Decoupled CFD simulation of furnace and heat exchangers in a lignite utility boiler

In this work, we simulated the convective section of Unit I of Meliti Power Plant (330 MWel) in Florina, Greece, using the macro heat exchanger model (MHEM). As boundary conditions, previous temperature and velocity field data have been used, referring to the exit surface of combustion chamber. The MHEM approximates the pressure losses, using the porous media model, and the heat transfer, using the number of transfer units (NTU) model. The results have been validated against standard operating data, provided by the plant manufacturer. The working fluid outlet temperature for each heat exchanger, the total heat transfer, and the temperature distribution throughout the whole convective section have been calculated, showing good agreement with the respective data, under full operational load. Further, a parametric investigation of the level has been conducted, in order to validate the applied boundary conditions. Overall, we evidence that the MHEM can be a quite effective alternative for heat exchanger simulations.