Bubble Absorption Research Articles

In Plasma Catalytic Oxidation of Toluene Using Monolith CuO Foam as a Catalyst in a Wedged High Voltage Electrode Dielectric Barrier Discharge Reactor: Influence of Reaction Parameters and Byproduct Control.

Volatile organic compounds (VOCs) emission from anthropogenic sources has becoming increasingly serious in recent decades owing to the substantial contribution to haze formation and adverse health impact. To tackle this issue, various physical and chemical techniques are applied to eliminate VOC emissions so as to reduce atmospheric pollution. Among these methods, non-thermal plasma (NTP) is receiving increasing attention for the higher removal efficiency, non-selectivity, and moderate operation, whereas the unwanted producing of NO2 and O3 remains important drawback. In this study, a dielectric barrier discharge (DBD) reactor with wedged high voltage electrode coupled CuO foam in an in plasma catalytic (IPC) system was developed to remove toluene as the target VOC. The monolith CuO foam exhibits advantages of easy installation and controllable of IPC length. The influencing factors of IPC reaction were studied. Results showed stronger and more stable plasma discharge in the presence of CuO foam in DBD reactor. Enhanced performance was observed in IPC reaction for both of toluene conversion rate and CO2 selectivity compared to the sole NTP process at the same input energy. The longer the contributed IPC length, the higher the toluene removal efficiency. The toluene degradation mechanism under IPC condition was speculated. The producing of NO2 and O3 under IPC process were effectively removed using Na2SO3 bubble absorption.

Key Factors for Rapid Detecting 1,1-dimethylhydrazine in Air by Solution Absorption/Spectrophotometry Method

In order to improve the detection efficiency of 1,1-dimethylhydrazine in air by solution absorption/spectrophotometry method, some key factors were analysed, such as the absorption velocity and the number of large bubble absorber tubes. The results of this method were compared with that of Chinese national standard method under different concentration of UDMH. The results showed that two bubble tubes in series could meet the collection efficiency and the best absorption velocity was 0.2 L min−1. The standard deviation of the method was less than 5%, and the error of the method and the national standard method was less than 2%. The proposed method has the characteristics of simple operation, high precision and high reliability.

CO2 absorption performance enhancement by dodecane nanoemulsion absorbents

Among the CO2 capture technologies, the physical absorption is one of the most common absorption methods. However, the physical absorption process is operated at extremely low temperature, and therefore huge freezing energy is required. The objective of this study is to develop the nanoemulsion absorbents that can be operated at room temperature. The nanoemulsion absorbents are prepared by the ultrasonication method. Based on the chemical properties, Span 60 and Tween 60 are added to maintain a good dispersion stability. CO2 absorption experiments using a porous nozzle absorber are conducted for various dodecane concentration (0.005–0.5 vol%) and CO2 flow rate (0.06–0.12 g/s). It is found that the CO2 absorption performance of 0.05 vol% nanoemulsion absorbents is 10% higher than that of pure methanol. Through the single CO2 bubble absorption visualization experiments, it is confirmed that the nanoemulsion absorbents cause faster bubble absorption than pure methanol does. The turbidity index (Nephelometry turbidity unit) of nanoemulsion absorbents is kept constant for seven days, which means a good dispersion stability. The enhancement mechanism of CO2 absorption is explained based on the Einstein-Stokes’ equation, cryogenic transmission electron images, and droplet size measurements. The key idea is that nano-sized dodecane (64 nm) absorbs the CO2 molecules and transports it to the bulk region by the Brownian diffusion. A random walk model is used to investigate the droplet size prediction and CO2 absorption performance enhancement.

