Critical heat fluxes of subcooled water flow boiling against Inlet subcooling in short vertical tube

摘要

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}(sub,in) = 48 to 148 K), the outlet subcoolings (△T{sub}(sub,out) = 10.5 to 95.1 K), the inlet pressure (P{sub}(in) = 753 to 995'kPa) and the outlet pressure (P{sub}(out) = 720 to 887 kPa). The SUS304 tubes of L = 67, 120 and 150mm for d = 3mm and L = 150mm for d = 6mm are used. The values of L/d are 22, 40 and 50 for d = 3 mm, and 25 for d = 6 mm, respectively. The CHFs, q{sub}(cr,sub) for a fixed △T{sub}(sub,out) become gradually lower with an increase in the L/d in the whole experimental range. The CHF correlation against outlet subcooling, which has been previously derived for Lid lower than 16, was modified to new one containing the Lid effect based on these experimental data. Furthermore, the relation between q{sub}(cr,sub) and L/d for a fixed △T{sub}(sub,in) was checked. The values of q{sub}(cr,sub) for a fixed △T{sub}(sub,in) became exponentially lower with the increase in L/d. CHF correlation against inlet subcooling has been given based on the experimental data for L/d ranging from 4.08 to 50. The correlations against outlet and inlet subcoolings can describe not only the CHFs obtained in this work for the inner diameter of 3 and 6 mm at the outlet pressure of around 800 kPa but also the authors' published CHFs data (1 611 points) for the wide ranges of P{sub}(in) = 159 kPa to 1 MPa, d = 3 to 12 mm, L =33 to 150 mm and u = 4.0 to 13.3 m/s within 15% difference for 30 K < △T{sub}(sub,out) ≤ 140 K and 40 K ≤△T{sub}(sub,in) ≤ 151 K.