Dynamic characteristics of an environment-friendly refrigerant: Ammonia-water based TiO2 nanofluids

A device combining operation and dispersion was constructed to investigate the dynamic characteristics of ammonia-water based TiO2 nanofluids, including suspending ability, viscosity and surface tension for the first time. The results show that the dynamic circulating process can greatly improve the suspending ability of ammonia water based TiO2 nanofluids. Effect of sodium dodecyl benzene sulfonate (SDBS) on the suspending ability is investigated experimentally and theoretically. The absorbency ratio of TiO2 nanofluids with SDBS declines faster than that without surfactant at first, and then trends to gentle or even increase slightly in the later stages, which exhibits a better suspending ability for a long-term operation. Ultrasonic vibration brings a sudden but unsustainable rise in suspending ability. The results also showed that the dynamic circulating process has little effect on the viscosity of TiO2 nanofluids and the surface tension is primarily determined by the addition of SDBS.