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.

Pass-through furnace for heat recovery in the heat treatment of aggregates of metallic articles or parts

Abstract: For recovery of heat, aggregates of metallic articles through which gas can flow are carried in a succession of baskets through a preheat zone, a treatment zone and a cooling zone of a heat treatment furnace and a heat transfer gas is constrained to flow vertically through the baskets in succession, beginning with the basket farthest advanced through the furnace, so far as concerns the basket in the cooling and preheat zone, the baskets having bottoms through which the gas can flow into or out of the aggregates. The heat transfer gas flows directly from the cooling zone. This may be done through the treatment zone where it may pick up additional heat. Heat may be removed from the heat transfer gas in a return circulation path outside the furnace. When the path of the basket is horizontal through the preheat and cooling zones, the flow of heat transfer gas is in transverse countercurrent to the advancement of the work, but if vertical transport of baskets is provided in the preheat and cooling zones, simple countercurrent operation can be provided with vertical flow through the baskets and aggregates. The ratio of heat capacity flow of the work to that of the heat transfer gas in the cooling and/or preheat zones is controlled to keep these heat capacity flows approximately equal and the preheat and cooling zones are so designed that the thermal exchange coefficient epsilon between the work and the heat transfer gas is consistently greater than 0.5.

Process and device for obtaining a compressed product by low temperature separation of air

Abstract: The process and device are used to obtain a compressed product by low temperature separation of air in a rectification system which has a pressure column and a low pressure column. A first flow of compressed and purified feedstock air is cooled in a main heat exchanger system and is fed into the pressure column. At least one fraction from the pressure column is expanded and fed into the low pressure column. An oxygen-rich fraction from the low pressure column is liquid-pressurized and delivered to a mixing column. A heat exchange medium is fed into the lower area of the mixing column and is brought into countercurrent contact with the oxygen-rich fraction. A gaseous top product is removed from the upper area of the mixing column. A product fraction is removed from the rectification system, liquid-pressurized, vaporized in indirect heat exchange with the gaseous top product of the mixing column and is withdrawn as the compressed product. Indirect heat exchange is carried out for vaporization of the liquid-pressurized product fraction in the main heat exchanger system.

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

Abstract: A differential equation model of the renal countercurrent system has been developed and physiological data from nephron segments were incorporated together with recently suggested urea recycling from renal pelvis to inner medulla and, particularly, an exponential reduction in the number of collecting tubules towards the renal papilla. The role of these features for the countercurrent concentrating mechanism has been studied by simulation runs. The computations, using the multiple shooting method, provide predictions about concentration profiles for salt and urea in tubes (nephron segments) and in the central core along the entire medullary countercurrent system. The results indicate that this model, without active salt or urea transport in the inner medulla, yields concentration gradients along the medullary axis compatible with those measured in the tissue.