Topic

# 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.

##### Papers published on a yearly basis

##### Papers

More filters

••

TL;DR: In this article, a theory for the fully-developed flow of gas and particles in a vertical pipe is presented, and the relation between gas pressure gradient and the flow rates of the two phases is predicted, over the whole range of cocurrent and countercurrent flows, together with velocity profiles for both phases and the radial concentration profile for the particles.

Abstract: A theory is presented for the fully-developed flow of gas and particles in a vertical pipe. The relation between gas pressure gradient and the flow rates of the two phases is predicted, over the whole range of cocurrent and countercurrent flows, together with velocity profiles for both phases and the radial concentration profile for the particles. The gas and the particles interact through a drag force depending on their relative velocity, and there are mutual interactions between pairs of particles through inelastic collisions. This model is shown to account for marked segregation of gas and particles in the radial direction, and the predicted relation between the pressure gradient and the flow rates of the two phases is surprisingly complex.

613 citations

••

TL;DR: A new simplified three-dimensional bioheat equation is derived to describe the effect of blood flow on blood-tissue heat transfer and shows that the vascularization of tissue causes it to behave as an anisotropic heat transfer medium.

Abstract: A new simplified three-dimensional bioheat equation is derived to describe the effect of blood flow on blood-tissue heat transfer. In two recent theoretical and experimental studies [1, 2] the authors have demonstrated that the so-called isotropic blood perfusion term in the existing bioheat equation is negligible because of the microvascular organization, and that the primary mechanism for blood-tissue energy exchange is incomplete countercurrent exchange in the thermally significant microvessels. The new theory to describe this basic mechanism shows that the vascularization of tissue causes it to behave as an anisotropic heat transfer medium. A remarkably simple expression is derived for the tensor conductivity of the tissue as a function of the local vascular geometry and flow velocity in the thermally significant countercurrent vessels. It is also shown that directed as opposed to isotropic blood perfusion between the countercurrent vessels can have a significant influence on heat transfer in regions where the countercurrent vessels are under 70-micron diameter. The new bioheat equation also describes this mechanism.

428 citations

•

01 Jan 1960

TL;DR: In this article, the authors present an approach to unit operations in chemical engineering, including the following: Mass Transfer, Heat Transfer, Evaporation and Crystallization, Humidification, and Drying.

Abstract: Unit Operations in Chemical Engineering. STAGE OPERATIONS. Mass Transfer Operations. Phase Relations. Equilibrium Stage Calculations. Countercurrent Multistage Operations. Countercurrent Multistage Operations with Reflux. Simplified Calculation Methods. Multicomponent State Operations. MOLECULAR AND TURBULENT TRANSPORT. Molecular Transport Mechanism. Differential Mass, Heat, and Momentum Balances. Equations of Change. Turbulent-Transport Mechanism. Fundamentals of Transfer Mechanisms. Interphase Transfer. APPLICATIONS TO EQUIPMENT DESIGN. Heat Transfer. Mass Transfer. Simultaneous Heat and Mass Transfer--Humidification. Simultaneous Heat and Mass Transfer--Drying. Simultaneous Heat and Mass Transfer--Evaporation and Crystallization. The Energy Balance in Flow Systems. Fluid Motive Devices. Particulate Solids. Flow and Separation through Fluid Mechanics.

375 citations

••

TL;DR: In this article, the authors report flow experiments involving cocurrent and countercurrent spontaneous water/oil imbibition performed on the same laterally coated sample of a natural porous medium with local saturation measurements and various boundary conditions.

Abstract: This paper reports flow experiments involving cocurrent and countercurrent spontaneous water/oil imbibition performed on the same laterally coated sample of a natural porous medium with local saturation measurements and various boundary conditions. The experiments with countercurrent imbibition showed slower oil recovery, a smoother water/oil front, and slightly lower ultimate oil recovery than those with predominantly cocurrent imbibition. Numerical simulations revealed that the relative permeabilities that enabled good prediction of countercurrent oil recovery rate are about 30% less than the conventional cocurrent relative permeabilities at a given water saturation. Viscous coupling is assumed to be the origin of this difference. A new formulation of Darcy equations that uses a matrix of mobilities was found to be in qualitative agreement with experimental results.

271 citations

••

TL;DR: In this article, a layered pressure swing adsorption (LPSA) process is proposed to selectively remove carbon dioxide and nitrogen from low and medium natural gas flowrates, which is composed of a zeolite 13X to selectively removing carbon dioxide followed by a layer of carbon molecular sieve 3K to make the separation of nitrogen from methane.

268 citations