The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-circular tube caused by a rapid
decrease in velocity from non-boiling regime are systematically measured for various initial flow velocities,
initial heat fluxes, inlet liquid temperatures, outlet pressures and decelerations caused by a rapid
decrease in velocity by the experimental water loop comprised of a multistage canned-type circulation
pump controlled by an inverter. The SUS304-circular tubes of inner diameter (d = 6 mm), heated length
(L = 59.5 mm), L/d (=9.92) and wall thickness (d = 0.5 mm) with average surface roughness (Ra = 3.89 lm)
are used in this work. The flow transient CHFs for SUS304-circular tube are compared with authors’
steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-circular tubes and the values
calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty
circular tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused
by a rapid decrease in velocity (a) on the flow transient CHF are investigated into details and the widely
and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the circular
tube is given based on the experimental data. The correlations can describe the flow velocity and the
CHFs at the flow transient CHFs for SUS304-circular tube obtained in this work within ± 20% difference.