Improvement of Heat Transfer Performance of Loop Heat Pipe for Electronic Devices

2011 ◽  
Author(s):  
Tomonao Takamatsu ◽  
Katsumi Hisano ◽  
Hideo Iwasaki
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Thermal Energy ◽  
Heat Load ◽  
Cooling System ◽  
Electronic Devices ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Reserve Area ◽  
Heat Transport Capability

In this paper is presented the results on performance of the cooling model using Loop Heat Pipe (LHP) system. In recent years, ever-ending demand of high performance CPU led to a rapid increase in the amount of heat dissipation. Consequently, thermal designing of electronic devices need to consider some suitable approach to achieve high cooling performance in limited space. Heat Pipe concept is expected to serve as an effective cooling system for laptop PC, however, it suffered from some problems as follows. The heat transport capability of conventional Heat Pipe decreases with the reduction in its diameter or increase in its length. Therefore, in order to use it as cooling system for future electronic devices, the above-mentioned limitations need to be removed. Because of the operating principle, the LHP system is capable of transferring larger amount of heat than conventional heat pipes. However, most of the LHP systems suffered from some problems like the necessity of installing check valves and reservoirs to avoid occurrence of counter flow. Therefore, we developed a simple LHP system to install it on electronic devices. Under the present experimental condition (the working fluid was water), by keeping the inside diameter of liquid and vapor line equal to 2mm, and the distance between evaporator and condenser equal to 200mm, it was possible to transport more than 85W of thermal energy. The thickness of evaporator was about 5mm although it included a structure to serve the purpose of controlling vapor flow direction inside it. Successful operation of this system at inclined position and its restart capability are confirmed experimentally. In order to make the internal water location visible, the present LHP system is reconstructed using transparent material. In addition, to estimate the limit of heat transport capability of the present LHP system using this thin evaporator, the air cooling system is replaced by liquid cooling one for condensing device. Then this transparent LHP system could transport more than 100W of thermal energy. However, the growth of bubbles in the reserve area with the increase in heat load observed experimentally led to an understanding that in order to achieve stable operation of the LHP system under high heat load condition, it is very much essential to keep enough water in the reserve area and avoid blocking the inlet with bubbles formation.

An Experimental Study of Heat Transfer Characteristics in Miniature Loop Heat Pipes With Rectangular Shaped Evaporator

2011 ◽  
Author(s):  
Z. R. Lin ◽  
Z. Y. Lee ◽  
L. W. Zhang ◽  
S. F. Wang ◽  
A. A. Merrikh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Sink ◽  
Thermal Design ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transport Capability

Loop heat pipe (LHP) is a highly efficient cooling device. It has gained great attention in the electronics cooling industry due to its superior heat transport capability — that is, its ability to carry heat over long distances. For this article, a miniature flat loop heat pipe (MFLHP) with rectangular-shaped evaporator was developed. The LHP’s evaporator was combined with the compensation chamber. MFLHPs with different diameters and lengths for the connecting pipeline were selected for a series of experimental studies on their heat transfer characteristics. In these experiments, pure water was used as the working fluid. The studies showed that the heat transport capability of a MFLHP with 4 mm diameter was better than that a MFLHP with 3 mm diameter. At a low thermal resistance of 0.04°C /W (at 200W), an optimal length for the connecting pipeline for a particular MFLHP with 4 mm diameter was identified. Finally, a heat sink attached to a MFLHP was developed for cooling a graphics processing unit (GPU), the thermal design power (TDP) of which was 200 W. The results showed the GPU heat sink with MFLHP had good performance and satisfied GPU cooling requirements. Compared to the conventional heat pipe solutions, only one MFLHP was able to cope with high power dissipation, offering the potential to make a lighter heat sink.

Experimental study on the supercritical startup and heat transport capability of a neon-charged cryogenic loop heat pipe

2017 ◽  
Vol 134 ◽  
pp. 178-187 ◽  
Author(s):  
Yuandong Guo ◽  
Guiping Lin ◽  
Jiang He ◽  
Lizhan Bai ◽  
Hongxing Zhang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Heat Pipe ◽  
Heat Transport ◽  
Loop Heat Pipe ◽  
Heat Transport Capability

scholarly journals Development of a loop heat pipe with kW-class heat transport capability

2021 ◽  
Vol 183 ◽  
pp. 116169
Author(s):  
Yoshitada Aono ◽  
Noriyuki Watanabe ◽  
Ai Ueno ◽  
Hosei Nagano
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Loop Heat Pipe ◽  
Heat Transport Capability

