Supercritical “boiling” number, a new parameter to distinguish two regimes of carbon dioxide heat transfer in tubes

Abstract

Abstract The objective of this paper is to develop a criterion to predict the onset of heat transfer deterioration (HTD) for supercritical CO2 heat transfer. A new mechanism is proposed by assuming supercritical pseudo-boiling. Before bulk fluid reaches pseudo-critical temperature (Tpc), the tube cross-section contains a vapor layer and a liquid-like fluid. The saturation temperature interface is defined at T\u202f=\u202fTpc, inside and outside which are a vapor layer (T\u202f>\u202fTpc) and a subcooled liquid (T\u202f 5.126 × 10 − 4 and the critical heat flux is expressed as q C H F = 5.126 × 10 − 4 G i pc . It is shown that our new criterion is also suitable for other experiments reported in literature, providing a general guidance to design and operate S CO2 heaters to avoid HTD.