Temperature Influence on Absorption and Stripping Processes

1987 ◽  
Vol 19 (5-6) ◽  
pp. 877-888
Author(s):  
Boris M. Khudenko ◽  
Alberto Garcia-Pastrana
Keyword(s):  
Simulation Analysis ◽  
Critical Energy ◽  
Temperature Correction ◽  
Gas Absorption ◽  
Gas Transfer ◽  
Distribution Law ◽  
Transfer Energy ◽  
Transfer Rates ◽  
Influence Of Temperature On ◽  
Transfer Apparatus

The influence of temperature on mass transfer rates in gas absorption and stripping processes has been evaluated. A computer simulation analysis has been used to identify fundamental reasons for variations among temperature correction factors published in the literature. A critical molecular transfer energy was postulated and the temperature correction factor was developed based on the Maxwell distribution law. The critical energy hypothesis was experimentally validated and the critical energy of molecules crossing the gas-liquid interface of 2.6.10−13 erg was determined for both methane and oxygen in the temperature range from 5° to 75°C. The critical energy was found to be a constant value for various hydrodynamic conditions and also for water with and without surfactants. The temperature correction expression derived based on the critical energy hypothesis was compared with several published relationships. The comparison has corroborated that the developed temperature correction relationship is applicable to various gas transfer apparatus and hydrodynamic regimes.

Simulation Analysis for Reinforced Concrete Aqueduct of Lijia Pumping Station

2014 ◽  
Vol 488-489 ◽  
pp. 605-608
Author(s):  
Xiang Zan Xie
Keyword(s):  
Reinforced Concrete ◽  
Simulation Analysis ◽  
Water Pressure ◽  
Water Diversion ◽  
Distribution Law ◽  
Masonry Arch ◽  
Pumping Station ◽  
Earthquake Effect ◽  
Concrete Masonry ◽  
Cushion Layer

Reinforced concrete masonry arch aqueduct is a common water diversion engineering structure. Aqueduct is decorated on the concrete cushion layer, cushion layer effects on masonry arch, the structures stress is uniform, carrying capacity is strong. This paper adopts finite element method to carry out force analysis for reinforced concrete masonry arch aqueduct of Lijia pumping station, considering aqueduct weight, water pressure and earthquake effect, etc. Researching stress and deformation distribution law of reinforced concrete masonry arch aqueduct.

scholarly journals A frequency quantum interpretation of the surface renewal model of mass transfer

2017 ◽  
Vol 4 (7) ◽  
pp. 170103 ◽  
Author(s):  
Chanchal Mondal ◽  
Siddharth G. Chatterjee
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Frequency Distribution ◽  
Age Distribution ◽  
Gas Absorption ◽  
Bulk Liquid ◽  
Gas Transfer ◽  
Transfer Resistance ◽  
Surface Renewal ◽  
Two Parameter

The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature.

Calculation and Analysis of Reinforced Concrete Continuous Box-Girder Overpass

2011 ◽  
Vol 101-102 ◽  
pp. 463-466
Author(s):  
Dong Yu Ji
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Simulation Analysis ◽  
Great Influence ◽  
Distribution Law ◽  
Box Girder ◽  
Common Structure ◽  
Element Simulation ◽  
Stress And Deformation ◽  
Calculation Software

Reinforced concrete continuous box-girder overpass is a common structure form, Wangzhuang overpass is example, this paper adopts universal finite element calculation software to carry out finite element simulation analysis for reinforced concrete continuous box-girder overpass. Considering the influence of overpass structure weight and driveway load, the distribution law of overpass stress and displacement were researched. Analysis results show that, load’s short-term effect combination has great influence on overpass structure, driveway slanting load’s influence on overpass structure’s stress and deformation can not be ignored.

Use of an intravascular gas exchanger: is low systemic heparinization safe?

Perfusion ◽  
1993 ◽  
Vol 8 (6) ◽  
pp. 449-458 ◽  
Author(s):  
LK von Segesser ◽  
M. Pasic ◽  
M. Tönz ◽  
M. Lachat ◽  
B. Leskosek ◽  
...  
Keyword(s):  
Coagulation System ◽  
Gas Transfer ◽  
Thrombin Time ◽  
Loading Dose ◽  
Coagulation Time ◽  
Blood Samples ◽  
Transfer Rates ◽  
Fluoroscopic Control ◽  
Systemic Heparinization ◽  
Activated Coagulation Time

