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Flow of Fluids in Food Processing
Published in Susanta Kumar Das, Madhusweta Das, Fundamentals and Operations in Food Process Engineering, 2019
Susanta Kumar Das, Madhusweta Das
This generalized equation for pressure drop in the packed bed is known as Ergun equation. In other form, it can be written as Δpd¯pρfh(G′)2(ε31−ε)=150μf(1−ε)d¯pu¯oρf+1.75=150NRe,p+1.75
Experimental Study on Combustion Characteristics of Lean Methane-air Mixture in a Combustor Filled with Staggered Alumina Cylinders
Published in Combustion Science and Technology, 2021
Meng Yue, Maozhao Xie, Junrui Shi, Hongsheng Liu
Figure 7 presents variations of the pressure drops and friction factors for the cold-state flow. The pressure drop in the reaction flow is very different from that at clod flow state. However, in this study the pressure drop is only measured for cold-state flow because the manometer can only be used at ambient temperature. The experimental results show that the measured pressure drop increases almost linearly with the increasing Re as shown in Figure 7a. The pressure drop predicted by Equation (4) is also shown in Figure 7a as the red curve. The same trend can be found in the prediction. The pressure drop in the present experiment was lower than the value calculated. The differences between the experiment and calculation are nearly constant. The reason is that the hydrodynamic characteristics in the structured and randomly packed beds are quite different, while the Ergun equation is valid only for the randomly packed bed. The tortuosity in the structured porous bed is much smaller, so that the pressure drop would be significantly lower than the value given by the Ergun equation. Figure 7b shows that as Re increased, the friction factor obviously decreased at the smaller Re and then the curves became relatively flat with Re increased. With increasing Re, the inertial effect is enhanced and becomes the dominant factor while the viscosity effect is weakened, thus the friction factor decreases with increasing Re.
Pressure Drops and Dryout Heat Fluxes of Packed Beds with Cylindrical Particles
Published in Heat Transfer Engineering, 2020
Liangxing Li, Shuangbao Zhang, Kailin Wang, Huasheng Wang
For a bed packed with non-spherical particles such as cylindrical particles, it is found that the pressure drops in the packed beds are much higher than the predictions of Ergun equation [20] (see Eq. 1) if the diameters of non-spherical particles such as cylinders are employed in the equation [15]. The increase in tortuosity is considered as the reason why non-spherical particle beds generated higher pressure drop. A generally-accepted approach by most researchers is to introduce a shape factor (ψ) in Eq. (1) and replace the Ergun constants with new constants based on their experimental data, yielding the following format of the pressure gradient in porous media.
Water Processing for Isotope Recovery Using Porous Zero Valent Iron
Published in Fusion Science and Technology, 2020
George Larsen, Simona E. Hunyadi Murph, Kaitlin Coopersmith, Lucas Mitchell
The pressure drop across a packed bed containing materials of interest is an important gas processing parameter. Gas will not flow through a loop if the pressure drop is too large for the system’s pump or blower. The pressure drop for a packed bed reactor can be calculated through the Ergun equation in the general case.20 For laminar flows, the simpler Kozeny-Carman equation can be used: