Subcooled boiling heat transfer in a short vertical SUS304-tube at liquid Reynolds number range 5.19 × 10 4 to 7.43 × 10 5

Abstract

The subcooled boiling heat transfer and the steady-state critical heat fluxes (CHFs) in a short vertical SUS304-tube for the flow velocities ( u = 17.28–40.20 m/s), the inlet liquid temperatures ( T in = 293.30–362.49 K), the inlet pressures ( P in = 842.90–1467.93 kPa) and the exponentially increasing heat input ( Q = Q 0 exp( t/ τ), τ = 8.5 s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tubes of inner diameters ( d = 3 and 6 mm), heated lengths ( L = 33 and 59.5 mm), effective lengths ( L eff = 23.3 and 49.1 mm), L/ d (=11 and 9.92), L eff / d (=7.77 and 8.18), and wall thickness ( δ = 0.5 mm) with average surface roughness ( Ra = 3.18 μm) are used in this work. The inner surface temperature and the heat flux from non-boiling to CHF are clarified. The subcooled boiling heat transfer for SUS304 test tube is compared with our Platinum test tube data and the values calculated by other workers’ correlations for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated into details and the widely and precisely predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical SUS304-tube is given based on the experimental data. The correlation can describe the subcooled boiling heat transfer obtained in this work within 15% difference. Nucleate boiling surface superheats for the SUS304 test tube become very high. Those at the high flow velocity are close to the lower limit of Heterogeneous Spontaneous Nucleation Temperature. The dominant mechanisms of the flow boiling CHF in a short vertical SUS304-tube are discussed.