Numerical study of parametric effects on heat transfer deterioration of supercritical CO2/DME mixture flowing in a horizontal tube

Compared to using pure CO 2 as a working fluid, mixing CO 2 with dimethyl ether (DME) in specific ratios can enhance heat transfer efficiency and reduce system operating pressure. However, the issue of heat transfer deterioration (HTD) in supercritical CO 2 /DME mixtures has received limited attention. This study conducts a numerical analysis of the heat transfer characteristics of these mixtures in horizontal tubes. We conducted a systematic study for the first time on how various operating parameters influence the HTD mechanism and establish multiscale correlations between mixture thermophysical nonlinearities and thermal transport instabilities.The findings offer valuable insights for the safe operation of next-generation energy systems. Results show that DME addition delays HTD, while increasing system pressure and mass flux helps mitigate its severity. Moreover, gravitational acceleration introduces asymmetry in the local heat transfer coefficient (HTC) distribution. Under normal gravity conditions (g y = −9.8 m/s 2 ), HTC suppression is observed compared to the zero-gravity condition (g y = 0 m/s 2 ).