In order to ensure that the supercritical CFB boiler has good wide-load operation characteristics and the ability of deep peak regulation

the transient heat transfer characteristics between the working fluid and the water wall under the change of transcritical pressure are experimentally studied. Experiment adopted Φ25.0 mm×3.5 mm vertical upward tube

the near-critical steady heat transfer experiment and the transcritical pressure step transient heat transfer experiment were carried out under the experimental conditions of 20～23 MPa of pressure and 400～800 kg/(m2·s) of mass flow rate. The results showed that under the near-critical pressure

increasing the flow rate

reducing the heat flux on the inner wall

and reducing the pressure can reduce the dryness when the DNB heat transfer deterioration occurs

and increase the corresponding fluid enthalpy value

and delay the occurrence of the heat transfer deterioration. When the transcritical pressure step changes

the heat transfer deterioration may occur in the heating pipe

resulting in the wall temperature rising rapidly

but the temperature will fall back to the normal value with the increase of the flow rate. The heat transfer between the wall temperature rising point and the inner wall surface goes through the heat transfer deterioration stage

the subcooled boiling heat transfer enhancement stage and the single liquid phase heat transfer stage. The influence of each parameter on the heat transfer deterioration in the transcritical pressure step change experiment is the same as that in the near-critical steady state experiment. The decrease of flow rate and the increase of heat flux on the inner wall will advance the location of the heat transfer deterioration

and the wall temperature rise will be greater.