An experimental study was conducted to investigate the thermal performances of a new type of copper wire-bonded flat heat pipe using water, ethanol and nanofluids as working fluids. The influences of the working fluid, the operating temperature or operating pressure, the wire diameter and the space gap between two wires on the thermal performances of the heat pipe were investigated. Experimental results show that the wire diameter has an important effect on the heat transfer coefficient but has hardly impact on the maximum heat flux. The space gap between two wires not only has an important effect on the heat transfer coefficient but also has a significant impact on the maximum heat flux. The maximum heat power increases apparently with increasing the operating temperature. Using nanofluid as working fluid can improve the heat transfer performance of the heat pipe; the best heat transfer performance of heat pipe is achieved at the concentration of 1.0 wt.% under different saturation temperature conditions with different nanofluid; nanofluid is a kind of new working fluid to the copper wire-bonded flat heat pipe. (C) 2013 Elsevier Ltd. All rights reserved.