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.

An Experimental Investigation of Heat Transport Capability in a Nanofluid Oscillating Heat Pipe

2006 ◽  
Vol 128 (11) ◽  
pp. 1213-1216 ◽  
Author(s):  
H. B. Ma ◽  
C. Wilson ◽  
Q. Yu ◽  
K. Park ◽  
U. S. Choi ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Heat Transport ◽  
Working Fluid ◽  
New Approach ◽  
Oscillating Heat Pipe ◽  
Diamond Nanoparticles ◽  
Hplc Grade Water ◽  
Oscillating Motion ◽  
Heat Transport Capability

An experimental investigation of a nanofluid oscillating heat pipe (OHP) was conducted to determine the nanofluid effect on the heat transport capability in an OHP. The nanofluid consisted of HPLC grade water and 1.0vol% diamond nanoparticles of 5-50nm. These diamond nanoparticles settle down in the motionless base fluid. However, the oscillating motion of the OHP suspends the diamond nanoparticles in the working fluid. Experimental results show that the heat transport capability of the OHP significantly increased when it was charged with the nanofluid at a filling ratio of 50%. It was found that the heat transport capability of the OHP depends on the operating temperature. The investigated OHP could reach a thermal resistance of 0.03°C∕W at a heat input of 336W. The nanofluid OHP investigated here provides a new approach in designing a highly efficient next generation of heat pipe cooling devices.

Copper Oxide (CuO) Effect on Heat Transfer Performance in an Oscillating Heat Pipe

2012 ◽  
Author(s):  
Yulong Ji ◽  
Chen Xu ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Copper Oxide ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Inner Surface ◽  
Copper Tubing ◽  
Adiabatic Section

An experimental investigation of an oscillating heat pipe (OHP) with an inner surface coated with a copper oxide (CuO) layer was conducted. The OHP has six turns and three sections: evaporator, condenser and adiabatic section with the lengths of 40 mm, 64 mm and 51 mm, respectively. The cleaned copper tubing was chemically treated with a chemical solution and heated in a furnace. A layer of CuO was formed in the inner surface of the OHP. A working fluid (water in this study) at filling ratios ranging from 40% to 70% was studied. The experimental results show that the CuO layer can enhance the heat transfer performance of the OHP. The investigation results in a new way to enhance the heat transfer performance of an OHP.

Heat Transport Limitation of a Triangular Micro Heat Pipe

2003 ◽  
Author(s):  
D. Sugumar ◽  
Kek Kiong Tio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Operating Temperature ◽  
Working Fluid ◽  
Transport Capacity ◽  
Condenser Section ◽  
Micro Heat Pipe ◽  
Evaporator Section ◽  
Higher Temperature ◽  
Specific Temperature

A micro heat pipe will operate effectively by achieving its maximum possible heat transport capacity only if it is to operate at a specific temperature, i.e., design temperature. In reality, micro heat pipe’s may be required to operate at temperatures different from the design temperature. In this study, the heat transport capacity of an equilateral triangle micro heat pipe is investigated. The micro heat pipe is filled optimally with working fluid for a specific design temperature and operated at different operating temperatures. For this purpose, water, pentane and acetone was selected as the working fluids. From the numerical results obtained, it shows that the optimal charge level of the micro heat pipe is dependent on the operating temperature. Furthermore, the results also shows that if the micro heat pipe is to be operated at temperatures other than its design temperature, its heat transport capacity is limited by the occurrence of flooding at the condenser section or dryout at the evaporator section, depending on the operating temperature and type of working fluid. It is observed that when the micro heat pipe is operated at a higher temperature than its design temperature, the heat transport capacity increases but limited by the onset of dryout at the evaporator section. However, the heat transport capacity decreases if it is to be operated at lower temperatures than its design temperature due to the occurrence of flooding at condenser end. From the results obtained, we can conclude that the performance of a micro heat pipe is decreased if it is to be operated at temperatures other than its design temperature.

