Energetic Liquid Droplet Boiling on High-Temperature Metal Surfaces

Experimental studies of thermal interactions of cold liquid droplets impinging on metal surfaces have been performed and the result of these studies are summarized in this paper. In these experiments rapid, energetic (explosive) breakup of the liquid drops were observed using high-speed video camera recordings. These energetic interactions occurred over a range of high temperatures of the metal surfaces and varied with the type of metal employed. Three metals were used in the study, namely, copper, brass, and stainless steel. The test sections included curved-plate (sections machined from metal cylinders) and flat-plate geometries. The choice of metals was determined by the objective of establishing the influence of thermal diffusivity of the hot material on the thermal interaction between the cold liquid droplet and the hot metal surface, and the two metal surface geometries were used to study the influence of droplet spreading behavior after impact with the hot metal surface. Metal surface temperatures ranged from 30°C to 700°C and controlled single water droplets at a temperature of 25°C were released from a specially designed rig employing a small fast–opening/closing solenoid valve. Experimental results are presented in this paper that demonstrate the processes that occur during the interaction of the droplet with the hot metal surface during a time frame of 1 to 20 ms.