Effect of Sintering Temperature Curve in Wick Manufactured for Loop Heat Pipe

This investigation examines the effect of the sintering temperature curve in manufactured nickel powder capillary structure (wick) for a loop heat pipe (LHP). The sintering temperature curve is composed of a region of increasing temperature; a region of constant temperature and a region of declining temperature. The most important region is that in which the temperature increases, as an index in the stage in which the temperature increases. The wick of nickel powder is manufactured in the stage of fixed sintering temperature and the time between the stage of constant temperature and the stage of falling temperature. When the slope of the curve in the region of increasing temperature is unity (equivalent to 10 °C/min), the structure of the wick is complete and the heat transfer performance is optimal. The result of experiment test demonstrates that the heat transfer performance is optimal at 320W; the minimal total thermal resistance is approximately 0.18°C/W, and the heat flux is 17W/cm2; the internal parameters of the wick are an effective pore radius of 3.1 μm, a permeability of 3.25×10-13m2 and a porosity of 71%.

Authors:

• Shen-Chun Wu
• Chuo-Jeng Huang
• Wun-Hong Yang
• Jy-Cheng Chang
• Chien-Chun Kung

Keywords:

• Loop heat pipe (LHP)
• capillary structure (wick)
• sintered temperature curve.

References:

[1] Maidanik, Y. F., Vershinin, S. V., Kholodov, V. F. and Dolgirev, J. E.,
"Heat Transfer Apparatus", US Patent, No. 4515209, 1985.
[2] Wolf, D. A., Ernst, D. M., and Phillips, A. L., "Loop Heat Pipes-Their
Performance and Potential", SAE Paper, No.941575, 1994.
[3] Gernert, N. J., Baldassarre, G. J. and Gottschlich, J. M., "Fine pore loop
heat pipe wick structure development", SAE Paper, No.961319, 1996.
[4] Cheung, K. H., Hoang, T. T., Ku. J. and Kaya, T., "Thermal Performance
and Operational Characteristics of Loop Heat Pipe (NRL LHP)", SAE
Paper, No. 981813, 1998.
[5] Kaya T. and Jentung Ku, "Thermal Operational Characteristics of a
Small-Loop Heat Pipe", J. Thermophys. Heat tr., Vol.17 No.4, 2003, pp.
464-470.
[6] Maidanik, Y. F., "Loop Heat Pipes-review", Appl. Therm. Eng., Vol.25,
No.5-6, 2005, pp. 635-657.
[7] Li, J., Zou, Y., Cheng, L., Singh, R. and Akbarzadeh A., "Effect of
fabricating parameters on properties of sintered porous wicks for loop
heat pipe", Powder Technology, Vol.204 No.2-3, 2010, pp.241-248.
[8] Tang, Y., Zhou, R., Lu, L. and Xie, Z., "Anti-Gravity Loop-Shaped Heat
Pipe with Graded Pore-Size Wick", Appl. Therm. Eng., In Press,
Accepted Manuscript, 2011.
[9] Tracey, V. A., "Effect of sintering conditions on structure and strength of
porous nickel", Powder Metallurgy, No. 2, 1979, pp. 45-48.
[10] Wu, S. C., Huang, C. J., Wei, K. H. and Chen, Y. M., "Enhanced
performance of monoporous wick applications at Loop Heat Pipe by
experimental design", Appl. Therm. Eng., (2011) Submitted.
[11] Tracey, V. A., "Pressing and Sintering of Nickel Powders", International
Journal of Powder Metallurgy and Powder Technology, Vol.20, 1984,
pp.281-285.
[12] ASTM E128-61, "Standard test method for maximum pore diameter and
permeability of rigid porous filters for laboratory use".
[13] Kline, S. J. and McClintock, F. A., "Describing Uncertainties in Single
Sample Experiments", Mechanical Engineering, Vol.75, 1953, pp.3-8.