A numerical study is conducted for laminar natural convection heat transfer occurring in a vertical stack of parallelogrammic partial enclosures. The partitions separating adjacent enclosures are always parallel to each other. however their angle relative to the horizontal can change. The length of each partition is less than the width of the main enclosure, which has an aspect ratio of 5. Adjacent enclosures are thermally linked through the fluid exchange. and through the finite thermal conductivity of the partitions. The thermal diode effect offered by the geometry is analyzed in terms of the partitions' inclination angle and materials for different thermal boundary conditions/operating conditions. The thermal diode effect, and even its actuating direction, can be changed by changing the inclination angle of the partitions. The main focus of the present work deals with the heat transfer analysis based on the overall Nusselt number, and the visualization of the flow field and heat transfer mechanisms, by using the isotherms, the streamlines and the heatlines. Results clearly indicate the high potential of this configuration, based on the thermal diode effect, to be used as an effective heat transfer device in real situations of thermal engineering. The number of governing parameters is high, and the results are presented only for situations selected on the basis of their relevance. For computational expediency, it is analyzed the solution obtained for one single parallelogrammic partial enclosure of the stack, which is thermally linked with its adjacent enclosures by using vertical cyclic boundary conditions. This procedure has some potential, since it yields results with good accuracy to predict the overall thermal behavior of the stack. (C) 2004 Elsevier Ltd. All rights reserved.