Heat Transport Characteristics in Closed Loop Oscillating Heat Pipes

2005 ◽  
Author(s):  
Shuangfeng Wang ◽  
Shigefumi Nishio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Closed Loop ◽  
Flow Behavior ◽  
Working Fluid ◽  
Liquid Volume ◽  
High Heat Flux ◽  
Two Phase ◽  
Working Fluids ◽  
Inner Diameter

Heat transport rates of micro scale SEMOS (Self-Exciting Mode Oscillating) heat pipe with inner diameter of 1.5mm, 1.2mm and 0.9mm, were investigated by using R141b, ethanol and water as working fluids. The effects of inner diameter, liquid volume faction, and material properties of the working fluids are examined. It shows that the smaller the inner diameter, the higher the thermal transport density is. For removing high heat flux, the water is the most promising working fluid as it has the largest critical heat transfer rate and the widest operating range among the three kinds of working fluids. A one-dimensional numerical simulation is carried out to describe the heat transport characteristics and the two-phase flow behavior in the closed loop SEMOS heat pipe. The numerical prediction agrees with the experimental results fairly well, when the input heat through was not very high and the flow pattern was slug flow.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

scholarly journals Experimental Investigation of the Thermal Performance of a Wickless Heat Pipe Operating with Different Fluids: Water, Ethanol, and SES36. Analysis of Influences of Instability Processes at Working Operation Parameters

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 80 ◽  
Author(s):  
Rafal Andrzejczyk
Keyword(s):  
Heat Pipe ◽  
Input Power ◽  
Liquid Pool ◽  
Filling Ratio ◽  
Working Fluid ◽  
Operating Pressure ◽  
Two Phase ◽  
Condenser Section ◽  
Transfer Resistance ◽  
Working Fluids

In this study, the influences of different parameters on performance of a wickless heat pipe have been presented. Experiments have been carried out for an input power range from 50 W to 300 W, constant cooling water mass flow rate of 0.01 kg/s, and constant temperature at the inlet to condenser of 10 °C. Three working fluids have been tested: water, ethanol, and SES36 (1,1,1,3,3-Pentafluorobutane) with different filling ratios (0.32, 0.51, 1.0). The wall temperature in different locations (evaporation section, adiabatic section, and condenser section), as well as operating pressure inside two phase closed thermosyphon have been monitored. The wickless heat pipe was made of 0.01 m diameter copper tube, which consists of an evaporator, adiabatic, and condensation sections with the same length (0.4 m). For all working fluids, a dynamic start-up effect caused by heat conduction towards the liquid pool was observed. Only the thermosyphon filled with SES36 was observed to have operation limitation caused by achieving the boiling limit in TPCTs (two-phase closed thermosyphons). The geyser boiling effect has been observed only for thermosyphon filled with ethanol and for a high filling ratio. The performance of the thermosyphon determined the form of the heat transfer resistance of the TPCT and it was found to be dependent of input power and filling ratio, as well as the type of working fluid and AR (aspect ratio). Comparison with other authors would seem to indicate that lower AR results in higher resistance; however, the ratio of condenser section length to inside diameter of pipe is also a very important parameter. Generally, performance of the presented thermosyphon is comparable to other constructions.

Analysis of the Evaporating Characteristics of the Grooved Micro Heat Pipe with Alkali Metals as Working Fluid

2012 ◽  
Vol 516-517 ◽  
pp. 84-87 ◽  
Author(s):  
Lei Yu ◽  
Wei Qiang Liu
Keyword(s):  
Thin Film ◽  
Mathematical Model ◽  
Heat Flux ◽  
Heat Pipe ◽  
Alkali Metals ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Working Fluids ◽  
High Temperature Heat Pipe

This paper has built a mathematical model for the evaporating characteristics of the grooved micro heat pipe’s thin film region and computed them in a specific working condition. The evaporating model of Wayner was employed in this mathematical model. The results from computation showed, for the H2O and NH3 as working fluid, at the beginning of the thin film region, the heat flux raised rapidly to a peak value and then declined to almost 0 also rapidly in a very short distance. Differently, for the Na and K as working fluid, the heat flux raised quickly but declined slower. Therefore, the alkali metals working fluids had larger area of high heat flux covered. The results indicated that the alkali metals working fluid has better evaporating characteristics for the high-temperature heat pipe than normal working fluids.

