Influence of filling ratio on the thermal performance and efficiency of a thermosyphon operating with Al2O3-water based nanofluids

Abstract Two-phase closed thermosyphons (TPCTs) are excellent heat transfer devices, widely used in the industry for heat transfer applications. This work examines the effect of employing Al2O3-water based nanofluids at different concentrations and the influence of different factors, such as filling ratio (FR) and power inputs, on the thermal performance and operation limits of a glass TPCT. The results show that the efficiency of the TPCT can be increased by up to 14.8% by using an alumina nanofluid at 0.1 wt% (instead of water), a 45% FR, and 60 W of power. However, similar results were also found when the FR of water was increased. Finally, different operating limits such as dry-out limit, geyser boiling as well as nanoparticle barrier were observed as a result of modifications of experimental conditions and their effects on thermal performance, it was concluded that operating limits involves a negative impact on the thermal performance of the TPCT, nevertheless, the enhancement of the TPCT performance with the nanofluid at 0.1 wt% and 60 W was achieved due to geyser boiling.