Numerical study of the temperature distribution of combustion products in different parts of the fire-tube boilers to evaluate boiler steam generation

In this research, a three-pass fire tube boiler has been numerically simulated in order to investigate temperature distribution of combustion products in different parts of a sample boiler. The turbulent flow of the flame and combustion products are simulated by the finite volume approach by using Discrete Ordinates model to simulate radiation and Species Transport model to simulate combustion phenomenon. Each part has been separately simulated with inlet characteristics of the outlet of the last part and the smoke temperature distribution in each part has been presented. In addition, effective parameters of burner capacity, furnace type (corrugated or plain), furnace and tube length and diameter have been studied on the temperature distribution of combustion product and boiler performance. According to the obtained results, with increasing the length by ۵۵% or diameter by ۵۴% of the furnace, steam production increases by ۶.۵۶% and ۱.۵% respectively. With corrugating the furnace, the gas outlet temperature reduces and the boiler capacity of steam production increases. Reducing the diameter of the tubes by ۲۰% and increasing the length of the tubes by ۲۵% in the ۲nd pass and ۱۸% in the ۳rd pass (with the same heat transfer surface of the tubes in pass ۲ and ۳), leads to steam production increase by ۳% and ۱.۶۸%, respectively. Results showed that for larger proportion of ۳rd pass tubes, boiler performance increases. Also increasing in the burner capacity (by ۳۳%) leads to same value increase in the steam production.

Keywords:

Fire-Tube Boiler , CFD Simulation , Geometrical Study , Boiler Performance , Burner Capacity , temperature distribution