A liquid and vapour flow model coupled to a thermal model is presented for a flat plate heat pipe with micro-grooves. This model allows the calculation of the liquid and vapour pressures and velocities, the meniscus curvature radius in the grooves and the temperature field in the heat pipe wall from the heat source to the heat sink. The meniscus curvature radius is introduced in the thermal model to take into account the heat transfer at the liquid-vapour interface. Experimental measurements of the meniscus curvature radius as well as temperature measurements along a grooved heat pipe are compared to the model results. Both comparisons show the good ability of the numerical model to predict the maximum heat transport capability and the temperature field in the heat pipe. The model is used to optimize the heat pipe dimensions in order to-improve its thermal performances. (C) 2008 Elsevier Ltd. All rights reserved.