Volume 22: Sustainable Energy Solutions for a Post-COVID Recovery towards a Better Future: Part V

Experimental Study on Suppressing Heat Transfer Deterioration of Supercritical CO2 Heated in Vertical Tubes Based on Helmholtz oscillator Yong Cao, Xiaoxiao Xu, Dan Li, Shijie Zhang, Chao Liu

Abstract

Heat transfer deterioration (HTD) of supercritical CO2 heated in a tube will influence the thermal efficiency and safe operation of the energy system due to the occurrence of local high temperatures. To suppress the HTD of supercritical CO2, the Helmholtz oscillator is applied at the inlet of the test section. The experiments are conducted at the conditions of the mass flux from 121 to 600 kg m-2 s-1 and the heat flux from 14.7 to 106.1 kW m-2 with the operating pressure of 8.0 MPa. The heat transfer and comprehensive thermal performance are discussed with and without the Helmholtz oscillator. The results show that it can significantly suppress the HTD, and the overall thermal performance factor can be up to 2.28. The main reason is that the Helmholtz oscillator can strengthen the mutual disturbance between near-wall fluid with high temperature and central fluid. Therefore, the buoyancy effect is weakened and heat transfer to supercritical CO2 gets enhanced.

Keywords Supercritical CO2, Helmholtz oscillator, Heat transfer deterioration, Buoyancy, Waste heat recovery