Numerical simulation and experiment for R124-DMAC bubble absorption process in a vertical tubular absorber

A comparing investigation between the simulated model and experimental verifications for the R124 (2-chloro-l,l,l,2,-tetrafluoroethane)-DMAC (N′, N′- dimethylacetamide) bubble absorption process in a vertical tubular absorber were performed. The objective of the investigation was to model the R124-DMAC bubble absorption process and to verify the model results with visual and non-visual experiments under similar operating conditions. The comparing results between the model and experiments were consistent well. The two-phase and single-phase convective heat transfer coefficient and two-phase mass transfer coefficient enhanced with increase of vapor and solution flow rates, and decreased with increase of solution inlet temperature, solution inlet mass fraction and nozzle orifice diameter. The two-phase mass transfer coefficient varied slightly with vapor flow rates rising. Finally, new correlations of the bubble absorption height, two-phase and single-phase convective heat transfer coefficients and two-phase mass transfer coefficient for R124-DMAC bubble absorption process in a vertical tubular bubble absorber were proposed. All of the correlation equations could predict about 90% of these parameters at a margin of error less than 15% under the operating conditions.

Corrigendum: Numerical study of heat and mass transfer enhancement for bubble absorption process of ammonia-water mixture without and with nanofluids

NUMERICAL STUDY OF HEAT AND MASS TRANSFER ENHANCEMENT FOR BUBBLE ABSORPTION PROCESS OF AMMONIA-WATER MIXTURE WITHOUT AND WITH NANOFLUIDS by Mohamed Bechir BEN HAMIDA, Jalel BELGHAIEB, and Nejib HAJJI Research Unit of Energy and Environment, National School of Engineers of Gabes, University of Gabes, Gabes, Tunisia Original scientific paper https://doi.org/10.2298/TSCI170313229B published in the journal Thermal Science, Year 2018, No. 6B, Vol. 22, pp. 3107-3120 since due to mistake of the Editorial staff, affiliations have not been written correctly, and are the following: NUMERICAL STUDY OF HEAT AND MASS TRANSFER ENHANCEMENT FOR BUBBLE ABSORPTION PROCESS OF AMMONIA-WATER MIXTURE WITHOUT AND WITH NANOFLUIDS by Mohamed Bechir BEN HAMIDA1, Jalel BELGHAIEB2,3, and Nejib HAJJI2,3 1 College of Engineering, Chemical Engineering Department, Hail University, Hail City, Saudi Arabia 2National School of Engineers of Gabes (ENIG), Department of Process Engineering, University of Gabes, Tunisia 3Research Unit of Energy & Environment Ionized, National School of Engineers of Gabes (ENIG), University of Gabes, Tunisia. <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/TSCI170313229B">10.2298/TSCI170313229B</a></b></u>

Effect of vibration parameters on the bubble absorption characteristics of working fluids R134a–DMAC in a vertical tube

Two-phase flow pattern evolvement characteristic of working pair R134a–DMAC as well as the relationship between the bubble absorption height and vibration parameters (amplitude and frequency) were studied experimentally. Results showed that the bubble behavior and two-phase flow patterns became more complicated and disturbed under the vibration state, besides the bubble jolting and disintegration phenomena were observed. Stability of bubble absorption was also influenced by the vibration parameters. The most significant enhancement effectiveness of system vibration to the bubble absorption of R134a–DMAC occurred when amplitude was 0.4 mm and frequency was 25 Hz within the testing conditions. Finally, absorption pressure and temperature, solution flow rate and solution concentration were testified to influence the bubble absorption height and flow patterns under the vibration conditions.

The influence of hohlraum dynamics on implosion symmetry in indirect drive inertial confinement fusion experiments

High laser energy (>1.2 MJ) implosion experiments on the National Ignition Facility show that low mode implosion symmetry is highly dependent on an expanding high-Z wall “bubble” plasma feature. The bubble is caused by the early time deposition of laser beams incident on the interior near the entrance of the cylindrical hohlraum (outer cone beams). It absorbs beams designated for the waist of the hohlraum (inner cone beams) causing a redistribution of x-ray flux on the capsule. From measurements, we are able to quantify the absorption and expansion of this bubble. Measurements show that the resulting hot spot is more oblate when there is more inner beam absorption in the bubble. We find absorption in the bubble to be between 51 ± 3% and 62 ± 2%. This bubble absorption is found to evolve predictably as a function of the early time outer cone laser pulse fluence and the pulse length. From this, a phenomenological model of the effective drive symmetry and subsequent implosion shape is found indicating a very strong dependence of implosion shape on early time laser fluence and laser pulse duration.

