The challenge of simulating a boiler

The application of CFD to boilers has limited most of the times to the furnace (the area where the combustion takes place), not accounting for the heat recovery zone (HRZ). Why? The HRZ is full of bank tubes (with a typical diameter of a few centimeters), for whose detailed simulation (coupled with a combustion model) a huge computational mesh would be needed, of the order of hundreds of millions of cells. The time required and the economic cost of such a simulation makes it unfeasible.

Our approach to CFD simulation of boilers

nablaDot has develeoped a multiscale CFD model that allows for a comprehensive simulation of the furnace and the HRZ in a boiler with an affordable cost. To do this, the HRZ is depicted with a subgrid, 1D model, which is coupled with the 3D CFD model of the boiler.

Modelo caldera


Thanks to this model, we can analyze strategies for the reduction of NOx emissions in a boiler and study their effects in the heat recovery zone. This can be especially useful in those boilers where there is no attemperator. Moreover, the CFD model developed can be applied to study problems related to damage on tubes, to analyze retrofitting or new designs for a boiler or to evaluate the behavior after load changes or loads below minimum technical rating (with the aim of improving the flexibility of the boiler).

caldera temperaturas calor banco tubos calderas



nablaDot has applied this model to 4 boilers in thermal power plants, having received a very positive feedback by our clients.


The innovation associated to this model has resulted in its presentation in several events, such as:

NAFEMS seminar: CFD-Flow Simulation in Engineerin. Madrid 2018.

– 10th European Conference on Industrial Furnaces and Boilers. Oporto 2015.