Heat Transport Characteristics of a Pulsating Heat Pipe

2007 ◽  
Author(s):  
Takao Nagasaki ◽  
Toshiyuki Hokazono ◽  
Yutaka Ito
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Heat Load ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Load Range ◽  
Large Heat ◽  
Inner Diameter ◽  
Bottom Heat ◽  
Better Than

Heat transport characteristics of a closed loop pulsating heat pipe (PHP) have been investigated experimentally. The heat pipe consists of 12 turn copper pipes with 2mm inner diameter. The lengths of heating, adiabatic and cooling sections are 53mm, 100mm and 51mm, respectively. The heat load was varied up to nearly 1000W for water and R141b as the working fluid. Three kinds of orientation, bottom heat vertical, horizontal, and top heat vertical, were tested. Detailed measurements of wall temperature fluctuations for water revealed several characteristic operating behaviors, such as intermittent oscillation and thermosyphon-like behavior. The performance of PHP with R141b is better than that with water in small heat load range due to its independence of orientation, conversely, PHP with water was more efficient than R141b in large heat load range. In order to improve the performance of PHP with R141b, diamond particles were added, resulting in better performance than water in the whole range of heat load.

Experimental Study on Heat Transfer Capability of a Miniature Loop Heat Pipe

2016 ◽  
Author(s):  
Guohui Zhou ◽  
Ji Li ◽  
Lucang Lv
Keyword(s):  
Heat Pipe ◽  
Heat Load ◽  
Electronics Cooling ◽  
High Heat ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Evaporator Temperature ◽  
Liquid Line ◽  
Horizontal Orientation ◽  
Flat Evaporator

In this paper, a miniature loop heat pipe (mLHP) with a flat evaporator is illustrated and investigated experimentally, with water as the working fluid. The mLHP can be applied for the mobile electronics cooling, such as tablet computers and laptop computers, with a 1.2 mm thick ultra-thin flat evaporator and a thickness of 1.0 mm for the vapor line, liquid line and condenser. A narrow sintered copper mesh in the liquid line and a part of the condenser as the secondary wick can promote the flow of the condensed working fluid back to the evaporator. The experimental results showed that the mLHP could start up successfully and operate stably at low heat load of 3 W in the horizontal orientation, and transport a high heat load of 12 W (the heat flux of 4 W/cm2) with the evaporator temperature below 100 °C in different test orientations by natural convection, showing good operational performance against gravity field. The minimum mLHP thermal resistance of 0.32 K/W was achieved at the input heat load of 12 W in the horizontal orientation.

Visualization of Two-Phase Flow in 3D Printed Polycarbonate Pulsating Heat Pipe With Aluminum Substrate

2018 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Kawaji ◽  
Yasushi Koito
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Two Phase Flow ◽  
Aluminum Plate ◽  
Working Fluid ◽  
Phase Flow ◽  
Pulsating Heat Pipe ◽  
Two Phase ◽  
Flow Channels ◽  
Heat Transport Capability

A pulsating heat pipe (PHP) is a passive device with a good heat transport capability compared to other heat pipes. This paper describes an experimental investigation of a PHP with a serpentine channel fabricated by using a 3-D printer. The configuration of the flow channels in the PHP was close to that of commercially available PHPs made entirely of aluminum. To improve the heat transport capability and enable flow visualization, an aluminum plate was used on one side as the heat-transfer surface, on which transparent flow channels were fabricated by a 3-D printer and a polycarbonate filament. The interface between the aluminum plate and polycarbonate flow channel was cemented with a heat-resistant glue to ensure long term sealing. HFE-7000 was used as a working fluid. Oscillating two-phase flow in the PHP was observed with a high-speed digital video camera and transient surface temperatures at evaporator, insulator and condenser sections were measured by fine diameter thermocouples. The two-phase flow and thermal characteristics of the PHP at different heater power levels are presented.

Effect of Al2O3 Microparticles on the Heat Transport Capability in an Oscillating Heat Pipe

2007 ◽  
Author(s):  
Hongtao Gao ◽  
Xiangyang Gao ◽  
Hongbin Ma ◽  
Anjun Jiao
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Volume Ratio ◽  
Working Fluid ◽  
Transport Capacity ◽  
Oscillating Heat Pipe ◽  
Copper Tubing ◽  
Oscillating Motion ◽  
Heat Transport Capability ◽  
Adiabatic Section

An experimental investigation was conducted to determine the microparticle effect on the heat transport capability of an oscillating heat pipe (OHP). The OHP was fabricated from copper tubing with inside diameter of 1.52 mm. The heat pipe consists of the evaporator, adiabatic section, and condenser. When heat load was added to the evaporator of OHP, the strong oscillating motion was generated. Due to the strong oscillation and circulation motions, the heat transport capability of OHP was significantly increased. The experimental results show that there exists an optimum volume ratio of microparticles added into the working fluid. The effects of filling ratio and tilted angle on the heat transport capacity were also conducted.

