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Principles of Lubrication
Published in Heinz P. Bloch, Kenneth E. Bannister, Practical Lubrication for Industrial Facilities, 2020
Heinz P. Bloch, Kenneth E. Bannister
Since the laminae travel at different speeds, each lamina must slide upon another, and a certain force is required to make it do so. Specific resistance to this force is known as shear stress, and the cumulative effect of shear stress is fluid friction. Viscosity is a function of shear stress, i.e., viscosity equals shear stress divided by shear rate. Therefore, fluid friction is directly related to viscosity.
Viscous Flow and Boundary Layer
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
The viscosity of a fluid usually changes with temperature and pressure. For example, honey stored in a cold place appears to be very thick, but when it is heated, it will become runny. This also is true for lubrication oil, hydraulic fluids, and water. Normally, the viscosity of a liquid decreases with the increase of temperature. That is because the bond between liquid molecules becomes more relaxed when its temperature increases, i.e. the molecules are less restricted, and are able to move more freely. Figure 3.2 shows the changes of dynamic viscosity of water with temperature (Figure 3.2 diagram made from the data in Chemical Engineers’ Handbook, edited by Perry, 1941).
Uses of anti-foaming agents in paints and surface coatings
Published in David R. Karsa, Surfactants in Polymers, Coatings, Inks and Adhesives, 2020
Low-viscosity liquids generally have a fast flow and fast drainage, and higher viscosity liquids have a slower flow. This surface flow is also influenced by the presence of surfactants (Figure 4.8). Surfactants often create a structure in water, e.g. by long chains of poly(ethylene oxide). Therefore, the drainage is reduced in surfactant double layers.
An improved correlation for thermophysical properties of binary liquid mixtures
Published in Chemical Engineering Communications, 2023
Gustavo A. Iglesias-Silva, José J. Cano-Gómez, Mariana Ramos-Estrada, Kenneth R. Hall
The kinematic viscosity is defined as the ratio of the dynamic viscosity to the fluid density. It is a measure internal resistance of the fluid to flow under a gravitational field. The data for methanol (1) + toluene (2) at 298.15 K (Hammond et al. 1958) illustrate this property. This system presents a maximum and a minimum in the viscosity and in the viscosity deviation when plotted versus mole fraction. Figure 4 presents the performance of Equations (4), (16) and (17). Equations (16) and (17) can adequately predict the behavior of these properties while Equation (4) cannot correlate the thermophysical property and cannot predict the viscosity deviation. Table 1 contains values of the objective functions and the number parameters for each equation while Table 2 has the average absolute percentage deviation, calculated as, where and are the experimental data and calculated values, respectively; and N is the total number of data. Parameters for the equations are shown in Table 3.
Impact of magnetohydrodynamics in bidirectional slip flow of Maxwell fluid subject to stretching, radiation, and variable properties
Published in Numerical Heat Transfer, Part A: Applications, 2023
The viscosity of fluids varies according to changes in pressure, temperature, and shear rate. As a consequence, it is essential to look at specific qualities in the paper industry, plastics extrusion in Rayon and Nylon production, the textile sector, and other industries. In such a way, the model is more precisely anticipated when the flow configuration comprises viscosity and thermal conductivity of the fluid as a function of temperature. Ahmad and Iqbal [26] examined temperature-dependent viscosity fluctuations in ferro fluids, as well as velocity slip and viscous dissipation effects. Iqbal et al. [27] discussed the influence of temperature dependent viscosity over a convective sheet. Abbas et al. [28] examined MHD Carreau fluid flow over a stretching permeable sheet with variable viscosity and thermal conductivity. Irfan [29] studied Brownian motion and thermophoretic diffusion on nonlinear mixed convection flow of Carreau nanofluid subject to variable properties. Gladys and Reddy [30] presented contributions of variable viscosity and thermal conductivity on the dynamics of non-Newtonian nanofluids flow past an accelerating vertical plate.
Second law analysis on EMHD with variable viscosity and thermal conductivity of hybrid nanofluid over a rotating disk: an application in solar systems
Published in Waves in Random and Complex Media, 2022
Thermal conductivity refers to some kind of a material’s ability to transport heat and it plays an important role in cooling. It has numerous practical applications in the domains of metallurgy and chemical engineering, such as heat-treated materials moving between a wind-up roll and on conveyor belt or conveyors feed roll. However, the geometry, volume fraction and temperature all have an impact on the yield of the hybrid nanofluid. Actually, hybrid nanofluids are designed to improve thermal conductivity. On the other hand, the practical conditions allow for a variable aspect of thermal conductivity. Temperature changes as a function of frictional forces. As a result, it’s impossible to expect that thermal conductivity would remain constant. The temperature of a fluid can also alter its viscosity. Crude oil extraction, geothermal processes, metal wire tinning, fuel cells and nuclear reactors are just a few of the engineering applications for variable thermal conductivity [10]. Das et al. [11,12] explored the MHD of variable thermal conductivity with entropy generation over a convectively heated stretching cylinder.