Numerical study of heat and mass transfer enhancement for bubble absorption process of ammonia-water mixture without and with nanofluids

Numerical study of heat and mass transfer enhancement for bubble absorption process of ammonia-water mixture without and with nanofluids

A Theoretical-Experimental Comparison of an Improved Ammonia-Water Bubble Absorber by Means of a Helical Static Mixer

The heat transfer in double pipe heat exchangers is very poor. This complicates its application in absorption cooling systems, however, the implementation of simple passive techniques should help to increase the heat and mass transfer mainly in the absorber. This paper carried out a simulation and its experimental comparison of a NH3-H2O bubble absorption process using a double tube heat exchanger with a helical screw static mixer in both central and annular sides. The experimental results showed that the absorption heat load per area is 31.61% higher with the helical screw mixer than the smooth tube. The theoretical and experimental comparison showed that the absorption heat load difference values were 28.0 and 21.9% for smooth tube and the helical mixer, respectively. These difference values were caused by the calculation of the log mean temperature difference in equilibrium conditions to avoid the overlap of solution temperatures. Therefore, the theoretical and experimental results should be improved when the absorption heat is included in the heat transfer equation or avoiding the operation condition when output is lower than input solution temperature.

Mass transfer analysis for CO2 bubble absorption in methanol/Al2O3 nanoabsorbents

In this paper computational fluid dynamics (CFD) analysis is carried out to investigate CO2 bubble absorption characteristics in methanol/Al₂O3 nanoabsorbents. Bubble size, rising velocity and mass transfer rate are compared to the previous experimental results for validation. It is found that the distance traveled for each CO2 bubble increases as the concentration of Al2O3 increases, which, in consequence, increases the residence time between liquid and gas phases resulting in higher interfacial mass transfer rates. For the case of a bubble rising in the gap between walls, the wall shear stress has a major effect on the bubble diameter and rising velocity which in consequence affects the mass transfer coefficient. It is concluded that the mass transfer coefficient enhances by about 40% by adding Al₂O3 nanoparticles (0.01vol%) compared with pure methanol absorbent from the experimental and simulation results. It is also concluded that the use of nanoparticles has a higher impact on mass transfer rate than it does on mass transfer amount, which depends on the residence time and travel distance of CO2 bubbles.

Experimental investigation for heat and mass transfer characteristics of R124-DMAC bubble absorption in a vertical tubular absorber

Experimental investigation for a copper vertical tubular bubble absorber was done with R124 (2-chloro-l,l,l,2,-tetrafluoroethane)-DMAC (N′,N′-dimethylacetamide) as working fluid. The objective of the investigation was to explore key parameters affecting heat and mass transfer characteristics of the bubble absorber and propose new correlations for heat and mass transfer coefficients respectively for the R124-DMAC bubble absorption. The parameters include vapor and solution flow rates, solution inlet temperatures and mass fractions, nozzle orifice diameters and cooling water inlet temperatures. The results showed that to reduce the solution, cooling water inlet temperature and nozzle orifice diameter or to increase vapor and solution flow rate could enhance the heat and mass transfer performance of the absorber. Finally, correlations of Nusselt number and Sherwood number for calculating heat and mass transfer coefficients were proposed, respectively. Both correlations could predict about 90% of the experimental values at a margin of error less than 20%.

