NUMERICAL STUDY OF HEAT TRANSFER AND FLY ASH DEPOSITION CHARACTERISTICS FOR TWO KINDS OF H-TYPE FINNED TUBES
Three-dimensional numerical simulations are carried out on two kinds of H-type finned tubes to obtain the heat transfer and pressure drop characteristics. A deposition model was developed to predict the deposition rate of ash particles on the H-type finned tubes by considering particle transport, adhesion and removal behaviors. Then the particulate deposition characteristic was also studied by using the discrete phase model and the deposition model. The results show that the Nusselt number increases with the increasing Reynolds number, while the Euler number drops gradually. The deposition decreases rapidly with the increase of velocity of and diameter of particles. The particles deposit primarily in the flow stagnation region in front of the tubes and the recirculation region behind the tubes. The gap between two single H-type finned tubes caused the increasing turbulence which enhanced heat transfer but also increased the pressure drop and particulate deposition. While as for double H-type finned tubes, the gap was replaced by the connected fin, which reduced the turbulence between two tubes and got better pressure drop and fouling performance at the expense of a small amount of heat transfer performance. The comparison results between the two models show that the heat transfer performance of the single H-type finned tubes is better than the double H-type finned tubes, but the pressure drop and fouling performance are not as good as the double ones.