scholarly journals Thermal Performances Investigation of Anti-Gravity Heat Pipe with Tapering Phase-Change Chamber

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5036
Author(s):  
Jianhua Xiang ◽  
Xi-bo Chen ◽  
Jiale Huang ◽  
Chunliang Zhang ◽  
Chao Zhou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Cross Sectional ◽  
Start Up ◽  
Transfer Capability ◽  
Frequent Switching ◽  
Wick Structure ◽  
Better Than

The objective of this study was to fabricate anti-gravity heat pipes with a tapering column phase-change chamber and changeable cross-sectional wick structure. The thermal performances of the anti-gravity heat pipes were experimentally investigated. Results show that the thermal resistances of the different heat pipes are less than 0.03 °C/W, except for the sharp conical chamber heat pipe under anti-gravity heating conditions (0.121 °C/W). Start-up times of different types of heat pipes are similar and the temperatures are steady within 3 to 5 min. The heat transfer ability of a conical chamber is always better than that of a cylindrical one. The performance of the sharp conical chamber heat pipe is the best under gravity assistance heating conditions. Contrarily, the blunt conical chamber heat pipe has the best heat transfer ability under anti-gravity heating conditions. Moreover, the heat transfer capability of the blunt conical chamber heat pipe is unaffected by the relative position of the heat and cold sources, which is suitable for constant temperature cooling applications with frequent switching of the heat and cold sources.

Experimental Study on Heat Transfer Characteristic of Plate Pulsating Heat Pipe

2009 ◽  
Author(s):  
Li Quan ◽  
Li Jia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Cross Section ◽  
Heat Pipes ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Pulsating Heat Pipe ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Start Up

An experimental system of flat plate pulsating heat pipe was established and experimental research was carried out in this system to understand the mechanism of heat transfer and operating characteristics. The effects of start-up time, operating characteristics, and structures of passage, incline angle, fill ratio and working fluid on plate pulsating heat pipe were discussed. The results indicate that temperature of heating section decreases and the temperature of cooling section increases, then the thermal resistant of PHP is decreased once the plate pulsating heat pipe starts to work. Different start-up powers are needed for different fill ratios and incline angles. The inter pressure of PHP has some impacts on the start-up and operation of PHP. The pulsating heat pipes with different structures have different heat transfer performance. Increasing cross-sectional area and the number of turnings of the heat pipe can improve the heat transfer characteristics of heat pipes. Cross-section shape was also an important influencing factor. With the same cross-sectional area, heat pipe with triangular cross-section of the inner tubes gives better performance than that with rectangular cross-section.

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.

Fundamental Heat Transfer Experiments of Heat Pipes for Turbine Cooling

1998 ◽  
Vol 120 (3) ◽  
pp. 580-587 ◽  
Author(s):  
S. Yamawaki ◽  
T. Yoshida ◽  
M. Taki ◽  
F. Mimura
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Cooling System ◽  
Infrared Image ◽  
Heat Pipes ◽  
Performance Criteria ◽  
Working Fluid ◽  
Steel Shell ◽  
Turbine Cooling ◽  
Start Up

Fundamental heat transfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, and infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm2. The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the startup time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.

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 Fundamental Heat Transfer Experiments of Heat Pipes for Turbine Cooling

1997 ◽  
Author(s):  
Shigemichi Yamawaki ◽  
Toyoaki Yoshida ◽  
Masanobu Taki ◽  
Fujio Mimura
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Cooling System ◽  
Infrared Image ◽  
Heat Pipes ◽  
Performance Criteria ◽  
Working Fluid ◽  
Steel Shell ◽  
Turbine Cooling ◽  
Start Up

Fundamental heat transfer experiments were carried out for three kinds of heat pipes which may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium(Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium(NaK). Heat pipes B and C included non-condensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm2. The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus adding non-condensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 degrees. There was no significant gravitational dependence on heat transport for heat pipes including non-condensible gas.

The Start-Up Performance of Pulsating Heat Pipe With Communicating Pipe at Different Inclination Angles

2019 ◽  
Author(s):  
Fu-Min Shang ◽  
Shi-Long Fan ◽  
Jian-Hong Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Pulsating Heat Pipe ◽  
High Heat Transfer ◽  
Start Up ◽  
Inclination Angles

Abstract The pulsating heat pipe (PHP) is a passive cooling device, which has the advantages of simple structure, high heat transfer performance and low production cost. The complex vapor-liquid phase change occurs in the in the initial stage of PHP. In this work, we explore the start-up performance of PHP at different inclination angles and the experiment shows that start-up performance is respectively different when the angles are 0°, 45°, 90°, 135° and 180°. Since the gravitational auxiliary function, the working fluid in the communicating pipe which takes longer time to vaporize change phase earlier than that in PHP’s loop when the angles are 0° and 45°. Nevertheless, when the angle is 90°, the phase change of working fluid in communicating pipe and in the loop occurs at the same time. Meanwhile, the oscillating mode affects the stability of the starting and heat transfer performance of the PHP.

scholarly journals Performance of a flat grooved heat pipe with a localized heat load

