Natural-convection heat transfer to air from a vertical array of two horizontal circular cylinders

An experimental study was conducted of steady-state natural-convection heat transfer to air from two horizontal cylinders arranged in a vertical line. Variation of heat-transfer coefficients of both cylinders with cylinder spacing and surface temperature is presented, and it is shown that the heat transfer around the upper cylinder was strongly affected by the buoyant plume induced by the lower cylinder. Flow patterns and temperature profiles around the two-cylinder arrays are also presented, and interactions between the convections around each cylinder are discussed. On the basis of these experimental results, a simple model is proposed to evaluate the effects of the interaction of the heat-transfer coefficient of the upper cylinder. The behavior of the experimental heat-transfer coefficient is well elucidated by this model.