Visual experiment of oscillating flow heat pipe with nanofluids

Abstract

The effect of solid particles on the performance of oscillating flow heat pipe (O-HP) has been investigated using a visualized loop O-HP experimental system. The O-HP system was made of Al plate with 2×2 mm chase and flow inside the chase was visualized through transparent plastic cover. Al 2O3 nano particles (30 nm nominal diameter) were dispersed into ethanol and water as working fluids of O-HP. Heat transfer performance of the O-HP was tested under concentration of 0 - 3.0 wt% of Al2O 3 nanofluids at volume filling ratio of 50%. Experimental results show that the water-based nanofluids enhances the heat transfer performance of the O-HP; however, after repeating the operation, the heat transfer performance decreases as the nano particles deposits. Once the deposits occur, it is difficult to recover the performance without an external manipulation. The reason of the particle deposition was experimentally investigated. The results imply that the particle deposition can be caused by the rapid increase of local particle concentration during evaporation process in narrow chase. Furthermore, physical properties (viscosity, thermal conductivity) of the nanofluids were measured and the mechanism of existence of optimal particle concentration was discussed. © 2013 The Japan Society of Mechanical Engineers.