Extracorporeal membrane oxygenation (ECMO) is a cumbersome procedure. Alternatively, mechanical lung assist can be realized with an intravascular gas exchanger (IVOX). To assess the degree of initial anticoagulation required during intravascular lung assist, we evaluated two regimens of systemic heparinization in 10 bovine experiments. The animals were randomly assigned to two groups with either full systemic heparinization (heparin loading dose 300 IU/kg bodyweight; activated coagulation time (ACT) > 480 s) or low systemic heparinization (heparin loading dose 100 IU/kg bodyweight; ACT > 180 s). The surface heparinized intravascular gas exchanger was placed in the caval axis under fluoroscopic control, and a standard battery of blood samples was drawn before and at regular intervals during the procedure. After six hours of intravascular lung assist the device was explanted, drained, weighed, and carefully analysed. Preassist haematocrit was 25 ± 5% for full versus 24 ± 7% for low (NS) as compared with 23 ± 8% for full versus 26 ± 3% for low (NS) postassist. Platelet levels were 100 ± 25 for full versus 100 ± 21 % for low (NS) preassist as compared with 64 ± 22% for full versus 78 ± 22% for low (NS) postassist. Mean ACT was 157 ± 12 s for full versus 158 ± 18 for low (NS) preassist as compared with 800 ± 244 s versus 219 ± 25 for low (p < 0.05) postassist. Thrombin time was 20 ± 2 s for full versus 23 ± 2 s for low (NS) as compared with > 200 s for both groups after assist. Relative fibrinopeptide A levels were 7.3 ± 1.1 ng/ml for full versus 6.3 ± 1.6 ng/ml for low (NS) preassist as compared with 4.7 ± 4.1 ng/ml for full versus 5.8 ± 0.9 ng/ml for low (NS) postassist. CO2 transfer was 40 ± 10 ml/min for full versus 36 ± 10 ml/min for low (NS) at the begining as compared with 45 ± 25 ml/min for full versus 46 ± 15 for low (NS) at the end. Weight increase due to device deposits (clots) was 14 ± 11 g for full versus 13 ± 10 g for low systemic heparinization (NS). Intravascular lung assist with low versus full systemic heparinization appeared to result in similar activation of the coagulation system, device deposits and gas transfer rates. Considering our clinical experience we can say that application of the device with reduced systemic heparinization is useful in selected patients.

Wind-Induced Dynamic Analysis and Construction Measures of Large Diameter Spherical Tank

2013 ◽  
Vol 351-352 ◽  
pp. 46-49
Author(s):  
Bao Hui Xu ◽  
Jing Ji
Keyword(s):  
Simulation Analysis ◽  
Large Diameter ◽  
Wind Load ◽  
Distribution Law ◽  
Finite Element Software ◽  
Spherical Tank ◽  
Actual Design ◽  
Tank System ◽  
Practical Engineering ◽  
Large Spherical

It is easy for the bulky spherical tank to take place wind-induced buckling under wind load, combined with the Daqing region specific practical engineering, simulation analysis of spherical tank system with 15.7m under random wind loads has been carried out by using ANSYS finite element software. The author investigates the mechanical properties of spherical tanks with the actions of self-weight and wind load, and obtains the deformation and stress distribution law of the tank, pillars and drawbars, at last construction suggestions of spherical tank is given, and these can provide technical support for improving the actual design for large spherical tank.

Application of Finite Element Method for Dry Masonry Overflow Dam Analysis

2013 ◽  
Vol 394 ◽  
pp. 332-335
Author(s):  
Min Tan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Mechanical Characteristics ◽  
Simulation Analysis ◽  
Process Analysis ◽  
Construction Process ◽  
Distribution Law ◽  
Operational Process ◽  
Reservoir Construction ◽  
Element Method

Through analyzing dry masonry overflow dam structures mechanical characteristics in construction process and operational process, this paper adopts finite element method to carry out simulation analysis for dry masonry overflow dam of Daxilong reservoir. Deducing distribution law of the dams stress and displacement in construction process and operational process. Analysis results show that, dry masonry overflow dam of Daxilong reservoir construction is reasonable, it meets the requirements for design.

Effects of Blood Flow Pulse Frequency on Mass Transfer Efficiency of a Commercial Hollow Fibre Oxygenator

1998 ◽  
Vol 21 (9) ◽  
pp. 535-541 ◽  
Author(s):  
G.B. Fiore ◽  
G. Pennati ◽  
F. Inzoli ◽  
F. Mastrantonio ◽  
D. Galavotti
Keyword(s):  
Blood Flow ◽  
Blood Perfusion ◽  
Blood Flow Rate ◽  
Pulse Frequency ◽  
Hollow Fibre ◽  
Gas Transfer ◽  
Transfer Rates ◽  
Inlet Conditions ◽  
Pulsatile Perfusion

The clinical advantages achievable through pulsatile blood perfusion during cardio-pulmonary bypass have recently suggested the design of new pulsatile systems for extracorporeal circulation. Still it is not clear whether current commercial membrane oxygenators could be adopted with such systems, since their behaviour with pulsatile perfusion has not been satisfactorily documented yet. In a previous paper, we assessed that pulsatile perfusion of a widely used hollow fibre oxygenator (Sorin® Monolyth) at 60 bpm provides more time-consistent oxygen transfer than steady perfusion. The present work is aimed to evaluate how the pulse frequency influences the gas transfer performance of the same device. The oxygenator was subjected to in vitro trials using a roller pump with pulsatile module (Stöckert Instrumente®) to generate pulsed flow. Four different pulse frequencies (45, 60, 75 and 90 bpm) were investigated at a fixed blood flow rate (4.0 l/min). The experiments lasting six hours were carried out using bovine blood with inlet conditions according to AAMI standards requirements. Blood samples were withdrawn every hour and O2 and CO2 transfer rates were evaluated. The experimental findings confirm that with pulsatile blood flow no time decay take place during prolonged perfusion. Moreover, when pulse frequency increases, transition levels occur for both O2 and CO2. Over these thresholds gas transfer rates display significant increases (p < 0.05), though of little magnitude (up to 2.5% for oxygen over 60 bpm; up to 3.7% for carbon dioxide over 75 bpm).

