|M.Sc Thesis||Department of Mechanical Engineering|
|Prof. Emeritus Grossman Gershon|
|Dr. Amiram Leitner|
Airborne systems have electronic components that could fail as a result of high temperatures developing during flight. Due to its low weight, small dimensions and ability to transfer a large amount of heat, the heat pipe can be an appropriate device for cooling the electronic component.
The main goal of the present research was to investigate the feasibility of heat pipe in airborne systems. The work included both numerical and experimental investigations. Severe ambient conditions (extreme accelerations and temperatures) were assumed. A thermo-hydrodynamic numerical model, which combines a “Resistor-Capacitors” thermal model and a hydrodynamic model was written using commercial heat transfer software Sinda/G.
Experiments were performed to verify, analyze and calibrate the model.
An experiment setup that enabled to conduct experiments at various temperatures in the range of 25-85°C was built. To impose accelerations in different directions in the range of 3-12 g, the set up was positioned on a centrifuge.
The static experiments (no acceleration) demonstrated the advantage of heat pipe as an efficient heat transfer device.
In the dynamic experiments, no influence of acceleration perpendicular to the heat pipe liquid flow on the heat pipe performance was observed.
When acceleration was imposed against the liquid flow direction, even the minimum acceleration ( 3 g ) prevented the circulation of the working fluid in the heat pipe causing it to stop working.
An intriguing phenomenon was observed at accelerations in the direction of the liquid flow. While small acceleration improved the heat pipe performance, at higher accelerations instability developed which caused strong fluctuations in the heat pipe performance.
The instability is thought to be related to the geyser effect observed in thermosyphons. When corrected to include this effect, the model succeeded to predict the fluctuation.