scholarly journals Heat pipe dryout and temperature hysteresis in response to transient heat pulses exceeding the capillary limit

2020 ◽  
Vol 148 ◽  
pp. 119135 ◽  
Author(s):  
Kalind Baraya ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Pipe ◽  
Temperature Hysteresis ◽  
Capillary Limit ◽  
Heat Pulses

Analysis of Structural Parameters of Grooved-Wicksin Micro Heat Pipes Based on Capillary Limits

2012 ◽  
Vol 499 ◽  
pp. 21-26 ◽  
Author(s):  
Xi Bing Li ◽  
Z.M. Shi ◽  
S.G. Wang ◽  
Q.M. Hu ◽  
L. Bao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Small Angle ◽  
Structural Parameters ◽  
Heat Pipes ◽  
Groove Depth ◽  
High Heat ◽  
High Heat Flux ◽  
Capillary Limit ◽  
Micro Heat Pipes

For great progress in heat pipe technology, a micro heat pipe has become an ideal heat dissipating device in high heat-flux electronic products, and capillary limit is the main factor affecting its heat transfer performance. Based on analyses of capillary limit and currently commonly-used groove structures, this paper built capillary limit models for micro heat pipes with dovetail-groove, rectangular-groove, trapezoidal-groove and V-groove wick structures respectively for theoretical analyses. The analysis results show that better heat transfer performances can be obtained in micro heat pipes with small-angle dovetail (i.e. a sector structure), rectangular and small-angle trapezoidal grooved wick structures when groove depth is 0.2-0.3mm and top-width-to-depth ratio is 1.2-1.5.

Operational Limitations of Heat Pipes With Silver-Water Nanofluids

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Lazarus Godson Asirvatham ◽  
Rajesh Nimmagadda ◽  
Somchai Wongwises
Keyword(s):  
Silver Nanoparticles ◽  
Heat Pipe ◽  
Heat Load ◽  
Operating Temperature ◽  
Particle Diameter ◽  
Heat Pipes ◽  
Working Fluid ◽  
Limit Value ◽  
Capillary Limit ◽  
Nanoparticles Concentration

The paper presents the enhancement in the operational limits (boiling, entrainment, sonic, viscous and capillary limits) of heat pipes using silver nanoparticles dispersed in de-ionized (DI) water. The tested nanoparticles concentration ranged from 0.003 vol. % to 0.009 vol. % with particle diameter of <100 nm. The nanofluid as working fluid enhances the effective thermal conductivity of heat pipe by 40%, 58%, and 70%, respectively, for volume concentrations of 0.003%, 0.006%, and 0.009%. For an input heat load of 60 W, the adiabatic vapor temperatures of nanofluid based heat pipes are reduced by 9 °C, 18 °C, and 20 °C, when compared with DI water. This reduction in the operating temperature enhances the thermophysical properties of working fluid and gives a change in the various operational limits of heat pipes. The use of silver nanoparticles with 0.009 vol. % concentration increases the capillary limit value of heat pipe by 54% when compared with DI water. This in turn improves the performance and operating range of the heat pipe.

A Mathematical Modeling Method for Capillary Limit of Micro Heat Pipe with Sintered Wick

2011 ◽  
Vol 175 ◽  
pp. 335-341
Author(s):  
Xi Bing Li ◽  
Chang Long Yang ◽  
Gong Di Xu ◽  
Wen Yuan ◽  
Shi Gang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat Dissipation ◽  
High Heat ◽  
Experimental Investigations ◽  
High Heat Flux ◽  
Micro Heat Pipe ◽  
Copper Powders ◽  
Capillary Limit

With heat flux increasing and cooling space decreasing in microelectronic and chemical products, micro heat pipe has become an ideal heat dissipation device in high heat-flux products. Through the analysis of its working principle, the factors that affect its heat transfer limits and the patterns in which copper powders are arrayed in circular cavity, this paper first established a mathematical model for the crucial factors in affecting heat transfer limits in a circular micro heat pipe with a sintered wick, i.e. a theoretical model for capillary limit, and then verified its validity through experimental investigations. The study lays a powerful theoretical foundation for designing and manufacturing circular micro heat pipes with sintered wicks.

Instability of Heat Pipe Performance at Large Axial Accelerations

2006 ◽  
Vol 129 (2) ◽  
pp. 137-140 ◽  
Author(s):  
A. Asias ◽  
M. Shusser ◽  
A. Leitner ◽  
A. Nabi ◽  
G. Grossman
Keyword(s):  
Heat Pipe ◽  
Liquid Flow ◽  
Heat Input ◽  
Large Amplitude ◽  
Heat Pipes ◽  
Strong Increase ◽  
Evaporator Temperature ◽  
Optimal Heat ◽  
Capillary Limit

To investigate the feasibility of using heat pipes in airborne systems, heat pipe performance at large axial accelerations in the range of 3–12g was studied experimentally. The heat input chosen corresponded to the optimal heat pipe performance without acceleration. When applied against the direction of the liquid flow (unfavorable orientation) the accelerations were large enough to exceed the capillary limit, as was seen from the strong increase in the evaporator temperature. The influence of accelerations in the direction of the liquid flow (favorable orientation) was found to be more complicated. While at the acceleration of 3g the heat pipe performance improved, at higher accelerations instability developed with resulting large-amplitude oscillations of the evaporator temperature. The instability found in these experiments is thought to be related to the geyser effect observed in thermosyphons.

Heat Transfer Limitation of a Micro Heat Pipe

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
K. N. Shukla
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transport ◽  
Analytical Expression ◽  
Micro Heat Pipe ◽  
Capillary Limit ◽  
Heat Transport Capability

An analytical expression for the heat transport capability of micro heat pipe is derived. The vapor continuum limitation has been considered in deriving the heat transport capability of a micro heat pipe. As the micro heat pipe uses sharp-cornered square, triangular, or other polygonal channels that can serve as capillary arteries, its transport capability depends on the capillary limit. It has been shown that the operating limit of the micro heat pipe depends on the vapor continuum limitation, capillary limit, and the gravity.

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