Experimental and Numerical Study of Emulsion Lubricated Strip Rolling

2005 ◽  
Author(s):  
P. B. Kosasih ◽  
A. K. Tieu
Keyword(s):  
Film Thickness ◽  
Numerical Study ◽  
Rolling Process ◽  
Work Zone ◽  
Contact Ratio ◽  
Strip Rolling ◽  
Two Phase ◽  
Oil Concentration ◽  
Mixed Film ◽  
Inlet Zone

An experimental and numerical study of cold rolling lubricated by O/W emulsion has been carried out. The experimental measurements are compared to the computed results from the numerical scheme developed by the authors. The scheme, which is based on two-phase lubricant model, is able to calculate oil concentration at any point within the inlet zone and work zone, rolling pressure, film thickness, and fractional contact ratio associated with strip rolling under mixed film lubrication at different rolling speed. The study encompassed extensive mixed film regime for speed, S ranges from 10−5 to 10−1, and supply oil concentration level λds ranges from 1% to 10%, and oil droplet size ranges from Ds from 5 to 20. The numerical results show the occurrence of moderate oil concentration increase in the inlet zone followed by a sharp one at the beginning of the work zone. The effect of the concentration process is predominantly seen in the film thickness and the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without detrimental effects on the rolling process and indeed use this principle to control the outlet lubricant film thickness.

Modeling and Optimization of Rolling Process: A Multi-Objective Approach

2020 ◽  
Vol 19 (02) ◽  
pp. 343-364
Author(s):  
S. Panda ◽  
S. N. Panda
Keyword(s):  
Cold Rolling ◽  
Film Thickness ◽  
Temperature Rise ◽  
High Speed ◽  
Rolling Process ◽  
Response Analysis ◽  
Strip Rolling ◽  
Multi Objective ◽  
Inlet Zone ◽  
Cold Strip Rolling

In a high-speed cold strip rolling process, it is necessary to optimize the process parameters for improved quality in the product. In this study, two separate multi-objective optimization problems for a cold rolling process are formulated. The objectives in one of the cases are minimum isothermal film thickness and film temperature rise in the inlet zone and in another case it is minimum thermal film thickness and film temperature rise in the inlet zone. Particle swarm optimization algorithm has been used for solving the optimization problem. The key input parameters for the cold rolling process are identified and prioritized through the convergence study and the coefficient of variation analysis. A response analysis is performed on the critical input variables. This study assists the process engineer to understand the lubrication in cold strip rolling at high speed and select an appropriate lubricant for a given combination of strip and rolls.

Elastohydrodynamic Lubrication With O/W Emulsions

1994 ◽  
Vol 116 (2) ◽  
pp. 310-319 ◽  
Author(s):  
D. Zhu ◽  
G. Biresaw ◽  
S. J. Clark ◽  
T. J. Kasun
Keyword(s):  
Film Thickness ◽  
Transition Region ◽  
High Speed ◽  
Critical Speed ◽  
Two Phase ◽  
Ph Values ◽  
Wide Range ◽  
Oil Concentration ◽  
Oil Pool ◽  
Inlet Zone

This paper presents a set of experimental results of the EHL film thickness with oil-in-water (O/W) emulsions in a wide range of rolling speed for different oil concentrations and pH values. The O/W emulsions have wide applications in metal-forming and machining processes as well as hydraulic systems. However, their lubrication mechanisms are very complex and have not been fully understood. A newly developed high speed optical EHL rig was used to measure the film thickness and observe the two-phase flow around the EHL point and line contacts. Experimental observations indicate that phase inversion/oil pool formation mechanism around the inlet zone takes place only at very low speeds, which are most likely far below practical speed ranges for major industrial applications. When the speed is low, the lubricant film thickness is dominated by the bulk properties of oil phase, and can be estimated by the conventional EHL theory together with the consideration of starvation effect. After the speed exceeds a certain limit, called first critical speed, there is a transition region, where no stable oil pool is observed and the film thickness starts to decrease, or increases slightly then decreases. It is believed that in this transition region there is still a considerable amount of oil concentrated in the inlet zone, and this local oil concentration decreases as the speed increases. The film thickness appears to be dominated by the entrainment of oil-enriched two-phase lubricant in the inlet zone. The increase of film thickness is due to entraining effect and the decrease due to the increased oil phase starvation. If the speed is further increased exceeding a second critical speed, the film thickness will stop decreasing and start to increase again. In this high speed region the local oil concentration of entrained lubricant in the inlet zone is believed to become quite constant and close to that of the bulk lubricant supply. The film thickness, therefore, continuously increases for all of the tested line and point contact cases as the speed goes up, and is always significantly smaller than that of neat oil but larger than that of pure water. The destabilized emulsions with lower pH values can form more stable oil pools and considerably thicker films. This is because the oil droplets in these low pH emulsions can be more easily trapped and brought into the contact by the solid surfaces. However, for the tested emulsions, the oil pools still cannot survive reasonably high speeds.

