Effect of a Triangular Configuration of Heat Exchanging Tubes on Local Heat Transfer Coefficient in Bubble Column Reactor

Abstract

The effect of a triangular configuration of heat exchanging tubes (HETs) on the instantaneous and local heat transfer coefficient (LHTC) has been investigated and quantified in an air-water bubble column (BC) utilising an advanced heat transfer technique. The bundle of heat exchange tubes was designed to cover 25% of the column's cross-sectional area (CSA) to simulate the heat exchanger tubes used in the industrial Fischer Tropsch (FT) process. The local heat flux, surface temperature, bulk temperature, and heat transfer coefficient (HTC) were investigated instantaneously in a Plexiglass BC under a wide range of superficial gas velocity (5-45 cm/s). The obtained results reveal that the presence of a bundle of (HETs) and their arrangement effect the (HTC) in the bubble column, where unsymmetrical profiles for (HTC) were obtained with triangular tube pitch arrangement. Additionally, steeper (HTC) profiles notice were when the triangular tube pitch arrangement was utilized. High (HTC) values were obtained at the core region of the column relative to the wall region under all the studied operating conditions. It was discovered that the local and (HTC) increase as superficial gas velocity increases despite the fact that the bubble column is heavily packed with a bundle of (HETs). The rise in HTCs was higher at the core than at the wall region of the column. For example, at a superficial gas velocity of 45 cm/s and at an axial height of 65 cm (Z/D=5), compared to the wall, the HTC in the core of the column increased by 131 %.