The thermal and hydrodynamic characteristic of straight-channel longitudinal fin heat sink under forced air-cooling is studied experimentally and numerically using a Phoenics 3.3 (CHAM, UK) CFD software. The aim of the study is to simulate and compare the viability of employing Phoenics code as effective and efficient means gathering the vast amount of data required to adequately quantify heat sink characteristics on the lower scale with the two scale experimental data reduced according to requirements of VAT. For this case is analyzed the basic homogeneous heat transfer performance features and shown insolvency of using heat transfer and effectiveness parameter. A number of data reduction parameters and procedures were developed using scaling heterogeneous formulation by volume averaging theory (VAT). Analysis brought in this work supports the procedures used to connect the two scale VAT experiment with the full lower scale direct numerical modeling for the semiconductor heat sink.