Heat transfer enhancement in chilldown process with electrospun nanofiber coating

Abstract

In this study, a method to enhance boiling heat transfer in cryogenic fluids by using nanofiber coating was proposed and validated. For this method, a nanofiber coating of polyvinyl alcohol (PVA) was fabricated on the surface of a copper plate via electrospinning, which is a technique that uses a high-voltage electric field. A chilldown experiment conducted with the copper plate and liquid nitrogen revealed that the nanofiber coating had the potential to reduce the chilldown time drastically. It was observed that the heat flux through the nanofiber-coated plate increased immediately after the chilldown period began, and it exceeded that of the plate without coating for the entire test duration. Consequently, the chilldown (boiling) curve did not have a minimum heat flux point, which is generally seen in pool boiling process. The critical heat flux was twice as large as that of the conventional method with a bare copper plate. Overall, the chilldown curve of the nanofiber-coated plate was distinct from a conventional boiling curve with a bare plate.