Effect of Surface Roughness on Fouling of Calcium Carbonate: An Experimental Investigation

2010 ◽  
Author(s):  
M. Izadi ◽  
D. K. Aidun ◽  
P. Marzocca ◽  
H. Lee
Keyword(s):  
Surface Roughness ◽  
Calcium Carbonate ◽  
Rough Surface ◽  
Smooth Surface ◽  
Rough Surfaces ◽  
Operating Conditions ◽  
Tubular Heat Exchanger ◽  
Analytical Microscopy ◽  
Deposit Layer ◽  
Effect Of Surface

The effect of surface roughness on the fouling behavior of calcium carbonate is experimentally investigated. The real operating conditions of a tubular heat exchanger are simulated by performing prolonged experiments with duration of 3 to 7 days. The solution used is a mixture of sodium bicarbonate and calcium chloride in de-ionized water with the concentration of 0.4 g/l of each. An on-line fouling evaluation system was developed such that the fouling resistance for a selected solution could be measured in real time. The experiments are repeated with the same procedure for 90/10 Cu/Ni tubes with different internal surface roughness. After the experiment the surface is analyzed by analytical microscopy to investigate the morphology of the deposit layer. Comparison of the experimental results of smooth and rough surfaces shows that a combination of aragonite and calcite polymorphs are formed on rough surface while only dendritic porous aragonite crystals are formed on smooth surface. Accordingly, the deposit layer formed on rough surface is denser and has a higher thermal resistance comparing to that formed on smooth surface. The fouling factor-time curves of smooth and rough surfaces obtained by the current experimental study agree with the results found by the analytical microscopy of the surface and show higher fouling resistances for rough surface. Experimental data is significantly important for the design, and formulating operating, and cleaning schedules of the equipment.

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 Nanocontact: Quasicontinuum Simulation

2012 ◽  
Vol 502 ◽  
pp. 342-347 ◽  
Author(s):  
Wu Gui Jiang ◽  
Zheng Wei Wang
Keyword(s):  
Rough Surface ◽  
Smooth Surface ◽  
Characteristic Size ◽  
Contact Forces ◽  
Atomic Scale ◽  
Quasicontinuum Method ◽  
Cu Substrate ◽  
Nonlinear Fashion ◽  
Effect Of Surface ◽  
Good Agreement

By using the two-dimensional quasicontinuum method, the nanocontact between Ni indenter and single crystal Cu substrate with a smooth or rough surface is simulated. The contact force varies in a nonlinear fashion with the increasing indenter displacement, including several force drops. The atomic-scale deformation mechanism in the Cu substrate during nanocontact process is monitored. Shockley partials, Lomer-Cottrel locks as well as twinning faults are observed at the force drops. The Lomer-Cottrel locks play an important role in smooth surface nanocontact process, and they insure that Cu substrate undergoes elastic deformation dominantly during nanocontact process. The contact forces calculated from the Maugis-Dugale (M-D) theory show a good agreement with those obtained by the QC simulation in the smooth surface nanocontact process. It must be noted that the M-D theory is no longer suitable to describe the rough surface nanocontact problem due to the severe plastic deformation in the asperities of the substrate when the characteristic size of roughness is on the order of the indenter depth.

The Effect of Surface Roughness on Efficiency of Low Pressure Turbines

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Raúl Vázquez ◽  
Diego Torre
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Slope Angle ◽  
Low Pressure ◽  
Operating Conditions ◽  
Specific Work ◽  
Pressure Losses ◽  
Comparison Of The Results ◽  
Very High ◽  
Effect Of Surface

The effect of surface roughness on the efficiency of low pressure turbines (LPTs) was experimentally investigated in a multistage turbine high-speed rig. The rig consisted of three stages of a state-of-the-art LPT. The stages were characterized by a very high wall-slope angle, reverse cut-off design, very high lift, and very high aspect ratio airfoils. Two sets of airfoils (both stators and rotors) were tested. The first set was made of airfoils with a roughness size of 0.7 μm Ra (25–35 × 10−5 ks/Cm), which was representative of LPT polished airfoils. The surface finish for the second set of airfoils was 1.8 μm Ra for blades and 2.5 μm Ra for stators (approximately 90 × 10−5 in terms of ks/Cm for both stators and blades). The resulting roughness of this set was representative of “as-cast” airfoils of low pressure turbines. The airfoil geometries, velocity triangles, leading and trailing edge locations, and flowpath were maintained between both sets. They were tested with the same instrumentation and at the same operating conditions with the intention of determining the isolated impact of the surface roughness on the overall efficiency. The turbine characteristics: sensitivity to speed, specific work, Reynolds number, and purge flows, were obtained for both sets. The comparison of the results suggests that the efficiency and capacity of both types of airfoils exhibit the same behavior. No significant differences in the results can be distinguished for the range of operating conditions in this study. The results agree with previous studies of distributed roughness in turbines: the use of as-cast rough airfoils in some low pressure turbines at high altitude does not introduce additional pressure losses.

