scholarly journals Removal of Dissolved Oxygen from Water by Nitrogen Stripping Coupled with Vacuum Degassing in a Rotor–Stator Reactor

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1354
Author(s):  
Zemeng Zhao ◽  
Zhibang Liu ◽  
Yang Xiang ◽  
Moses Arowo ◽  
Lei Shao
Keyword(s):  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Operating Conditions ◽  
Harmful Substance ◽  
Vacuum Degassing ◽  
Vacuum Degree ◽  
Experimental Values ◽  
Corrosion And Oxidation

Oxygen is a harmful substance in many processes because it can bring out corrosion and oxidation of food. This study aimed to enhance the removal of dissolved oxygen (DO) from water by employing a novel rotor–stator reactor (RSR). The effectiveness of the nitrogen stripping coupled with vacuum degassing technique for the removal of DO from water in the RSR was investigated. The deoxygenation efficiency (η) and the mass transfer coefficient (KLa) were determined under various operating conditions for the rotational speed, liquid volumetric flow rate, gas volumetric flow rate, and vacuum degree. The nitrogen stripping coupled with vacuum degassing technique achieved values for η and KLa of 97.34% and 0.0882 s−1, respectively, which are much higher than those achieved with the vacuum degassing technique alone (η = 89.95% and KLa = 0.0585 s−1). A correlation to predict the KLa was established and the predicted KLa values were in agreement with the experimental values, with deviations generally within 20%. The results indicate that RSR is a promising deaerator thanks to its intensification of gas–liquid contact.

scholarly journals Mass Transfer Correlation and Optimization of Carbon Dioxide Capture in a Microchannel Contactor: A Case of CO2-Rich Gas

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5465
Author(s):  
Nattee Akkarawatkhoosith ◽  
Wannarak Nopcharoenkul ◽  
Amaraporn Kaewchada ◽  
Attasak Jaree
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Co2 Capture ◽  
Volumetric Flow Rate ◽  
Absorption Efficiency ◽  
Operating Conditions ◽  
Molar Ratio ◽  
Volumetric Mass Transfer Coefficient

This work focused on the application of a microchannel contactor for CO2 capture using water as absorbent, especially for the application of CO2-rich gas. The influence of operating conditions (temperature, volumetric flow rate of gas and liquid, and CO2 concentration) on the absorption efficiency and the overall liquid-side volumetric mass transfer coefficient was presented in terms of the main effects and interactions based on the factorial design of experiments. It was found that 70.9% of CO2 capture was achieved under the operating conditions as follows; temperature of 50 °C, CO2 inlet fraction of 53.7%, total gas volumetric flow rate of 150 mL min−1, and adsorbent volumetric flow rate of 1 mL min−1. Outstanding performance of CO2 capture was demonstrated with the overall liquid-side volumetric mass transfer coefficient of 0.26 s−1. Further enhancing the system by using 2.2 M of monoethanolamine in water (1:1 molar ratio of MEA-to-CO2) boosted the absorption efficiency up to 88%.

Sequential Control of Multichannel On–Off Valves for Linear Flow Characteristics Via Averaging Pulse Width Modulation Without Flow Meter: An Application for Pneumatic Valves

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Kanchit Pawananont ◽  
Thananchai Leephakpreeda
Keyword(s):  
Flow Rate ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Single Channel ◽  
Flow Characteristics ◽  
Volumetric Flow Rate ◽  
Operating Conditions ◽  
Mean Flow ◽  
Flow Meter ◽  
Linear Flow

Control of on–off valves for linear flow characteristics is a challenging design problem due to nonlinearity of valve mechanism and fluidic properties under various operating conditions. In this study, averaging pulse width modulation (PWM) is proposed as a control valve signal by implementing PWM with predetermined duty period so that overflow at the open position and underflow at the closed position are divided proportionately around desired mean flow rates during entire cycle periods. Multichannels in a parallel pattern are implemented to yield linear flow characteristics with higher resolution than a single channel. With pressure and temperature measurements, the volumetric flow rate is determined by an empirical model of flow characteristics across flow control valves at given operating conditions. The experimental results on achieving the desired volumetric flow rate of air under actual flow conditions without a flow meter are presented for viability of the proposed methodology in practical uses.

