Supercritical carbon dioxide heat transfer in horizontal tube based on the Froude number analysis

Abstract

The heat transfer and pressure drop (ΔP) of supercritical fluid are crucial for the safety of advanced power cycles. Here, experiments were performed for sCO2 in a horizontal tube with inner diameter (din) of 10 mm, covering in the ranges of (G): 496.7–1346.2 kg/m2, heat flux (qw): 97.4～400.3 kW/m2 and pressure (P): 7.53–23.51 MPa. Inspired by the similarity of the outer wall temperature (Tow) distributions between the sCO2 flow and those of stratified-wavy-flow in subcritical pressures, the multiphase flow theory is introduced in subcritical pressures to deal with the sCO2 heat transfer. In the two-phase-like (TPL) regime, heat transfer coefficients (HTC) and friction factors (f) of sCO2 are found to significantly deviate from the correlations based on the single-phase flow theory. Further, the vapor-like Froude number FrVL is proposed to develop new correlations for both the heat transfer and the flow resistance covering the whole data range. The present paper establishes a connection between the flow resistance and heat transfer in supercritical pressures, which is important for the design and operation of sCO2 power cycles.