Abstarct: The purpose of this study is laboratory evaluation of cooling and heat transfer of the electronic components by the use of different fluids in slow flowing regime in heat sinks of copper made of CNC machine with the accuracy of ± 0.01 mm in three geometries of vertical, porous environment, and oblique. Regarding the previous studies, there has been no special attention to researches about the geometry changes of heat sink and comparing those changes in the electronic components cooling and by the use of nanofluids. In this study, the three mentioned geometries have been tested and the final results have been compared to each other. The tested fluids were distilled water and water-alumina nanofluids used with the volume percentages of 0.1 and 0.2 respectively. All of the experiments were done in different discharges and two fixed heat flux of 100 and 150 watts and the results were compared with each other. In order to increase the experiments’ accuracy and the reliability of the results, each experiment was replicated three times in the intended discharge and the fixed hear flux and the gathered data have been analyzed in accordance to statistical tables. The coefficients of convection heat transfer, final temperatures, the mean of the difference of logarithmic temperatures and heat resistance of the electronic component have been reported for a range of parameters. The results show the maximum increase of 16.3% of heat transfer in the heat sink of the porous environment geometry than the state of oblique groove geometry and the increase of 47.7% in compared with the state of vertical groove geometry. In addition, maximum increase of 37.36% related to the heat transfer of 0.2 % nanofluids has been observed in compared to the baxse fluid (distilled water) in the heat sink with the porous environment geometry. Consequently, the degree of heat transfer in the porous environment geometry is much better than the other used geometries in this study.