Experimental Investigation of Ultrasonic Frequency Effect on an Oscillating Heat Pipe

2016 ◽  
Author(s):  
Nannan Zhao ◽  
Benwei Fu ◽  
Hongbin Ma ◽  
Fengmin Su
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transport ◽  
Frequency Effect ◽  
Ultrasonic Frequency ◽  
Sound Effect ◽  
Oscillating Heat Pipe ◽  
Ultrasonic Sound ◽  
Heat Transfer Capacity ◽  
Heat Transport Capability

The heat transport capability in an oscillating heat pipe (OHP) significantly depends on the oscillating frequency. An external frequency directly affects the natural frequency in the system. In this investigation, the ultrasound sound effect on the heat transport capability in an OHP was conducted with focus on the ultrasonic frequency effect on the oscillating motion and heat transfer capacity in an OHP. The ultrasonic sound was applied to the evaporating section of the OHP by using the electrically-controlled piezoelectric ceramics. The heat pipe was tested with or without the ultrasonic sound with different frequencies. In addition, the effects of operating temperature, heat load from 25 W to 150 W were investigated. The experimental results demonstrate that the heat transfer capacity enhancement of the OHP depends on the frequency of the ultrasound field, and there exists an optimum combination of the frequencies which will lead to the largest enhancement of the heat transfer capacity of the OHP.

Investigation of a Novel Flat Heat Pipe

2005 ◽  
Vol 127 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Yaxiong Wang ◽  
G. P. Peterson
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Thermal Design ◽  
Experimental Results ◽  
Design Parameters ◽  
Working Fluid ◽  
Transport Capacity ◽  
Maximum Heat ◽  
Mesh Screen ◽  
Flat Heat Pipe

A novel flat heat pipe has been developed to assist in meeting the high thermal design requirements in high power microelectronics, power converting systems, laptop computers and spacecraft thermal control systems. Two different prototypes, each measuring 152.4 mm by 25.4 mm were constructed and evaluated experimentally. Sintered copper screen mesh was used as the primary wicking structure, in conjunction with a series of parallel wires, which formed liquid arteries. Water was selected as the working fluid. Both experimental and analytical investigations were conducted to examine the maximum heat transport capacity and optimize the design parameters of this particular design. The experimental results indicated that the maximum heat transport capacity and heat flux for Prototype 1, which utilized four layers of 100 mesh screen were 112 W and 17.4W/cm2, respectively, in the horizontal position. For Prototype 2, which utilized six layers of 150 mesh screen, these values were 123 W and 19.1W/cm2, respectively. The experimental results were in good agreement with the theoretical predictions for a mesh compact coefficient of C=1.15.

Experimental Investigation of a Three-Layer Oscillating Heat Pipe

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
C. D. Smoot ◽  
H. B. Ma
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Transport ◽  
Total Power ◽  
Oscillating Heat Pipe ◽  
Layer Effect ◽  
Layering Effect ◽  
Heat Transport Capability

An experimental investigation of a compact, triple-layer oscillating heat pipe (OHP) has been conducted to determine the channel layer effect on the heat transport capability in an OHP. The OHP has dimensions 13 mm thick, 229 mm long, and 76 mm wide embedded with two-independent closed loops forming three layers of channels. The unique design of the investigated OHP can be readily used to explore the channel layering effect on the heat transport capability in the OHP. The experimental results show that the addition of channel layers can increase the total power and at the same time, it can increase the effective thermal conductivity of the OHP. When the OHP switches from one layer of channels to two layers of channels, the highest effective thermal conductivity can be increased from 5760 W/mK to 26,560 W/mK. At the same time, the dryout limit can be increased. With three layers of channels, the OHP investigated herein can transport a power up to 8 kW with a heat flux level of 103 W/cm2 achieving an effective thermal conductivity of 33,170 W/mK.

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.

The Effect of Type of Working Fluid on the Heat Transport Capacity of a Micro Heat Pipe

2005 ◽  
Author(s):  
Sugumar Dharmalingam ◽  
Kek Kiong Tio
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Operating Temperature ◽  
Working Fluid ◽  
Liquid Viscosity ◽  
Transport Capacity ◽  
Temperature Range ◽  
Controlling Effect ◽  
Micro Heat Pipe

In order to elucidate the effects of working fluid’s properties on the heat transport capacity of a micro heat pipe, 3 commonly used fluids are selected for this study: water, ammonia and methanol. From the results obtained, it shows that for operating temperatures lower than 50°C, ammonia is preferred, but if the operating temperature exceeds 50°C, water is more suitable in transferring heat. Over the temperature range of 20°C∼100°C, the behavior of the heat transport capacity is found to be dominated by a property which is the ratio of the working fluid’s surface tension and liquid viscosity. This property which has the dimension of velocity has a controlling effect on the working fluid’s rate of circulation and therefore, the heat transport capacity.

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