Rapid cooling using electrodeposited porous copper material in liquid nitrogen

When cryogenic liquids are used in various fields and applications, e.g., space rockets, freezing food, and superconducting magnets, all of the components that contact the cryogenic liquid should be cooled to below the saturation temperature of the cryogenic liquid. However, the latent heat of the cryogenic liquid is low; thus, the required precooling time is long. A highly efficient cooling method is required to reduce the precooling time. Adding a frost layer to the heat transfer surface is a useful method to rapidly cool an object in a cryogenic liquid. However, with this technique, it is difficult to control the formation of the frost layer at room temperature conditions. This paper proposes an ultra rapid cooling method in cryogenic liquid using a porous copper material made by the electrodeposition method. The proposed method is based on a plating technique that is widely used in industrial fields, thereby making it easy to production of layers with frost layer-like geometry. Experimental results demonstrate that the porous copper material reduced the cooling time by 90 % compared bare surface. In addition, the rapid cooling mechanism was investigated through observations using a high-speed camera. Initially, the early boiling transition on the porous copper surface was confirmed. Following the quenching on the surface of the porous copper material, the local collapse of the film boiling and the recovery of the vapor film were observed to occur repeatedly. Surface analysis results indicate that the cooling enhancement rate is associated with low thermal effusivity and high wickability of the porous copper.