Stagewise parametric insights into Marangoni-driven heat transfer in dropwise condensation on micropillars

Designing micropillar surfaces requires understanding how microgeometry and operating conditions balance conduction and Marangoni-driven convection, from droplet nucleation through bridging to top spreading. To find these contributions, a validated four-stage COMSOL framework is modeled. A stage-dependent sensitivity is explored for geometric parameters ( L , H, and d) in the range 50 − 120 μ m , θ i = 100 ∘ − 150 ∘ , T sat = 323 , 343 , and 373 K. Marangoni convection, induced by temperature gradients, enhances heat flux in all stages and reduces conduction by redistributing temperature. Consequently, Q total , Mar / Q total , cond is lowest during bridging (about 1.5 − 2 ), where conductive dominates, and peaks in late, resistance-limited stages (about 2.6 − 3.3 ). Geometry effects are strongly stage-dependent. Reducing spacing from L = 120 μ m to 70 μ m increases heat flux twofold in Stage 1 and fourfold in Stage 3 due to stronger confinement and sharper temperature gradient, while Stage 2 is nearly insensitive. Increasing height penalizes bridging, decreasing about 40 % of heat flux when H =  50 μ m increases to 100 μ m . Moreover, increasing diameter strengthens late growth, Stage 3 flux rises 3–4-fold when d =  50 increases to 120 μ m . Rising T sat , driving force, increases conduction-only heat flux by more than 55 % ; however, it reduces Q total , Mar / Q total , cond . For example, Q total , Mar / Q total , cond = 2.2 reduces to 1.5 in Stage 1 by changing T sat = 323 K to 373 K . These stage-wise maps provide design rules for Marangoni-leveraged micropillar condensers.