Fluid Flow in Heat Exchangers Whose Flow Passages Contain Periodically Deployed Tubes

Abstract

This article is concerned with duct flows in which the fluid encounters a patterned array of structures along its path of flow. A heat-exchanger tube bank is an example of a patterned array of structures, whose deployment repeats periodically in the flow direction. There are three issues to be highlighted here. The first relates to the model used in standard commercial software that deals with periodic structures. That model envisions the periodic structure to be a porous medium. This approach is also used in the analysis of heat-exchanger performance.The second issue concerns the nature of the flow that follows the breakdown of the friction-dominated laminar regime. The third focus is the identification of the location of the maximum velocity within the periodic structure. It was found that the porous-medium model is a viable approach, thereby adding support to current heat and fluid-flow models of heat exchangers. The nature of the flow following the breakdown of the friction-dominated laminar regime is shown to be a continuation of laminar flow, but with important contributions of momentum transfer. This finding definitively excludes the hypothesis that the onset of turbulence occurs immediately following the breakdown of laminar flow. The location of the maximum velocity was shown not to correspond to the location of the minimum free-flow area.