Computational Fluid Dynamics Based Approach for Predicting Heat Transfer and Flow Characteristics of Inline Tube Banks with Large Transverse Spacing

Abstract

Inline tube configuration is used in various heat exchangers, such as power plant superheaters. The important design parameters are the longitudinal and transverse spacing between the tubes, as they determine the flow and heat transfer characteristics of the tube bank. In superheaters, the transverse tube spacing is often relatively large in order to avoid clogging of the flow passages due to deposition of particulate matter. To design and optimize superheaters is a challenging task, especially because of the complicated vortex-shedding phenomenon. This also complicates the computational fluid dynamics (CFD) modeling, because unsteady simulation approach is required. This paper discusses about various factors that affect the accuracy of prediction of heat transfer and flow characteristics of inline tube banks with large transverse spacing. A suitable CFD model is constructed by comparing different boundary conditions, domain dimensions, domain size, and turbulence models in unsteady simulations. The numerically obtained Nusselt numbers are evaluated against available heat transfer correlations. The correlation of Gnielinski is recommended for tube banks with large transverse spacing, as it agrees within ±13% with the numerically obtained values. The guidelines presented in the paper can serve as reference for future simulations of unsteady flow phenomena.