EFFECT OF SURFACE ROUGHNESS ON MASS TRANSFER IN A FLAT-PLATE MICROCHANNEL BIOREACTOR

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1559-1562 ◽  
Author(s):  
Y. ZENG ◽  
T. S. LEE ◽  
P. YU ◽  
H. T. LOW
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Flat Plate ◽  
Species Concentration ◽  
Solute Depletion ◽  
Smooth Channel ◽  
Dimensional Parameters ◽  
Microfabrication Technique ◽  
Volume Method ◽  
Effect Of Surface

Surface roughness exists in most microfluidic devices due to the microfabrication technique or particle adhesion. In this study, a numerical model based on Finite Volume Method has been developed to simulate the mass transfer in a flat-plate microchannel bioreactor with semi-circular protrusions uniformly distributed on the bottom. The results show that the mass transfer in rough channel is enhanced, as shown by lower minimum species concentration in the rough channel compared with that in smooth channel. Non-dimensional parameters such as Peclet number (Pe), Damkohler number (Da) and the roughness size ratio (β) can influence the effect of roughness greatly. However, it is important to ensure that the minimum species concentration in the rough channel is adequate for cell growth. The results would provide guidance on the perfusion requirements to avoid solute depletion or toxicity during cell culture.

scholarly journals The Effect of Surface Roughness on Diffusion and Chemical Reaction Controlled Limiting Currents on a Rotating Cylinder Electrode in Deaerated Solutions with and Without CO2

CORROSION ◽  
10.5006/2552 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 971-983 ◽  
Author(s):  
M. Al-Khateeb ◽  
R. Barker ◽  
A. Neville ◽  
H.M. Thompson
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Sherwood Number ◽  
Schmidt Number ◽  
Rotating Cylinder ◽  
Operating Conditions ◽  
Limiting Current ◽  
Surface Roughening ◽  
Rotating Cylinder Electrode ◽  
Effect Of Surface

The influence of surface roughness on mass transfer on a rotating cylinder electrode apparatus is investigated experimentally for a roughness pattern consisting of grooves parallel to the direction of fluid flow. Mass transfer from four different samples, with roughness values of 0.5 μm, 6 μm, 20 μm, and 34 μm, is measured using the limiting current technique for a range of rotational speeds in NaCl solutions saturated with N2 at pH = 3 and 4. Comparison with available correlations for the Sherwood number in literature (which are independent of surface roughness and are either for specific or arbitrary roughness patterns) shows that H+ mass transfer only correlates well for particular levels of roughness and that their accuracy can be increased if a correlation is utilized which is a function of surface roughening. A new correlation for Sherwood number as a function of the Reynolds number, Schmidt number, and surface roughness is proposed which agrees well with the mass transfer observed from all of the rough surface cases considered for this particular roughness pattern. Complementary experiments in CO2 environments were used to assess the combined limiting current associated with H+ and H2CO3 reduction (with the latter occurring via the buffering effect and being associated with the slow CO2 hydration step). Although the increase in sample roughness clearly leads to an increase in the rate of H+ mass transfer, in the CO2 environments considered, surface roughness is found to have no significant influence on the limiting current contribution from H2CO3, which can therefore be determined from Vetter’s equation across this range of operating conditions.

Effect of surface roughness on the kinetics of mass transfer during gas carburizing*

2008 ◽  
Vol 63 (5) ◽  
pp. 257-264 ◽  
Author(s):  
O. Karabelchtchikova ◽  
Chr. A. Brown ◽  
R. D. Sisson
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Gas Carburizing ◽  
Kinetics Of ◽  
Effect Of Surface

NUMERICAL STUDY ON THE INFLUENCE OF SURFACE ROUGHNESS ON FLUID FLOW AND MASS TRANSFER IN A FLAT-PLATE MICROCHANNEL BIOREACTOR

2007 ◽  
Vol 18 (02) ◽  
pp. 131-155 ◽  
Author(s):  
YAN ZENG ◽  
THONG-SEE LEE ◽  
PENG YU ◽  
HONG-TONG LOW
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Shear Stress ◽  
Fluid Flow ◽  
Cell Growth ◽  
Flat Plate ◽  
Numerical Study ◽  
Maximum Shear Stress ◽  
Critical Conditions ◽  
Minimum Concentration

Surface roughness exists in most microfluidic devices due to the microfabrication technique or particle adhesion. The present study has developed a numerical model based on Finite Volume Method to simulate the fluid flow and mass transfer in a flat-plate microchannel bioreactor with an array of rough elements uniformly placed on the bottom wall. Both semicircle and triangle roughness are considered to include more shapes of roughness elements. A monolayer of cells is assumed to attach to the base of the channels and consumes species from culture medium. The results show that the roughness size ratio (α) and the roughness distribution ratio (β) have direct and significant effects on fluid flow and mass transfer. The dimensionless parameters Peclet number (Pe) and Damkohler number (Da) can also influence mass transfer greatly. Although the two types of roughness have similar effects, at the same condition, the triangle roughness has larger effect on shear stress by showing higher dimensionless values at the channel base; the semicircle roughness has larger effect on mass transfer by showing lower dimensionless minimum base concentration [Formula: see text] and higher dimensionless absorption rate (Δj%). However, it is important to ensure the lower maximum shear stress and the adequate minimum species concentration for cell growth in rough channels. Hence, if the maximum shear stress and minimum concentration in rough channels can satisfy the critical conditions for cell growth, rough channels would be better than smooth channels because of their lower shear stress at the flat-bed part and higher mass transfer efficiency. The results would provide guidance on the flow and perfusion requirements to avoid shear stress damage and solute depletion or toxicity during cell culture.

Effect of Surface Roughness on Film Cooling Performance

1985 ◽  
Vol 107 (1) ◽  
pp. 111-116 ◽  
Author(s):  
R. J. Goldstein ◽  
E. R. G. Eckert ◽  
H. D. Chiang ◽  
E. Elovic
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Experimental Investigation ◽  
Rough Surface ◽  
Film Cooling ◽  
Free Stream ◽  
Cooling Performance ◽  
Effect Of Surface

An experimental investigation of film cooling on a rough surface has been performed using a mass transfer technique. Two injection geometries (one and two rows of holes) and six roughness patterns were used. The density of the injected gas was close to that of the free-stream air. The presence of roughness causes a decrease in the spanwise-averaged effectiveness for both injection geometries at low blowing rates, and an increase in the effectiveness for one-row injection at high blowing rates, but not for two-row injection. The results for two-row injection (with or without roughness) can be correlated by a parameter used to correlate slot-injection data. The influence of roughness pattern on the average effectiveness and on the lateral uniformity of the effectiveness is described.

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