Simulation of Mass Flow Rate of Air through Rectangular Split Duct

Abstract

Adequate supply of oxygen is essential for the complete combustion of fuel in the furnace of a boiler and defective duct design may cause serious loss in the boiler efficiency due to incomplete combustion. In boiler there is a system which controls the air flow rate reaching to the furnace. FD fan helps to build the pressure and force the air to pass through the duct and wind box. In wind box, this air will be sent to the furnace for helping combustion process. The main objective of this work was to simulate the flow of air from blower to the inlet of a wind box through rectangular split duct to see whether it could provide improved flow conditions and to see whether there was equal mass flow rate of air through both the legs of a split duct. The purpose of providing a split duct was to eliminate one blower which would otherwise be required for two separate ducts arrangement. A 3D model using CFD was prepared to capture the changes in the mass flow distribution in the duct at two different outlets. Through this analysis, it was found that the mass flow rates of air through the two legs of the split duct were not equal. The damping needs to be provided for the duct having longer length in order to have equal mass flow rate of air through both the legs of the duct.