Gas turbine cooling has steadily acquired major importance whenever engine performances have to be improved. Among various cooling techniques, film cooling is probably one of the most diffused systems for protecting metal surfaces against hot gases in turbine stages and combustor liners. Most recent developments in hole manufacturing allow us to perform a wide array of microholes, currently referred to as effusion cooling. Though some drawbacks of such a concept still need to be solved (manufacturing costs, holes blockage, and then system reliability), its potential is now worth investigating. This paper presents the validation of a simplified numerical two-dimensional conjugate approach through a comparison with the experimental results of effectiveness for an effusion plate. A preliminary test is performed with the steady-state technique, using thermochromic liquid crystal wide-band formulations. Results are obtained in terms of local distributions of adiabatic effectiveness. Average values are compared with calculations to validate the numerical code. Then, the design of experiment approach is used to perform several conjugate numerical tests (about 180), so as to derive the behavior of different effusion plates in terms of overall effectiveness and mass flow rate. Data are analyzed in detail, and a correlative approach for the overall effectiveness is proposed.