Publication Date

Fall 2019

Degree Type


Degree Name

Master of Science (MS)


Mechanical Engineering


Nicole Okamoto


Ammonia Filled, Heat Pipe, Start-up power, Thermosyphon

Subject Areas

Mechanical engineering


Boiling and condensing of internal working fluids are essential heat transfer concepts which heat pipe technology relies on for transporting a large amount of heat between two distanced points effectively. Tilt angle and working fluid saturation temperature have a direct impact on how well the evaporator is flooded. This paper focuses on how the tilt angle and the working fluid saturation temperature affect the start-up heat input requirements for an S shaped axial grooved ammonia thermosyphon heat pipe. A series of experiments was performed by supplying and extracting heat to the evaporator and condenser of the thermosyphon heat pipe. Temperature of the evaporator and condenser was monitored to capture start-up behavior upon heat input. The evaporator temperature was found to be slightly elevated before the internal working fluid begins to boil. It decreased once boiling starts and initiates the thermosyphon process. The test results showed that the evaporator start-up temperature difference was found to be higher as fluid saturation temperature increases, and becomes lower as the fluid saturation temperature decreases. The start-up heat input requirement to initiate start-up in the evaporator was determined to be constant throughout the range of tilt angles and saturation temperatures.