Dimensional analysis of critical heat flux in subcooled water flow under one-side heating conditions for fusion application

Critical heat flux (CHF) experiments have been carried out to design a high performance cooling device with pressurized subcooled water flow under one -side heating conditions for plasma facing components. Swirl, screw and hyp ervapotron tubes are the most efficient geometries to remove high incident heat fluxes. A dimensional analysis shows that CHF phenomenon can be featur ed by dimensionless groups that are the critical Boiling, the Eckert and th e Reynolds numbers, the mass enthalpic quality and the ratio between liquid and vapor densities. CHF for uniformly heated smooth tubes, the maximum wa ll heat flue for smooth and for swirl tubes under one-side heating conditio ns are predicted with a reasonable accuracy by correlating these five dimen sionless groups. An enhancement factor featuring the difference between one -side and uniform heating is also introduced. CHF occurrence under one-side heating is characterized by a normalized temperature, ratio between the ma ximal wall temperature and the onset of nucleate boiling temperature, which only depends on the pressure. According to finite element calculations per formed for smooth and swirl tubes, temperature and heat flux are distribute d along the inner wall of the cooling channel under one-side heating condit ions. These distributions are characterized by two dimensionless numbers fo r each geometry: a peaking factor, which is the ratio between the maximal h eat flux at the inner wall of the cooling channel and the incident heat flu x, and a full width angle at half maximum of wall heat flux at the inner wa ll of the cooling channel. This study draws the dimensionless groups featur ing CHF phenomenon not only under uniform heating, but also under one-side heating, which involve additional normalized parameters. (C) 1998 Elsevier Science S.A. All rights reserved.