China
Africa
Explore chapters and articles related to this topic
Gas-Solid Noncatalytic Reactions
Published in James J. Carberry, Arvind Varma, Chemical Reaction and Reactor Engineering, 2020
L. K. Doraiswamy, B. D. Kulkarni
Even in instances when the bulk-flow effects are not present (no mole change), pressure gradients may arise due to temperature gradients. In the presence of pressure gradients it has been shown (Wong et al., 1976; Hite and Jackson, 1977) that the conventional Weisz-Prater temperature holds true only in the case of Knudsen diffusion. Significant alterations occur 2 when bulk diffusion prevails. In fact, an additional term (βm2/4) is included in the equation for maximum temperature rise where βm refers to the thermicity factor. Pressure gradients can thus have a significant effect on the conversion-time relations, depending on the regime of diffusion. In the case of gas-solid reactions, the presence of structural effects continually alters the diffusional regimes. The effects of pressure gradients cannot therefore be ignored all through the course of conversion. The influence of pressure gradients in gas-solid reactions following SIM has been examined by Deb Roy and Abraham (1974) and Turkdogan et al. (1973). Detailed numerical solutions have been obtained to the pressure gradients that arise because of Knudsen flow in the ash layer with small pores and due to the reactant gas having a diffusivity different from that of the product.
Indoor Air Quality Investigation and Mitigation
Published in Benjamin Alter, Environmental Consulting Fundamentals, 2019
Chemical smoke tubes can be used to determine pollutant pathways in the study area, between sections of the building, as well as from outside the building. A micromanometer (or equivalent) can measure the pressure gradient between areas. Switching air handlers or exhaust fans on and off, opening and closing doors, and simulating the range of operating conditions in other ways can reveal the different ways that airborne contaminants move within the building.
Fluid Mechanics
Published in Raj P. Chhabra, CRC Handbook of Thermal Engineering Second Edition, 2017
Stanley A. Berger, Stuart W. Churchill, J. Paul Tullis, Blake Paul Tullis, Frank M. White, John C. Leylegian, John C. Chen, Anoop K. Gupta, Raj P. Chhabra, Thomas F. Irvine, Massimo Capobianchi
The first term on the right side of Equation 2.6.6 contains the influence of wall shear stress. Since τw is always positive in the direction of the flow, it always causes θ to increase with x. The second term on the right side contains the pressure gradient, which can have either sign. Therefore, the effect of the pressure gradient can be to either increase or decrease the rate of growth of boundary layer thickness.
Influence of polymers on flow and heat transfer due to peristaltic waves: a molecular approach
Published in Waves in Random and Complex Media, 2022
Maria Athar, Khalid Saeed, Adeel Ahmad, Junaid Anjum
The study of the pressure gradient is important because it has a great impact on a flow. It is well known that the shear stress due to viscosity results in a retarding effect on the flow. Such an effect is overcome by providing the negative pressure gradient to the flow which is advantageous as it enables the flow. The adverse pressure gradient is associated with a positive pressure gradient, and it has the opposite effect (i.e. it resists the flow). The negative pressure gradient is observed in Figure 1. As the channel width becomes small, an increase in the negative pressure gradient is observed. This figure also shows that by increasing polymer concentration, the absolute value of the pressure gradient increases. This means that the presence of polymers significantly affects the peristaltic flow. Figures 2 and 3 show that an increase in relaxation time a and Weissenberg number Wi significantly increases the pressure gradient in all parts of the channel except for the wider part. Weissenberg number measures the ratio of elastic to viscous forces, and a greater Weissenberg number means higher the elastic effects. Figure 4 shows that increasing the phase difference results in a decrease in the pressure gradient.
Hydrodynamics of air and oil–water dispersion/emulsion in horizontal pipe flow with low oil percentage at low fluid velocity
Published in Cogent Engineering, 2018
Laura Edwards, Dillon Jebourdsingh, Darryan Dhanpat, Dhurjati Prasad Chakrabarti
Research into three phase flow characteristics is limited and relies on an adjusted two phase model to account for the physical properties of the liquid phases. Generally, the pressure gradient increases in proportion to increasing gas and liquid flow rates. More specifically, the pressure gradient is dependent on the flow regime. Low gas and liquid superficial velocities such as to cause stratified and partially mixed oil and water flow, causes slight increases in pressure gradient. Increasing the superficial gas velocity over 1 ms−1 to the slug or continuous oil–water flow results in a strong increase in pressure drop. Moreover, for dispersed liquid systems, the pressure gradient was found to be higher for oil dominated as compared to water dominated due to the change in the continuous phase (Sarica & Zhang, 2006). Furthermore, a two-fluid model has been used by treating the dispersed phase as a continuous phase that interacts with the actual continuous phase (Brennen, 2005). The two liquid phases are reduced to a single phase, a pseudo-liquid, allowing it to be modelled as two phase flow. Three phase pressure drop was examined by Pan (1996) in which the two immiscible liquid phases were treated as a single phase, enabling two phase correlations to be used to model the pressure gradient. In the present study, it has been tried to explore air and emulsion phase flow patterns and their transitions. This is the novel part of the study.
Entropy analysis of peristaltic flow over curved channel under the impact of MHD and convective conditions
Published in Numerical Heat Transfer, Part B: Fundamentals, 2023
Arooj Tanveer, Muhammad Bilal Ashraf, Maryam Masood
The goal of this section is to assess the efficacy of the governing problem’s velocity, temperature profile, pressure gradient, stream function, entropy generation rate, and Bejan number. The effect of the Hartman number on axial velocity is shown in Figure 2. This graph demonstrates how the flow has slowed as a result of the rising Hartman number. Higher Hartman numbers are compatible with a strong external magnetic field. This force illustrates the resistance of the flow field to the flowing material. Figure 3 illustrates that velocity is decreasing with an increase in flow rate q. The temperature distribution graphs are plotted for different values of Biot number Bi and Brinkman number Br. An increasing trend is observed for rising Bi values as shown in Figure 4. It is due to the increase in resistance to heat transfer from the surface to its surroundings. The impact of Br on temperature profile is seen in Figure 5. This is due to the addition of a viscous dissipation term. The temperature of the fluid is consequently increased as a result of some of the liquid’s kinetic energy being converted to thermal energy. It would seem justified in this circumstance for the curved channel to have a better temperature distribution. The pressure gradient is shown to be increasing with higher values of the viscosity coefficient s in Figure 6. According to Figure 7, an increase in magnetic parameters causes a decrease in the pressure gradient. It is as a result of the Lorentz force’s resistance. As shown in Figure 8, it is clear that the pressure gradient changes dramatically as curvature increases. It is because the pressure gradient lessens as we travel near an occlusive zone.