Formulation of Generalized Mass Transfer Correlations for Blood Oxygenator Design

This paper numerically investigates non-Newtonian blood flow with oxygen and carbon dioxide transport across and along an array of uniformly square and staggered arranged fibers at various porosity (ε) levels, focussing on a low Reynolds number regime (Re < 10). The objective is to establish suitable mass transfer correlations, expressed in the form of Sherwood number (Sh = f(ε, Re, Sc)), that identifies the link from local mass transfer investigations to full-device analyses. The development of a concentration field is initially investigated and expressions are established covering the range from a typical deoxygenated condition up to a full oxygenated condition. An important step is identified where a cut-off point in those expressions is required to avoid any under- or over-estimation on the Sherwood number. Geometrical features of a typical commercial blood oxygenator is adopted and results in general show that a balance in pressure drop, shear stress, and mass transfer is required to avoid potential blood trauma or clotting formation. Different definitions of mass transfer correlations are found for oxygen/carbon dioxide, parallel/transverse flow, and square/staggered configurations, respectively. From this set of correlations, it is found that transverse flow has better gas transfer than parallel flow which is consistent with reported literature. The mass transfer dependency on fiber configuration is observed to be pronounced at low porosity. This approach provides an initial platform when one is looking to improve the mass transfer performance in a blood oxygenator without the need to conduct any numerical simulations or experiments.

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LABORATORY OBSERVATIONS OF DISSOLVED CARBON DIOXIDE TRANSPORT UNDER REGULAR BREAKING WAVES

Coastal Engineering Proceedings ◽

10.9753/icce.v36.waves.77 ◽

2018 ◽

pp. 77

Author(s):

Junichi Otsuka ◽

Yasunori Watanabe

Keyword(s):

Carbon Dioxide ◽

Wind Speed ◽

Turbulent Flows ◽

Surf Zone ◽

Breaking Waves ◽

Gas Transfer ◽

Carbon Dioxide Transport ◽

Dissolved Carbon ◽

Strong Turbulence ◽

Dissolved Carbon Dioxide

Air bubbles and strong turbulence that form in water from breaking waves play important roles in gas transfer across the air-sea interface (Melville, 1996). The entrained bubbles increase the total area of air-water interface per unit volume and enhance local gas dissolution into water. The dissolved gases mix in the water mass diffuse by the strong turbulence. These gas transfer-enhancing factors have been parameterized by only wind speed in models of gas transfer velocity in the deep ocean. Bulk parameters based on wind speed cannot be used for a surf zone, where waves break due to shoaling. In a surf zone, the cross-shore distributions of entrained bubbles and the turbulent intensity vary as waves propagate. The physical process of gas transfer under the complex air-water turbulent flows in breaking waves has not been clarified. Thus, breaking-wave factors that enhance gas transfer in a surf zone cannot be parameterized. In this study, we observed the transport process of dissolved carbon dioxide (DCO2) under air-water turbulent flows in a laboratory surf zone using image measurement systems.

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Local Mass Transfer From Rotating Wedge-Shaped Blades

Journal of Heat Transfer ◽

10.1115/1.3450754 ◽

1977 ◽

Vol 99 (4) ◽

pp. 634-640 ◽

Cited By ~ 2

Author(s):

H. Koyama ◽

A. Nakayama ◽

K. Sato ◽

T. Shimizu

Keyword(s):

Mass Transfer ◽

Reynolds Number ◽

Pressure Gradient ◽

Sherwood Number ◽

Negative Pressure ◽

Local Mass ◽

Contour Lines ◽

Local Mass Transfer ◽

Theoretical Considerations ◽

Local Sherwood Number

The purpose of this investigation is to determine the mass transfer from rotating wedge-shaped blades in an air environment. Through theoretical considerations, effect of negative pressure gradient has been emphasized wherever possible. The experimental results are correlated with local Sherwood number and Reynolds number. Furthermore, a new method has been proposed to judge the flow type by reading directly the slope of contour lines of equal sublimation drawn on the surface.

