Abstract
Water bath fire tube heaters, so-called line heaters, are commonly used for industrial applications from small scales to large scales. The main problem of such heaters is the very low effectiveness of the heater due to the inefficient heat transfer within the heater (mainly between the fire tube and gas flow). The effects of using a specific type of twisting tape on the performance of these heaters, a typical heater used in natural gas pressure reductions points, were recently investigated. This study assesses the impacts of twisting tapes with different styles placed in the gas coil of the heater on the entropy generation and exergy performance of these heaters via computational fluid dynamic methods. For this, a typical gas mixture and typical line heater were considered. The results show that twisting tapes with larger numbers of twists and shorter twist pitch better enhance the exergy efficiency of the heater and decrease the rate of entropy generation over the gas heating process. Based on the obtained results, twisting tapes with the 17 and 68 twists decrease the rate of entropy generation by 16.8% and 27.1% and decrease the Bejan number for, respectively, over 36% and 77%.