The electrohydrodynamic (EHD) enhancement of pool boiling from smooth and ribs surfaces in R113 is studied experimentally in this paper. Measurements and visualization methods are utilized to record and observe boiling heat transfer phenomena on heated surfaces with different rib heights (0 mm, 0.2 mm, 0.5 mm and 2.0 mm), and the "field trap effect" on rib surfaces is discussed. It is found that the boiling curve under an imposed electric field can be divided into three regions: low-superheat, medium-superheat and high-superheat regions, and EHD enhancement mechanisms on pool boiling heat transfer in these regions are investigated. In the low-superheat region, electroconvection is the main mechanism for heat transfer enhancement. In the medium-superheat region, both electroconvection and nucleate boiling heat transfer exist but bubble growth and departure are inhibited by the electrical force, and thus nucleate boiling heat transfer deteriorates. In the high-superheat region, because vapor columns are broken into small vapor slugs under the action of the electrical force, boiling heat transfer and critical heat flux are thus enhanced. (C) 2015 Elsevier Ltd. All rights reserved.