The mechanisms and corresponding correlations for the subcooled water flow boiling CHFs for outlet subcoolings in a vertical tube having an inside diameter, D, and length-to-diameter, L/D, ratio for a flow velocity with outlet pressure as a parameter were previously clarified by the authors based on the existing flow boiling CHF data measured using the tubes having the diameters ranging from 0.4 to 12 mm, and the L/D ratios ranging from 2.4 to 96.6 for the flow velocities ranging from 5 to 130 m/s, at the pressures ranging from 0.34 to 17.2 MPa. Namely the CHF, qcr,sub, versus outlet subcooling, Δsub,out, for a flow velocity with outlet pressure as a parameter were divided into four regions for outlet subcoolings: first the CHF decreased down to minimum one (first region), secondly it increased up to maximum one (second region), thirdly it decreased down to minimum one (third region), and finally it again increased monotonously with an increase in outlet subcooling. The CHFs belonging to third region became significant with a decrease in diameter for the smaller tubes with diameters such as around 1 mm, and on the other hand, those almost disappeared with an increase in diameter for the larger tubes with the diameters such as around 9 mm. The CHFs belonging to second region significantly depending on the pressure and tube diameter, and those belonging to fourth region being almost independent of the pressure, and tube inside diameter, D, and length-to-diameter, L/D, ratio were well expressed by the unified subcooled water flow boiling CHF correlations representing the CHF resulting from the hydrodynamic instability, HI, and those representing the CHF resulting from the heterogeneous spontaneous nucleation, HSN, on the inside surface near the exit of heated tube respectively. In the present paper, the generalized evaluation of the maximum qcr,sub of the qcr,sub data belonging to 2nd region resulting from the HI unsolved before was realized solving the simultaneous equations consisted with the unified qcr,sub correlation representing qcr,sub resulting from the HI previously derived and the generalized correlation for the Δsub,out,max at corresponding qcr,sub,max newly derived.

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