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 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.

An Experimental Study on the Thermal Performance of the Flat Heat Pipe

2016 ◽  
Author(s):  
Hao Xiaohong ◽  
Jiqing Guan ◽  
Jingbo Zhao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Electronic Devices ◽  
Heat Pipes ◽  
Deionized Water ◽  
Working Fluid ◽  
Nano Fluid ◽  
Flat Heat Pipe

As the rapid growing of the semiconductor logic gate number and operation speed, the heat dissipated from electronic devices increases drastically. Moreover, most of the heat flux can reach about 100 W/cm2, therefore efficient removal of the heat from the electronic devices is essential to ensure the reliable operation of the electronic devices. The traditional direct cooling system, such as air cooling, liquid cooling, would not be able to transfer the high heat flux owing to their heat transfer limits, so advanced cooling solutions are necessary. The flat heat pipes have some advantages, such as small scale, strong heat transfer capacity, low weight penalty and low environmental requirements, therefore, in recent years, researchers have shown great interest for the flat heat pipe. But most of them played the important on the structure design of the flat heat pipes, and few of them focused on the study of the effect of the working fluid on the heat transfer performance. In this paper, a flat heat pipe with rectangular channel is designed and manufactured, and an experimental set up was built to study working fluid on the effects of the flat heat Pipe thermal performance. The flat heat pipe is heated via a 35mmx20mm rectangular electrical resistance (the evaporator side), and the other side (the condenser side) is cooled by convection of a heat sink. In the experimental work, three types of working fluid are used in the heat pipe: (A) deionized water, (B) deionized water-based Fe3O4 nano fluid (1, 1.5wt%). A comparison is performed for the thermal performance of different size flat heat pipe. Finally, the experimental results showed that nano fluid could improve the thermal performance of the FHP. With the same charge volume, the heat transfer coefficient of the FHPs filled with nano fluid were higher than that of DI water. There was an optimal mass concentration which was estimated to be 1.5 wt% to achieve the maximum heat transfer enhancement.

Experimental Investigation of Solar Heat Pipes With Ethanol Solution as Working Fluid

2010 ◽  
Author(s):  
Hang Guo ◽  
Hai Yan Du ◽  
Fang Ye ◽  
Chong Fang Ma
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Ethanol Solution ◽  
Working Fluid ◽  
Incline Angle ◽  
Water Heater ◽  
Solar Heat ◽  
Pipe Water

As working fluid of heat pipes, water is widely used in solar heat pipe water heater. But water causes poor performance of heat transfer under low temperature and freezing in cold winter. In this paper, ethanol-water solution is used as working substance in heat pipe. The static heat transfer and start-up performance of heat pipe are experimentally studied in this paper. The experimental results showed that when the heat flux is low, the heat transfer of heat pipe with 40% voluminal concentration ethanol solution is better than that of heat pipe with pure water. Start-up speed and temperature of ethanol solution heat pipe are higher than that of water heat pipe. In the low temperature condition, ethanol solution is more competent than water for working medium of solar heat pipe. In addition, heat transfer performance is also influenced by incline angle of heat pipes, charge quantity and heat flux. The effect of incline angle on heat transfer performance of heat pipes becomes distinct with the increasing of heat flux. The reason is that the heat flux becomes high and reflux condensate becomes much with the increasing of heating power. The optimal incline angle of heat pipe with 40 vol. % ethanol solution is 45° and the optimal charge quantities is 11.8 vol. %. The experimental results are helpful for widely use of solar heat pipe water heater in north China.

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.

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.

scholarly journals Transport in Flat Heat Pipes at High Heat Fluxes From Multiple Discrete Sources

2004 ◽  
Vol 126 (3) ◽  
pp. 347-354 ◽  
Author(s):  
Unnikrishnan Vadakkan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Heat Pipe ◽  
Three Dimensional ◽  
Heat Pipes ◽  
Density Change ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Energy Equations

A three-dimensional model has been developed to analyze the transient and steady-state performance of flat heat pipes subjected to heating with multiple discrete heat sources. Three-dimensional flow and energy equations are solved in the vapor and liquid regions, along with conduction in the wall. Saturated flow models are used for heat transfer and fluid flow through the wick. In the wick region, the analysis uses an equilibrium model for heat transfer and a Brinkman-Forchheimer extended Darcy model for fluid flow. Averaged properties weighted with the porosity are used for the wick analysis. The state equation is used in the vapor core to relate density change to the operating pressure. The density change due to pressurization of the vapor core is accounted for in the continuity equation. Vapor flow, temperature and hydrodynamic pressure fields are computed at each time step from coupled continuity/momentum and energy equations in the wick and vapor regions. The mass flow rate at the interface is obtained from the application of kinetic theory. Predictions are made for the magnitude of heat flux at which dryout would occur in a flat heat pipe. The input heat flux and the spacing between the discrete heat sources are studied as parameters. The location in the heat pipe at which dryout is initiated is found to be different from that of the maximum temperature. The location where the maximum capillary pressure head is realized also changes during the transient. Axial conduction through the wall and wick are seen to play a significant role in determining the axial temperature variation.

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.

