The effect of an electric field on the evaporation/boiling heat-transfer characteristic of an evaporation surface with rectangular microgrooves was experimentally investigated. R141b was used as the working fluid. The operating pressure was 1.01 x 10(5) Pa. Experimental results showed that electric field significantly affected the thermal performance of the evaporation/boiling surface. The heat-transfer enhancement effects increased with increased electric field strength. The heat-transfer coefficient enhancement factor could reach as high as 1.45 under the applied electric field. A visualization experimental study on the bubble behavior and nucleate site density was also conducted. Visualization experiment results indicated that the bubble departure time and nucleate site density decreased with increased electric field strength. (C) 2014 Elsevier Ltd. All rights reserved.