Optimum spacing for maximum heat transfer density in tube bundle.

The optimal spacing between tubes in a tube bundle is of fundamental and practical importance. This paper numerically investigates heat transfer, fluid dynamics, fluid forces, vortex shedding frequency, optimum spacing, and relationship between flow structures and heat transfer from a group of tubes in a tube bundle for the radial gap spacing ratio g^* (=g/d) = 0.1–5, where d is the diameter of a tube. The key objective is to find the optimum g^* for maximum heat transfer density. The heat transfer from the tubes is highly sensitive to g^*. With increasing g^*, the heat transfer density first increases and reaches a peak before declining, yielding the optimum spacing at g^* = 0.5 (void fraction, VF = 0.56) or g^* = 0.6 (VF = 0.60) depending on the tube orientations with respect to the flow. The small tubes with g^* > 0.25 perform better in view of heat transfer than the big tube of the bundle diameter. In addition, g^* effects on fluid forces, vortex shedding frequencies, and wake structure and their relationships with heat transfer are discussed in detail. [ABSTRACT FROM AUTHOR]