Dryout occurring in a heat pipe evaporator section is caused by insufficient coolant supply of wick structure, and generally considered as a failure mode of heat pipe operation. However, traditional dryout theory does not fit the bi-porous (bi-wick) wick structure research on the new mass transfer mechanism, such as liquid splash at high heat flux. The reported maximum heat flux on the similar wick structure may show a large deviation. Accordingly, dryout studies of bi-wick structures become critical and necessary to understand the limitation of the heat and mass transfer. In this article, carbon nanotube (CNT) clusters are used to investigate dryout of bi-wick structures. Within a closed system, evaporation and boiling phase change on CNT bi-wick structures is visualized to provide direct views on the occurrence and expansion of dryout zone. At the same time, the evaporator temperature variations versus heat flux are measured to characterize the temperature responses upon the bi-wick dryout. Investigations based on both visualization and measurement results show that dryout of CNT bi-wick structures are caused by insufficient liquid supply to create temperature elevation and in-plane heat transfer increase of the evaporator substrate. On the curvatures of heat flux versus the evaporator temperature, dryout can be defined as the appearance of the inflexion point on the heating section, and associated by the existence of large hysteresis of heat transfer performance. Numerical modeling of the temperature distribution on dried wick structure further indicates that traditional temperature measurement approaches are hardly to detect the occurrence of dryout and to provide the maximum temperature. High temperature hotspot on dried wick structure can be more destructive than temperature sensor measured.
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ASME/JSME 2011 8th Thermal Engineering Joint Conference
March 13–17, 2011
Honolulu, Hawaii, USA
Conference Sponsors:
- Heat Transfer Division
ISBN:
978-0-7918-3892-1
PROCEEDINGS PAPER
Dryout Studies of Carbon Nanotube Bi-Porous Structure
Qingjun Cai,
Qingjun Cai
Teledyne Scientific & Image Co., Thousand Oaks, CA
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Ya-Chi Chen,
Ya-Chi Chen
Teledyne Scientific & Image Co., Thousand Oaks, CA
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Chung-lung Chen
Chung-lung Chen
Teledyne Scientific & Image Co., Thousand Oaks, CA
Search for other works by this author on:
Qingjun Cai
Teledyne Scientific & Image Co., Thousand Oaks, CA
Ya-Chi Chen
Teledyne Scientific & Image Co., Thousand Oaks, CA
Chung-lung Chen
Teledyne Scientific & Image Co., Thousand Oaks, CA
Paper No:
AJTEC2011-44168, T30048; 7 pages
Published Online:
March 1, 2011
Citation
Cai, Q, Chen, Y, & Chen, C. "Dryout Studies of Carbon Nanotube Bi-Porous Structure." Proceedings of the ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASME/JSME 2011 8th Thermal Engineering Joint Conference. Honolulu, Hawaii, USA. March 13–17, 2011. T30048. ASME. https://doi.org/10.1115/AJTEC2011-44168
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