M.S. Thesis Presentation by Christy Lynn Etter
Monday, May 15, 2000

(Dr. James Hartley, advisor)

"Numerical Model of the Transient Behavior of a Copper-Water Heat Pipe"


Heat pipes are reliable, low cost method of heat removal.  They utilize the latent heat of vaporization of working fluid to dissipate extremely high input heat fluxes.  A typical heat pipe is a closed tube lined with a porous wicking structure saturated with the liquid phase of a working fluid.  Heat is applied to the evaporator section where the liquid in the wick is vaporized.  This vapor then travels to the condenser section where it is cooled and condenses into the wick.  The liquid is transported back to the evaporator section by capillary action in the wick.  The heat pipe repeats this cycle continuously during normal operation.

Copper-water heat pipes may be used to cool telecommunications equipment enclosed in cabinets located outside.  It is necessary to understand the transient performance of these heat pipes under various operating temperatures since the heat pipes may be exposed to may different temperature due to changing weather and operating conditions.  A numerical model was designed to investigate the transient start-up behavior of copper-water heat pipes.  Energy balances were performed on each heat pipe section and the resulting differential equations were solved using a differential equation solver.  The model allows the used to modify the heat pipe characteristics and operating conditions to model many different situations.

The results of this research showed that the model predicts the steady state performance of a wide range of heat pipes extremely well, while under-predicting the thermal time constant.  Heat pipes were shown to operate well in a wide range of conditions while removing high levels of heat input.