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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.


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Patent
07 Apr 1983
TL;DR: In this paper, the authors proposed a method for processing a material into a granular product, which involves atomising the suspension, feeding a heat transfer medium (4) in a helical stream into a zone which is situated below the atomising zone, drying the suspension with the aid of the heat transferred medium in cocurrent and in countercurrent motion downwards up to a temperature at which the required product properties are achieved, and ducting off the heat-treated material from the heat treatment zone.
Abstract: The invention involves the technology of processing a material into a granular product. The invention involves atomising the suspension (1), feeding a heat transfer medium (4) in a helical stream into a zone which is situated below the atomising zone, drying the suspension (1) with the aid of the heat transfer medium (4) in cocurrent and in countercurrent thereto while at the same time separating the fine fractions (5) of the dried material by the cocurrent stream of the heat transfer medium (4), ducting off the spent heat transfer medium (4), the heat treatment of the grains formed during drying in countercurrent to the specified heat transfer medium (4) during their helical motion downwards up to a temperature at which the required product properties are achieved, and ducting off the heat-treated material from the heat treatment zone. The device for implementing this process comprises a chamber (3) which is designed so as to have a cross-section which varies with height, means (2) for atomising the suspension (1), which are arranged in the upper part of chamber's (3) which has the largest dimensions, means (13,27) for feeding in the heat transfer medium (4), which are arranged helically in the lower part of the chamber (3), the pitch and the diameter of the helix turns being designed to a variable with the chamber height and increasing in size in the direction towards the means (2) for atomising the suspension (11). The invention can be used in the heat treatment of mineral suspensions, for example of chalk and cement raw material muds or ore concentrates and for processing wastes in various branches of production.

3 citations

Journal ArticleDOI
TL;DR: In this article, a double-pass laminar countercurrent operation was investigated theoretically by using an eigenfunction expansion in power series, and the theoretical predictions of mass-transfer efficiency enhancement in doublepass parallel-plate mass exchangers were represented graphically and compared with those in an open duct of single-pass operation.
Abstract: A permeable barrier was inserted to divide an open duct into two subchannels of uniform wall fluxes for conducting double-pass laminar countercurrent operations. The mass transfer rate of such a double-pass device was substantially improved and has been investigated theoretically by using an eigenfunction expansion in power series. The theoretical predictions of mass-transfer efficiency enhancement in double-pass parallel-plate mass exchangers were represented graphically and compared with those in an open duct of single-pass operation (without a permeable barrier inserted). The results show that the double-pass operation can effectively enhance the mass transfer efficiency and especially when the permeable-barrier position is appropriately adjusted.

3 citations

Journal ArticleDOI
TL;DR: Analysis of the countercurrent process provides some insights into the importance of tracer exchange between capillaries in vascular beds not arranged in orderly countercurrent networks.
Abstract: A model for passive countercurrent capillary exchange is presented, and solutions for transient responses are obtained. The model is applied to an analysis of hydrogen gas exchange in the renal medulla. Estimates of medullary flow per gram tissue are in reasonable agreement with estimates obtained with vascular tracers and similar to the values for whole kidney. Semilog plots of tissue washout curves appear nearly linear but will overestimate flow if the countercurrent process is inefficient and will underestimate flow if the countercurrent exchange is efficient. Analysis of the countercurrent process also provides some insights into the importance of tracer exchange between capillaries in vascular beds not arranged in orderly countercurrent networks. Capillaries in other vascular beds that are close enough together to permit considerable exchange of inert gas tracers may simulate countercurrent effects if some of the adjacent capillaries are in countercurrent or staggered cocurrent arrangements.

3 citations

Journal ArticleDOI
TL;DR: Weakly nonlinear stability analysis of a falling film with countercurrent gas-liquid flow has been investigated in this paper, where both supercritical stability and subcritical instability are possible for a film flow system when the gas flows in the countercurrent direction.
Abstract: Weakly nonlinear stability analysis of a falling film with countercurrent gas–liquid flow has been investigated A normal mode approach and the method of multiple scales are employed to carry out the linear and nonlinear stability solutions for the film flow system The results show that both supercritical stability and subcritical instability are possible for a film flow system when the gas flows in the countercurrent direction The stability characteristics of the film flow system are strongly influenced by the effects of interfacial shear stress when the gas flows in the countercurrent direction The effect of countercurrent gas flow in a falling film is to stabilize the film flow system

3 citations

Patent
15 May 1971
TL;DR: In this article, a guide strip passes spirally through the shell and thereby forms an elongated helical flow channel for one medium, through which the tube bundle for the other medium also extends.
Abstract: Countercurrent heat exchanger consists of an elongated shell, feed and discharge pipes for two heat exchange media and a system of tubes for one of these. A guide strip passes spirally through the shell and thereby forms an elongated helical flow channel for one medium, through which the tube bundle for the other medium also extends.

3 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202358
2022115
202127
202041
201947
201849