Study of the effect of tilt angle on the vaporization processes in a flat gravity heat pipe with a threaded evaporator.

This article was to study vaporization phenomena in a flat gravity heat pipe (GHP) with a threaded evaporator in the active boiling mode. For this purpose, a flat GHP with a threaded evaporator was made with the following parameters: length—245 mm; cross-sectional dimensions—15.5 mm × 4 mm; length of the evaporative threaded section—40 mm; threaded pitches 0.5 mm. A window measuring 9.5 mm × 240 mm covered with a hermetically sealed sight glass was made in the upper face of the heat pipe. Ethanol was used as the working fluid. The heater was powered at 50 W. The condenser section was cooled by forced air convection. The authors visually observed and analyzed the specific features of boiling at 6 different tilt angles (90°, 75°, 60°, 45°, 30° and 15°) and showed the effect of tilt angle of a flat GHP with a threaded evaporator on its thermal performance. The study determined the effect of tilt angle on the temperature distribution along the heat pipe, the average temperature in the heating zone, thermal resistance and heat-transfer coefficients. It was found that in the heating zone, the temperature did not exceed 67 °C, while the lowest value of thermal resistance, 0.295–0.3 °C W−1, was observed at the tilt angles of 75–90°. A comparison of the thermal performance of flat GHPs with threaded and bare evaporators showed an improvement in the thermal performance of a flat GHP with a threaded evaporator compared to a bare evaporator. The results of the study show good prospects for the use of inexpensive flat gravity heat pipes with a threaded evaporator for electronic equipment cooling systems. [ABSTRACT FROM AUTHOR]