the consistency of CFD tools for modeling methods to separation applications.

Influence of structured packing geometric parameters on flow and mass transfer performance of liquid nitrogen and oxygen for cryogenic distillation

Normally, the design of the cryogenic structured packings mainly relies on the hydraulic experiments of room temperature fluids such as water due to the difficulties and high cost of conducting cryogenic experiments. This may result in significant performance discrepancies in cryogenic distillation applications since cryogenic fluids have quite different properties. In this work, with the help of the CFD combing VOF method, a three-dimensional structured packing model of counter-current flow was established. The flow characteristics and mass transfer performance of the LN2-O2 system (liquid nitrogen and gaseous oxygen) under different packing parameters including B (base), S (side), H (height), and β (crimping angle) were comprehensively coupled and analyzed. In particular, the flow morphology, and local wetting rate were analyzed to reveal the differences in flow characteristics between the LN2-O2 system and the water–air system. Furthermore, the mass transfer coefficient, mass transfer rate, and pressure drop of the LN2-O2 system were analyzed to obtain a deep understanding of the cryogenic distillation process under different packing geometric parameters. According to the results, the flow of the water–air system and LN2-O2 system is significantly different. As the specific values of base B, side S, and height H decrease, the water remains in rivulet flow, while LN2 changes from film flow to rivulet flow, which indicates the effect of the contact points on the flow of liquid nitrogen is more significant than that of water. With a constant specific surface area, as the crimping angle β increases from 60°to 120°, the wettability of liquid nitrogen on the suspended surface can be significantly improved. The wetting rate of LN2 increases by 9.78%, resulting in the mass transfer rate increasing by 9.02%, and the wet pressure drop decreasing by 9.60%. It shows the structured packing with the higher crimping angle β of 120° has a good application prospect in cryogenic distillation.

Study on the Hydrodynamic Performance of a Countercurrent Total Spray Tray under Sloshing Conditions

In this paper, a new type of total spray tray (TST) with gas–liquid countercurrent contact is proposed to solve the problem of slight operation flexibility and poor sloshing resistance in towers under offshore conditions. Its hydrodynamic performance indicators, such as pressure drop, weeping, entrainment, and liquid level unevenness, were experimentally studied under rolling motion. A tower with an inner diameter of 400 mm and tray spacing of 350 mm was installed on a sloshing platform to simulate offshore conditions. The experimental results show that the rolling motion affected the hydrodynamic performance of the tray under experimental conditions. When the rolling amplitude did not exceed 4°, the degree of fluctuation of the hydrodynamic performance was small, and the tray could still work stably. With increasing rolling amplitude, the TST wet plate pressure drop, weeping, and liquid level unevenness fluctuations also increased. When the rolling amplitude reached 7°, the maximum fluctuation of the wet plate pressure drop was 8.9% compared to that in the static state, and the plate hole kinetic energy factor, as the TST reached the lower limit of weeping, increased rapidly from 6.2 at rest to 7.8 under the experimental conditions. It can be seen that the TST still exhibits good hydrodynamic performance under rolling motion.

Simulation of Forced Convection Frost Formation in Microtubule Bundles at Ultra-Low Temperature

Hypersonic vehicles are an important area of research in the aerospace field today. One of the important issues is the power of the engine. In order to achieve large-span flight speeds, a more efficient approach is to use combined power systems. However, the problem of pre-cooler icing can occur in combined engine applications. The flow in the pre-cooler is extremely complex. Outside the tube is the high-temperature wet air entering from the engine intake, and the tube cooling is the ultra-low temperature cooling medium. Icing not only increases the heat exchange resistance of the pre-cooler during operation and affects the heat exchange performance of the pre-cooler, but also causes a large total pressure loss, resulting in a degradation of the engine performance. There is a lack of research on the icing law of the pre-cooler under different parameters. Therefore, it is necessary to conduct a corresponding numerical calculation study on pre-cooler icing and explore the influence of various influencing factors on icing. In this paper, a mathematical model of icing (frost) is established for the frosting phenomenon that may occur during the operation of the pre-cooler. Additionally, the principle of heat and mass transfer in the icing process is described by the mathematical model, and the influence of different parameters on the frosting parameters is explored by using the computational fluid dynamics (CFD) method. The law of tube bundle icing under different parameters was calculated, and the variation laws of frost layer morphology and wet air pressure drop were obtained. The laws of tube bundle icing under different parameters were calculated, and the changes in frost layer pattern and wet air pressure drop when each parameter was changed, which can provide guidance for the design and application of pre-coolers in the future.

Structured packing improves wet scrubbing of airborne molecular contaminants in cleanroom make-up air units

The use of wet scrubbing to remove airborne molecular contaminants in cleanroom make-up air units has economic benefits and good application prospects. Still, problems with this method include low removal efficiency and large water consumption. To improve scrubbing performance, we built a full-scale scrubbing experiment platform using SO2 as the removal object. In addition, we applied structured packing in the scrubbing process to enhance the mass transfer between gas and liquid, and we tested the wet scrubbing removal efficiency and pressure drop under a variety of operating conditions. Results showed that under the condition of double-row spraying only, the SO2 removal efficiency increased with increasing liquid-gas ratio. The efficiency ranged from 57% to 83.9% and the pressure drop ranged from 6 to 15 Pa. After adding structured packing, the removal efficiency under different liquid-gas ratios improved significantly. Improvement was more apparent, ranging from 72.2% to 86.2%, when the liquid-gas ratio was low. The pressure drop also increased, ranging between 59 Pa and 100 Pa. In addition, we changed the packing thickness and the number of stages, and found that when the packing thickness was 0.2 m and the two-stage spacing was 0.15 m, removal efficiency improved up to 89.7%. The research results are significant for optimizing wet scrubbing performance and, at the same time, have practical engineering value for controlling the concentration of airborne molecular contaminants in the cleanrooms.

