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.

Permeability criteria for effective function of passive countercurrent multiplier

Abstract: The urine concentrating effect of the mammalian renal inner medulla has been attributed to countercurrent multiplication of a transepithelial osmotic difference arising from passive absorption of N...

Analysis of Membrane Separation Parameters. II. Counter-current and Cocurrent Flow in a Single Permeation Stage

Abstract: Analytical expressions are presented for calculating the extent of separation of binary gas mixtures achievable in a permeation stage, as well as the required membrane area, when the high- and low-pressure streams in the stage flow either countercurrently or cocurrently to each other. The derivations are similar to those of Oishi et al., but are cast in a form suitable for computer calculations. The results of a parametric study on the separation of oxygen from air are presented for four different flow patterns inside the stage: (a) countercurrent flow, (b) cocurrent flow, (c) cross-flow, and (d) perfect mixing. In the first three cases it is assumed that no mixing occurs on the two sides of the stage (or membrane). The type of flow in the permeation stage can have a significant effect on the degree of separation, but has relatively little effect on the membrane area at low separation factors. Countercurrent flow is the most efficient flow pattern, whereas perfect mixing is the least efficient on...

Combination direct and indirect closed circuit evaporative heat exchanger with blow-through fan

Abstract: A heat exchange apparatus which can be used as an evaporative condenser, fluid cooler or wet-air cooler, is provided with a direct evaporative heat exchange section overlying an indirect evaporative heat exchange section. An air entry zone common to both heat exchange sections receives an air stream blown into this zone by at least one fan, thereby pressurizing the plenum such that the air stream is forced to split and enter each section while inside the apparatus. This eliminates the need for separate air entries, thus condensing the size and cost of the apparatus, while increasing heat exchange capacity. A countercurrent air flow pattern through the direct section provides a uniformly cooled evaporative liquid for use in the indirect section. The evaporative liquid flow is parallel to the air stream provided in the indirect section. A process fluid inside the circuits of the indirect section can accept or reject heat from the evaporative liquid received from the direct section, with a part of the heat being is transferred into the indirect section air stream in sensible and latent form, thus increasing or decreasing the enthalpy of the air stream. The remaining heat can be either stored or released from the evaporative liquid to increase or decrease its temperature. The evaporative liquid is collected in a sump and then pumped upwardly for re-distribution across the direct evaporative heat exchange section.