Working Fluid Inventory Effect on Heat Transfer Performance of a Grooved Micro Heat Pipe

2013 ◽  
Vol 589-590 ◽  
pp. 559-564
Author(s):  
Xi Bing Li ◽  
Yun Shi Ma ◽  
Xun Wang ◽  
Ming Li
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Mathematic Model ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Transfer Performance ◽  
Flux Concentration

As a highly efficient heat transfer component, a micro heat pipe (MHP) has been widely applied to the situations with high heat flux concentration. However, a MHPs heat transfer performance is affected by many factors, among which, working fluid inventory has great influence on the security, reliability and frost resistance of its heat transfer performance. In order to determine the appropriate working fluid inventory for grooved MHPs, this paper first analyzed the working principle, major heat transfer limits and heat flux distribution law of grooved MHPs in electronic chips with high heat flux concentration, then established a mathematic model for the working fluid inventory in grooved MHPs. Finally, with distilled water being the working fluid, a series of experimental investigations were conducted at different temperatures to test the heat transfer performances of grooved MHPs, which were perfused with different inventories and with different adiabatic section lengths. The experimental results show that when the value of α is roughly within 0.40±0.05, a grooved MHP can acquire its best heat transfer performance, and the working fluid inventory can be determined by the proposed mathematic model. Therefore this study solves the complicated problem of determining appropriate working fluid inventory for grooved MHPs.

Experimental Investigation of Heat Transfer of Refrigerant Fluid Pulsating Heat Pipe

2017 ◽  
Vol 865 ◽  
pp. 137-142
Author(s):  
Somchai Maneewan ◽  
Chantana Punlek ◽  
Hoy Yen Chan ◽  
Atthakorn Thongtha
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Input ◽  
Filling Ratio ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Filling Volume ◽  
Volume Filling

Heat transfer performances of a pulsating heat pipe (PHP) having internal and external diameter with 4.5 mm and 6 mm with various contents of refrigerant are experimentally investigated. The working fluid as R404A refrigerant was filled in the volume ratios from 0% to 80% and the heat input was controlled in the range from 10 W to 80 W. Obtained results exhibited the ability of R404A refrigerant can enhance the thermal performance in steady state condition. The average temperature difference of the evaporating section and condensing section in the 80% filling volume ratio decreased from 9.5 °C to 2.5 °C when the heating power increase from 10 W to 80 W. The thermal resistance of evaporator and condenser decreased with an increase of the heat input as well. For other filling volume ratios, the trend of temperature difference and thermal resistance was similar to that of the 80% volume filling ratio. Considering the same heat input, the highest heat transfer performance was found at the 80% volume filling ratio. Refrigerant with a relatively low dynamic consistency can lead to relatively high velocity in the PHP that can reduce the temperature difference between the evaporating section and condensing section.

scholarly journals Fluid flow and heat transfer in a dual-wet micro heat pipe

2007 ◽  
Vol 589 ◽  
pp. 1-31 ◽  
Author(s):  
JIN ZHANG ◽  
STEPHEN J. WATSON ◽  
HARRIS WONG
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Heat Pipe ◽  
Contact Line ◽  
Heat Pipes ◽  
Dimensionless Parameters ◽  
Micro Heat Pipes

Micro heat pipes have been used to cool micro electronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. In this work, a dual-wet pipe is proposed as a model to study heat transfer in micro heat pipes. The dual-wet pipe has a long and narrow cavity of rectangular cross-section. The bottom-half of the horizontal pipe is made of a wetting material, and the top-half of a non-wetting material. A wetting liquid fills the bottom half of the cavity, while its vapour fills the rest. This configuration ensures that the liquid–vapour interface is pinned at the contact line. As one end of the pipe is heated, the liquid evaporates and increases the vapour pressure. The higher pressure drives the vapour to the cold end where the vapour condenses and releases the latent heat. The condensate moves along the bottom half of the pipe back to the hot end to complete the cycle. We solve the steady-flow problem assuming a small imposed temperature difference between the two ends of the pipe. This leads to skew-symmetric fluid flow and temperature distribution along the pipe so that we only need to focus on the evaporative half of the pipe. Since the pipe is slender, the axial flow gradients are much smaller than the cross-stream gradients. Thus, we can treat the evaporative flow in a cross-sectional plane as two-dimensional. This evaporative motion is governed by two dimensionless parameters: an evaporation number E defined as the ratio of the evaporative heat flux at the interface to the conductive heat flux in the liquid, and a Marangoni number M. The motion is solved in the limit E→∞ and M→∞. It is found that evaporation occurs mainly near the contact line in a small region of size E−1W, where W is the half-width of the pipe. The non-dimensional evaporation rate Q* ~ E−1 ln E as determined by matched asymptotic expansions. We use this result to derive analytical solutions for the temperature distribution Tp and vapour and liquid flows along the pipe. The solutions depend on three dimensionless parameters: the heat-pipe number H, which is the ratio of heat transfer by vapour flow to that by conduction in the pipe wall and liquid, the ratio R of viscous resistance of vapour flow to interfacial evaporation resistance, and the aspect ratio S. If HR≫1, a thermal boundary layer appears near the pipe end, the width of which scales as (HR)−1/2L, where L is the half-length of the pipe. A similar boundary layer exists at the cold end. Outside the boundary layers, Tp varies linearly with a gradual slope. Thus, these regions correspond to the evaporative, adiabatic and condensing regions commonly observed in conventional heat pipes. This is the first time that the distinct regions have been captured by a single solution, without prior assumptions of their existence. If HR ~ 1 or less, then Tp is linear almost everywhere. This is the case found in most micro-heat-pipe experiments. Our analysis of the dual-wet pipe provides an explanation for the comparatively low effective thermal conductivity in micro heat pipes, and points to ways of improving their heat transfer capabilities.

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