Characterization of the Performance of Flat Heat Pipes for Electronics Cooling

2000 ◽  
Author(s):  
Unnikrishnan Vadakkan ◽  
Suresh V. Garimella ◽  
Choondal B. Sobhan
Keyword(s):  
Heat Pipe ◽  
Heat Input ◽  
Energy Transport ◽  
Temperature Drop ◽  
Thermal Conductance ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Flow And Heat Transfer ◽  
Parametric Studies ◽  
Axial Heat

Abstract A computational model has been developed to analyze the transient and steady-state performance of flat heat pipes and assess their performance under different operating and geometric parameters, in order to arrive at optimal designs. The model assumes two-dimensional fields for flow and heat transfer and solves the governing differential equations using a finite-difference approach. The wick region of the heat pipe is analyzed using transport equations for a porous medium. The influence of axial heat conduction along the wall, as well as the energy transport in the wick, on the velocity and temperature distributions is examined. The overall performance of the heat pipe is quantified by calculating an effective thermal conductance from the heat input and the temperature drop along the heat pipe wall. Parametric studies are conducted using the model to investigate the dependence of the heat pipe performance on the heat input at the evaporator, the containing wall thickness, and the porosity of the wick.

Novel Fluorescent Visualization Method to Characterize Transport Properties in Micro/Nano Heat Pipe Wick Structures

2009 ◽  
Author(s):  
Pramod Chamarthy ◽  
H. Peter J. de Bock ◽  
Boris Russ ◽  
Shakti Chauhan ◽  
Brian Rush ◽  
...  
Keyword(s):  
Heat Pipe ◽  
High Performance ◽  
Gravitational Force ◽  
Driving Forces ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
High Permeability ◽  
Permeability Characteristics ◽  
Wick Structure ◽  
Initial Results

Heat pipes have been gaining a lot of popularity in electronics cooling applications due to their ease of operation, reliability, and high effective thermal conductivity. An important component of a heat pipe is the wick structure, which transports the condensate from condenser to evaporator. The design of wick structures is complicated by competing requirements to create high capillary driving forces and maintain high permeability. While generating large pore sizes will help achieve high permeability, it will significantly reduce the wick’s capillary performance. This study presents a novel experimental method to simultaneously measure capillary and permeability characteristics of the wick structures using fluorescent visualization. This technique will be used to study the effects of pore size and gravitational force on the flow-related properties of the wick structures. Initial results are presented on wick samples visually characterized from zero to nine g acceleration on a centrifuge. These results will provide a tool to understand the physics involved in transport through porous structures and help in the design of high performance heat pipes.

Modeling of the Flow and Heat Transfer in Micro Heat Pipes

2004 ◽  
Author(s):  
C. B. Sobhan ◽  
G. P. (Bud) Peterson
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Radius Of Curvature ◽  
Vapor Flow ◽  
Axial Distribution ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Physical Phenomena ◽  
Micro Heat Pipes

The fluid flow and heat transfer characteristics of micro heat pipes are analyzed theoretically, in order to understand the physical phenomena and quantify the influence of various parameters on overall thermal performance of these devices. A one-dimensional model is utilized to solve the governing equations for the liquid/vapor flow and the heat transfer in the heat pipe channel. Variations in the liquid and vapor cross-sectional areas along the axial length of the heat pipe are included and the equations are solved using an implicit finite difference scheme. Appropriate models for fluid friction in small passages with varying cross-sectional areas have been incorporated to yield the axial distribution of the meniscus radius of curvature and the velocity, temperature and pressure in both the liquid and the vapor phases. Using this information, the effective thermal conductivity of the micro heat pipe is modeled, and parametric studies are performed by changing the heat load and cooling rate. The results of the analysis are discussed and compared with other theoretical models and experimental results found in the literature. By so doing, this analysis provides greater insight into the physical phenomena of flow and heat transfer in micro heat pipes and identifies a methodology for optimizing the design of these devices.

