Subcooled Boiling Heat Transfer for Turbulent Flow of Water in a Short Vertical Tube

The subcooled boiling heat transfer and the critical heat flux (CHF) due to exponentially increasing heat inputs with various periods (Q=Q0 exp(t/τ), τ=22.52 ms–26.31 s) were systematically measured by an experimental water loop flow and observed by an infrared thermal imaging camera. Measurements were made on a 3 mm inner diameter, a 66.5 mm heated length, and a 0.5 mm thickness of platinum test tube, which was divided into three sections (upper, mid, and lower positions). The axial variations of the inner surface temperature, the heat flux, and the heat transfer coefficient from nonboiling to critical heat flux were clarified. The results were compared with other correlations for the subcooled boiling heat transfer and authors’ transient CHF correlations. The influence of exponential period (τ) and flow velocity on the subcooled boiling heat transfer and the CHF was investigated and the predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical tube was derived based on the experimental data. In this work, the correlation gave 15% difference for subcooled boiling heat transfer coefficients. Most of the CHF data (101 points) were within 15% and −30 to +20% differences of the authors’ transient CHF correlations against inlet and outlet subcoolings, respectively.