Study of the influence of the mesh density on the heat transfer coefficient in numerical modeling of the transverse flow around a tube bundle of the corridor type

Abstract

Background: The paper considers numerical modeling of the transverse flow around a five-row corridor-type tube bundle with an air flow at coupled heat exchange. The studied model is typical for air-cooled heat exchangers such as air condensers, oil coolers or cooling towers. The outer surface of the pipes had a temperature higher than the temperature of the air flow. The air flow rate corresponded to the Reynolds number in the narrow section of the tube bundle, typical for heat exchangers of the abovementioned type. The results of numerical modeling are determined by the quality of the mesh. At the same time, the more the calculation cells and the smaller their size, the more computational power and time budget are required to solve the problem. However, the results obtained are closer to a field experiment.

Aim: Determination of the level of detail of the mesh, at which obtaining correct results of numerical simulation of coupled heat transfer is possible.

Results: The influence of the quantitative characteristics of six mesh variants on the value of the average heat transfer coefficient is estimated. The variants differed in the degree of detail: the number and size of cells (from large to small). In each case, the values of the average heat transfer coefficient are obtained, determined by the degree of error of the numerical experiment. The data obtained were compared with the data obtained when solving the criterion equations of convective heat transfer using three methods.

Conclusion: The error of finding the heat transfer coefficient by the considered methods is determined. It is found that the results of numerical modeling with a high degree of detail are close to the results obtained in the calculation using the Baer method. The results obtained can be useful in numerical modeling of flows in heat exchangers with transverse flow around tube bundles.

Keywords

convection / heat transfer coefficient / numerical modeling / Computational Fluid Dynamics (CFD) / mesh / tube bundle

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