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.

An experimental investigation of the countercurrent flow limitation

Abstract: An Experimental Investigation of the Countercurrent Flow Limitation.(May 2008) Matthew A. Solmos, B.S., Purdue University Chair of Advisory Committee: Dr. Karen Vierow A new correlation for the prediction of the Countercurrent Flow Limitation (CCFL) in a large diameter tube with a falling water film is proposed. Different from previous correlations, it predicts the onset of flooding by considering the relative velocities of the working fluids and the film thickness of the liquid layer. This provides a more complete accounting of the physical forces contributing to CCFL. This work has been undertaken in order to provide a better estimate of CCFL for reactor safety codes such as MELCOR, MAAP, and SCDAP/RELAP. Experiments were conducted to determine the CCFL for a 3-inch inner diameter smooth tube with an annular liquid film and air injection from the bottom. The size of the test section and the range of working fluid flow rates were based on a scaling analysis of the surge line of a Pressurized Water Reactor pressurizer. An experimental facility was designed and constructed based on this analysis in order to collect data on the CCFL phenomenon. In order to capture some of the physical phenomena at the onset of flooding visual pictures were taken at high speed. These pictures provided a new understanding of the process of transition to flooding. The facility also produced a new set of flooding data. This can also lead to a more comprehensive mechanistic model.

Countercurrent flow in a semi-infinite gas centrifuge. preliminary results

Abstract: Preliminary results on optimum and practical countercurrent tlow in gas ultracertrifuges are presented. An irternal flow problem for countercurrent centrifuges was solved for a semi-infinite-length case. The lowest mode results indicate that at values of the speed parameter above about 2.5, decay lengths are higher than those calculated in an isothermal version of the problem. (J.R.D.)

Influence of membrane selectivity on helium recovery from natural gas

Abstract: The process of helium recovery from helium-containing natural gas at high pressure using membrane technologies has been addressed. A two-stage scheme of countercurrent flow cascade with recirculation splitter as the second step has been chosen as the processing route. The influence of membrane selectivity on energy efficiency of natural gas cleaning of helium has been examined.

TRANSPORT AND EXCHANGE OF RESPIRATORY GASES IN THE BLOOD | Root Effect: Molecular Basis, Evolution of the Root Effect and Rete Systems

Abstract: The Root effect describes the property of hemoglobins (Hbs) of some fishes such that in the presence of acid, it is impossible for the Hb molecule to be completely saturated with oxygen, even at extremely high oxygen partial pressures. The Root effect, together with a vascular countercurrent system called rete mirabile, is essential for diffusive oxygen supply to poorly vascularized fish retinas. In several fish groups the Root effect has been co-opted for oxygen secretion into the swimbladder. Structure–function analyses show that the Root effect is not an exaggerated Bohr effect of mammalian Hb but based on a different molecular mechanism. Root-effect Hb evolved before a choroid rete mirabile in the eye or a swimbladder rete mirabile and may originally have facilitated blood oxygen transport at moderate pH values, just like Bohr-effect Hb of mammals.