Dynamic simulation on ash deposition and heat transfer behavior on a staggered tube bundle under high-temperature conditions

Abstract

In this paper, a predictive tool was developed to simulate the formation of ash deposit on tube bundles under high-temperature conditions based on ANSYS FLUENT platform. The effects of the factors on ash deposition and heat transfer performance were investigated, including the morphology variation, wall temperature, transverse pitch, and longitude pitch of the tube bundle. It was found that impact mass flux on the tube bundle was significantly reduced by the changed morphology of the tubes during the growth of ash deposit. The final thermal efficiency of the tube bundle increased with the increase of the wall temperatures of the tubes. Furthermore, the thermal efficiency of the tube bundle decreased from 0.74 to 0.65 when the ratio of the transverse pitch and tube diameter increased from 1.58 to 2.63. However, it was slightly affected by the change of the longitude pitch with the same change as the transverse pitch. The results indicate that it will be an effective way to reduce ash deposition by changing the shape of the tubes with considering the temperature-dependent thermal conductivity of ash deposit. Additionally, a small transverse pitch for the tube bundle with a proper longitude pitch is recommended for this simulation condition.