Heat Transfer Enhancement of Small-Diameter Two-Phase Closed Thermosyphon Using Cellulose Nanofiber and Hydrophilic Surface Modification

Abstract

In this study, we observed the Geyser phenomenon that occurs in a small-diameter two-phase closed thermosyphon (confinement number of 0.245). This phenomenon interferes with the natural circulation of the internal working fluid and increases the thermal resistance of the system. This study attempts to improve the thermal performance of the system using cellulose nanofiber as the working fluid and hydrophilic surface modification at the inner surface of the evaporator section. As a result, the total thermal resistance showed average reduction rates of 47.51%, 36.69%, and 22.56% at filling ratios of 0.25, 0.5, and 0.75, respectively.

Experimental Study on the Quenching Behavior of a Copper Cube in the Cellulose Nanofiber Solution

“…A vessel with a size of 275 × 200 × 135 mm was filled with DI water and CNF solutions with concentrations of 0.01%, 0.1% and 0.5%. These discretized domains are obtained from the previous researches where significant differences during heat transfer were found due to the different weight percentage of the CNF solution [ 10 , 11 , 12 ]. The pool temperature was maintained by two hot plates below the vessel and monitored using a K-type thermocouple (TC2).…”

“…Choi et al [ 11 , 12 ] also verified CNF as a possible working fluid using a two-phase closed thermosyphon (TPCT). They designed a closed copper pipe and heated it until the working fluid inside the pipe boiled.…”