Showing papers by "Ralph L. Webb published in 1989"
TL;DR: The methode LMED (difference d'enthalpie logarithmique moyenne) as mentioned in this paper is a methode NUT-efficacite for the conception de tours de refroidissement.
Abstract: Developpement de la methode NUT-efficacite pour la conception de tours de refroidissement: introduction de l'enthalpie de l'air sature en parametre et definition du nombre d'increments correspondant a la precision desiree Presentation de la methode LMED (difference d'enthalpie logarithmique moyenne) et comparaison des deux methodes sur des exemples
199 citations
TL;DR: In this article, the authors deal with effectiveness-NTU relations for crossflow heat exchangers and propose algebraic relations for two limiting cases: unmixed and mixed flows, which will yield performance between the above limiting cases.
Abstract: This paper deals with effectiveness-NTU relations for crossflow heat exchangers. The literature contains algebraic relations for two limiting cases: “unmixed” and “mixed” flows. These are simply thermodynamically defined limiting cases. The authors argue that many practical flow situations may not satisfy either of the above cases. Rather, conditions of “partial mixedness” may exist, which will yield performance between the above limiting cases. Algebraic relations are provided to calculate the effectiveness-NTU relationship for arbitrary values of partial mixedness. Graphs are provided for 25, 50, and 75 % mixedness. It is argued that inadequate knowledge of the actual flow structure exists to define the actual mixedness that will occur in various actual heat exchanger-surface geometries. Definition of the actual mixedness would require measurement of the spatial temperature distribution leaving the heat exchanger. The problem addressed is of particular importance for high effectiveness designs....
14 citations
01 Jan 1989
TL;DR: In this article, the results of accelerated particulate fouling tests performed on two enhanced tubes used in water chiller condensers were described. But the results were limited to the use of a single tube and the main purpose of the tests was to determine the fouling rate of the enhanced tubes compared to that of a plain tube.
Abstract: This paper describes the result of accelerated particulate fouling tests performed on two enhanced tubes used in water chiller condensers. The fouling tests were performed using ferric oxide powder as the foulant material with foulant concentrations between 1000 and 2000 ppm. Data are also presented for on-line brush cleaning and high-velocity flush cleaning. The water used in these tests is much dirtier than would be expected in an actual operating system. The key purpose of the tests was to determine the fouling rate of the enhanced tubes compared to that of a plain tube.
7 citations