The Contact of Two Nominally Flat Rough Surfaces

1970 ◽  
Vol 185 (1) ◽  
pp. 625-633 ◽  
Author(s):  
J. A. Greenwood ◽  
J. H. Tripp
Keyword(s):  
Surface Roughness ◽  
General Theory ◽  
Rough Surface ◽  
Rough Surfaces ◽  
Deformation Mode ◽  
Surface Model ◽  
Geometrical Properties ◽  
Rough Plane ◽  
Surface Contact ◽  
Compliance Curve

Most models of surface contact consider the surface roughness to be on one of the contacting surfaces only. The authors give a general theory of contact between two rough plane surfaces. They show that the important results of the previous models are unaffected: in particular, the load and the area of contact remain almost proportional, independently of the detailed mechanical and geometrical properties of the asperities. Further, a single-rough-surface model can always be found which will predict the same laws as a given two-rough-surface model, although the required model may be unrealistic. It does not seem possible to deduce the asperity shape or deformation mode from the load-compliance curve.

Effect of soil surface roughness and scene components on soil surface bidirectional reflectance factor

2012 ◽  
Vol 92 (2) ◽  
pp. 297-313 ◽  
Author(s):  
Z. Wang ◽  
C. A. Coburn ◽  
X. Ren ◽  
P. M. Teillet
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Zenith Angle ◽  
Smooth Surface ◽  
Soil Surface ◽  
Bidirectional Reflectance ◽  
Imaging Spectrometer ◽  
Bidirectional Reflectance Factor ◽  
Reflectance Factor ◽  
Soil Surface Roughness

Wang, Z., Coburn, C. A., Ren, X. and Teillet, P. M. 2012. Effect of soil surface roughness and scene components on soil surface BRF. Can. J. Soil Sci. 92: 297–313. Bidirectional Reflectance factor (BRF) data of both rough [surface roughness index (SRI) of 51%] and smooth soil surfaces (SRI of 5%) were acquired in the laboratory under 30° illumination zenith angle using a Specim V10E imaging spectrometer and an Ocean Optics non-imaging spectrometer mounted on the University of Lethbridge Goniometer System version 2.5 (ULGS-2.5) and version 2.0 (ULGS-2.0), respectively. Under controlled laboratory conditions, the rough soil surface exhibited higher spectral reflectance than the smooth surface for most viewing angles. The BRF of the rough surface varied more than the smooth surface as a function of the viewing zenith angle. The shadowing effect was stronger for the rough surface than for the smooth surface and was stronger in the forward-scattering direction than in the backscattering direction. The pattern of the BRF generated with the non-image based data was similar to that generated with the whole region of interest (ROI) of the image-based data, and that of the whole ROI of the image-based data was similar to that of the illuminated scene component. The BRF of the smooth soil surface was dominated by illuminated scene component, i.e., the sunlit pixels, whereas the shaded scene component, i.e., the shaded pixels, was a larger proportion of the BRF of the rough soil surface. The image-based approach allowed the characterization of the contribution of spatial components in the field of view to soil BRF and improved our understanding of soil reflectance.

A Study of Elastohydrodynamic Lubrication of Rough Surfaces

1991 ◽  
Vol 113 (1) ◽  
pp. 110-115 ◽  
Author(s):  
L. Chang ◽  
M. N. Webster
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Rough Surface ◽  
Contact Zone ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Micro Deformation ◽  
Sinusoidal Functions ◽  
Sensitive Parameters ◽  
Pressure Perturbations

This paper reports some results of rough-surface, elastohydrodynamically lubricated (EHD) contacts obtained using a previously developed transient EHD model. The surface roughness is modeled with sinusoidal functions of small wavelength compared to the contact zone. Results are presented showing how the operating conditions affect the film thickness, micro-deformation of the roughness, and the pressure perturbations due to motion and interaction of roughness within the contact. This preliminary work suggests that the entraining velocity and the slide-to-roll ratio are the most sensitive parameters influencing the lubrication process of rough-surface EHD contacts.

scholarly journals Indentation and flattening of rough surfaces spherical asperities

