Triple-finned tubes – Increasing efficiency, decreasing CO2 pollution of a steam boiler

Abstract

This paper presents the results of techno-economical analysis of a proposal of the utilization of TFT (triple-finned tubes) in a boiler's tube banks. The following three tube bank arrangements were compared: (A) the base – staggered plain tube bank; (B) the combination of triple-finned and plain tubes – two rows of triple-finned tubes every 10 rows; (C) the alternating tube bank, where half of the plain tubes were replaced by triple-finned tubes in an in-line arrangement.The results of CFD calculations of heat load q let to obtain relative values of the Nu number on the tube bank in (B) and (C) arrangements and the base arrangement (A) were carried out in a 2D model using the CFD (computational fluid dynamics) code Fluent.Heat transfer values of an ECO (economizer) with triple-finned tubes were obtained for the calculation of outlet flue gas temperature and outlet loss. Calculations of the Nu number of the tube were performed for all arrangements. Next, boiler efficiency and fuel consumption were calculated by 0D modelling. Received results were used to make economical analysis. In the case of modernization in the (C) arrangement, efficiency would be 90.67%, which is an increase of 1.1%. This is related to the reduction of flue gas temperature to 138 °C from 158.8 °C.Economically, the most advantageous solutions, are the variants of modernization (B) and (C) for the newly formed boiler. In both cases, SPBT (simple payback time) capital payback period is very short - close to half of a year.It is worth noting that the proposed modernizations of the arrangement (B) and (C), will respectively reduce CO2 emissions by 550 t/a and 826 t/a.The results show that triple-finned tubes can be used to increase the performance of cross-flow tube banks.