This study presents the use of Silver-Carbon Quantum Dots (Ag-CQD) hybrid nanofluids,prepared by a facile wet chemical method,for heat transfer enhancement of wet cooling towers systems.The samples were characterized using different analyses,including FT-IR,XRD and TEM.After synthesizing the CQD,it was hybridized with silver nanopartieles and dispersed in water,using ultrasonic probe.The viscosity and density of the prepared nanofluid were investigated as a function of temperature and nanoparticles concentration,which demonstrated that there were no noticeable changes at lower particles concentration.Then,thermal conductivity and convective heat transfer coefficient were measured to evaluate the heat transfer enhancement of the nanofluid.At 45℃ and 0.5 wt％,the most significant thermal conductivity improvement compared to the base fluid was 24％;and 28％ enhancement of the heat transfer coefficient was obtained at Reynolds number of 15529.The nanofluid performance was evaluated in a wet cooling tower for investigating the efficiency and water consumption rate.The results indicated that the efficiency of the cooling tower,by applying Ag-CQD nanofluid,enhanced from 23.72％ to 28.23％;consequently,the amount of the consumed water decreased from 80.76 mL·min-1 to 69.67 mL·min-1 The results proved that the prepared nanofluid is a successful and promising candidate to enhance heat transfer.