Numerical investigation of double-flame hot-water boilers under steady-state operation

Abstract

This study investigates the optimal arrangement of combustion chambers in double-flame hot-water boilers using computational fluid dynamics (CFD) under steady-state and laminar conditions. The study considers two arrangements: horizontal and vertical. In the horizontal layout, the study tests three vertical distances of Y*=-0.25, 0, and 0.25 from the center of the boiler and three horizontal gap spaces of S*=0.05, 0.1, and 0.15 between two chambers. In the vertical layout, the study examines three vertical distances of S*=0.1, 0.2, and 0.3. The computations for both layouts are conducted for Richardson numbers ranging from 0.1 to 10 under a constant Reynolds number of 50. The Navier–Stokes equations along with the energy equation are implicitly computed based on the finite volume approach for single-phase water flow inside a simplified two-dimensional model. The results are validated for a single-flame hot-water boiler in terms of the Nusselt number and non-dimensional pressure drop, and a good agreement has been achieved. The study shows that the geometric parameters considered in the study, as well as the Richardson number, have significant impacts on the boiler performance. The study finds that the horizontal arrangement with S*=0.05 and Y*=-0.25 offers the highest thermal-hydraulic performance, regardless of the Richardson number.