Influencia de la convección natural externa y de la radiación externa sobre la convección forzada laminar en tubos horizontales

Abstract

A study of the laminar forced convection in a horizontal tube as the fluid flow interchanges heat with the environment by natural convection only and by natural convection and combined radiation is presented. Consequently, the temperature difference between the tube s superficie and the environment changes along the length of the tube. The external convection coefficient, which depends on the temperature differences, also changes along the length of the tube. The inclusion of thermic radiation has an important role when cooling is done by natural convection. The problem cited before is reformulated with the line s method. This method generates a first order ordinary differencid equations system, which is resolved with Runge-Kutta s algorithm using a reduced number of radial intervaiues. With the results obtained, some of the industrial applications in which air, water and oil flows are used in horizontal tube exposed to the environment composed of also air, water and oil, are examined. The results for each fluid combination leads to the fact that volumetric temperature distribution as well as temperature distribution in the tube s wall, are very sensitive to the variable natural convection and the radiation presence. Theses results with only ten lines meet satisfactorily those obtained by techniques mostly numerical using extremely thin meshes.

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