2018 ◽  
Vol 7 (2.23) ◽  
pp. 188
Author(s):  
Petr Ogar ◽  
Denis Gorokhov ◽  
Elena Ugryumova
Keyword(s):  
Rough Surface ◽  
Half Space ◽  
Smooth Surface ◽  
Rough Surfaces ◽  
Reference Surface ◽  
Initial Part ◽  
Roughness Model ◽  
Rigid Smooth ◽  
Contact Pressures ◽  
Surface Curve

The paper indicates that the application of roughness models and the theories of contacting rough surfaces developed by Greenwood-Williamson and N.B. Demkin for solving the problems of hermetology leads to significant errors. This is explained by much greater contact pressures than for the tribology problems, by describing only the initial part of the reference surface curve, the lack of allowance for the plastic extrusion of the material. A brief review of methods for describing the introduction of a sphere into an elastoplastic reinforced half-space is given. The properties of the elastoplastic reinforced material are described by the power law of Hollomon. To describe the indentation and flattening of single spherical asperity, the results of finite element modeling are used. The cases of contacting a rigid rough surface with an elastoplastic half-space and a rigid smooth surface with a rough surface are considered. To determine the relative contact area, the discrete roughness model is used in the form of a set of spherical segments distributed along the height in accordance with the curve of the reference surface. 

scholarly journals Influence of design parameters and operating conditions on performance indicators of magnetic fluid seals of electric motor shafts

Vestnik IGEU ◽  
2019 ◽  
pp. 40-47
Author(s):  
A.M. Vlasov ◽  
Yu.B. Kazakov ◽  
V.A. Poletaev
Keyword(s):  
Surface Roughness ◽  
Magnetic Fluid ◽  
Electric Motor ◽  
Performance Indicators ◽  
Rough Surfaces ◽  
Rotation Frequency ◽  
Friction Torque ◽  
Operating Conditions ◽  
Design Parameters ◽  
External Temperature

Magnetic fluid seals (MFS) are beginning to be used to seal rotating shafts in electric motors operating in conditions of high humidity, dust and pollution. Friction torque and heating are the most important operational indicators of MFS depending on the design parameters and operation conditions: rotation frequency, operation time, temperature and clearance (taking into account roughness and waviness). An urgent task is to study the influence of design parameters and operating conditions on the performance indicators of MFS of such electric motor shafts. The modeling of rough surfaces was performed using orthogonal transformations of roughness matrix vectors and a visual representation. The contact area of the magnetic fluid with rough surfaces was determined by mathematical modeling. The experimental studies were performed on a test bench. Wear sleeves and poles made of various steels with different roughness parameters were used. Models of MFS clearances formed by surfaces with different roughness have been obtained. The contact areas of the magnetic fluid with the surfaces of MFS at different roughness values have been determined. Nonlinear dependences and variation limits of the friction torque and MFS temperature on the surface roughness of the poles and sleeves, rotation frequencies of the electric motor, and the external temperature have been obtained. Clearance models allow determining the roughness of MFS surfaces. The developed experimental unit allows carrying out studies on the effect of changes of design parameters and operating conditions on the performance indicators of MFS. At a 5,21 time higher rotation frequency (from 556 to 2897 rpm), the MFS temperature can increase by up to 2 times, the friction torque – by up to 2,2 times. If the temperature rises by 50 оC, the friction torque can drop by up to 3 times. With an increase in the surface roughness from 0,357 to 7,21 μm, the temperature of the MFS can rise by 20 %, and the friction torque by 55 %.

Surface Roughness Characterization of al Films by Spectroscopic Ellipsometry

1985 ◽  
Vol 54 ◽  
Author(s):  
J. R. Blanco ◽  
K. Vedam ◽  
P. J. McMarr ◽  
J. M. Bennett
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Spectroscopic Ellipsometry ◽  
Rough Surfaces ◽  
Scalar Theory ◽  
Nondestructive Technique ◽  
Aluminum Films ◽  
Random Rough Surfaces ◽  
Scalar Theory Of Diffraction

ABSTRACTWell characterized rough surfaces of aluminum films have been studied by the nondestructive technique of Spectroscopie Ellipsometry (SE). The roughness of the aluminum specimens had been characterized earlier by Total Integrated Scattering and Stylus Profilometry techniques to obtain numerical estimates of ras roughness and autocovariance lengths. The present SE measurements on these specimens were carried out at a number of angles of incidence in the range 30–80° and at a number of discrete wavelengths in the spectral range 300–650nm. The SE results were then analyzed by the scalar theory of diffraction from random rough surfaces by treating the surface as a simple random rough surface. The results of such analyses of the SE measurements are compared with the results of the earlier characterization techniques.

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