A Simplified Thermodynamic Analysis of a LiBr-H2O Vertical Tube Absorber

2002 ◽  
Author(s):  
E. D. Rogdakis ◽  
V. D. Papaefthimiou
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Water Vapour ◽  
Liquid Water ◽  
Mass Fraction ◽  
Superheated Steam ◽  
Vertical Tube ◽  
Solution Temperature ◽  
Absorption Process

One of the most important components of an absorption air-conditioning/heat pump system is the absorber, where the refrigerant water vapour is absorbed into the liquid solution. While absorption systems have been in use for several years, the complex transport phenomena occurring in the absorber are not fully elucidated yet. Thus, an attempt is made to model the absorption process of water vapour in aqueous solutions of lithium bromide considering a falling-film, vertical-tube absorber. The proposed analysis is based on the formulation of four differential equations describing the spatial variation (parallel to the tube-axis) of solution mass, temperature, mass fraction and coolant temperature. The system of ordinary differential equations is numerically solved using a non-stiff numerical method. Thermophysical properties and especially, heat and mass transfer coefficients are calculated using widely-accepted and reliable relationships, which are extracted from the literature using recently published information on wavy-laminar flows. In the present study, the questionable assumption of treating the water vapour as an ideal gas is heavily modified utilizing. Consequently, the hypothesis of saturated water vapour at the steam-solution interaction surface is revised by introducing an energy difference between the superheated steam and the liquid water within the binary solution. The last correction encouraged us to compare theoretical results for solution temperature, mass fraction and mass flow rate, which were obtained using both assumptions. It was proved that the initial treatment causes an underestimation of the absorbed steam mass and correspondingly, an underestimation of solution temperature and mass fraction at the mass exchange interface. An attempt is made also to identify the effect of mass transfer coefficient on the effectiveness of the absorption process and on the energy differences between the superheated steam and the liquid water either as pure substance or as component of the binary mixture. It was shown that the increase of mass transfer coefficient leads to an increase of steam mass transfer rate and to a corresponding decrease of solution temperature slope at the entrance of a tube. Correspondingly, the increase of mass transfer coefficient results in an increase of heat of absorption and heat of dilution at the same variation range of the solution mass fraction.

ABSORBSI H2S MENGGUNAKAN LARUTAN Fe-EDTA DALAM PACKED COLUMN

EKUILIBIUM ◽  
2011 ◽  
Vol 10 (2) ◽  
Author(s):  
Endang Kwartiningsih ◽  
Arif Jumari
Keyword(s):  
Mass Transfer ◽  
Liquid Phase ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Phase ◽  
Reaction Rate ◽  
Packed Column ◽  
Reaction Rate Constant ◽  
Absorption Process ◽  
Edta Solution

<p><strong><em>Abstract:</em></strong><strong><em> </em></strong><em>Gas purification from the content of H<sub>2</sub>S using  Fe-EDTA (Iron Chelated Solution) gave  several advantages. The advantages were  the absorbent solution can be regenerated that means  a cheap operation cost,  the separated sulfur was a solid that is easy to handle and is save to be disposal to environment. This research was done by simulation and experimental. The simulation step was done by mathematical model arrangement representing the absorption process in packed column through mass transfer arrangement such as mass transfer equations and chemical reaction. The experimental step was done with the making of Fe-EDTA solution from FeCl<sub>2</sub> and EDTA. Then Fe-EDTA solution was flown in counter current packed column that was contacted with H<sub>2</sub>S in the methane gas. By comparing gas composition result of experiment and simulation, the value of mass transfer coefficient in gas phase ( k<sub>Ag</sub>a), mass transfer coefficient in liquid phase (k<sub>Al</sub>a) and the reaction rate constant ( k) were found. The values of mass transfer coefficient in liquid phase (k<sub>Al</sub>a) were lower than values of mass transfer coefficient in gas phase (k<sub>Ag</sub>a) and the reaction rate constant (k). It meant that H<sub>2</sub>S absorption  process using Fe-EDTA absorbent solution was determined by mass transfer process in liquid phase. The higher flow rate of absorbent, the higher value of mass transfer coefficient in liquid phase. </em><em>The smaller packing diameter, the higher value of mass transfer coefficient in liquid phase.From analysis of dimension, the relation of dimensionless number between Sherwood number and flow rate of absorbent, packing diameter was</em><strong></strong></p><p> <strong><em>Keywords:</em></strong><strong><em> </em></strong><em>chemical reaction, Fe-EDTA, H<sub>2</sub>S absorption, mass transfer</em></p>

Errors in Measurement of Interfacial Area and Mass Transfer Coefficient in Liquid in Apparatus with Mobile Packing

1993 ◽  
Vol 58 (6) ◽  
pp. 1345-1353
Author(s):  
Zdeněk Palatý
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Interfacial Area ◽  
Solution Temperature ◽  
Adsorption Solution ◽  
Specific Interfacial Area ◽  
Interfacial Areas ◽  
Error Of Measurement

The paper deals with an analysis of errors of measurement of interfacial area and mass transfer coefficient in liquid in an absorber with mobile packing. The system of CO2-NaOH has been used for the testing with recirculation of the adsorption solution. The error of measurement of the absorption solution temperature, CO2 concentration in the gas, the composition of absorption solution, the mass transfer coefficient in gas, and the volume of absorption solution at the beginning and at the end of the measurement have been investigated with regard to their effects upon the resulting values of specific interfacial area and mass transfer coefficient in liquid. From the simulation calculations if follows that the interfacial areas most strongly affected by the error of measurement of CO2 concentration in gas, whereas the mass transfer coefficient in liquid is considerably affected by inaccuracies in measuring the volume of absorption solution at the beginning and at the end of experiment.

