Microscale to Macroscale—Extending Microscale Enhancement Techniques to Large-Scale Boiling Equipment

Abstract

Boiling is a multiscale phenomenon. Nucleation and rapid bubble growth at the heated wall provide a highly localized mechanism for heat transfer to the surrounding liquid. The liquid–vapor interface of the growing bubble supplies latent heat needed to evaporate the liquid and sustain the bubble activity. Although the boiling process is efficient in removing large amounts of heat, further improvements are needed to increase the critical heat flux (CHF) as well as heat transfer coefficient (HTC) in many applications. Recent developments in enhancing boiling heat transfer have mainly focused on small-scale heaters, typically on the order of a centimeter, that are particularly relevant in electronics cooling application. Many of these developments are based on fundamental understanding of the microscale processes of bubble nucleation, bubble growth and removal from the heater surface, and supply of liquid to the active nucleation sites. Some of these microscale enhancement techniques have set new records in heat dissipation (both CHF and HTC). This paper explores the potential of these microscale enhancement techniques in large-scale boiling equipment, such as boilers, reboilers, and evaporators in power generation, refrigeration, air conditioning, cryogenic, desalination, chemical, petrochemical, pharmaceutical, and other industries. Implementation of the microscale enhancement technologies in macroscale boiling equipment will provide the next level of energy efficiency and energy savings in the face of climate change and environmental concerns.