scholarly journals Newly Developed Pediatric Membrane Oxygenator that Suppresses Excessive Pressure Drop in Cardiopulmonary Bypass and Extracorporeal Membrane Oxygenation (ECMO)

Membranes ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 362
Author(s):  
Makoto Fukuda ◽  
Asako Tokumine ◽  
Kyohei Noda ◽  
Kiyotaka Sakai
Keyword(s):  
Blood Flow ◽  
Pressure Drop ◽  
Extracorporeal Membrane Oxygenation ◽  
High Performance ◽  
Flow Channel ◽  
Gas Transfer ◽  
Membrane Oxygenator ◽  
Excessive Pressure ◽  
Transfer Rates ◽  
Membrane Oxygenation

This article developes a pediatric membrane oxygenator that is compact, high performance, and highly safe. This novel experimental approach, which imaging the inside of a membrane oxygenator during fluid perfusion using high-power X-ray CT, identifies air and blood retention in the local part of a membrane oxygenator. The cause of excessive pressure drop in a membrane oxygenator, which has been the most serious dysfunction in cardiovascular surgery and extracorporeal membrane oxygenation (ECMO), is the local retention of blood and air inside the oxygenator. Our designed blood flow channel for a membrane oxygenator has a circular channel and minimizes the boundary between laminated parts. The pressure drop in the blood flow channel is reduced, and the maximum gas transfer rates are increased by using this pediatric membrane oxygenator, as compared with the conventional oxygenator. Furthermore, it would be possible to reduce the incidents, which have occurred clinically, due to excessive pressure drop in the blood flow channel of the membrane oxygenator. The membrane oxygenator is said to be the “last stronghold” for patients with COVID-19 receiving ECMO treatment. Accordingly, the specification of our prototype is promising for low weight and pediatric patients.

A method to test blood flow limitation of peritoneal-blood solute transport.

1997 ◽  
Vol 8 (3) ◽  
pp. 471-474 ◽  
Author(s):  
M Kim ◽  
J Lofthouse ◽  
M F Flessner
Keyword(s):  
Blood Flow ◽  
Solute Transport ◽  
Abdominal Wall ◽  
Tissue Level ◽  
Gas Transfer ◽  
Local Blood Flow ◽  
Transport Models ◽  
Doppler Flowmetry ◽  
Transfer Rates ◽  
Blood Flow Control

Current transperitoneal transport models assume that effective blood flow to the microcirculation does not limit solute exchange with dialysate in the cavity. Despite evidence that gas transfer across the peritoneum (assumed to equal the effective blood flow) occurs at rates that exceed maximum urea transfer rates by a factor of two to three, the assumption has been strongly challenged. To address this problem at the tissue level, a technique to determine the effect of local blood flow on small-solute transport was developed in this study. Diffusion chambers were affixed to the serosal side of the anterior abdominal wall of rats, and solutions containing radiolabeled urea or mannitol were placed in the chambers. During each experiment, the local blood flow beneath the chamber was monitored with laser Doppler flowmetry and the disappearance of the tracer versus time was simultaneously measured under three conditions of blood flow: control, 30% of control, and zero blood flow. The results demonstrated no significant differences for either solute between control and the condition in which blood flow was reduced by 70%. However, there was a significant reduction in the rate of mass transfer with no blood flow. It was concluded that blood flow at > or = 30% of control values does not limit solute transfer across the abdominal wall peritoneum during dialysis.

Force Analysis of Inclined Asphalt Concrete Wall Rockfill Dam Structure

2011 ◽  
Vol 391-392 ◽  
pp. 724-727
Author(s):  
Li Xin Han
Keyword(s):  
Asphalt Concrete ◽  
Simulation Analysis ◽  
Process Analysis ◽  
Construction Process ◽  
Force Analysis ◽  
Distribution Law ◽  
Concrete Wall ◽  
Operational Process ◽  
Rockfill Dam ◽  
Reservoir Construction

Through analyzing inclined asphalt concrete wall rockfill dam structure’s mechanical characteristics in construction process and operational process, this paper adopts finite element method to carry out simulation analysis for inclined asphalt concrete wall rockfill dam of Mobankeng reservoir. Deducing distribution law of the dam’s stress and displacement in construction process and operational process. Analysis results show that, inclined asphalt concrete wall rockfill dam of Mobankeng reservoir construction is reasonable, it meets the requirements for design.

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