Partial Film Lubrication Characteristics of Inlet Zone in Cold Strip Rolling

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Kuo Fu ◽  
Yong Zang ◽  
Zhiying Gao
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Contact Area ◽  
Friction Stress ◽  
Area Ratio ◽  
Work Zone ◽  
Zone Length ◽  
Inlet Zone ◽  
Pressure Stress ◽  
Contact Area Ratio

According to the average flow Reynolds equation and rolling theory, a partial film lubrication model of inlet zone has been developed. The model mainly simulates and reflects the influence of surface topography on the inlet film thickness and inlet zone length. Based on the surface topography analysis, a method to judge the friction condition was proposed. All the calculation was conducted by a numerical method. The result shows that the transverse stripe increases the inlet film thickness and the inlet zone length, while the longitudinal stripe decreases them. The surface roughness will enhance this effect. The surface roughness and the stripe direction also have a significant influence on the contact area ratio and the distribution of stress and film thickness in work zone. Transverse stripe increases the lubricant film thickness and separates the roll and the sheet with a larger distance in work zone. It also decreases the contact area ratio, the pressure stress and friction stress of the work zone. Whereas longitudinal stripe decreases the film thickness and increases the contact area ratio, pressure stress and friction stress. The surface roughness increases the contact area ratio, pressure stress and friction stress.

Numerical Study on Gas-Yield Power-Law Fluid in T-Junction Minichannel

2019 ◽  
Author(s):  
Abdalsalam Ihmoudah ◽  
Mohamed M. Awad ◽  
Aziz Rahman ◽  
Stephen D. Butt
Keyword(s):  
Film Thickness ◽  
Power Law ◽  
Xanthan Gum ◽  
Numerical Study ◽  
Superficial Velocity ◽  
Bubble Velocity ◽  
Two Phase ◽  
Ansys Fluent ◽  
Power Law Fluids ◽  
Taylor Bubbles

Abstract In this study, a computational examination of Taylor bubbles was performed for gas/non-Newtonian fluid two-phase flows developed in a minichannel T-junction mixer with a hydraulic diameter of 1 mm. The investigations employed three separate aqueous xanthan gum solutions at concentrations of 0.05, 0.1 and 0.15 w/w, which are referred to as non-Newtonian (yield power-law) fluids. The effective concentration of the xanthan gum solutions and superficial velocity of the inlet liquid phase on the length, velocity, and shape of the Taylor bubbles was studied using the ANSYS FLUENT 19 software package. The simulation results show an increase in bubble velocity with increasing film thickness, particularly in solutions of higher viscosity XG-0.15%. Furthermore, bubble lengths decreased as the xanthan gum concentrations increased, but bubble shapes underwent alterations when the concentrations increased. Another interesting result of the tests shows that when the liquid inlet velocity increases, bubble lengths decrease during lower liquid superficial velocity, whereas during higher velocities, they change only slightly after increases in concentration. Finally, with increasing XG concentration, the liquid film thickness around the bubble increased. The results show good agreement with correlations after modifying a capillary number (Ca*) for non-Newtonian liquids in all cases.

scholarly journals Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3634
Author(s):  
Grzegorz Czerwiński ◽  
Jerzy Wołoszyn
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Heat Dissipation ◽  
Cooling System ◽  
Numerical Study ◽  
Relaxation Parameter ◽  
Phase Changes ◽  
Transfer Time ◽  
Two Phase ◽  
Time Relaxation

With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

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