Performance Analysis on the Internally Cooled Dehumidifier Using Two Liquid Desiccant Solutions

2012 ◽  
Author(s):  
I. P. Koronaki ◽  
R. I. Christodoulaki ◽  
V. D. Papaefthimiou ◽  
E. D. Rogdakis
Keyword(s):  
Mass Transfer ◽  
Theoretical Model ◽  
Heat And Mass Transfer ◽  
Flow Rate ◽  
Air Conditioning ◽  
Cooling Water ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Liquid Desiccant ◽  
Internally Cooled

Liquid desiccant air conditioning systems have recently been attracting attention due to their capability of handling the latent load without super-cooling and then reheating the air, as happens in a conventional compression-type air conditioning system. This paper presents the results from a study of the performance of an internally cooled liquid desiccant dehumidifier. A plate heat exchanger is proposed as the internally cooled element of the dehumidifier and water as the cooling fluid. The desiccant solution is sprayed into the internally cooled dehumidifier from the top and flows down by gravity. At the same time, fresh humid air is blown from the bottom or top, counter-flowing or co-flowing with the desiccant solution. The desiccant is in direct contact with the air, allowing for heat and mass transfer. The cooling water, flowing inside the plates of the dehumidifier, carries out the heat of the crossed air and solution. A heat and mass transfer theoretical model has been developed, based on the Runge-Kutta fixed step method, to predict the performance of the device under various operating conditions. Experimental data from previous literature have been used to validate the model. Excellent agreement has been found between experimental tests and the theoretical model, with the deviation not exceeding ±4.1% for outlet air temperature and ±4.0% for outlet humidity ratio. Following the validation of the mathematical model, the dominating effects on the absorption process have been discussed in detail. Namely, effects of flow configuration, air inlet temperature, humidity and flow rate, as well as desiccant inlet temperature, concentration and flow rate have been investigated against the dehumidification rate and the cooling efficiency. The two most commonly used liquid desiccant solutions, namely LiCl and LiBr have been also evaluated against each other. The results suggested that high dehumidification mass rate can be achieved under counter flow between air and solution, low air mass flow rates, low cooling water temperature, low desiccant temperature and LiCl as the desiccant solution.

scholarly journals Development and evaluation of silicone membrane as aerators for membrane bioreactors

2005 ◽  
Author(s):  
◽  
Xolani Proffessor Mbulawa
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Silicone Rubber ◽  
Convective Transport ◽  
Operating Conditions ◽  
Pure Oxygen ◽  
Bulk Liquid ◽  
Dissolved Oxygen Concentration

In bubble-less aeration oxygen diffuses through the membrane in a molecular form and dissolves in the liquid. Oxygen is fed through the lumen side of silicone rubber tube. On the outer surface of the membrane there is a boundary layer that is created by oxygen. This then gets transported to the bulk liquid by convective transport created by water circulation through the pump. The driving force of the convective transport is due to concentration difference between the dissolved oxygen in water and oxygen saturation concentration in water at a particular temperature and pressure. The design of a membrane aerated bioreactor needs an understanding of the factors that govern oxygen mass transfer. It is necessary to know the effects of operating conditions and design configurations. Although various methods of bubble-less aeration have been reported, there still exists a lack of knowledge on the immersed membrane systems. This study is aiming at contributing to the development of an immersed membrane bioreactor using silicone rubber tubular membrane as means of providing oxygen. The secondary objective was to investigate the influence that the operating conditions and module configuration have on the system behaviour. From the experimental study, the characteristic dissolved oxygen -time curve show that there is a saturation limit equivalent to the equilibrium dissolved oxygen concentration, after which there is no increase in dissolved oxygen with time. At ambient conditions the equilibrium dissolved oxygen is approximately 8 mg/L. This is when water is in contact with air at one atmospheric pressure. At the same conditions the equilibrium dissolved oxygen concentration when water is in contact with pure oxygen is approximately 40 mg/L. This is why all the experiments were conducted from 2mg/L dissolved oxygen concentration in water, to enable enough time to reach equilibrium so as to determine mass transfer coefficient. The most important parameters that were investigated to characterise the reactor were, oxygen supply pressure, crossflow velocity, temperature and module orientation. Observations from the experimental study indicated that when the system is controlled by pressure, crossflow does not have a significant effect on mass transfer. When the system is controlled by the convective transport from the membrane surface to the bulk liquid, pressure does not have a significant effect on mass transfer. All four effects that were investigated in the study are discussed.

scholarly journals Mass Transfer in Multiphasic Gas/Liquid/Liquid Systems. KLa Determination Using the Effectiveness-Number of Transfer Unit Method