Numerical study of heat and mass transfer enhancement for bubble absorption process of ammonia-water mixture without and with nanofluids

Numerical study of heat and mass transfer enhancement for bubble absorption process of ammonia-water mixture without and with nanofluids

Mass transfer performance enhancement by nanoemulsion absorbents during CO2 absorption process

In this study, nanoemulsion absorbents (silicone oil/methanol) were manufactured by adding nano-size oil to absorbents for CO2 absorption performance enhancement. To evaluate the dispersion stability of the nanoemulsion, oil droplet size measurement, turbidity measurement, and Tyndall effect visualization experiments were conducted. The effect of the ratio and concentration of oil and surfactants on the mass transfer enhancement was evaluated through thermal conductivity measurement using the transient hot wire method and the visualization analysis of CO2 bubble absorption. The oil (silicone) and surfactant ratio of 2:1 was found to be the optimum condition through the results of dispersion stability analysis. In the CO2 bubble absorption results obtained through the visualization analysis, the nanoemulsion with 0.01vol% oil concentration showed the most significant absorption performance improvement. It was found that nano-size oil dispersion contributed to mass transfer enhancement, which was caused by the convective motion of nano-size oil droplets, not by enhanced thermal conductivity. Finally, the mechanisms of mass transfer enhancement by nanoemulsions are proposed, and it is concluded that the CO2 absorption performance is enhanced by the shuttle effect and the hydrodynamic effect by the nanoemulsion absorbents.

3D simulation of sintering flue gas desulfurization and denitration in a bubbling gas absorbing tower

A full-scale three-dimensional Eulerian-Eulerian numerical model was established considering absorbing reactions in which the two-film theory model was adopted to describe the absorption process of SO2 and NOx. The established model was firstly verified by the industrial operation data of a 2×220m2 sintering flue gas desulfurization tower. Then, using the model, numerical simulations of simultaneous desulfurization and denitration process were carried out based on three different methods including spraying-inside tower oxidation absorption of the composited NaClO2/NaClO/Ca(OH)2 slurry, oxidation absorption of the composited NaClO2/NaClO/Ca(OH)2 slurry and bubble absorption of Ca(OH)2 slurry. Numerical results revealed that the first method, spraying-inside tower oxidation absorption of the composited NaClO2/NaClO/Ca(OH)2 slurry had the best performance on denitration without influencing on the desulfurization efficiency. The result was then further verified by an industrial scale test on a 2×220m2 sintering flue gas desulfurization tower.

Heat and mass transfer characteristics of R124-DMAC bubble absorption in a vertical tube absorber

Experimental investigation for a visual vertical tubular bubble absorber was done with R124 (2-chloro-l,l,l,2,-tetrafluoroethane)-DMAC (N′,N′- dimethylacetamide) as working fluid. The objective of this investigation was to obtain key parameters that affect on the heat and mass transfer performance of R124-DMAC bubble absorption, such as vapor and solution flow rates, solution inlet temperatures and mass fractions, and nozzle orifice diameters. The results showed that the overall heat and volumetric mass transfer coefficients increased with increase of vapor and solution flow rates, and decreased with increase of solution inlet temperatures and mass fractions, and the nozzle orifice diameter. Especially, solution inlet mass fractions and the nozzle orifice diameter significantly influenced on mass transfer performance, while solution inlet temperatures and vapor flow rates influenced greatly on the heat transfer performance. A correlation of Sherwood number for R124-DMAC mixture in a visual vertical tubular bubble absorber was provided by the method of multiple linear regressions. The error band from the present study was within ±15%.

Visual experimental research on the effect of nozzle orifice structure on R124–DMAC absorption process in a vertical bubble tube

A visual experimental platform for R124–DMAC bubble absorption in a vertical tube absorber was designed and built for this research. The bubble behaviors, flow pattern characteristics and distributions are observed and the bubble absorption heights (BAHs) were measured when the two kinds of different structure nozzles (single-orifice or multi-orifice nozzle) were applied in the absorber. The results showed that the BAH will heighten with increases of vapor flow rate and nozzle flow area. Based on visual experimental observations, the BAH or bubble absorption performance was significantly affected by the velocity of vapor from the nozzle rather than by the nozzle structure. The proportion of slug flow in BAH or the BAH can be decreased by using a multi-orifice nozzle in the absorber under the same flow area condition. However, the flow resistance of the vapor through the nozzle will increase, which has a negative action on the performance of absorption refrigeration systems. So, using multi-orifice nozzle does not improve the absorption performance of the bubble absorber under the same nozzle flow resistance condition.

