Start-up characteristics of gravity heat pipes with a threaded evaporator
Abstract
The authors experimentally study start-up characteristics of copper gravitational heat pipes with a threaded evaporator filled with four different heat transfer fluids — methanol, R141b refrigerant, isobutane (refrigerant R600a), and n-pentane — that do not freeze at temperatures as low as –30°C. The heat pipes were 260 mm long, had a diameter of 12 mm, a thread length in the evaporation zone of 45 mm, a thread pitch of 0. 5 mm, and a fluid volume of 1.6 – 1.7 ml (filling ratio of 50 – 55%). It was shown that changing the inclination angle (15°, 60°, 90°) does not significantly affect the temperature in the heating zone of the heat pipe (maximum 5°C for methanol). More significant is the influence of the ambient air temperature (–30°C, +20°C and +40°C). The maximum thermal regime stabilization time (22 – 24 min) was observed in the heat pipe with methanol at an ambient temperature of –30°C, while the minimum stabilization time (11 – 12 min) was recorded for heat pipes with isobutane and n-pentane at an air temperature in the chamber of +40°C.
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Copyright (c) 2024 Roman Melnyk, Dmitry Kozak , Yurii Nikolaenko, Demyd Pekur
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