Heat Transfer Enhancement of a Zirconium Heater Rod Using a Chromium Coating During Quenching

Transient pool boiling experiments were conducted in a distilled water pool to investigate the effect of Chromium coating on Zirconium heated rod. Chromium is one of the candidates for accident tolerant fuel (ATF). Zirconium samples were coated using cathodic arc physical vapor deposition (CA-PVD), which forms a thin layer of Chromium. Bare Zirconium and Chromium-coated samples were quenched in a 3-degree and 10-degree subcooled pool under atmospheric pressure. Quenching in a 3°C subcooled pool forms a thick layer of vapor which suppresses the effect of Chromium coating. In contrast to quenching in a 3°C subcooled pool, the heat transfer rate for the Cr-coated rod in the 10°C subcooled pool is larger than the uncoated Zr rod during film boiling due to the surface microstructure of Cr coating, which enhances heat transfer during film boiling. The Minimum Film Boiling Temperature (T_MFB) for the Cr-coating sample does not vary significantly with pool temperature. On the contrary, the T_MFB for the Zirconium sample increased dramatically with increasing subcooling. Both samples quench faster in a higher subcooled pool. The effect of Cr-coating was found to be insignificant on quench time due to the fact that it was only around three micrometers in thickness. In all tests, the quench time significantly decreased when liquid subcooling is increased.