Heat Transfer Characteristics during Rapid Quenching of a Thin Wire in Water

Rapid quenching of thin horizontal platinum wires (0.3 and 0.5 mm in diameter) was studied experimentally using pure water as a quenching liquid. The cooling curve was measured in the ranges of water temperature of 0 to 50°C, falling velocity of the wire of 0.1 to 1.5 m/s, and initial wire temperature of 600 to 1 400°C. The boiling curve for the rapid quenching process was obtained from the cooling curve. The degree of superheat at the minimum heat flux point was around 350 K irrespective of the water temperature, the falling velocity and the wire diameter. The heat flux in the film, transition and nucleate boiling regions increased with increasing degree of subcooling and falling velocity. A numerical analysis of transient film boiling on a horizontal cylinder with upward liquid flow was performed. The measured heat flux was about 30% higher than the calculated value at the forward stagnation point.