Visual experimental research on bubble absorption in a vertical tube with R124–DMAC working pair

Visual experimental investigations were carried out on a vertical co-current glass tube absorber to observe the behavior of the R124 (2-chloro-l,l,l,2,-tetrafluoroethane)–DMAC (N′,N′-dimethylacetamide) bubble absorption process and study the effects of different operating conditions on absorption performance. The results show that the refrigerant vapor flow rate, absorption solution flow rate, concentration, temperature and nozzle orifice diameter significantly affect the flow pattern and absorption height. As the vapor flow rate, absorption solution concentration and temperature, and nozzle orifice diameter increases, the absorption height increases. As the absorption solution flow rate increase, the absorption height reduces. Under the conditions of a large refrigerant vapor flow rate, high solution inlet concentration and temperature, three kinds of flow pattern, namely churn, slug and bubbly flow, can be simultaneously observed in the absorption tube.

Numerical Analysis of Ammonia Bubble Absorption in a Binary Nanofluid

An absorber is a major component in absorption refrigeration systems, and its performance remarkably affects the overall system performance. A mathematical model for ammonia bubble absorption was developed to analyze the mechanism of the binary nanofluid enhancing bubble absorption. It considers the effects of nanoparticles on heat transfer, mass transfer, and bubble size in bubble absorption. It agrees well with experimental results in an ammonia-water mixture without nanoparticles, and the maximum relative error is less than 8.2%. The prediction shows that the most significant factor affecting the average absorption rate is the mass transfer enhancement caused by the nanoparticles addition. The average absorption rate increases nonlinearly with the effective mass diffusivity of the binary nanofluid increasing. This article presents a better understanding of the mechanism of the binary nanofluid enhancing bubble absorption in thermally driven absorption refrigeration systems.

Thermal performance estimation of ammonia-water plate bubble absorbers for compression/absorption hybrid heat pump application

The objectives of this paper are to analyze the heat transfer characteristics during the NH3–H2O absorption process in plate heat exchangers and to develop the experimental correlations of the heat transfer coefficient for the compression/absorption hybrid heat pump application. The parametric analysis on the effects of the absorber internal pressure, ammonia weak solution concentration and absorber geometric dimensions on the absorber capacity and system COP (coefficient of performance) is carried out. From the experimental results, the maximum absorber capacity of 7.3 kW, COP of 2.66 and the maximum hot water outlet temperature of 80.7 °C are obtained. It is concluded that the heat transfer coefficient of solution side increases with increasing the aspect ratio (L/D) while it does not significantly depend upon the aspect ratio (W/D). Finally, an experimental Nusselt number correlation is developed with ±20% error band and compared with the other correlation from the literature.

Mass transfer enhancement during CO2 absorption process in methanol/Al2O3 nanofluids

The objectives of this paper are to analyze the mass transfer characteristics during CO2 bubble absorption and diffusion processes in nanofluid with Al2O3 nanoparticles. To analyze the effect of the nanoparticles on the mass transfer enhancement, the surface tension and viscosity of the nanofluids are measured. It is found that Al2O3 nanoparticles enhance CO2 absorption rate and increase the viscosity as high as 11% at 0.01vol% but the surface tension keeps almost constant. The images of bubble absorption and diffusion are captured by a high-speed camera with the shadow-graph method. It is found that the mass transfer coefficient is enhanced up to 26% at 0.01vol% compared with pure methanol.