This research reports the simulation done to a heat sink of a commercial TEM with a Peltier module. The analysis was done at the central fin for 4 cases of separation of the fins at the cold and hot side [p=5.08, 3.81, 2.54, 1.27 mm] and 6 cases of convective heat transfer [h=5, 20, 50, 100, 150 and 200 W/[m2K]]. Results show that the thermal behavior is similar for each separation of fin without significant difference of temperature. The main differences were observed at the hot side were the case of p=1.27mm and h=200 W/[m2K] is the best option to reduce the temperature of the heat sink in the hot side of a TEM.