Study on a Pulsating Heat Pipe With Self-Rewetting Fluid

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Koji Fumoto ◽  
Masahiro Kawaji ◽  
Tsuyoshi Kawanami
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heated Surface ◽  
Input Power ◽  
Water Mixture ◽  
Pulsating Heat Pipe ◽  
Maximum Heat ◽  
Dry Spot ◽  
Heat Transport Capability

This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn toward a heated surface if a dry spot appears and thus to improve boiling heat transfer. In experiments, 1-butanol and 1-pentanol were added to water at a concentration of less than 1 wt % to make self-rewetting fluid. A pulsating heat pipe made from an extruded multiport tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of 4 when the maximum heater temperature was limited to 110°C. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes.

Performance Improvement in Pulsating Heat Pipes Using a Self-Rewetting Fluid

2009 ◽  
Author(s):  
K. Fumoto ◽  
M. Kawaji
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heated Surface ◽  
Heat Pipes ◽  
Input Power ◽  
Water Mixture ◽  
Pulsating Heat Pipe ◽  
Maximum Heat ◽  
Heat Transport Capability

New experimental results have been obtained on the enhancement of heat transport by a pulsating heat pipe (PHP) using a self-rewetting fluid. Self-rewetting fluids have a property that the surface tension increases with temperature unlike other common liquids. The increasing surface tension at a higher temperature could cause the liquid to be drawn towards a heated surface if a dry spot appears, and improving boiling heat transfer. In the present experiments, 1-butanol was added to water at a concentration of less than 1 wt% to make the self-rewetting fluid. A pulsating heat pipe made from an extruded multi-port tube was partially filled with the butanol-water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 120 °C. Thus, the use of a self-rewetting fluid in a PHP has been shown to be highly effective in improving the heat transport capability of pulsating heat pipes.

Effect of Self-Rewetting Fluids on Pulsating Heat Pipe Thermal Performance

2009 ◽  
Author(s):  
Koji Fumoto ◽  
Masahiro Kawaji ◽  
Tsuyoshi Kawanami
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heated Surface ◽  
Pure Water ◽  
Channel Cross Section ◽  
Working Fluid ◽  
High Heat Flux ◽  
Aqueous Alcohol ◽  
Water Mixture

Pulsating heat pipes (PHPs) have recently emerged as a possible cooling device for high heat flux electronics to replace conventional cooling devices. In this study, new experimental results were obtained for using self-rewetting fluids to enhance the heat transport of PHPs. Unlike other common liquids, the surface tension of self-rewetting fluids increases with temperature. The increase in surface tension at high temperatures causes the liquid to be drawn towards a heated surface if a dry spot appears, which improves boiling heat transfer. PHPs were constructed out of multiport extruded aluminum tubing with a square channel cross section. In experiments, heptanol was added to water at a concentration of less than 1 wt% to form the self-rewetting fluid. Several other parameters were adjusted for optimization, such as the aqueous alcohol solution concentration of the working fluid, the fluid fill ratio, and the heat pipe orientation. Using a self-rewetting fluid in PHPs was found to be highly effective in improving their heat transport capability. The PHPs delivered a better performance when oriented vertically rather than horizontally. As a working fluid, the heptanol water mixture outperformed both the butanol water mixture and pure water within the parameters of this experiment.

scholarly journals Thermal analysis of heat pipe using self rewetting fluids

2011 ◽  
Vol 15 (3) ◽  
pp. 879-888 ◽  
Author(s):  
Rathinasamy Senthilkumar ◽  
Subaiah Vaidyanathan ◽  
Sivaramanb Balasubramanian
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Pure Water ◽  
Heat Pipes ◽  
The Self ◽  
Working Fluid ◽  
Surface Tension Gradient ◽  
Condenser Section ◽  
Maximum Heat

This paper discuses the use of self rewetting fluids in the heat pipe. In conventional heat pipes, the working fluid used has a negative surface-tension gradient with temperature. It is an unfavourable one and it decreases the heat transport between the evaporator section and the condenser section. Self rewetting fluids are dilute aqueous alcoholic solutions which have the number of carbon atoms more than four. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature up to a certain limit. The experiments are conducted to improve the heat-transport capability and thermal efficiency of capillary assisted heat pipes with the self rewetting fluids like aqueous solutions of n-Butanol and n-Pentanol and its performance is compared with that of pure water. The n-Butanol and n-Pentanol are added to the pure water at a concentration of 0.001moles/lit to prepare the self rewetting fluids. The heat pipes are made up of copper container with a two-layered stainless steel wick consisting of mesh wrapped screen. The experimental results show that the maximum heat transport of the heat pipe is enhanced and the thermal resistances are considerably decreased than the traditional heat pipes filled with water. The fluids used exhibit an anomalous increase in the surface tension with increasing temperature.

