Dryout studies of carbon nanotube bi-porous structure

Qingjun Cai*, Ya Chi Chen, Chung-Lung Chen

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

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 biwick 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.

Original languageEnglish
Title of host publicationASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011
StatePublished - 1 Dec 2011
EventASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011 - Honolulu, HI, United States
Duration: 13 Mar 201117 Mar 2011

Publication series

NameASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011

Conference

ConferenceASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011
CountryUnited States
CityHonolulu, HI
Period13/03/1117/03/11

Keywords

  • Carbon nanotube
  • Dryout
  • Heat pipe
  • Wick structure

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  • Cite this

    Cai, Q., Chen, Y. C., & Chen, C-L. (2011). Dryout studies of carbon nanotube bi-porous structure. In ASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011 (ASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011).