Experimental Investigation to Elucidate the Temporal Effect of Nanofluids on the Thermal Performance of Heat Pipes

The perplexity associated with the relevant practical application of the nanofluid lies with the alteration of the surface morphology. In the context of a heat pipe, it is established that the nanofluids, when used for a longer duration, are prone to agglomerate, and using them as working fluid can influence the heat pipe's performance. The current work aims to examine the heat pipe performance deviation charged with Al2O3/de-ionized water nanofluid for extended operation periods of 0, 3, 6 and 12 months. The fabricated heat pipes charged with 40% of evaporator volume with various concentrations of Al2O3 base nanofluid (0.1%, 0.5%, and 0.8% volume fraction) were tested for various heat inputs (10, 30, and 60 W). The temporal effect of nanofluid on heat pipe performance was analyzed after successive intervals. The results propose that the heat pipe charged with nanofluid exhibits superior thermal performance in lieu of de-ionized water. Also, the performance characteristics of the heat pipe were more consistent and reliable for higher heat input of 60 W compared to 10 W when tested after a longer duration. The nanoparticles' sedimentation and accumulation on the mesh clog adversely affect the contact angle and thus help in increasing the boiling limit.