Critical heat flux and pool boiling heat transfer analysis of synthesized zirconia aqueous nano-fluids

Abstract

In this work, experimental investigation on the pool boiling heat transfer to zirconium oxide nano-fluids was carried out. Zirconium oxide was prepared using chemical sol-gel method. Characterization of synthesized nano-particles was performed using scanning electron microscopic, x-ray diffraction and particle size count tests. The obtained nano-powders were then dispersed in water–ethylene glycol mixture 50:50 as a base fluid at volumetric particle concentrations of 0.025%, 0.05%, 0.075%, and 0.1%. Before boiling experiments, thermal conductivity of zirconium oxide was experimentally measured at different weight percentages. Results demonstrated that pool boiling heat transfer coefficient can be enhanced up to 12% at vol. %=0.1. A very slight particle deposition was also observed on the surface after boiling experiments, which had no impact on heat transfer coefficient, but to enhance the critical heat flux value up to 29%. Surface characterization demonstrated that static contact angle of liquid drop on the surface decreases by forming the thin deposition layer on the surface, which increases the wettability and capillary wicking action as well. Roughness of surface was found to be increased due to the deposition of nano-fluids too.