Regulation of non-uniform electric field-induced bubble migration for pool boiling heat transfer enhancement on rib-structured surfaces

Pool boiling is a highly efficient thermal management method for high-heat-flux devices. Under high heat flux, intense bubble coalescence forms a persistent vapor layer. This layer blocks liquid replenishment, causing surface dryout and boiling crisis. Numerical simulations and flow visualization experiments are combined to investigate bubble dynamics and heat transfer of dielectric fluid HFE-7100 on ribbed surfaces under non-uniform electric fields. A 2D transient coupled model integrating electrostatics, two-phase flow, phase field, and phase-change heat transfer is established. Predicted bubble deformation and heat transfer trends are partially validated against experimental data. The effects of applied voltage, rib spacing, and wall superheat on electric field distribution, vapor redistribution, and regional enthalpy flux are analyzed. Results show that electric field intensity concentrates primarily at rib tips, followed by rib tops and roots. Under the adopted dielectric approximation, the interfacial permittivity gradient term drives the gas-liquid interface from high-field rib tip regions to low-field inter-rib regions. The temperature-permittivity gradient term induces secondary motion of near-wall liquid, enhancing local flow disturbances. For rib spacing R s = 7 mm, raising applied voltage from 0 to 45 kV increases the predicted global mean enthalpy flux by 84.3% at wall superheat Δ T = 35 K. At applied voltage U = 30 kV, increasing rib spacing from 3 to 9 mm raises the predicted critical enthalpy flux (CEF) from 160.1 to 238.1 kW/m 2 , a 48.7% improvement. Within the studied parameter range, smaller rib spacings perform better at low wall superheat. Larger rib spacings delay vapor film spreading at high wall superheat. These results provide a basis for understanding the coupled regulation of bubble migration, vapor redistribution, and local heat transfer by a non-uniform electric field and ribbed structures.