START-UP POWER REQUIREMENTS FOR AN AXIAL GROOVED THERMOSYPHON
Thermosyphons are used due to their passive nature and their ability to provide effective heat transfer with minimal losses. This paper investigates how the tilt angle and working fluid saturation temperature affects the start-up heat input requirements for an "S shaped" axial grooved ammonia thermosyphon. The start-up heat input requirements are analyzed from horizontal to vertical for reflux operation in increments of 10° at 20 °C saturation temperature, and vertical 90° reflux operation at a range of saturation temperatures from 20-60 °C in increments of 10 °C. Temperatures of the evaporator and condenser are monitored to capture start-up behavior upon heat input. The evaporator temperature decreases once boiling starts and initiates the thermosyphon process. The evaporator start-up temperature differences are recorded for the entire test matrix. It is found that the evaporator start-up temperature difference is higher for steeper tilt angle. It
becomes smaller as the tilt angle decreases. As for saturation temperature range, the evaporator start-up temperature difference is found to be higher for higher saturation temperature. It becomes smaller as the saturation temperature decreases.