Fig. 1. Experiment setup.

Fig. 2. Vertically positioned test tube.

Fig. 3. Vertically positioned test tube.

Fig. 4. Local inner wall (T_{w, in}), Bu, Ac distributions with bulk fluid enthalpy (i_b): (a) P = 8.220 MPa, G = 200 kg/(m²·s), q_w = 60 kW/m², (b) P = 8.220 MPa, G = 520 kg/(m²·s), q_w = 42 kW/m².

Fig. 5. Local inner wall (T_{w, in}), Bu, Ac distributions with bulk fluid enthalpy (i_b): (a) P = 8.220 MPa, G = 700 kg/(m²·s), q_w = 245 kW/m², (b) P = 8.220 MPa, G = 1000 kg/(m²·s), q_w = 245 kW/m².

Fig. 6. (a) Local inner wall T_{w, in}, (b) Bu, (c) Ac distributions with bulk fluid enthalpy i_b (NHT, normal heat transfer; HTD, heat transfer deterioration).

Fig. 7. Gr and Re^2.7 distribution at different mass flow rates

Fig. 8. Radial expansion model of supercritical fluids based on pseudo-boiling.

Fig. 9. Supercritical boiling number distinguishes the two regimes of heat transfer.