Thermal Characters of Mesh Structure in a Flat Heat Pipe

2003 ◽  
Author(s):  
Liang-Han Chien ◽  
Y.-C. Shih
Keyword(s):  
Heat Pipe ◽  
Inclination Angle ◽  
Mesh Size ◽  
Heat Pipes ◽  
Theoretical Models ◽  
Working Fluid ◽  
Internal Space ◽  
Mesh Structure ◽  
Horizontal Orientation ◽  
Plate Type

In this study plate type heat pipes having mesh capillaries were investigated experimentally and theoretically. A test apparatus was designed to test thermal performance of plate type copper-water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5-to-50 W heat input. The working fluid, water is charged with 25% or 33% volume of the heat pipe internal space. In addition to horizontal orientation, the heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances of the heat pipe were calculated separated. The effects of mesh size, charge volume, and inclination angle on each thermal resistance were discussed. In general, the #80 mesh yields lower thermal resistances than the #50 mesh; inclination angle has more significant effect on condenser than evaporator. Theoretical models of evaporation and condensation in flat heat pipes were proposed to interpolate the experimental results. The present evaporation model predicts the experimental data of evaporation resistance between −20% and +30%, and the condensation model predicts most condensation resistance data within ±30%.

An Experimental Study of Mesh Type Flat Heat Pipes

2011 ◽  
Vol 27 (2) ◽  
pp. 167-176 ◽  
Author(s):  
L.-H. Chien ◽  
Y.-C. Shih
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Volume Fraction ◽  
Mesh Size ◽  
Heat Pipes ◽  
Working Fluid ◽  
Internal Space ◽  
Horizontal Orientation ◽  
Semi Empirical

ABSTRACTFlat heat pipes having mesh capillaries were investigated experimentally in this study. An apparatus was designed to test thermal performance of plate type copper water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5 to 50 W heat input. The working fluid, water, is charged in volumes equivalent to 25%, 33%, or 50% of the internal space. In addition to horizontal orientation, heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances were calculated separately. The effects of mesh size, charge volume fraction, and inclination angle on thermal resistance were discussed. In general, the #80 mesh yielded lower thermal resistance than the #50 mesh. Inclination angle has a more significant effect on condenser than evaporator. Analysis of evaporation and condensation in flat heat pipes was conducted and semi-empirical correlations were derived. The present evaporation correlation predicts evaporation resistance between −20% and +30%, and the condensation correlation predicts most condensation resistance data within ±30% for 25% and 33% charge volume fraction.

Effect of Fluid Loading on the Performance of Wicked Heat Pipes

Volume 3 ◽  
2004 ◽  
Author(s):  
R. Kempers ◽  
A. Robinson ◽  
C. Ching ◽  
D. Ewing
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Working Fluid ◽  
Fluid Loading ◽  
Maximum Heat ◽  
Horizontal Orientation ◽  
Maximum Heat Flux ◽  
Dry Out

A study was performed to experimentally characterize the effect of fluid loading on the heat transport performance of wicked heat pipes. In particular, experiments were performed to characterize the performance of heat pipes with insufficient fluid to saturate the wick and excess fluid for a variety of orientations. It was found that excess working fluid in the heat pipe increased the thermal resistance of the heat pipe, but increased maximum heat flux through the pipe in a horizontal orientation. The thermal performance of the heat pipe was reduced when the amount of working fluid was less than required to saturate the wick, but the maximum heat flux through the heat pipe was significantly reduced at all orientations. It was also found in this case the performance of this heat pipe deteriorated once dry-out occurred.

Effects of Working Fluid, Fill Ratio and Orientation on Looped and Unlooped Pulsating Heat Pipes

2005 ◽  
Author(s):  
Kathryn Nikkanen ◽  
Christian G. Lu ◽  
Masahiro Kawaji
Keyword(s):  
Heat Pipe ◽  
Rectangular Channel ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Fill Ratio ◽  
Triangular Channel ◽  
Horizontal Orientation

