Heat transfer to a liquid bridge from a surrounding liquid via a heating/cooling ring. (January 2023) - Saifi, A.H.
Highlights: Effect of heater and cooler rings surrounding a capillary bridge has been analyzed. Heater causes a higher convection than a cooler, in general. Convection increases as the heater ring is moved upwards. Convection decreases as the cooler ring is moved upwards. Heat transfer rate is minimum for the cooler position midway between the discs. An oscillatory flow regime is discovered for lower bridge aspect ratios. Graphical abstract: Abstract: A centimeter-sized liquid bridge constrained between two insulated discs is surrounded by another immiscible liquid, which is heated or cooled via a ring heater/cooler. The effect of ring position on the circulation patterns and heat transfer is investigated with the help of 2D axisymmetric numerical simulations. Such systems are important in capillary adhesion devices, biological heat transfer and phase-change-material-based thermoelectric generators. An increase in the heat transfer rate is observed when the heating (cooling) ring is placed near the bottom (top) disc. However, the net heat transferred to the capillary bridge is not a monotonic function of the heater/cooler position. The cooler configuration shows a minimum heat transfer for the cooler ring lying midway between the two solid discs, whereas, for the heater configuration this occurs for a heater position further below this point. Moreover, the heat transfer rate changes drastically with respect to the cooler position near the top disc, whereas, it is more gradual in the cases with a heating ring surrounding the capillary bridge. Additionally, an unstable regime is discovered for low aspect ratios which causes temporal oscillations in the velocity and temperature fields.