Manufacturing and Investigation of the Effect of Sintered Nickel Wick Structures Produced by Debinding Process for Loop Heat Pipes
Date Issued
2005
Date
2005
Author(s)
Yeh, Chien-Chih
DOI
zh-TW
Abstract
This study reports the investigation of the heat transport capacity enhancement in miniature loop heat pipe (mini-LHP).First, the theoretical analysis about dry-out limits of wick structures has been performed. According as the result of the theoretical analysis is to show that, optimum values of heat transport capability occur due to the influence of the effective capillary radius of curvature and porosity on both capillary pressure and permeability values. Besides, porosity is the most important function of the effective capillary radius of curvature and permeability values. According to the above-mentioned result, open pores have been chosen to discuss principally in the study.
In the experiment, sintered nickel wick structures produced by debinding and pressuring process have been used in order to control the effective capillary radius of curvature and obtain higher capillary pressure. On the other hand, because of open pores produced by debinding process the permeability values can be increased. The maximum heat transport capability will improve on the basis of the foregoing two advantages. The binder system composed of polypropylene, paraffin wax, and stearic acid has been chosen to be the sacrificial layer in the study. Based on the properties of the binders, the binders are heated and uniformly mixed with nickel powders. The binders adhered to nickel powders. The binder system can be removed in order to form more open pores by chemical and heating ways.
After debindering stages of the wick structure, the wick structures will be applied to LHP and measured the performances of heat transport capability. Wick structure produced by debinding process with the porosity about 75%, the mean pore size lies in 4μm and the permeability of 3×10^-12m^2is installed into a LHP system. The maximum heat transport capability of present LHP system approaches 150W, and the thermal resistance is 0.27℃/W when the performance test is conducted under the operating temperature of 90℃ and the heat sink temperature of 40℃. The testing results show that, debinding wick structures are better in heat transport capability than only loose powder sintering wick structures because this method can increase 40% in heat transport capability.
Subjects
迴路式熱管
毛細結構
脫脂
黏結劑
loop heat pipe
wick structure
debinding
binder
Type
thesis
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