An Experimental Study of Micro Radially Rotating Heat Pipes With Water as the Working Fluid

2008 ◽  
Author(s):  
Yiding Cao ◽  
Jian Ling
Keyword(s):  
Heat Pipe ◽  
Thermal Conductance ◽  
Heat Pipes ◽  
Working Fluid ◽  
Rotating Speed ◽  
Copper Water ◽  
High Pressure Compressor ◽  
Potential Applications ◽  
Inner Diameter ◽  
Pressure Compressor

In this study, three copper-water rotating heat pipes having inner diameters of 1.5, 2, and 3 mm, respectively, are fabricated and tested. The effectiveness of the copper-water heat pipe is first validated by comparing its performance with that of a copper bar having the same inner and outer diameters. The heat pipes are then tested to prove their reliability, high effective thermal conductance, and critical working limitation. The experimental data shows that the critical limitation may be reached when the inner diameter of the heat pipe is below 1.5 mm under the condition of a low rotating speed. The tests of these water heat pipes could also explore potential applications of radially rotating heat pipes in disks/blades of a high-pressure compressor.

scholarly journals Heat and Mass Transfer in the Vicinity of the Vapor-Gas Front in a Gas-Loaded Heat Pipe

1972 ◽  
Vol 94 (2) ◽  
pp. 155-162 ◽  
Author(s):  
D. K. Edwards ◽  
B. D. Marcus
Keyword(s):  
Mass Transfer ◽  
Heat Pipe ◽  
Heat And Mass Transfer ◽  
Heat Pipes ◽  
Mass Diffusion ◽  
Working Fluid ◽  
Predictive Capability ◽  
Axial Mass ◽  
Axial Heat ◽  
And Control

An analysis is presented of axially conducting gas-controlled heat pipes leading to a predictive capability for the heat and mass transfer along the heat pipe. In addition, experimental results are presented which verify the analysis, and computational results are presented which show the relative influence of various parameters which affect the system behavior. In particular it was found that axial heat conduction is of much greater importance than axial mass diffusion in establishing the wall temperature profiles and condenser heat-transfer characteristics of gas-loaded heat pipes. However, mass diffusion and, consequently, the choice of working fluid and control gas are of considerable importance in establishing the “diffusion freezeout rate” if the potential exists for freezing of vapor which penetrates the gas-blocked portion of the condenser. It is believed that the analysis and associated computer program are useful tools for designing gas-loaded heat pipes.

A Simplified Conduction Based Modeling Scheme for Design Sensitivity Study of Thermal Solution Utilizing Heat Pipe and Vapor Chamber Technology

2003 ◽  
Vol 125 (3) ◽  
pp. 378-385 ◽  
Author(s):  
Ravi S. Prasher
Keyword(s):  
Heat Pipe ◽  
Temperature Drop ◽  
Heat Pipes ◽  
Sensitivity Study ◽  
Design Sensitivity ◽  
Thermal Design ◽  
Vapor Chamber ◽  
Modeling Tools ◽  
Heating Source ◽  
Thermal Solution

This paper introduces a simplified modeling scheme for the prediction of heat transport capability of heat pipes and vapor chambers. The modeling scheme introduced in this paper enables thermal designers to model heat pipes and vapor chambers in commercially available conduction modeling tools such as Ansys™ and IcePak™. This modeling scheme allows thermal designers to perform design sensitivity studies in terms of power dissipation of heat pipes and vapor chambers for different scenarios such as configurations, heat sink resistance for a given temperature drop between the heating source and the ambient. This paper also discusses how thermal designers can specify requirements to heat pipe/vapor chamber suppliers for their thermal design, without delving into the complete thermo-fluidic modeling of this technology.

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.

Analysis of Heat Pipe Filled with Several Oxide Nanofluids on the Start-Up Process

2014 ◽  
Vol 490-491 ◽  
pp. 251-255 ◽  
Author(s):  
Yu Ying Gong ◽  
Zong Ming Liu ◽  
Wei Lin Zhao
Keyword(s):  
Temperature Distribution ◽  
Heat Pipe ◽  
Temperature Drop ◽  
Heat Pipes ◽  
Condenser Section ◽  
Evaporator Section ◽  
Heating Section ◽  
Start Up

Three heat pipes with nanofluids of Al2O3-water, CuO-water and SiO2-water were tested experimentally. The temperature distribution of their start-up process was analysed, and compared the heat pipe with water. The results showed that the start-up way of heat pipe filled with nanofluids was coincident, the heat pipe filled with nanofluids showed a lower start-up temperature and a shorter start-up time in evaporator section compared with heat pipe filled with water, the temperature drop between evaporator section and condenser section for the heat pipe filled with nanofluids were reduced by 2-5°C than that of the heat pipe filled with water. The effect of the length of the heating section of heat pipe filled with nanofluids on the start-up process was little.