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 Working Fluid on Pulsating Heat Pipe Thermal Performance

2010 ◽  
Author(s):  
Koji Fumoto ◽  
Masahiro Kawaji ◽  
Tsuyoshi Kawanami
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Heat Transport ◽  
Thermal Performance ◽  
Heated Surface ◽  
Working Fluid ◽  
Device Performance ◽  
Pulsating Heat Pipe ◽  
Transport Efficiency ◽  
Heating Section

Pulsating heat pipes (PHPs) are complex heat transfer devices whose thermal performance is governed by a strong thermohydrodynamic coupling. Recently, PHPs have attracted attention as novel electronic cooling devices. In this study, we used a self-rewetting fluid and obtained new experimental results for the improvement of the heat transport efficiency in PHPs. In contrast to the case of common liquids, the surface tension of self-rewetting fluids increases with temperature. Because of the increase in the surface tension at high temperatures, these fluids tend to flow toward the dry spot appearing on a heated surface, and thus, the boiling heat transfer is improved. We constructed PHPs from multiport extruded aluminum tubes with square channels. The PHPs consisted of a heating section, an adiabatic section, and a condensation section with a heat sink. We investigated the effect of the type of working fluid and the fluid fill ratio on the device performance. The working fluids employed were a self-rewetting fluid, water, and ethanol. The thermophysical properties of the working fluid affected the device performance, which also depended strongly on the boundary conditions employed during the PHP operation. In particular, the use of a self-rewetting fluid in the PHPs helped enhance the heat transport efficiency to a considerable extent.

The Heat Transport Capacity of Micro Heat Pipes

1998 ◽  
Vol 120 (4) ◽  
pp. 1064-1071 ◽  
Author(s):  
J. M. Ha ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Original Model ◽  
Semiempirical Model ◽  
Transport Capacity ◽  
Predictive Tool ◽  
Maximum Heat ◽  
Micro Heat Pipes

The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

Theoretical Realizability of Dream-Pipe-Like Oscillating/Pulsating Heat Pipe

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Masao Furukawa
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Capillary Tube ◽  
Feasibility Studies ◽  
Temperature Fields ◽  
Pulsating Heat Pipe ◽  
Long Distance ◽  
Effective Thermal Diffusivity ◽  
Energy Equations ◽  
Adiabatic Section

The state of the art of thermally self-excited oscillatory heat pipe technology is briefly mentioned to emphasize that there exists no oscillating/pulsating heat pipe (OHP/PHP) suited to long-distance heat transport. Responding to such conditions, this study actively proposes a newly devised conceptually novel type of OHP/PHP. In that heat pipe, the adiabatic section works as it were the dream pipe invented by Kurzweg. This striking quality of the proposed new-style OHP/PHP produces high possibilities of long-distance heat transport. To support such optimistic views, an originally planned mathematical model is introduced for feasibility studies. Hydraulic considerations have first been done to understand what conditions are required for sustaining bubble-train flows in a capillary tube of interest. Theoretical analysis has then been made to solve the momentum and energy equations governing the flow velocity and temperature fields in the adiabatic section. The obtained analytical solutions are arranged to give algebraic expressions of the effective thermal diffusivity, the performance index combined with the tidal displacement, and the required electric power. Computed results of those three are displayed in the figures to demonstrate the realizability of that novel OHP.

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.

An Investigation of the Thermal Performance of a Novel Axial Grooved Heat Pipe

2012 ◽  
Vol 580 ◽  
pp. 223-226
Author(s):  
K.M. Yang ◽  
N.H. Wang ◽  
C.H. Jiang ◽  
L. Cheng
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Thermal Characteristics ◽  
High Heat ◽  
Input Power ◽  
Thermal Coefficient ◽  
Total Thermal Resistance ◽  
High Heat Transfer ◽  
Axial Temperature

Heat pipes are devices capable of very high heat transfer and have been widely used in many thermal management applications. An experimental investigation of thermal characteristics of heat pipe with axial ‘‘Ω”-shaped grooves was presented in this paper. The effects of angle of inclination and input power on thermal performance of heat pipe were investigated, the surface tension and gravity both impacted the fluid flow in heat pipe, and which one was dominating was analyzed. Experimental results indicate that the working temperature of heat pipe, the axial temperature differences and the maximum axial temperature differences increase when increasing the input heat flux. The total thermal resistances become smaller with the input power increasing, but become bigger with the angle of inclination increasing. And the trend of the thermal coefficient of heat pipe reverses that of the total thermal resistance. The influence of gravity on thermal performance is weaker than that of the surface tension.

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