Effects of surface properties on wall superheat at the onset of microbubble emission boiling

Abstract

Boiling heat transfer (BHT) is a promising technology for cooling the high heat flux emitted from next generation electronic devices. Pool boiling represents an eco-friendly cooling technology because its pumps do not require an external electronic power source. To increase the maximum heat flux of pool boiling beyond the critical heat flux, microbubble emission boiling (MEB) can be implemented with highly subcooled water. However, conventional MEB experiments use a copper heating surface, which can easily be oxidized in air. Thus, copper heating surfaces do not retain constant surface properties, especially when the BHT boiling pool is open to air. Applying a coating to the copper surface can enable further investigations of the MEB phenomenon and improve the reliability of MEB-based cooling devices. However, it is unclear which surfaces are suitable for promoting the onset of MEB. Herein, we experimentally investigated a stable hydrophilic black chrome plating on copper by performing subcooled pool boiling with water at atmospheric pressure. The results confirmed that the black chrome plating did not interrupt the onset of MEB, but rather, it enabled constant wall superheat during repeated experiments spanning the transition from nucleate boiling to MEB. Moreover, the threshold of liquid subcooling for the onset of MEB with the black chrome plating (20 K) was similar to that with a copper heat transfer surface.