Experimental Investigation on Nanofluids Effectiveness on Heat Transfer in Oscillating Heat Pipe

2013 ◽  
Vol 856 ◽  
pp. 98-102 ◽  
Author(s):  
Hamid R. Goshayeshi ◽  
Ali Khosravi ◽  
Mehdi Abedpour Karizaki
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Pipe ◽  
High Speed ◽  
Oscillatory Flow ◽  
Glass Tube ◽  
Heat Pipes ◽  
Oscillating Heat Pipe ◽  
Flow And Heat Transfer ◽  
Heat Loads

An experimental investigation of the oscillatory flow and heat transfer in a vertical oscillating heat pipe (OHP) was conducted. The oscillating heat pipe was made of a copper-glass tube. Flow inside the oscillating heat pipe at different heat loads was recorded by a high speed camera. Through this research, the authors investigated the effect of utilizing nanofluids on heat transfer amount in heat pipes. The employed nanofluids in this study were water-Fe2O3, water-SiO2and water-TiO2with various volumetric concentrations. The results show that after adding nanoparticles in the base fluid (here water) heat transfer rate increases significantly. It's also noteworthy, of the all applied nanofluids, water-TiO2mixture presents the best enhancement in heat transfer amount.

A Simplified Modeling Scheme for Design Sensitivity Study of Thermal Solution Utilizing Heat Pipe and Vapor Chamber Technology

2001 ◽  
Author(s):  
Ravi S. Prasher ◽  
James Shipley ◽  
Amit Devpura
Keyword(s):  
Heat Pipe ◽  
Temperature Drop ◽  
Heat Pipes ◽  
Sensitivity Study ◽  
Design Sensitivity ◽  
Thermal Design ◽  
Vapor Chamber ◽  
Modeling Tools ◽  
Heating Source ◽  
Simplified Modeling

Abstract This paper introduces a simplified modeling scheme for the prediction of heat transport capability of heat pipes and vapor chambers. The modeling scheme introduced in this paper enables thermal designers to model heat pipes and vapor chambers in commercially available conduction modeling tools such as Ansys™ and IcePak™. This modeling scheme allows thermal designers to perform design sensitivity studies in terms of power dissipation of heat pipes and vapor chambers for different scenarios such as configurations, heat sink resistance for a given temperature drop between the heating source and the ambient. This paper also discusses how thermal designers can specify requirements to heat pipe/vapor chamber suppliers for their thermal design, without delving into the complete thermofluidic modeling of this technology.

Entrainment Limitations in Thermosyphons and Heat Pipes

1991 ◽  
Vol 113 (3) ◽  
pp. 147-153 ◽  
Author(s):  
G. P. Peterson ◽  
B. K. Bage
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Recovery ◽  
Large Range ◽  
Heat Pipes ◽  
Working Fluid ◽  
Physical Parameters ◽  
Modeling Techniques ◽  
Fluid Properties ◽  
Axial Heat

The isothermal characteristics and high effective thermal conductivity of heat pipes and thermosyphons make them particularly useful in air to air and process to air heat recovery systems. Although previous investigations have developed successful techniques for predicting many of the transport limitations, entrainment remains the least understood. Current entrainment modeling techniques have resulted in a large range in the predicted axial heat flux required for the onset of entrainment. Included here is a review of the present analytical methods used to predict the liquid entrainment as a function of the pipe’s physical parameters and working fluid properties, for both thermosyphons and heat pipes. The results of the models are compared with existing experimental data in an effort to determine the accuracy of the predictive techniques. Using a sample copper/water thermosyphon and a similar screen wicked heat pipe, comparisons of the experimental entrainment limit and those predicted by seven thermosyphon and four heat pipe models were made. The results of this comparison can provide insight for designers developing heat pipe exchangers and will provide a basis for further understanding the phenomena which govern this limit.

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