Experimental Investigation on the Transcritical Dynamic Flow and Heat Transfer Characteristics of the Water Wall[J]. 2018, 52(11): 1-8+126.
DOI:
Experimental Investigation on the Transcritical Dynamic Flow and Heat Transfer Characteristics of the Water Wall[J]. 2018, 52(11): 1-8+126.DOI: 10.7652/xjtuxb201811001.
Experimental Investigation on the Transcritical Dynamic Flow and Heat Transfer Characteristics of the Water Wall
Aiming at the special flow and heat transfer characteristics in the transcritical variable-pressure operating process of the water-wall in the supercritical once through boiler
experiments were conducted to investigate the transcritical dynamic flow and heat transfer characteristics in a vertical upward heated pipe under 19-25 MPa of pressure
300-800 kg/(m
2
·s)of mass velocity and 60-250 kW/m
2
of heat flux on the pipe outerwall. The experimental results showed that a wall temperature rise always occurs in the transcritical dynamic process of the heated pipe
which is caused by the DNB heat transfer
deterioration in the near-critical pressure region. With the increase of the fluid pressure
the nearer is the fluid pressure close to the critical point
the lower is the fluid enthalpy needed to induce the occurrence of DNB
and the higher the deterioration degree will be. Moreover
DNB heat transfer deterioration even occurs when the working fluid is still in a subcooled state under most of our experimental cases
and this seriously threats the safe running of the water-wall system. Based on the parameter range of our experiments and the analysis on the operation of water-wall
DNB heat transfer deterioration is likely to occur in the transcritical dynamic process when the local fluid enthalpy in the heated pipe is higher than 1 600 kJ/kg. The experimental results in this research can provide a guidance for the design and adjustment of the operation conditions in the water-wall of the supercritical once through boiler.
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