Heat flux determination based on the waterwall and gas-solid flow in a supercritical CFB boiler

A heat flux determination method of combined thermal-hydraulics inside the waterwall tubes and thermal process on the furnace gas-solid side (HFW) is presented in this study, for the purpose of a detailed understanding of heat transfer characteristics on heating surface. The method consists of three main steps: 1. gas-solid hydrodynamic simulation by means of the Eulerian-Eulerian model; 2. bed-to-wall heat transfer coefficient calculation based on cluster renewal model; and 3. coupling thermal-hydraulic calculation at supercritical condition. Due to the effect of metal temperature on bed to wall heat transfer coefficient, it will be computed iteratively in latter two steps. By this method, the three-dimensional distributions of fluid temperature and heat flux in a 1000 MW supercritical circulating fluidized bed (CFB) boiler were presented. Results showed that fluid temperature increased with the increase of the furnace height, and the heat flux distributed uniformly along the width of furnace. In addition, the effect of operating parameters on fluid temperature profile was also studied. It turned out that fluid mass flux, inlet temperature and furnace temperature had a significant impact on temperature distribution along the tubes.