In this study, we established transient performance calculation models for air-cooled and heat pipe two-stage thermoelectric cooler devices operating in confined spaces with internal heat sources. We determined the variation laws of the cooling space temperature, temperature difference between the two junctions of the module, and cooling coefficient with time as well as compared the effects of the two heat dissipation methods on the device characteristics. We analyzed the effects of the operating current, thermocouple two-stage area ratio, and thermocouple leg length ratio on the temperature, elapsed time, and cooling coefficient. Our results showed that for an internal heat source power of 6W, the temperatures of the air-cooled and heat pipe coolers were 8.28 and 7.86℃ higher than that observed without a heat source. Furthermore, the cooling temperature of the heat pipe cooler was 1.85℃ lower than that of the air-cooled cooler, whereas its cooling coefficient was 12.12% higher than that of the air-cooled cooler.