Critical Heat Fluxes of Subcooled Water Flow Boiling against Inlet Subcooling in Short Vertical Tube

Abstract

The critical heat fluxes (CHFs) of subcooled water flow boiling for the test tube inner diameters (d = 3 and 6 mm) and the heated lengths (L = 67, 120 and 150 mm) are systematically measured for the flow velocities (u = 4.0 to 13.3 m/s), the inlet subcoolings (∆T sub,in = 48 to 148 K), the outlet subcoolings (∆T sub,out = 10.5 to 95.1 K), the inlet pressure (P in = 753 to 995 kPa) and the outlet pressure

Transient critical heat flux for subcooled boiling of water flowing upward through a vertical small-diameter tube with exponentially increasing heat inputs

“…Since the heat generation rate of the test tube increased rapidly under the transient condition, it is considered that the heat flux of the test tube increased until vapor film covered the heated surface of the test tube. In Fig.7, a dashed line represents the transient CHFs calculated by the following equation, which takes into account the e-folding time (Hata et al, 2004) but can be applied to an inner tube diameter of 3 to 9 mm. It is found that the CHF is higher than that predicted by Eq.…”

“…The experimental results revealed that the CHF was higher than that predicted by Eq. (19) obtained by Hata et al (2004) under steady state and transient conditions. Moreover, it was found that the Vandervort et al (1994) are plotted in Fig.6.…”

“…Since the wall temperature of the divertor increases rapidly, it is necessary to reduce the transient heat load caused by plasma disruption, using subcooled boiling of water. Bergles (1963), Nariai et al (1987), Celata et al (1993), Vandervolt et al (1994), Mudawar and Bowers (1999), and Hata et al (2004) experimentally investigated the CHFs for subcooled boiling of water under steady-state heat loads. They clarified the effects of mass flow rate, inner tube diameter, outlet pressure, inlet and outlet subcooling, and inlet qualities on CHF.…”

Forced convection heat transfer of subcooled liquid hydrogen in horizontal tubes

“…Hata et al [10] measured the DNB heat flux of subcooled water in vertically-mounted heated tubes in order to establish the database for high density cooling of fusion experimental devices. They derived the correlation, which is aimed for high heat flux cooling.…”

Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube

“…Many researchers have experimentally studied the CHF uniformly heated on the test tube by a steadily increasing current (1) - (7) . We have already measured the steady state CHF, q cr, sub, st , for wide range of experimental conditions to establish the database for designing the divertor of a helical type fusion experimental device, which is Large Helical Device (LHD) located in the National Institute for Fusion Science, Japan (8) - (16) . And, we have given the following steady state CHF correlations against outlet and inlet subcoolings based on the effects of test tube inner diameter (d), flow velocity (u), outlet and inlet subcoolings (∆T sub, out and ∆T sub, in ) and ratio of heated length to inner diameter (L/d) on CHF.…”