Visualization of the natural convection heat transfer of two heating spheres varying horizontal and vertical pitches

Abstract

Natural convection heat transfer of two heating spheres was investigated varying the horizontal and the vertical pitches. Based on the analogy concept, mass transfer experiments were carried out by adopting a copper sulfate-sulfuric acid (CuSO4-H2SO4) electroplating system. The sphere diameter was varied from 6 to 40 mm, which correspond to Grd of 9.10 × 103–2.70 × 106. The heat transfer of two spheres for both in-line and staggered arrangements under laminar and turbulent flow conditions were analyzed by four distinct effects: stagnant, preheating, initial velocity and chimney-like effects. The heat transfer of upper sphere was either enhanced by the initial velocity effect or impaired by the preheating effect. Notable observations were that the heat transfer of lower sphere was also affected by the stagnant flow and chimney effects due to the existence of the upper sphere. This was evidenced by the visualization of the local heat transfer by copper plating pattern.