Abstract
Abstract This paper addresses the practical calculation of the thermal performance of industrial chimneys by means of recent results in forced convection heat transfer. The temperature decay of the combustion gases is a result of heat transfer processes involving both internal forced convection and external heat transfer to the surroundings, and the analysis of the problem is scarcely treated in the energy- and environmental-related literature. Thermal design and performance estimations of chimneys are therefore based on engineering rules of thumb dictated by experience. The aim of this paper is to introduce rigorous heat transfer results into the subject, but from a framework accessible to design engineers. To this end, a 1-D lumped model of this kind of situations is used (Campo and Lacoa, 1994). Although largely simplified, the model provided adequate estimates of the mean bulk temperatures when compared with those computed with a 2-D distributed model (Campo and Lacoa, 1995), thus satisfying the requirements of simplicity and accuracy for the present purpose. The paper describes the design criteria for thermal calculation of industrial chimneys, the application of the 1-D lumped model through the use of standard heat transfer correlations, and several examples. The sequence of calculations is easy to accomplish and it is explained in such a way that it can be directly employed by engineers engaged in thermal design of tall chimneys.
Published Version
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