- Bejan, A., The optimal spacing for cylinders in crossflow forced convection,
Trans. ASME, J. Heat Transf. (USA), vol. 117 no. 3
pp. 767 - 70 .
(last updated on 2007/04/06)
In this paper I draw attention to a new fundamental aspect of the heat transfer performance of a bundle of parallel cylinders with crossflow forced convection, namely, the maximization of the thermal contact between the bundle and the fluid, when the volume occupied by the bundle is fixed. In the experiments described by Jubran et al. (1993) we have seen empirical evidence that the total heat transfer rate is maximum when the cylinder-to-cylinder spacing S has a certain value. This finding is important because it has been overlooked for decades, while forced convection from cylinders in crossflow grew into one of the most researched topics in heat transfer. Jubran et al. (1993) did not offer any theoretical explanation or way of predicting the optimal spacing. My objectives in this note are two: (a) I will show that the optimal S/D ratio can be predicted based on a simple theory (Bejan and Sciubba, 1992; Bejan, 1993), and that contrary to the conclusion of Jubran et al. the Sopt/D ratio is not a constant. (b) I will also show that, if the theory (a) is known, all the empirical information necessary for predicting Sopt/D accurately is already available in the large volume of heat and fluid flow data published for cylinders in crossflow