Experimental Investigation on the Thermal Performance of Axial Groove Heat Pipe with Various Orientations

Heat pipes are highly efficient thermal management devices widely utilized in aerospace applications, particularly aluminum/ammonia heat pipes. They remain a subject of continuous interest for researchers, engineers, and scientists. This study investigates the thermal performance of an aluminum/ammonia heat pipe with an axial groove wick. The heat pipe has a total length of 1000 mm, consisting of a 250-mm evaporator, 250-mm condenser, and 500-mm adiabatic section. Experiments were conducted under heat loads ranging from 50 W to 450 W, with a cooling water temperature of 30 °C and a flow rate of 1 LPM. The heat pipe was tested in both horizontal (0°) and vertical (90°) orientations. Results indicate that the vertical orientation significantly improves thermal performance, yielding lower axial temperatures and overall thermal resistance. At the maximum heat load, the evaporator temperature in the vertical position was 18–21 °C lower than that in the horizontal position. Additionally, the overall thermal resistance in the vertical orientation was 37.5–52.5% lower compared to the horizontal arrangement. The minimum total thermal resistance was recorded at 250 W, measuring 0.0494 °C/W in the vertical position and 0.0823 °C/W in the horizontal position. Furthermore, axial and circumferential temperature distributions were analyzed across the evaporator, adiabatic, and condenser sections. A comprehensive discussion of these findings is presented in this investigation.