Effect of natural convection and diffusion on liquid-liquid phase separation behaviors of partially miscible solutions with lower critical solution temperature

Abstract

Partially miscible solutions with lower critical solution temperature (LCST) have significant potential in improving the cooling performance of microchannel heat sinks, reducing pressure drop, and ensuring stable operation of the cooling system. Thereby, it is essential and meaningful to clearly understand the liquid-liquid phase separation process driven by natural convection and diffusion to enhance the cooling performance in microchannels further. In this paper, the liquid-liquid phase separation behaviors of 2-Butoxyethanol/water solutions in a slit cavity were visually investigated. Moreover, the effect of driven force was discussed on the temperature distribution, motion of boundaries and phase separation rate. Furthermore, the effect of the mass fraction was discussed on the phase separation temperature range and phase separation rate. The results proved that the phase separation rate was kept at 0.39%·s−1 on average in the whole slit cavity by the natural convection, whereas the driving force of diffusion was so weak that the phase separation rate rapidly decreased along the vertical direction. That means reasonable enhancements of the disturbance in the microchannel could significantly increase the phase separation rate. Moreover, the phase separation rate increased with an increase in the mass fraction, and the solution with the best cooling performance could be found at 27.4%≤ω2-BE≤35%. The results are expected to provide theoretical guidance to prepare solutions with suitable phase separation temperature range and excellent cooling performance.