Increasing the stability of nanofluids and its estimation methods

Nanoparticles are materials which have at least one of their dimensions (length, width, height) at the nano scale (among 1 and 100 nm). Nanofluids are obtained from the distribution of particles with nano dimensions in normal fluids. Common fluids such as water, oils and ethylene glycol, which are usually used in heat transfer, have limited ability in terms of thermal properties. The interesting properties of nanofluids (such as high heat transfer coefficient) and the great potential they show for increasing heat transfer have caused this group of fluids to be in the focus of researchers' attention in recent years. One of the key factors in optimizing the properties of these fluids is their stability. The gathering of particles and their agglomeration increases the possibility of sedimentation, reduces the stability of the suspension, and causes the loss of the properties of the suspension, such as thermal conductivity, viscosity, and increase in heat capacity. In this research, methods of increasing stability and inspection tools were investigated. The results showed that the simultaneous use of ultrasonic vibration and surface activating substances (surfactant) has a significant effect on the stability of nanofluid. And two methods of using DLS light scattering and ultraviolet-visible absorption spectrometry have been used by many researchers in their research in order to check stability.