A computational analysis in a rotary regenerative air preheater subject to pre-established mass flow rate is performed. The heat transfer rate, the pressure drop and the outlet temperatures of gas streams are calculated from different matrix porosity values. The fluid flow and the convective heat transfer coefficient are determined from correlations. The total heat transfer is obtained using the Effectiveness-NTU method specific to regenerative air preheaters. Three typical regenerative air preheaters with both streams under the laminar flow regime are investigated. A range of porosity values that provide good thermal exchange and low pressure drop in the equipment is chosen for each examined air preheater. The behavior of the outlet temperatures of each gas stream as function of porosity is also analyzed. The results show that the porosity ranges shorten when the typical pressured drop values for each regenerative air preheater are introduced in the analysis. In addition, the behavior of the outlet temperatures is compatible with the behavior of the heat transfer rate as the porosity changes.