Thermal Performance of Self-rewetting Fluid Heat Pipe Containing Dilute Solutions of Polymer-capped Silver Nanoparticles Synthesized by Microwave-Polyol Process
Masahide Sato, Yoshiyuki Abe, Yuki Urita, Roberto Di Paola, Anselmo Cecere and Raffaele Savino
Dilute aqueous solutions of higher carbon number (≥4) alkyl alcohols have particular properties that the surface tension increases with temperature. In the case of boiling phenomena, increasing surface tension at a higher temperature of such kinds of fluids causes supply of cooling liquid at dry patch on the heated surface. Therefore, using these kinds of fluid, named “self-rewetting fluid” as heat pipe working fluid has led to improvement of heat transfer performance comparing conventional heat pipe working fluid such as water. In this study, thermal performance of a new type of self-rewetting fluid heat pipe containing aqueous 1-butanolic solution with microwave-assisted synthesized very dilute (2.5 × 10–4 mol/dm3) polyvinylpyrrolidone (PVP) -capped silver nanoparticles (nano-self-rewetting fluid) has been investigated experimentally. Dryout limits of some PVP-capped silver nano-self-rewetting fluid heat pipe were almost twice as high as that of base working fluid heat pipe. Also, the positive surface tension gradients with temperature of same kinds of PVP-capped silver nano-selfrewetting fluids were increased. On the other hand, other thermophysical properties such as thermal conductivity and viscosity were almost same as those of base fluid. Thus, the thermal performance enhancement of heat pipes with PVP-caped silver nano-self-rewetting working fluids was mainly caused by the surface tension temperature dependencies changes of silver nano-self-rewetting fluids.
Keywords: Self-rewetting fluid, Nanofluid, Silver nanoparticle, Heat pipe, Dryout limit.