Study on thermal resistance distribution and local heat transfer enhancement method for SCO₂-water heat exchange process near pseudo-critical temperature

In this article, a coupled heat transfer between supercritical carbon dioxide (SCO₂) and water in a concentric tube heat exchanger is numerically studied. It is found that unlike air-water heat exchange process, the distribution of local thermal resistance in the concentric tube heat exchanger strongly depends on the inlet velocity of SCO₂ and water when the temperature of SCO₂ is near the pseudo-critical point. Based on the distribution of local thermal resistance, a new local heat transfer enhancement method is proposed to enhance the weakest region for the SCO₂-water heat exchange under different operating conditions. Further, the obtained numerical results confirm that the local heat transfer enhancement method can significantly improve the comprehensive heat transfer performance of heat exchanger. Compared to smooth tube heat exchanger, the local heat transfer enhancement method of heat exchanger with half-length sinusoidal corrugated surface can enhance the heat transfer by 15.8% compensated with 5.9% more pressure drop when the velocity of SCO₂ is comparable with that of water.