Influence of Foreign Body Blockage in Water Cooling Wall on Flow and Heat Transfer

Abstract

The ultra (super) critical units, as mainstream thermal power units, often need to participate in deep peak shaving. The variable load and high frequency peak regulation will lead to the partial increase of the temperature of the water-cooled wall and the phenomenon of local over-temperature. Aiming at this situation, the numerical investigation on the water-cooled wall of the #5 boiler in She-yang-gang was performed. The results show that the welding nodules and the foreign bodies in the water-cooled tube have a significant effect on the wall temperature. Moreover, with the increase of the blocking ratio (β), the mass flow in the tube decreases significantly, and the mass flow in the adjacent tubes rising. Further the increase of the mass flow is noteworthy in the nearest tubes. When the β of the target tube is higher than 0.4 the possibility of exceeding the maximum temperature limit of water-cooled wall tube material increases. The deposition of foreign body on the inner wall of the tube weakens the convective heat transfer between the inner wall and the fluid, which makes the wall temperature rise faster than other places. The more serious the deposition, the more obvious this phenomenon is.