Improved miniaturization and a trend towards increasingly dense and compact architectures have led to unmanageably high heat fluxes in electronic components. In order to keep temperatures at operational levels more advanced cooling solutions are being required that go beyond the solid heat sink and forced convection. Pulsating heat pipes made out of multi port extrusion tubing are a proposed solution. Typically, gas-liquid slug flow occurs in the serpentine channel imbedded in the pulsating heat pipe. Vapour is produced in the heated section and condensed in the cooled section located at opposite ends of the heat pipe. In this work, experiments were conducted on four Multi-Port Extruded (MPE) aluminum tubing heat pipes with different internal structures: rectangular channel looped, rectangular channel unlooped, triangular channel looped, and triangular channel unlooped. The effect of changing the working fluid (ethanol or de-ionized water), fill ratio, and orientation were measured and compared for the different heat pipes. It was found that most of the heat pipes performed better with ethanol than de-ionized water. Only the looped rectangular channel heat pipe performed satisfactorily with de-ionized water, which is attributed both to the larger channel size and the looped architecture. The unlooped heat pipes performed best at the lowest fill ratios (10%) while the looped heat pipes showed their best performances between 30 and 50% with marked decrease at the lower and higher fill ratios. Both looped heat pipes performed poorly in horizontal orientation as compared to vertical, however, the unlooped heat pipes performed quite well in both orientations. This may be more the effect of the fill ratio on horizontal performance as literature suggests that horizontal orientation requires a lower fill ratio to perform satisfactorily.

Experimental Investigation of High-Speed Rotating Heat Pipes

2003 ◽  
Author(s):  
F. Song ◽  
D. Home ◽  
T. Robinson ◽  
D. Ewing ◽  
C. Y. Ching
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
High Speed ◽  
Heat Pipes ◽  
Theoretical Models ◽  
Test Facility ◽  
Working Fluid ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Pipe Geometry

The steady state heat transfer characteristics of high-speed rotating heat pipes were measured using a newly commissioned high-speed rotating heat pipe test facility. The performance of two cylindrical and two tapered rotating heat pipes with different fluid loadings were tested for rotational speeds of 2,000 to 4,000 RPM and heat transfer rates up to 0.6 kW. The measurements were used to characterize the effects of rotational speed, working fluid loading, and heat pipe geometry on the performance of rotating heat pipes. The results were compared to previous theoretical models. There is a general agreement between test results and predictions from a model that accounts for natural convection within the liquid film at the evaporator at high accelerations. However, some results indicate that the model is not yet accounting for all the physics in a high-speed rotating heat pipe.

scholarly journals The effect of operating parameters on the heat transfer in the heat pipe

2021 ◽  
Vol 2119 (1) ◽  
pp. 012088
Author(s):  
A. A. Litvintceva ◽  
N. I. Volkov ◽  
N. I. Vorogushina ◽  
V. A. Moskovskikh ◽  
V. V. Cheverda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Pipes ◽  
Working Fluid ◽  
Operating Parameters ◽  
Temperature Stabilization ◽  
Ir Camera ◽  
Fluid Properties

Abstract Heat pipes are a good solution for temperature stabilization, for example, of microelectronics, because these kinds of systems are without any moving parts. Experimental research of the effect of operating parameters on the heat transfer in a cylindrical heat pipe has been conducted. The effect of the working fluid properties and the porous layer thickness on the heat flux and temperature difference in the heat pipe has been investigated. The temperature field of the heat pipe has been investigated using the IR-camera and K-type thermocouples. The data obtained by IR-camera and K-type thermocouples have been compared. It is demonstrated the power transferred from the evaporator to the condenser is a linear function of the temperature difference between them.

scholarly journals An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

2020 ◽  
Vol 21 (3) ◽  
pp. 309
Author(s):  
Maryam Fallah Abbasi ◽  
Hossein Shokouhmand ◽  
Morteza Khayat
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Double Layer ◽  
Electric Double Layer ◽  
Heat Pipes ◽  
The Body ◽  
Working Fluid ◽  
Two Phase ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

Metallic Mesh as Capillary Structure Applied in Heat Pipe Heat Exchanger for Heat Recovery

2014 ◽  
Vol 1082 ◽  
pp. 309-314 ◽  
Author(s):  
Diogo L.F. Santos ◽  
Larissa S. Marquardt ◽  
Paulo H.D. Santos ◽  
Thiago Antonini Alves
Keyword(s):  
Stainless Steel ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Capillary Structure ◽  
Porous Wick ◽  
Metallic Mesh ◽  
Heat Loads ◽  
Pipe Heat

