In this work we study heat transfer from a complex geometry consisting of crossing cylinders subject to forced convection. For several sizes of a wire-mesh inserts direct numerical simulations (DNS) are performed using an implicit implementation of the immersed boundary method (IBM) The local heat flux is studied and compared to the total heat flux. A heat transfer correlation is derived describing the Nusselt number as a function of the Reynolds number and the ratio of the pitch to the cylinder diameter, p / D. (C) 2014 Elsevier Ltd. All rights reserved.