Numerical analysis of the influence of packing corrugation angle on the flow and mass transfer characteristics of cryogenic distillation

The corrugation angle of structured packing is an important structural parameter that affects the mass transfer efficiency and pressure drop of distillation process. However, at present, the detailed effects of corrugation angle on the distillation performance of the cryogenic fluids are seldom reported due to the difficulties in conducting cryogenic experiment, which needs to be further revealed for the optimizing of cryogenic structured packing. In this work, a three-dimensional CFD model combing VOF method was established to investigate the flow characteristics of LOX in Mellapak 250 packing under different packing corrugation angles. The effects of corrugation angle on the component mass transfer rate of cryogenic fluids of oxygen and nitrogen were analyzed in detail. Results show that under the combined action of interfacial area, liquid film thickness and liquid residence time, the mass transfer rate decreases by about 30% with the increase of angle from 45° to 60°, while the decrease of wet pressure drop can reach 81.1%, much higher than the reduction ratio of mass transfer rate. It shows 60° packing has application potential and can be used in the middle part of the cryogenic distillation column where mass transfer force is very large, reducing pressure drop loss without substantially sacrificing mass transfer efficiency. 60° packing with higher specific area can also be applied. In addition, it is found that 50° packing can greatly reduce the loss of pressure drop (41.1%) with only a small amount of mass transfer rate loss (8.8%), which shows a good application prospect in cryogenic distillation.

Flow regimes and pressure drop of a composite tridimensional rotational flow sieve tray under concurrent gas‐liquid flow

A composite tridimensional rotational flow sieve tray (CTRST) is proposed. The flow patterns of CTRST were recognized visually, combined with the standard deviation of the pressure difference. In the TRST area of the internal packing-type tray, the membrane-drip column and foam-embolic flow is present, while bubbly and milk froth-ribbon flow is present in the packing area of the external packing-type tray. The effect of the tray structure parameters on the pressure drop under co-current flow was investigated. The dry and wet pressure drop is within 160 and 900 Pa, respectively. Under the same structural parameters, the pressure drop of the internal packing-type tray was higher than that of the external packing-type tray. The flow characteristics of the standard tray under the countercurrent flow were compared. The CTRST was found to be more suitable for co-current flow. A prediction model pressure drop under co-current was established with an error of 15.5%.

Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region

The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates. However, this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow, which is corresponding to a region of low Fr G (gas phase Froude number) in the flow pattern map of wet gases. In this study, the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low Fr G region. By the experiment, the flow pattern transition in the downstream of single-orifice plates, as well as the effects of Fr G and Fr L (liquid phase Froude number) on Φ G (gas phase multiplier), were determined and compared when the upstream is in the flow pattern transition and the stratified flow region, respectively. Prediction performances were examined on the available pressure drop models. It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low Fr G region with an acceptable accuracy. With a new method of correlating Fr G and Fr L simultaneously, new correlations were proposed for the low Fr G region. Among which the modified Chisholm model shows the best prediction accuracies, with the prediction deviations of Φ G being within 7% and 3% when the upstream is in flow pattern transition and stratified flow region, respectively.

Employing computational fluid dynamics technique for analyzing the PACK-1300XY with methanol and isopropanol mixture

In this study, an innovative wire gauze structured packing, namely PACK-1300XY with a specific surface area of 1300 m2/m3 has been characterized by performing computational fluid dynamics (CFD) approach. Indeed, different features of this packing (height equivalent to a theoretical plate, wet/dry pressure drop, and mass transfer efficiency) were analyzed by analyzing the flow regime using the three-dimensional CFD approach with the Eulerian–Eulerian multiphase scenario. The results showed the mean relative deviation of 16% (for wet pressure drop), 14% (for dry pressure drop), and 17% (for mass transfer efficiency) between the CFD predictions and experimental measurements. These excellent levels of consistency between the numerical findings and experimental observations approve the usefulness of the CFD-based approach for reliable simulation of separation processes.

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.

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.

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

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.

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.

Oil-mists coalescence performance of fibrous filters with superoleophilic and superoleophobic surface

The surface wettability of fibers in coalescing filter has a critical effect on filter’s performance. In this study, we employed common glass fiber filters as model and prepared superoleophilic and superoleophobic surface filters via a facile dip-coating method. The superoleophilic treatment shows a considerable reduction in pressure drop. The wet pressure drop at saturation decrease from 12.91 kPa to 8.56 kPa after superoleophilic coating. The filtration efficiency of fine particles (<100 nm) increase owing to coating treatment. The combinations of superoleophilic and superoleophobic filter and drainage strategy were also evaluated. The results show that the combination has no advantage due to emergency turn of wettability. The drainage layer with appropriate rank could enhance the drainage rate at unsaturation stage. However, the drainage strategy is never a good idea to improving coalescence performance because it brings the extra pressure drop.