Loop Heat Pipe
(LHP) performance strongly depends on the performance of a wick that is porous
media inserted in an evaporator. In this paper, the visualization results of
thermo-fluid behavior on the surface of the wick with microscopic infrared
thermography were reported. In this study, 2 different samples that simulated a
part of wick in the evaporator were used. The wicks were made by different two
materials: polytetrafluoroethylene (PTFE) and stainless steel (SUS). The pore radii
of PTFE wick and SUS wick are 1.2 μm and 22.5 μm. The difference of
thermo-fluid behavior that was caused by the difference of material was
investigated. These two materials include 4 different properties: pore radius,
thermal conductivity, permeability and porosity. In order to investigate the
effect of the thermal conductivity on wick’s operating mode, the phase diagram
on the q-keffplane was made. Based on the temperature line
profiles, two operating modes: mode of heat conduction and mode of convection
were observed. The effective thermal conductivity of the porous media has
strong effect on the operating modes. In addition, the difference of heat leak
through the wick that was caused by the difference of the material was
discussed.
References
[1]
Nagano, H., Fukuyoshi, F., Ogawa, H. and Nagai, H. (2011) Development of an Experimental Small Loop Heat Pipe with Polytetrafluoroethylene Wicks. Journal of Thermophysics and Heat Transfer, 25, 547-552. http://arc.aiaa.org/doi/abs/10.2514/1.T3614 http://dx.doi.org/10.2514/1.T3614
[2]
Nishikawara, M., Nagano, H. and Kaya, T. (2013) Transient Thermo-Fluid Modeling of Loop Heat Pipes and Experimental Validation. Journal of Thermophysics and Heat Transfer, 27, 641-647. http://dx.doi.org/10.2514/1.T3888 http://arc.aiaa.org/doi/abs/10.2514/1.T3888
[3]
Mitomi, M. and Nagano, H. (2014) Long-Distance Loop Heat Pipe for Effective Utilization of Energy. International Journal of Heat and Mass Transfer, 77, 777-784. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.06.001 http://www.sciencedirect.com/science/article/pii/S0017931014004669
[4]
Wu, S., Gu, T., Wang, D. and Chen, Y. (2015) Study of PTFE Wick Structure Applied to Loop Heat Pipe. Applied Thermal Engineering, 81, 51-57. http://www.sciencedirect.com/science/article/pii/S1359431115000629 http://dx.doi.org/10.1016/j.applthermaleng.2015.01.048
[5]
Demidov, A.S. and Yatsenko, E.S. (1994) Investigation of Heat and Mass Transfer in the Evaporation Zone of a Heat Pipe Operating by the “Inverted Meniscus” Principle. International Journal of Heat and Mass Transfer, 37, 2155-2163. http://www.sciencedirect.com/science/article/pii/0017931094903174 http://dx.doi.org/10.1016/0017-9310(94)90317-4
[6]
Kaya, T. and Goldak, J. (2006) Numerical Analysis of Heat and Mass Transfer in the Capillary Structure of a Loop Heat Pipe. International Journal of Heat and Mass Transfer, 49, 3211-3220. http://www.sciencedirect.com/science/article/pii/S001793100600113X http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.01.028
[7]
Ren, C. (2011) Parametric Effects on Heat Transfer in Loop Heat Pipe’s Wick. International Journal of Heat and Mass Transfer, 54, 3987-3999. http://www.sciencedirect.com/science/article/pii/S0017931011002444 http://dx.doi.org/10.1016/j.ijheatmasstransfer.2011.04.026
[8]
Zhang, X., Li, X. and Wang, S. (2012) Three-Dimensional Simulation on Heat Transfer in the Flat Evaporator of Miniature Loop Heat Pipe. International Journal of Thermal Sciences, 54, 188-198. http://www.sciencedirect.com/science/article/pii/S1290072911003553 http://dx.doi.org/10.1016/j.ijthermalsci.2011.12.002
[9]
Liao, Q. and Zhao, T.S. (2000) A Visual Study of Phase-Change Heat Transfer in a Two-Dimensional Porous Structure with a Partial Heating Boundary. International Journal of Heat and Mass Transfer, 43, 1089-1102. http://www.sciencedirect.com/science/article/pii/S0017931099002124 http://dx.doi.org/10.1016/S0017-9310(99)00212-4
[10]
Zhao, T.S. and Liao, Q. (2000) On Capillary-Driven Flow and Phase Change Heat Transfer in a Porous Structure Heated by a Finned Surface: Measurements and Modeling. International Journal of Heat and Mass Transfer, 43, 1141-1155. http://www.sciencedirect.com/science/article/pii/S0017931099002069 http://dx.doi.org/10.1016/S0017-9310(99)00206-9
[11]
Launay, S. and Mekni, N. (2010) Specifically Designed Loop Heat Pipe for Quantitative Characterization. Proceedings of the 15th International Heat Pipe Conference, Clemson, 25-30 April 2010.
[12]
Hemandez, A., Calvo, J.I., Pradanos, P. and Tejerina, F. (1996) Pore Size Distributions in Microporous Membranes. A Critical Analysis of the Bubble Point Extended Method. Journal of Membrane Science, 112, 1-12. http://www.sciencedirect.com/science/article/pii/0376738895000259 http://dx.doi.org/10.1016/0376-7388(95)00025-9
[13]
Singh, R., Akbarzadeh, A. and Mochizuki, M. (2009) Effect of Wick Characteristics on the Thermal Performance of the Miniature Loop Heat Pipe. Journal of Heat Transfer, 131, 1-10. http://dx.doi.org/10.1115/1.3109994 http://heattransfer.asmedigitalcollection.asme.org/article.aspx?articleid=1449646
[14]
Society of Japan Thermophysical Properties (2008) Thermophysical Properties Handbook. Yokendo Co., Ltd., Tokyo, 342.
