Large eddy simulation on heat transfer characteristics of supercritical water in double-pipe heat exchanger

Understanding the heat transfer clearly of supercritical water in a double-pipe heat exchanger is rather essential to design heat exchangers. At present, there is a lack of accurate and universal numeric calculation model and sufficiently understanding of heat transfer mechanism of supercritical fluids. In this study, The different effects on heat transfer characteristics of SCW in the double-pipe were first employed via Large Eddy Simulation based on published experimental data. The simulation results show that the peak heat transfer coefficient of the total exchanger increases from 3197.5 W·M⁻²·K⁻¹ to 3260.5 W·M⁻²·K⁻¹ and 3479.3 W·M⁻²·K⁻¹ when the pressure decreases from 27 Mpa to 25Mpa and 23Mpa, respectively. The difference between the pseudo-critical temperature and the temperature where the heat transfer coefficient arrives at the peak point decreases from 3.1 k to 0.9 K, which mainly results from the temperature gradient in the tube and shell side and the variable physical properties of the SCW. When the inlet temperature of tube decreases from 633 k to 613 k and 593 k, the peak heat transfer coefficient of the total exchanger decreases from 3430.5 W·M⁻²·K⁻¹ to 3283.0 W·M⁻²·K⁻¹ and 3229.7 W·M⁻²·K⁻¹, respectively, this phenomenon is caused by buoyancy force.