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Applications to River Flow
Published in Michio Sanjou, Turbulence in Open Channels and River Flows, 2022
FIG. 7.23(b) is a sketch of a Hjulstrom curve (Hjulstrom 1935) that illustrates the critical velocity, Uc, corresponding to the bottom erosion or deposition. An upper downward-convex curve means the fluid velocity at which the bottom-situated particle starts to move and erode. In the region where the particle size is small, the smaller the particle size, the larger the crucial flow velocity due to the cohesion. A lower curve means the fluid velocity at which the moving particles in the flow start to be deposited. It is easy to use because it is not necessary to consider the friction velocity. This is a great advantage in practice. The higher velocity can carry the larger particle without deposition. However, the drawback is that it does no take water depth into account. Even at the same velocity, the water depth and the bottom shear stress may change depending on the bed slope.
Spray-freeze-drying for soluble coffee production
Published in S. Padma Ishwarya, Spray-Freeze-Drying of Foods and Bioproducts, 2022
The higher ΔE value of FD sample vis-à-vis commercial product can be related to its long drying time that is known to degrade product color (Contreras et al., 2008; Ozkan et al., 2005). The freezing rate determines the lightness of soluble coffee. Due to its rapid freezing rate than the conventional freeze-drying, the SFD process resulted in a brighter soluble coffee product (higher L* value) than its FD counterpart. Generally, quick-frozen materials retain their brighter color than those frozen at a slower rate. This is because the pores originating from the sublimation of small ice crystals formed by rapid freezing scatters more light than large pores formed by slow freezing (Ceballos et al., 2012). Also, the redness, yellowness and chroma values were higher for the SFD coffee relative to the freeze-dried product (Table 6.3). Chroma (C) is an indicator of the intensity of product color. Generally, broader particle size distributions are responsible for the reduced color strength, as opacity or transparency of a substance is greatly influenced by the particle size (Heinrich, 2003). Thus, as mentioned in the previous section, the smaller particle size and monomodal particle size distribution of spray-freeze-dried soluble coffee compared to freeze-dried coffee are the underlying reasons for its desirable color parameters (Ishwarya & Anandharamakrishnan, 2015).
Properties of bulk materials
Published in D.V. Subba Rao, The Belt Conveyor, 2020
It is obvious that each definition has its own limitations and the usage of a particular definition of size depends on the method of measurement and the purpose for which that defined size is used. In an industrial situation, bulk materials comprise large number of particles of non-uniform sizes. In order to describe such materials completely, it is necessary to determine the particle size distribution. Particle size distribution refers to the manner in which particles are quantitatively distributed among various sizes; in other words, it is a statistical relation between quantity and size.
Physical and frictional behaviors of loblolly pine residues
Published in Biofuels, 2022
Oluwatosin Oginni, Oladiran Fasina
Flow index is defined as the inverse of flow function. Jenike [32] classified powder flowability based on flow index (FI) values as follows; very cohesive (FI < 2), cohesive (2 < FI < 4), easy flowing (4 < FI < 10), and free flowing (FI > 10). The flow index values for the fractionated materials were determined from the inverse of the slopes of the fit of linear equations to the experimentally determined flow function curves. Table 3 showed that except for the fractions with particle sizes of 1.40 mm and 1.00 mm, all the other fractions were classified as ‘Cohesive’. The cohesiveness of the materials increased (i.e. flow index decreased) with a decrease in the particle size. The unfractionated sample was also classified as cohesive. This is because all the fractions with particle sizes below 1.00 mm were classified as cohesive; thus, making the unfractionated material a cohesive material. The implication is that ground loblolly pine residues with large amount of 1.00 mm fractions and below, will experience flowability problem during unloading from storage bins and hopper (i.e. gravity discharge of the material will be impossible).
Treatment of produced water from Niger Delta oil fields using sequential mixture of bio-adsorbents
Published in Cogent Engineering, 2021
S.G Udeagbara, S.O Isehunwa, N.U Okereke, I. U Oguamah, A Kerunwa, O. Nwanwe
From Figure 11 with particle size of 300 micron, it was observed that after same 8 hours of treatment, some traces of copper (Cu) (0.015 ppm) was still present. This could be as a result of the particle size with smaller surface area when compared with that of 150 micron particle size. Another notable thing in Figure 11 was the absence of calcium (Ca) from the PW after 8 hours of treatment which was not obtained under 150 micron particle sizes. The results obtained with both particle sizes (150 and 300 micron) were all encouraging. This shows there is a great potential in using some of these low cost agricultural waste in the management of waste waters in general. Table 3 gives a more detail of the results and the extent to which the toxic metals concentration in the PW sample were greatly reduced. Averagely, 150 micron particle sizes produced a better result when compared with 300 micron particle sizes. In summary, according to the results obtained from the experiments, it was observed that particle size matters a lot no matter the nature and type of material used in the treatment. The results obtained validate the outcome of literature review which says that particle size is an important parameter in adsorption process. The smaller the particle size, the more the surface area of materials and the better the adsorption process. The large surface area is able to expose the adsorption sites very well and this promotes the adsorption process. From the results, 150 micron size of particles with large surface area produced excellent results when compared with 300 micron particles with smaller surface areas.
Mathematical modelling of sound transmission loss performances of different coloured surfaces coated with polyurethane-based paint
Published in Transactions of the IMF, 2020
H. Ergin Esen, M. Yagimli, H. Tozan, G. E. Yalcin, E. Arca
The selective absorption and reflection of various wavelengths of the light hitting the pigmented surface determine the tone of the pigment. The different absorption and reflection properties of compounds are linked to the arrangement of electrons in their molecules and their energy and frequency vibrations.14 Most coloured pigments provide strong absorption in the visible light spectrum but become transparent in the invisible spectrum.15 One of the most important factors affecting the reflection of light is the smoothness (or roughness) of the surface, and the roughness of the surface will also trigger the scattering of light. The colour properties of the pigments are generally influenced by the particle size and particle size distribution; this also affects the surface roughness and thus the scattering of light.16 The pigment concentration of polyurethane-based coatings affects the surface roughness, therefore, the surface tension energy, which is an important parameter in determining their service life.17,18 One of the methods used to determine surface properties is the determination of water retention (hydrophobic) and water absorption (hydrophilic).19 Determination of the polymeric insulators as hydrophobic or hydrophilic is possible by contact angle measurement.20,21