Heat transfer performance analysis of steam boilers-fin and tube heat exchangers under varying geometric dimensions

This study analyses the heat transfer performance of fin and tube heat exchangers in steam boilers, focusing on the impact of geometrical parameters such as the number of tube rows, tube diameter, fin pitch, fin thickness, and fin surface area on thermal efficiency. Flue gases typically exit at temperatures between 298K and 523K, resulting in energy losses of 10%-30% in industrial boiler systems. The analysis employed COMSOL Multiphysics® to model flue gas flow using three approaches: laminar flow modelling and two turbulence models (k-epsilon and k-omega), all based on Reynolds-averaged Navier-Stokes equations. The k-omega model provided the best alignment with experimental data (Wang et al., 2006), enhancing heat transfer predictions. The results show that heat transfer stabilises beyond six tube rows, with Nusselt numbers ranging from 10.97 to 21.16 and effectiveness reaching 0.54. Three parameters proved critical for maximising heat transfer performance: fin surface area, fin thickness, and tube diameter. The optimal flue gas flow rate was determined to be within the range of 0.02 to 0.2 kg/s. These findings guide the design of efficient heat exchangers for waste heat recovery, minimising energy losses in industrial applications.