Improvement of two-phased closed thermosyphon thermal performance by deploying nanofluids of metal nanoparticles decorated on CNT

In this investigation, nanofluids including CNT, milled CNT, and decorated Ag/CNT and Cu/CNT have been applied to enhance the thermal performance of a two-phase closed thermosyphon (TPCT). For better dispersing of carbon nanotube (CNT) in water and producing stable nanofluid, CNTs have been functionalized with hydrophilic groups such as carbocyclic acid and hydroxyl. A reducing agent and calcareous process are effective methods for decoration of CNT with NPs. Nanofluids were prepared in different weight concentrations (0.175%, 0.350%, 0.525% and 0.700%). Also, different input powers (40 W, 80 W, 120 W, 160 W, and 200 W) were applied to the evaporator section. According to the experimental results, it can be deduced that the effect of nanotubes functionalization on the thermal performance of thermosyphon decreases by increasing CNT concentration. Moreover, the transmission electron microscopy (TEM) images showed that functional group disjoins CNTs from each other and result in the formation of uniform silver and copper clusters that have been decorated on the surface of CNT. The results demonstrated that in the presence of nanoparticles (NPs), the thermal performance of thermosyphon improved through a reduction in thermal resistance by 34% (at 0.700 wt% for Ag), 36% (at 0.700 wt% for Cu), and 16% (for milled CNT). Furthermore, the decoration of CNTs improved the thermosyphon performance, especially at low input power.