A thermoplate is a heat transfer device consisting of two metallic sheets that are spot-welded according to an appropriate pattern over the whole surface area whereas the edges - except for connecting tubes - are continuously seam-welded. By applying a hydro-form technique, a channel having a complex geometry is established between the sheets. Such heat transfer devices are encountered in several areas of cooling and heating techniques and process technology, e. g. as condensers or evaporators. The objective of the described investigations was to numerically obtain the optimal geometry of the thermoplate with respect to heat transfer of the inside fluid that passes through the channel as a single phase. The numerical experiments show that the heat transfer potential of the thermoplate having a staggered arrangement of welding spots is markedly higher than that of a common flat channel, particularly at larger Reynolds numbers. The variations of the geometrical parameters show the potential for the heat transfer improvement in comparison to a corresponding parallel plate channel.