Decarburization and Inclusion Removal Process in Single Snorkel Vacuum Degasser

2017 ◽  
Vol 36 (5) ◽  
pp. 523-530 ◽  
Author(s):  
Geng Dian-Qiao ◽  
Hong Lei ◽  
Ji-Cheng He
Keyword(s):  
Mass Transfer ◽  
Spatial Distribution ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Mass Fraction ◽  
Removal Rate ◽  
Order Reaction ◽  
Volumetric Mass Transfer Coefficient ◽  
Inclusion Removal ◽  
First Order

AbstractIn the current work, the coupled mathematical models for decarburization, fluid flow model and inclusion collision-aggregation model were solved to investigate the spatial distribution of carbon, inclusion’s collision-aggregation and removal in a single snorkel vacuum refining furnace (SSF). The numerical results show that the turbulence kinetic energy of ladle in SSF is much greater than that in RH, which can shrink the dead zone and prompt the mixing in the ladle. The overall decarburization reaction rate can be described as a first-order reaction. On the condition of the same gas flow rate, the volumetric mass transfer coefficient for decarburization in SSF is almost twenty times bigger than that in RH, which leads to a much greater decarburization rate in SSF. The spatial distribution of carbon mass fraction in SSF is quite different from that in RH. There is the greater mass fraction of carbon at the recirculation zone under up-snorkel in RH, but this phenomenon disappears in SSF. The inclusion removal can be simplified as the mass transfer between liquid steel to slag, refractory wall and bubble surface. And the overall inclusion removal rate can be regarded as a first-order reaction. The volumetric mass transfer coefficient for inclusion removal in SSF is about three times as that in RH, the inclusion removal rate in SSF is greater than that in RH. The inclusions with different size have different removal rates in SSF. For inclusion flotation after deoxidization, the treatment time in SSF is less than that in RH.

scholarly journals Measurement of Mass Transfer Coefficient of CO2–Amine System from Absorption Process

2020 ◽  
Vol 859 ◽  
pp. 012011
Author(s):  
Thanakornkan Limlertchareonwanit ◽  
Kreangkrai Maneeintr ◽  
Tawatchai Charinpanitkul
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Absorption Process ◽  
Amine System

Condensation of Downward-Flowing Zeotropic Mixture HCFC-123/HFC-134a on a Staggered Bundle of Horizontal Low-Finned Tubes

1999 ◽  
Vol 121 (2) ◽  
pp. 405-412 ◽  
Author(s):  
H. Honda ◽  
H. Takamatsu ◽  
N. Takata
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Mass Fraction ◽  
Tube Bundle ◽  
Condensation Temperature ◽  
Finned Tubes ◽  
Hfc 134A ◽  
Hcfc 123

Experiments were conducted to obtain row-by-row heat transfer data during condensation of downward-flowing zeotropic refrigerant mixture HCFC-123/HFC-134a on a 3 × 75 (columns × rows) staggered bundle of horizontal low-finned tubes. The vapor temperature and the HFC-134a mass fraction at the tube bundle inlet were maintained at about 50°C and nine percent, respectively. The refrigerant mass velocity ranged from 9 to 34 kg/m2 s, and the condensation temperature difference from 3 to 12 K. The measured distribution of the vapor mass fraction in the tube bundle agreed fairly well with that of the equilibrium vapor mass fraction. The vapor phase mass transfer coefficient was obtained from the heat transfer data by subtracting the thermal resistance of the condensate film. The heat transfer coefficient and the mass transfer coefficient decreased significantly with decreasing mass velocity. These values first increased with the row number up to the third (or second) row, then decreased monotonically with further increasing row number, and then increased again at the last row. The mass transfer coefficient increased with condensation temperature difference, which was due to the effect of suction associated with condensation. On the basis of the analogy between heat and mass transfer, a dimensionless correlation of the mass transfer coefficient for the 4th to 14th rows was developed.

Characteristics of Liquid–Solid Mass Transfer in a Bubble Column Equipped with a Vertical Tube of Circular Fins

2011 ◽  
Vol 312-315 ◽  
pp. 647-652
Author(s):  
Hesham S. Bamufleh ◽  
S. A. Nosier ◽  
M. A. Daous
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Bubble Column ◽  
Mass Transfer Rate ◽  
Vertical Tube ◽  
Air Velocity ◽  
Continuous Increase ◽  
Diffusion Controlled ◽  
Solid Liquid

The solid-liquid mass transfer rate at a stack of circular fin surfaces in a bubble column was investigated. A diffusion-controlled dissolution technique of copper in an acidified chromate solution was employed. Variables studied included the number of actively exposed fins ranging from 5 to 20, pertinent physical properties of the solution, and air superficial velocity. Experimental data showed that the rate of the diffusion-controlled mass transfer increases with increasing superficial air velocity and decreases with increasing chromate solution acid concentration. Moreover, at relatively low superficial air velocity, increasing the number of actively exposed fins results into a continuous increase in the mass transfer coefficient. At relatively higher superficial air velocity, however, the mass transfer coefficient decreases in the 5 to 10 range of actively exposed fins and then reverts to increase in the 15 to 20 range.

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