Measurement of Variable Conductance Ultrathin Vapor Chambers to Double the Capillary Limit During Transient Startup

2021 ◽  
Author(s):  
Ryan Lewis ◽  
Y. C. Lee
Keyword(s):  
Capillary Limit

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.

Thermal performance and capillary limit of a ceramic wick applied to LHP and CPL

2012 ◽  
Vol 41 ◽  
pp. 92-103 ◽  
Author(s):  
Paulo H.D. Santos ◽  
Edson Bazzo ◽  
Amir A.M. Oliveira
Keyword(s):  
Thermal Performance ◽  
Capillary Limit

A Novel Thermo-Hydraulic Test Platform for Micropillared Array Thermal Wick Optimization

2012 ◽  
Author(s):  
Collier Miers ◽  
Geoff Wehmeyer ◽  
Carlos H. Hidrovo
Keyword(s):  
Analytical Model ◽  
Capillary Flow ◽  
Electronic Devices ◽  
Heat Removal ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Capillary Forces ◽  
Limiting Factor ◽  
Hydraulic Test ◽  
Capillary Limit

Heat pipes have immense potential in the future of thermal management in electronic devices. As a passive device, they rely solely upon capillary forces to recirculate the coolant from the condenser to the evaporator via a wicking structure. In intermediate temperature heat pipes the limiting factor for heat removal is the capillary limit, which indicates the maximum recirculation rate that the capillary forces can induce. This capillary limit must be increased to allow heat pipes to remain a viable option for heat management within electronic devices. The aim of this work is to characterize and optimize the capillary limit of micropillared thermal wicks for heat pipe application in micro-electronics cooling. Towards this goal, an analytical model, and a novel thermo-hydraulic experimental setup was developed. The analytical model of the micropillared array wicking structure provides a theoretical basis from which the pillar geometry and arrangement can be optimized. A capillary limit model was used to determine the geometric relationship between the pillar arrays and the maximum capillary flow rate through the wick. This model considers the effects of gravity and mass transfer due to evaporation. Finally, the thermo-hydraulic characterization setup, designed to minimize environmental losses, was used to experimentally determine the capillary limits of different silicon based micropillared wick samples. The heater and wicking structure were enclosed in a temperature and humidity controlled vacuum chamber. The results obtained from this setup were used to validate the analytical model shown in this paper.

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.

Sign in / Sign up

Export Citation Format

Share Document