Impact of Filling Ratio and Cellulose Nanofiber Nanofluid on the Total Thermal Resistance and the Startup of a Miniature Thermosyphon

Abstract

Thermosyphons are highly effective heat transfer devices used for thermal management in different fields, such as electronic systems, solar collectors and nuclear reactors. The working fluid within the thermosyphon provides the heat transport from the evaporator to the condenser and limits its thermal performance. In this study, the influence of filling ratio (FR) and the eco-friendly cellulose nanofiber (CNF) nanofluid concentration on the total thermal resistance and the startup of a two-phase closed thermosyphon (TPCT) at various heat loads are investigated experimentally. The working fluids are deionized water (DI) and CNF suspensions with 0.5, 1, and 2 vol.% and filling ratios were set to 25, 50, and 75%. Total thermal resistance of the TPCT was obtained using the recorded data of wall temperature distribution at the steady state of each experiment. Addition of CNF with 1 vol.% to DI at filling ratio of 75% reduced the evaporator wall temperature by 40% and 23%, also it reduced the total thermal resistance by 58.78% and 33.65% at 20 W and 80 W, respectively. Moreover, it shortened the startup duration by 33% and reduced its temperature by 42%. This paper contains important findings that prove that CNF enhanced the thermal performance of the TPCT when applying an appropriate concentration and filling ratio.