This work presents a theoretical and experimental analysis of a heat exchanger assisted by five heat pipes made of copper with a metallic mesh 100 of stainless steel which was used as capillary structure. All heat pipes used water as the working fluid and were designed based on the capillary limit model. The heat pipes were developed and tested under heat loads varying from 20 to 50 W before application into the heat exchanger. The theoretical and experimental results were compared and all heat pipes worked satisfactorily. Thereafter, it is presented the development of heat pipe heat exchanger which was tested under heat loads varying from 100 to 250 W. The highest temperature measured on the external surface of the heat pipes was 90 oC and the heat exchanger thermal efficiency varied from 74 to 80%. It is showed that the use of a stainless steel mesh as a porous wick was proved to work successfully in heat pipes.

Experimental Study on Oscillating Heat Pipe With Hydraulic Diameter Far Exceeding the Maximum Hydraulic Diameter

2019 ◽  
Author(s):  
Lilin Chu ◽  
Yulong Ji ◽  
Chunrong Yu ◽  
Yantao Li ◽  
Hongbin Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Transfer Performance ◽  
Vertical Orientation ◽  
Oscillating Heat Pipe ◽  
Horizontal Orientation ◽  
Small Bubbles

Abstract In order to understand the heat transfer performance, startup and fluid flow condition of oscillating heat pipe (OHP) with hydraulic diameter far exceeding the maximum hydraulic diameter (MHD), an experimental investigation on heat transfer performance and visualization was conducted. From the experimental performance, it is found that the OHP can still work well with ethanol as the working fluid when the tube diameter has exceeded the MHD of 91.6%. In addition, the detailed flow patterns of the OHP were recorded by a highspeed camera for vertical and horizontal orientation to understand its physical mechanism. In the vertical orientation, initially working fluid generates small bubbles, and then the small bubbles coalesce and grow to vapor plugs, the vapor plugs finally pushes the liquid slugs to oscillate in the tube. In the horizontal orientation, the working fluid surface fluctuates due to the vapors flow from the evaporator to the condenser and bubbles burst in the evaporator. When the peak of liquid wave reaches the upper surface of tube, a liquid slug has been formed, and then the steam flow pushes the liquid slugs to oscillate in the tube.

Experimental Study on Applied Thin Vapor Chamber and Embedded Heat Pipe Heat Sinks

2009 ◽  
Author(s):  
Garrett A. Glover ◽  
Yongguo Chen ◽  
Annie Luo ◽  
Herman Chu
Keyword(s):  
Heat Pipe ◽  
Heat Sink ◽  
High Performance ◽  
Structural Integrity ◽  
Heat Pipes ◽  
Electronic Cooling ◽  
Working Fluid ◽  
Vapor Chamber ◽  
Trade Offs ◽  
Pipe Heat

The current work is a survey of applied applications of passive 2-phase technologies, such as heat pipe and vapor chamber, in heat sink designs with thin base for electronic cooling. The latest improvements of the technologies and manufacturing processes allow achievable heat sink base thickness of 3 mm as compared to around 5 mm previously. The key technical challenge has been on maintaining structural integrity for adequate hollow space for the working fluid vapor in order to retain high performance while reducing the thickness of the overall vapor chamber or flattened heat pipe. Several designs of thin vapor chamber base heat sink and embedded heat pipe heat sink from different vendors are presented for a moderate power density application of a 60 W, 13.2 mm square heat source. Numerous works have been published by both academia and commercial applications in studying the fundamental science of passive 2-phase flow technologies; their performance has been compared to solid materials, like aluminum and copper. These works have established the merits of using heat pipes and vapor chambers in electronic cooling. The intent of this paper is to provide a methodical approach to help to accelerate the process in evaluating the arrays of different commercial designs of these devices in our product design cycle. In this paper, the trade-offs between the different types of technologies are discussed for parameters such as performance advantages, physical attributes, and some cost considerations. This is a bake-off evaluation of the complete heat sink solutions from the various vendors and not a fundamental research of vapor chambers and heat pipes — for that, it is best left to the vendors and universities.

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.

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