EFFECT OF WAVY TUBE STRUCTURE ON THE COMPREHENSIVE PERFORMANCE OF SUPERCRITICAL CARBON DIOXIDE AND LEAD BISMUTH EUTECTIC COMPACT HEAT EXCHANGER

In the combined system of lead-cooled fast reactor and supercritical carbon dioxide (S-CO₂) Brayton cycle, the intermediate heat exchanger plays a key role in the whole power system. However, the existing heat exchanger cannot meet the trend of miniaturization of lead-cooled fast reactors. Considering the thermo-physical properties and heat transfer behaviors in both S-CO₂ and liquid lead bismuth eutectic are significantly different, an asymmetric compact coupled heat exchanger learning from the Honeycomb structure is proposed. Then the effect of the Reynolds number on the coupling heat transfer is discussed. When the Reynolds number of the cold side was changed from 57600 to 145000, the heat transfer coefficient of the heat exchanger increases by 79%, but when the Reynolds number on the hot side is changed from 29600 to 118000, the heat transfer coefficient only increases by 4.6%. To enhance the heat transfer and reduced thermal resistance on the S-CO₂ side, a wavy channel was used. The results showed that the wavy channels could significantly improve the field-synergy angle. In the smooth pipe, the averaged field-synergy angle is 88.7°, while in the wavy channel, the averaged field-synergy angle becomes 84.1° at α = 1.5. With the increase of wavy amplitude in S-CO₂ channel, the heat transfer coefficient and the friction factor increased, but the comprehensive heat transfer coefficient is in non-monotonic variation. The overall heat transfer coefficient of the wavy channel is 1.56-1.81 times than that of the straight channel in the range of Re_SCO2 = 86700 ~ 145000.