Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

A Semi-Analytical Solution for Countercurrent Spontaneous Imbibition in Water-Wet Fractured Reservoirs

Abstract: Countercurrent spontaneous imbibition (SI) is an important flow mechanism for oil recovery in fractured reservoirs during waterflooding. SI plays a key role in the mobilization of oil in the matrix because it facilitates water infiltration by capillarity even when the matrix permeability is low, which limits fluid transport by advection. However, the modeling of SI in fractured media under dynamic conditions has been insufficiently studied. Most imbibition models assume conventional exponential functions and empirical constants based on experimental results of oil recovery under static conditions. Thus, the modeling of water distribution in the fracture and the matrix has been ignored which may lead to incorrect estimates of the efficiency of countercurrent SI to recover oil. Using the classic fractional flow equation, we present a semi-analytical solution to model countercurrent SI in a water-wet fractured medium by including a transfer function to account for continuous fluid exchange between the fracture and the matrix. The model is numerically solved using finite differences by including an effective imbibition time as a function of water advance in the fracture, which overcomes the difficulty of solving iterative numerical summations as shown in other imbibition models. The novelty of the presented solution is that it enables the modeling of water infiltration in the matrix under dynamic conditions. We verified the semi-analytical model against 2D numerical simulations and validated against experimental data to demonstrate that the model accurately predicts oil recovery and water infiltration in the matrix.

Mathematical modeling of continuous production of carbon nanofibers from methane in a reactor with a moving bed of a nickel-containing catalyst

Abstract: The continuous production of carbon nanofibers from methane on a Ni/Al2O3 catalyst (90 wt % Ni) in a plug-flow reactor with countercurrent or cocurrent flows of the phases is considered. The methane conversion, specific carbon content, and relative catalyst activity in the reactor are calculated as functions of the longitudinal coordinate, temperature, and specific gas and catalyst flow rates. It is shown that, at a fixed specific methane flow rate, there is an optimal specific catalyst flow rate at which the specific yield of carbon nanofibers is maximal, with this yield in the cocurrent reactor being higher than that the countercurrent reactor. At certain parameter values, the reactor may contain a region with a virtually deactivated catalyst, which is indicative of inefficiency of use of the reactor space.

Mass transfer between isobutanol and water in concurrent flow through a packed column

Abstract: Local and mean rates of transfer of isobutanol into the water-rich phase and of water into the isobutanol-rich phase were measured in concurrent upward flow through a column packed with glass spheres. The use of a two-component system permitted determination of the individual-phase coefficients. These are the first rate measurements for concurrent flow in a packed bed. Because the flow rates are not limited by flooding, much higher rates of transfer are attainable than in countercurrent flow.