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Combined Effects of Axial- and Radial-Gap Spacing on the Mass Transfer Characteristics of a Shrouded Rotor-Stator System

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/91-gt-347 ◽

1991 ◽

Author(s):

M. K. Chyu ◽

D. J. Bizzak

Keyword(s):

Mass Transfer ◽

Reynolds Number ◽

Sherwood Number ◽

Radial Clearance ◽

Average Mass ◽

Local Mass ◽

Local Mass Transfer ◽

Radial Gap ◽

Gap Spacing ◽

Shrouded Rotor

Heat transfer characteristics of a shrouded rotor-stator system are examined using a mass transfer analog technique. Both local and average mass-transfer coefficients for a naphthalene-coated disk rotating in a quiescent environment are obtained for 4.0×104 ≤ Re ≤ 2.4×105. The measured results, which correlate well with theoretical predictions, are used to evaluate the influence of radial-gap clearance and axial-gap spacing on average and local mass-transfer rates in a shrouded rotor-stator with no superposed coolant flow. Similar to a rotor-stator system without a shroud, a reduction in the axial gap tends to decrease the average mass transfer, with the magnitude of the decrease being inversely proportional to the Reynolds number. Such a reduction in mass transfer is also found to be influenced by the radial clearance gap. A reduction of the radial clearance from a/D=0.042 to 0.020 is shown to decrease the average Sherwood number by approximately 20 percent of the corresponding free disk value. Local mass transfer distributions illustrate a more significant axial gap effect. For small axial-gap spacings, local Sherwood number profiles are no longer uniform across the rotor face, but exhibit a significant increase near the rotor edge. The magnitude of this increase near the disk edge is shown to be inversely proportional to the radial clearance gap and the rotational Reynolds number.

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A Passive Model of the Heat, Oxygen and Carbon Dioxide Transport in the Human Body

Volume 2: Biomedical and Biotechnology Engineering ◽

10.1115/imece2009-11104 ◽

2009 ◽

Author(s):

Cyro Albuquerque-Neto ◽

Jurandir Itizo Yanagihara

Keyword(s):

Carbon Dioxide ◽

Mass Transfer ◽

Human Body ◽

Circular Cross Section ◽

The Body ◽

Heat Equations ◽

Carbon Dioxide Transport ◽

Small Vessels ◽

Hands And Feet ◽

Dissociation Curves

The aim of this work is the development of a mathematical model which integrates a model of the human respiratory system and a model of the human thermal system. Both models were previously developed at the same laboratory, based on classical works. The human body was divided in 15 segments: head, neck, trunk, arms, forearms, hands, thighs, legs and feet. Those segments have the form of a cylinder (circular cross-section) or a parallelogram (hands and feet) with the following tissue layers: muscle, fat, skin, bone, brain, lung, heart and viscera. Two different geometries are used to model the transport of mass and heat in the tissues. For the mass transfer, those layers are considered as tissue compartments. For the heat transfer, the body geometry is taken into account. Each segment contains an arterial and a venous compartment, representing the large vessels. The blood in the small vessels are considered together with the tissues. The gases are transported by the blood dissolved and chemically reacted. Metabolism takes place in the tissues, where oxygen is consumed generating carbon dioxide and heat. In the lungs, mass transfer happens by diffusion between an alveolar compartment and several pulmonary capillaries compartments. The skin exchanges heat with the environment by convection, radiation and evaporation. The differential transport equations were obtained by heat and mass balances. The discretization heat equations were obtained applying the finite volume method. The regulation mechanisms were considered as model inputs. The results show three different environment situations. It was concluded that the gas transport is most influenced by the temperature effects on the blood dissociation curves and the metabolism rise in a cold environment by shivering.

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Gray Box Modeling of Supercritical Nimbin Extraction from Neem Seeds Using Methanol as Co-Solvent

The Open Chemical Engineering Journal ◽

10.2174/1874123101004010021 ◽

2010 ◽

Vol 4 (1) ◽

pp. 21-30 ◽

Cited By ~ 1

Author(s):

G. Zahedi ◽

S. Azizi ◽

T. Hatami ◽

L. Sheikhattar

Keyword(s):

Experimental Data ◽

Carbon Dioxide ◽

Mass Transfer ◽

Supercritical Carbon Dioxide ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Sherwood Number ◽

System Model ◽

Neuro Fuzzy ◽

Fuzzy Network

In this paper yield of nimbin extraction from neem seeds using supercritical carbon dioxide with methanol as co-solvent has been studied. In this case mass transfer coefficient in terms of Sherwood number has been estimated by a neuro-fuzzy network. Then the estimated mass transfer coefficient has been fed to the system model which is set of partial differential equations. The proposed gray box model was validated with experimental data.

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