Processes ◽  
2018 ◽  
Vol 6 (9) ◽  
pp. 156 ◽  
Author(s):  
Éric Dumont
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Gas Flow ◽  
Absorption Capacity ◽  
Operating Conditions ◽  
Transfer Unit ◽  
Liquid Systems ◽  
Overall Mass Transfer Coefficient

The Effectiveness-Number of Transfer Unit method (ε-NTU method) was applied to determine the overall mass transfer coefficient, KLa, of operating gas-liquid absorbers treating Volatile Organic Compounds (VOCs). This method requires the knowledge of the operating conditions (gas flow rate, QG; liquid flow rate, QL; scrubber volume V), the measurement of gaseous concentrations at the inlet, CGin, and at the outlet, CGout, of the contactor (in order to determine the effectiveness of the absorber ε) and the calculation of the Henry coefficient of the VOC between the gas and the liquid phases (HVOC). Coupled with the “equivalent absorption capacity” concept, the ε-NTU method was used to determine KLa of absorbers contacting a gas and a mixture of water and a Non Aqueous Phase, successfully. The method, validated from literature data for configurations countercurrent scrubbers and stirred tank reactors, could be used to simply determine the overall mass transfer coefficient of systems for which the standard KLa determination methods still remain non-reliable or inaccurate (viscous solvents, mixture of immiscible liquids, fermentation broths…).

Experimental Investigation of Spray Cooling Heat Transfer on Circular Grooved Surface

2017 ◽  
Author(s):  
Azzam S. Salman ◽  
Jamil A. Khan
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
Target Surface ◽  
Spray Cooling ◽  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Flow Rates

An experimental study was conducted in a closed loop spray cooling system working with deionized water as a cooling medium, to investigate the effects of surface modification on the spray cooling heat transfer enhancement in the single-phase region. Plain copper surface with diameter 1.5 cm and an enhanced surface with circular grooves were tested under different operating conditions. The volumetric flow rate of the coolant ranged from 115 mL/min to 177 mL/min., and the water inlet temperature was kept between 21–23 °C. Also, the distances between the nozzle and the target surface were varied at 8, 10, and 12 mm respectively. The results show that the distance between the nozzle and the target surface did not have a significant effect on the heat transfer performance for the low flow rates, while it has a slight effect on high flow rates for both surfaces. Also, increasing the liquid volumetric flow rate increases the amount of heat removed, and the heat transfer coefficient for both surfaces. Moreover, the maximum enhancement ratios achieved were 23.4% and 31% with volumetric flow rates of 153 mL/min, and 177 mL/min respectively.

Influence of Physical Properties of Phases on Hydrodynamics and Mass Transfer Characteristics of a Liquid-Liquid Circular Microchannel

2016 ◽  
Author(s):  
Mehdi Sattari-Najafabadi ◽  
Bengt Sundén ◽  
Zan Wu ◽  
Mohsen Nasr Esfahany
Keyword(s):  
Mass Transfer ◽  
Physical Properties ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Rate Ratio ◽  
Operating Conditions ◽  
Flow Rate Ratio ◽  
Internal Diameter ◽  
Volumetric Mass Transfer Coefficient

The influences of operating conditions and physical properties of the two phases on the hydrodynamics and mass transfer in a circular liquid-liquid microchannel have been investigated. The polytetrafluoroethylene (PTFE) microchannel has an internal diameter of 0.7 mm and a T-shaped mixing junction. Sodium hydroxide solution was used as the aqueous phase. N-hexane and toluene were employed as the organic phases to investigate the effect of physical properties. Regarding the results, at constant total flow rate, raising the flow rate ratio enhanced the overall volumetric mass transfer coefficient. Using toluene as the organic solvent enhanced the overall volumetric mass transfer coefficient in average by 64.7% and 100.27% comparing to n-hexane-water at flow rate ratio of 1 and 0.5, respectively. This increment resulted in a decrement in the required mass transfer time and length in the microchannel. The length of the slugs had no considerable variation as n-hexane was replaced with toluene. Thus, the significant improvement of the overall volumetric mass transfer coefficient was because of the increment of the overall mass transfer coefficient, not the specific interfacial area.

