Ultrafast cooling of a hot moving steel plate by using alumina nanofluid based air atomized spray impingement

• Enhancement of spray cooling heat transfer rate by alumina nanofluid is studied.
• Cooling experiments are conducted from a high initial plate temperature of >900 °C.
• Effect of surfactants on cooling capacity of alumina nanofluid is also investigated.
• A cooling rate of 230 °C/s is achieved for application in ROT of a hot strip mill.

The objective of the present work is to examine the heat transfer aspect of alumina nanofluid based air atomized spray impingement on a hot moving steel plate with an initial temperature well above the Leidenfrost point. The influence of surfactants in increasing the effectiveness of nanofluid as a heat transfer media has also been investigated. The experimental study has been conducted with four different types of coolants namely water, water-alumina, water-alumina-SDS and water-alumina-tween20. The thermo-physical properties (viscosity and thermal conductivity) of the coolants have been measured as they affect the heat transfer rate. The heat transfer result indicates that enhanced cooling rates are obtained using nanofluids as compared to that of water.