The effect of hygroscopic liquids on the spatial controlling of condensation on low-temperature surfaces

Condensation is a ubiquitous natural phenomenon with both detrimental and beneficial implications. The key point to minimize its harmful effects while harnessing its potential for various applications is the spatial controlling of condensation. In recent years, using hygroscopic liquids for spatially controlling condensation has gradually emerged as a promising strategy. However, the underlying mechanisms and influencing parameters of controlling condensation with hygroscopic liquids remain insufficiently understood. In this paper, the effect of hygroscopic droplets in suppressing condensation on low-temperature surfaces, specifically -15 ℃ to 15 ℃, under different conditions, including substrate temperature, cooling time, droplet volume are studied. A typical hygroscopic liquid, dipropylene glycol, was employed to illustrate this issue. The results indicated that distinct ring-shaped dry zone forms around dipropylene glycol droplets on low-temperature surfaces, evidencing their efficacy in inhibiting condensation. Experiments and theoretical analysis reveal that the ratio of the dry-zone radius to the droplet radius is a function of substrate surface temperature, scaling as 1/( T dew - T c ). The results also show that cooling time has a negligible effect on this ratio over short periods. Furthermore, the ratio slightly decreases with increasing droplet volume at higher substrate temperatures, while remaining nearly constant at lower temperatures. These findings may enhance our understanding of the condensation inhibition effect of hygroscopic droplets and also provide valuable insights for potential applications in condensation control.