scholarly journals Development of a low-cost prototype

2021 ◽  
Vol 9 (8) ◽  
pp. 328-337
Author(s):  
Katiane Pereira da Silva ◽  
Enoque Coutinho dos Santos ◽  
Ramildo Felipe Silva Gonçalves ◽  
Antonio Thiago Madeira Beirão ◽  
Fábio Israel Martins Carvalho ◽  
...  
Keyword(s):  
Undergraduate Students ◽  
Flow Rate ◽  
Teaching And Learning ◽  
Low Cost ◽  
Volumetric Flow Rate ◽  
Experimental Models ◽  
Theory And Practice ◽  
Theoretical Concepts ◽  
Experimental Values

This study aims to develop a low-cost prototype to measure the mass and volumetric flow rate of fluids through the construction of a Pitot Tube. This meter must be able to measure the mass flow rate of air for different pressure values using only the water height level variation. For the development of the prototype, low-cost materials were used, in addition to some necessary tools. These experimental models are a didactic proposal for teaching and learning about the flow of fluids discipline, where it was verified that the experimental values found presented satisfactory results correlated with the theoretical concepts of an ideal fluid present in the literature. Thus, the Bernoulli and Torricelli equations were applied to assess the quality of the measurement method, to facilitate the learning of undergraduate students in the Production Engineering Course through conciliation between theory and practice in the Fluid Mechanics Laboratory discipline classes. Finally, the prototype experiment was exposed to other students at the institutional event called “I Integrar Produção” held by UFRA at the Parauapebas Campus.

Absorption and Mass Transfer of CO2 in Monoethanolamine Solution

2016 ◽  
Vol 859 ◽  
pp. 153-157
Author(s):  
Pao Chi Chen ◽  
Sheng Zhong Lin
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Liquid Flow Rate ◽  
Bubble Column ◽  
Operating Conditions ◽  
Gas Flow Rate ◽  
Constant Ph ◽  
Gas Liquid Flow

This work uses a continuous bubble-column scrubber for the absorption of CO2 with a 5M MEA solution under a constant pH environment to explore the effect of the pH of the solution and gas-flow rate (Qg) on the removal efficiency (E), absorption rate (RA), overall mass-transfer coefficient (KGa), liquid flow rate (QL), gas-liquid flow ratio (γ), and scrubbing factors (φ). From the outlet CO2 concentration with a two-film model, E, RA, KGa, QL, γ, and φ can be simultaneously determined at the steady state. Depending on the operating conditions, the results show that E (80-97%), RA(2.91x10-4-10.0x10-4mol/s-L), KGa (0.09-0.48 1/s), QL(8.74-230.8mL/min), γ (0.19-5.39), and φ (0.031-0.74 mol/mol-L) are found to be comparable with other solvents. In addition, RA, KGa, E, and QL have been used to correlate with pH and Qg, respectively, with the results further explained.

scholarly journals Removal of Cu(II) by Fixed-Bed Columns Using Alg-Ch and Alg-ChS Hydrogel Beads: Effect of Operating Conditions on the Mass Transfer Zone

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2345
Author(s):  
Ilse Paulina Verduzco-Navarro ◽  
Nely Rios-Donato ◽  
Carlos Federico Jasso-Gastinel ◽  
Álvaro de Jesús Martínez-Gómez ◽  
Eduardo Mendizábal
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Linear Regression Analysis ◽  
Fixed Bed ◽  
Operating Conditions ◽  
Column Height ◽  
Thomas Model ◽  
Hydrogel Beads ◽  
Mass Transfer Zone ◽  
Transfer Zone

The removal of Cu(II) ions from aqueous solutions at a pH of 5.0 was carried out using fixed-bed columns packed with alginate-chitosan (Alg-Ch) or alginate-chitosan sulfate (Alg-ChS) hydrogel beads. The effect of the initial Cu(II) concentration, flow rate, pH, and height of the column on the amount of Cu removed by the column at the breakpoint and at the exhaustion point is reported. The pH of the solution at the column’s exit was initially higher than that at the entrance, and then decreased slowly. This pH increase was attributed to proton transfer from the aqueous solution to the amino and COO− groups of the hydrogel. The effect of operating conditions on the mass transfer zone (MTZ) and the length of the unused bed (HLUB) is reported. At the lower flow rate and lower Cu(II) concentration used, the MTZ was completely developed and the column operated efficiently; by increasing column height, the MTZ has a better opportunity to develop fully. Experimental data were fitted to the fixed-bed Thomas model using a non-linear regression analysis and a good correspondence between experimental and Thomas model curves was observed.

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