[en] In this study, the impact of thermal radiation on fluid flow and heat transfer within a square enclosure filled with ethylene glycol- Co₃O₄-diamond hybrid nanofluid on the basis of experimental data is investigated. The governing equations are being solved by employing the finite volume method and the SIMPLER algorithm. In investigating this problem, the Rayleigh number is taken from $Ra={10}^3$ to $Ra={10}^5$ and the volume fraction of nanoparticles in the range from 0.0 to 0.075 percent and the values from 0 to 2 are considered for the radiation parameter. It is observed from the results that in all the considered volume fractions, the average Nusselt number is increased by increasing the value of the radiation parameter. In all of the considered values for Ra and the volume fractions, the most relevant enhancement in the average Nusselt number corresponding to the enhancement of the radiation parameter is 200.25 percent which occurs in $Ra={10}^5$ while the volume fraction is 0.075. In all volume fractions investigated, the maximum value of the stream function is increased by increasing the value of the radiation parameter. For all Rayleigh numbers in each of the investigated values of the radiation parameter, the maximum value of the stream function decreases by increasing the volume fraction of nanoparticles. The results of this study reveal that the effect of the thermal radiation in high Rayleigh numbers is not considerable.