Circulation Effectiveness of Working Fluid in Inclined Micro Heat Pipes

2015 ◽  
Vol 789-790 ◽  
pp. 422-425
Author(s):  
Fun Liang Chang ◽  
Yew Mun Hung
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Circulation Rate ◽  
Working Fluid ◽  
High Heat Flux ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

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.

scholarly journals Thermal Assessment of Nano-Particulate Graphene-Water/Ethylene Glycol (WEG 60:40) Nano-Suspension in a Compact Heat Exchanger

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1929 ◽  
Author(s):  
M. Sarafraz ◽  
Mohammad Safaei ◽  
Zhe Tian ◽  
Marjan Goodarzi ◽  
Enio Bandarra Filho ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Ethylene Glycol ◽  
Thermal Performance ◽  
Evaluation Criteria ◽  
High Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
High Heat Flux ◽  
Micro Channel

In the present study, we report the results of the experiments conducted on the convective heat transfer of graphene nano-platelets dispersed in water-ethylene glycol. The graphene nano-suspension was employed as a coolant inside a micro-channel and heat-transfer coefficient (HTC) and pressure drop (PD) values of the system were reported at different operating conditions. The results demonstrated that the use of graphene nano-platelets can potentially augment the thermal conductivity of the working fluid by 32.1% (at wt. % = 0.3 at 60 °C). Likewise, GNP nano-suspension promoted the Brownian motion and thermophoresis effect, such that for the tests conducted within the mass fractions of 0.1%–0.3%, the HTC of the system was improved. However, a trade-off was identified between the PD value and the HTC. By assessing the thermal performance evaluation criteria (TPEC) of the system, it was identified that the thermal performance of the system increased by 21% despite a 12.1% augmentation in the PD value. Furthermore, with an increment in the fluid flow and heat-flux applied to the micro-channel, the HTC was augmented, showing the potential of the nano-suspension to be utilized in high heat-flux thermal applications.

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.

Effects of Surface Coating of Nanoparticles on Thermal Performance of Open Loop Pulsating Heat Pipes

2012 ◽  
Author(s):  
Mehdi Taslimifar ◽  
Maziar Mohammadi ◽  
Ali Adibnia ◽  
Hossein Afshin ◽  
Mohammad Hassan Saidi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Surface Coating ◽  
Heat Pipes ◽  
Open Loop ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Performance Of Heat Transfer

Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated. Experimental results show that ferrofluid has better heat transport capability relative to SC ferrofluid. Furthermore, application of magnetic field improves the heat transfer performance of OLPHPs charged with both ferrofluids.

High Flux Value Micro-Heat Pipe Arrays

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001760-001807
Author(s):  
Daniel K. Harris ◽  
Robert Dean ◽  
Ashish Palkar ◽  
Gary Wonacott
Keyword(s):  
Liquid Metal ◽  
Heat Pipe ◽  
Experimental Work ◽  
Performance Enhancement ◽  
Performance Testing ◽  
Heat Pipes ◽  
Working Fluid ◽  
Working Fluids ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

The concept of heat pipes was introduced by R.S.Gaugler in 1940s and Cotter first introduced the idea of “micro” heat pipes in 1984. Cotter in his paper, defined the micro heat pipe as being one in which the mean curvature of the vapor-liquid interface is comparable in magnitude to the reciprocal of the hydraulic radius of the total flow channel. The Micro Heat Pipes (MHPs) work efficiently through the use of two-phase heat transfer. Various working fluids have been tried in combination with various substrate materials. In this experimental work the main focus was to study the behavior of liquid metal filled MHPs made from silicon as the substrate material. Specially designed MHPs were assembled and charged with mercury as the working fluid. A special test setup was designed and built for the experimental work and the response of the MHPs to the controlled increment in the input power is presented. A number of experiments were carried out on the specimen MHPs to determine their effective thermal conductivity, the variation of the temperature along the axial length and the performance enhancement factor. Effective thermal conductivities as high as 900 W/m-K with a silicon equivalence of 6 were achieved with the liquid metal MHP. Based on the results from the various performance testing parameters, it was observed that the liquid metal charged MHPs performed substantially better than conventional MHPs filled with organic working fluids. The limitations and the possible methods of improving the performance of the MHPs are discussed.

An Experimental Investigation on Micro Heat Pipe with a Trapezium-Grooved Wick Structure

2010 ◽  
Vol 29-32 ◽  
pp. 1695-1700
Author(s):  
Shi Gang Wang ◽  
Xi Bing Li ◽  
Bai Rui Tao ◽  
Hong Xia Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Pipe ◽  
Optimum Design ◽  
Heat Pipes ◽  
Micro Heat Pipe ◽  
Capillary Limit ◽  
Heat Transfer Capacity ◽  
Wick Structure ◽  
Micro Heat Pipes

Through combination of experimental investigation with theoretical optimum design, this paper determined the crucial factors in affecting the heat transfer capacity in micro heat pipes with a trapezium-grooved wick structure are capillary limit and entrainment limit, and verified the validity of the heat transfer models thus built.

scholarly journals Experimental study on the performance limitation of micro heat pipes of non circular cross-sections

2008 ◽  
Vol 12 (3) ◽  
pp. 91-102 ◽  
Author(s):  
Lutful Mahmood ◽  
Razzaq Akhanda
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Cross Sections ◽  
Heat Pipes ◽  
Working Fluid ◽  
Electric Heater ◽  
Condenser Section ◽  
Inclination Angles ◽  
Micro Heat Pipes

