Computational Model for a Condensing Boiler with Finned Tubes Heat Exchanger

European regulations state a minimum boiler efficiency for the main steady-state functioning conditions and for the overall heating season conditions. In order to comply the demands of the new regulations, more and more boiler manufacturers are switching the gas boilers production to condensing functioning. In the paper we present the numerical and computational modeling of a boiler made out of packages of finned tubes and packages of smooth pipes. Validation of the computational results is made by comparison with experimental results obtained in a certified laboratory for the modelled equipment (boiler). The modelling was set on an aluminium finned tubes heat exchanger existent in the testing laboratory (part of a condensing boiler). The geometry modeling considered the discretization of the heat exchanger in several zones, characterized by homogenous flue gas flow speed, flow geometry and heat transfer characteristics (mainly feature-length). A good correlation between measured and calculated values was obtained, the error ranging +/- 1% for the total and sensible heat and for thermal efficiency.