A Hybrid CFD-Mathematical Model for Simulation of a MEMS Loop Heat Pipe

2004 ◽  
Author(s):  
M. Ghajar ◽  
J. Darabi ◽  
N. Crews
Keyword(s):  
Pressure Drop ◽  
Heat Pipe ◽  
Heat Transport ◽  
Capillary Tube ◽  
Heat Rate ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Transport Distance ◽  
Compensation Chamber

A Hybrid CFD-Mathematical (HyCoM) model was developed to predict the performance of a Micro Loop Heat Pipe (MLHP) as a function of input heat rate. A micro loop heat pipe is a passive two-phase heat transport device, consisting of microevaporator, microcondenser, micro-compensation chamber (CC), and liquid and vapor lines. A CFD model was incorporated into a loop solver code to identify heat leak to the CC. Two-phase pressure drop in the condenser was calculated by several two phase correlations and results were compared [2]. Capillary tube correlations [3] were used for pressure drop calculations in fluid lines. Effects of working fluid and change in geometry were studied. For a heat transport distance of 10 mm, the base model MLHP was 50mm long, 16mm wide and 1mm thick. In the base model, widths of the grooves, liquid and vapor lines, evaporator, and condenser were 55μm, 200μm, 750μm, 2mm, and 4mm respectively.

Experimental Investigation of Heat Transfer Performance of a Miniature Loop Heat Pipe with Flat Evaporator

2011 ◽  
Vol 71-78 ◽  
pp. 3806-3809
Author(s):  
Xian Feng Zhang ◽  
Shuang Feng Wang
Keyword(s):  
Heat Pipe ◽  
Heat Load ◽  
Temperature Oscillation ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Operating Characteristics ◽  
Maximum Heat ◽  
Power Cycle ◽  
Flat Evaporator ◽  
Compensation Chamber

The present work experimentally investigated the operating characteristics of a miniature loop heat pipe (LHP) under different power cycle. The miniature LHP with flat evaporator of 8mm thick is made of copper. The evaporator with sintered copper power wick is in series structure with compensation chamber. Water is working fluid. It is found that the LHP can start up at heat load of 15W with temperature oscillation and the maximum heat load is 160W with Rl=0.068°C/W. The LHP operates unstably under low heat load. The oscillating frequency of temperature rises with heat load increased. The operating performance of the LHP is affected by the power cycle.

Steady State Modeling of LHP and Analysis

2010 ◽  
Author(s):  
Yan Chen ◽  
Lin Cheng ◽  
Gongming Xin ◽  
Tao Luan
Keyword(s):  
Steady State ◽  
Ambient Temperature ◽  
Heat Pipe ◽  
Heat Sink ◽  
Heat Load ◽  
Operating Temperature ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Heat Sink Temperature ◽  
Transition Heat

The loop heat pipe (LHP) was invented in Russia in the early 1980’s. It is a two-phase heat transfer device that utilizes the evaporation and condensation of a working fluid to transfer heat, and the capillary force developed in fine porous wicks to circulate the fluid. The temperature of LHP evaporator as functions of the heat load, sink temperature, ambient temperature is an important parameter which can reflect the performance of an LHP. Many factors can affect the LHP operating temperature and which can be divided into two parts: external and internal. The external factors including heat sink temperature, ambient temperature, fluid forces, the position between heat source and heat sink and the heat exchange between LHP and ambient. The internal factors related to the design and structure of the LHP, for example, the charging amount of the working fluid and the distribution status of the liquid phase during the LHP operating. Based on Sinda/Fluint software an ammonia-stainless steel steady state model of loop heat pipe was established, the impacts on the LHP operating temperature induced by alterable heat loads under 3 operating cases (the different position between evaporator and condenser, the changing of ambient temperature and the changing of heat sink temperature) were analyzed and conclusions were made. Changing the position between evaporator and condenser has a significant influence on the LHP operating temperature. Anti-gravity operation will reduce the performance of the LHP, this phenomenon is obviously in low heat load range. Further more, increasing of fluid pressure drop in the loop will induce decreasing of the LHP performance. The temperature difference between ambient and heat sink will influence the transition heat load (from variable conductance mode to fixed conductance mode), the bigger the temperature difference the higher the transition heat load.

Sign in / Sign up

Export Citation Format

Share Document