2021 ◽  
Vol 321 ◽  
pp. 04010
Author(s):  
Ramazan Aykut Sezmen ◽  
Barbaros Çetin ◽  
Zafer Dursunkaya
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Heat Sources ◽  
High Heat Transfer ◽  
Wide Range

Heat pipes are phase change heat transfer devices used in wide range of heat transport applications due to their high thermal transport capacities with low temperature differences. Heat pipes are especially preferred for electronic cooling applications and aerospace avionics to satisfy high heat transfer rate requirements. In this study, heat transfer and phase change mechanisms of working fluid are investigated and modeled using a 3-D thermal resistance network for multichannel flat grooved heat pipes. First, heat transfer and fluid flow are modeled in half of a single grooved structure due to symmetry, and is subjected to uniform heat flux. Radius of meniscus curvature and temperature distribution along the groove are calculated. Results are compared with experiments in the literature and show good agreement. The validated heat transfer and fluid flow models are extended to a multichannel model to observe performance of grooved heat pipes with localized heat sources, not covering the entire width, a vital feature for realistic simulation of operational devices. Predictions of the temperature distribution along the multichannel of the heat pipe are provided and the effect of the distribution of heat sources on the heat pipe is discussed.

Fabrication of Heat Pipes on an Acrylic Resin Board

2013 ◽  
Author(s):  
Yasushi Koito ◽  
Hiroyuki Maehara ◽  
Toshio Tomimura
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Acrylic Resin ◽  
Working Fluid ◽  
Liquid Volume ◽  
Wiring Board ◽  
Phase Change Heat Transfer

As a first step to develop an electronic wiring board in which micro or miniature heat pipes are internally fabricated, the experimental and analytical studies are performed on a wickless gravity-assisted heat pipe, namely thermosyphon, fabricated on a surface of an acrylic resin board. This proposal aims at performing a phase-change heat transfer inside an electronic wiring board having a low thermal conductivity. In experiments, the evaporator section of the heat pipe is heated by a heater while the condenser section is water-cooled by a heat sink. Water is used as a working fluid. Changing a heat input and a liquid volume ratio inside the heat pipe, the temperature distribution is measured by thermocouples and then compared to the case where the working fluid is not charged. Moreover, the simple model of the heat pipe is made based on a thermal resistance network, and the analysis is performed on a phase-change heat transfer and a conductive heat transfer inside the resin board having the heat pipe. The effective thermal conductivity of the heat pipe is evaluated. Although this study is an initial stage, the operational and the heat transfer characteristics of the resin board having the heat pipe are confirmed.

scholarly journals Experimental Research on the Thermal Performance and Semi-Visualization of Rectangular Flat Micro-Grooved Gravity Heat Pipes

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2480
Author(s):  
Xiang Gou ◽  
Qiyan Zhang ◽  
Yamei Li ◽  
Yingfan Liu ◽  
Shian Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Bipolar Transistors ◽  
Load Range ◽  
Equivalent Thermal Conductivity ◽  
Start Up ◽  
Phase Behaviors

To strengthen the heat dissipating capacity of a heat pipe used for integrated insulated gate bipolar transistors, as an extension of our earlier work, the effect of micro-groove dimension on the thermal performance of flat micro-grooved gravity heat pipe was studied. Nine pipes with different depths (0.4 mm, 0.8 mm, 1.2 mm) and widths (0.4 mm, 0.8 mm, 1.2 mm) were fabricated and tested under a heating load range from 80 W to 180 W. The start-up time, temperature difference, relative thermal resistance and equivalent thermal conductivity were presented as performance indicators by comparison of flat gravity heat pipes with and without micro-grooves. Results reveal that the highest equivalent thermal conductivity of the flat micro-grooved gravity heat pipes is 2.55 times as that of the flat gravity heat pipe without micro-grooves. The flat gravity heat pipes with deeper and narrower micro-grooves show better thermal performance and the optimal rectangular micro-groove dimension among the selected options is determined to be 1.2 mm (depth) × 0.4 mm (width). Furthermore, the liquid–vapor phase behaviors were observed to verify the heat transfer effects and analyze the heat transfer mechanism of the flat micro-grooved heat pipes.

scholarly journals Testing algorithm for heat transfer performance of nanofluid-filled heat pipe based on neural network

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 751-760
Author(s):  
Lei Lei
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Volume Fraction ◽  
Heat Pipes ◽  
Transfer Performance ◽  
Analysis Model ◽  
Accurate Analysis ◽  
Testing Algorithm

AbstractTraditional testing algorithm based on pattern matching is impossible to effectively analyze the heat transfer performance of heat pipes filled with different concentrations of nanofluids, so the testing algorithm for heat transfer performance of a nanofluidic heat pipe based on neural network is proposed. Nanofluids are obtained by weighing, preparing, stirring, standing and shaking using dichotomy. Based on this, the heat transfer performance analysis model of the nanofluidic heat pipe based on artificial neural network is constructed, which is applied to the analysis of heat transfer performance of nanofluidic heat pipes to achieve accurate analysis. The experimental results show that the proposed algorithm can effectively analyze the heat transfer performance of heat pipes under different concentrations of nanofluids, and the heat transfer performance of heat pipes is best when the volume fraction of nanofluids is 0.15%.

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