Computational Fluid Dynamics (CFD) simulations of the gas flow inside a Heat Recovery Steam Generator (HRSG) are presented. The CFD model can be employed for numerical simulation of existing and very different possible operation situations and for the purpose of solving problems in power plants operating in working conditions subjected to change (change of the gas turbine load, the fuel quality, etc.). The CFD results provide detailed information of local values, as well as corresponding fields of variables, such as velocity components, temperature and pressure drop of the gas.

Besides its multiple potential applications in the design phase of a HRSG, here the simulation tool is intended to be used by plant operators and associated plant personnel in charge of the optimal operation of the plant, so that they can obtain a graphically detailed understanding of the flow process. CFD offers a graphic display that permits the operator to “see” the flow inside the HRSG and understand the effect changes in operational conditions have on the flow. For instance two cases are presented here. First the characteristics of the flow at different thermal loads and the associated heat transfer are examined. Second the effect on the flow of changing the swirl angle at the HRSG inlet is analyzed.

Model validation was performed comparing simulation data to power plant data. Even though a relatively good agreement was obtained, it is clear that model validation is a difficult task due to the scarce data from commercial utilities. In this context validation should refer more to agreement in trends than absolute values. This validation strategy, however, can allow personnel from the plant to use CFD tools to obtain a qualitative and intuitive understanding of the flow process in the plant.

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