An experimental study of three different cross-sections (circular, semicircular and rectangular) of micro heat pipes having same hydraulic diameter (D= 3mm) is carried out at three different inclination angles (0?, 45?, 90?) using water as the working fluid. Evaporator section of the pipe is heated by an electric heater and the condenser section is cooled by water circulation in an annular space between the condenser section and the water jacket. Temperatures at different locations of the pipe are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a voltmeter. It is found that thermal performance tends to deteriorate as the micro heat pipe is flattened. Thus among all cross-sections of the pipes circular cross-section exhibits the best thermal performance followed by semicircular and rectangular cross-sections. Moreover maximum heat transfer capability of the pipes also decreases with decreasing of its inclination angle. A correlation is developed using all the gathered data of the present study to predict the heat transfer coefficient of micro heat pipes of different cross-sections placed at different inclination angles.

scholarly journals Kinerja Termal Pipa Kalor Tembaga pada Fluida Kerja Air

Jurnal METTEK ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 52
Author(s):  
David Febraldo ◽  
Wayan Nata Septiadi ◽  
Ketut Astawa
Keyword(s):  
Heat Transfer ◽  
Heat Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Temperature Difference ◽  
Heating Temperature ◽  
Heat Pipes ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Two Phase

Pipa kalor (Heat pipe) merupakan salah satu teknologi penukar kalor dua fase sistem pasif, pipa kalor itu sendiri memiliki struktur dengan konduktivitas termal tinggi, hal ini memungkinkan transportasi panas dengan mempertahankan perbedaan suhu sehingga seragam di sepanjang bagian yang dipanaskan dan didinginkan. Kinerja termal pipa kalor dapat ditentukan dari nilai hambatan panas. Ketika hambatan panas bernilai kecil, maka laju perpindahan kalor meningkat begitu pula sebaliknya. Pengujian kinerja termal  pipa kalor tembaga pada fluida kerja air telah dilakukan. Kinerja termal dapat diamati dari hasil pengambilan data temperatur dan pengolahan data. Hasil dari penelitian ini menunjukkan perbedaan temperatur antara temperatur pemanas dan dan temperatur fluida terus meningkat dengan kenaikan laju perpindahan panas dari variasi beban pemanasan 70 volt, 90 volt, 110 vot, 130 volt, dan 150 volt. Heat pipe is a passive two-phase heat exchanger technology, heat pipe itself has a structure with high thermal conductivity, this allows heat transportation by maintaining a uniform temperature difference along the heated and cooled part. Thermal performance of heat pipes can be determined from the value of heat resistance. When heat resistance is small, the heat transfer rate increases and vice versa. Testing the thermal performance of copper heat pipes on the working fluid of water has been carried out. Thermal performance can be observed from the results of temperature data collection and data processing. The results of this study indicate the temperature difference between heating temperature and fluid temperature continues to increase with increasing heat transfer rates from variations in heating loads of 70 volts, 90 volts, 110 vot, 130 volts, and 150 volts.

Experimental Investigations on Thermal Performance of a Multi-Turn Closed Loop Pulsating Heat Pipe

2012 ◽  
Vol 433-440 ◽  
pp. 5854-5860 ◽  
Author(s):  
Yu Wang ◽  
Wei Yi Li
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Input ◽  
Closed Loop ◽  
Research Work ◽  
Design Parameters ◽  
Working Fluid ◽  
High Heat Flux ◽  
Pulsating Heat Pipe

Closed loop pulsating heat pipe (CLPHP) is a relatively new two-phase passive heat transfer device to suit present requirement of high heat flux dissipation in modern electronic components. The operating mechanism of CLPHP is not well understood and the present state of the technology cannot predict required design parameters for a given task. The aim of research work presented in this paper is to better understand thermal performance of CLPHP. A series of experimental investigation were conducted on a multi-turn CLPHP made of copper capillary tube of 2-mm inner diameter. Two kinds of working fluids viz. ethanol and acetone were employed. The influence characterization has been studied for the variation of heat input and filling ratio (FR) of the tested CLPHP. Thermal performance of the CLPHP is evaluated by heat transfer and thermal resistance. The results strongly demonstrate the effect of heat input and FR of the working fluid on thermal performance of the device.

Improve the Performance of Micro Heat Pipe by Surface Modification

2017 ◽  
Vol 868 ◽  
pp. 21-26
Author(s):  
Yi Luo ◽  
Si Di Li ◽  
Zi Cheng Yu ◽  
Xiao Dong Wang
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
High Power ◽  
High Heat ◽  
Cover Plate ◽  
Working Fluid ◽  
High Heat Flux ◽  
Glass Cover ◽  
Micro Heat Pipe ◽  
High Power Led

The appearance of high power LED has put forward higher requirements for thermal management. The micro heat pipe (MHP) has high heat transfer ability and plays an important role in high power LED and other high heat flux device cooling. In this paper, we designed and fabricated a micro heat pipe with fluoroalkyl silane (FAS) surface modified glass cover. The contact angle of the working area of glass cover reached 95.49° and made working fluid drops fall back to micro groove of silicon substrate more quickly. Thus the new glass cover can speed up the circulation of working fluid and enhance the heat transfer. The experimental results also proved that hydrophobic glass cover has a better heat transfer capability. Besides, this novel MHP reached the stable working status faster. When the input heat power was 10 W, the balance temperature of MHP with hydrophobic glass cover was 22 oC lower than traditional MHP, while the balance time is 58 seconds less. The work presented in this paper provides a new direction for optimize the MHP, not only the wick structure in substrate, but also the wettability of cover plate.

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