Experimental Investigation and Performance Evaluation of a Multi Turn Closed Loop Pulsating Heat Pipe

2014 ◽  
Vol 592-594 ◽  
pp. 1554-1558 ◽  
Author(s):  
N. Narendra Babu ◽  
Rudra Naik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Closed Loop ◽  
Experimental Result ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids

Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

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.

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.

scholarly journals Nonlinear Analysis of Chaotic Flow in a Three-Dimensional Closed-Loop Pulsating Heat Pipe

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
S. M. Pouryoussefi ◽  
Yuwen Zhang
Keyword(s):  
Lyapunov Exponent ◽  
Heat Pipe ◽  
Closed Loop ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Periodic Behavior ◽  
Working Fluids ◽  
Chaotic Flow ◽  
Temperature Oscillations

Numerical simulation has been conducted for the chaotic flow in a 3D closed-loop pulsating heat pipe (PHP). Heat flux and constant temperature boundary conditions were applied for evaporator and condenser sections, respectively. Water and ethanol were used as working fluids. Volume of fluid (VOF) method has been employed for two-phase flow simulation. Spectral analysis of temperature time series was carried out using power spectrum density (PSD) method. Existence of dominant peak in PSD diagram indicated periodic or quasi-periodic behavior in temperature oscillations at particular frequencies. Correlation dimension values for ethanol as working fluid were found to be higher than that for water under the same operating conditions. Similar range of Lyapunov exponent values for the PHP with water and ethanol as working fluids indicated strong dependency of Lyapunov exponent on the structure and dimensions of the PHP. An O-ring structure pattern was obtained for reconstructed 3D attractor at periodic or quasi-periodic behavior of temperature oscillations. Minimum thermal resistance of 0.85 °C/W and 0.88 °C/W were obtained for PHP with water and ethanol, respectively. Simulation results showed good agreement with the experimental results from other work under the same operating conditions.

Radial, Two-Phase Heat Transport Device Driven by Electrohydrodynamic Conduction Pumping

2011 ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Heat Source ◽  
Liquid Film ◽  
Heat Pipe ◽  
Heat Transport ◽  
Working Fluid ◽  
Bottom Surface ◽  
Two Phase ◽  
Transport Device

Electrohydrodynamic (EHD) conduction pumping can be readily used to pump a thin film of a dielectric liquid along a surface, using electrodes that are embedded into the surface. This effect has been demonstrated under adiabatic conditions and has also been used to create a two-phase heat transport device that is similar to a heat pipe, but with the wicking structure replaced by an EHD conduction pump. In this study, a circular two-phase heat transport device is created. The device features circular electrodes that are arranged concentrically on the bottom surface and that pump a liquid film towards a heat source located at the center of the device. This heat source evaporates the liquid, and a large annular condenser at the periphery of the bottom surface provides a continuous supply of fresh liquid. This radial pumping configuration provides several advantages. Most notably, the heat source is wetted with fresh liquid from all 360 degrees, thereby reducing the amount of distance that must be travelled compared to a linear device. Consequently, the heat flux that can be removed from the central heat source far exceeds the normal critical heat flux of the working fluid. Electrodes are embedded in the condenser, adiabatic, and evaporator sections to maximize the amount of pumping head that can be generated and thereby maximize the heat flux removal.

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.

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.

Experimental Investigations on Thermal Performance of a Multi-Turn Closed Loop Pulsating Heat Pipe

2012 ◽  
Vol 433-440 ◽  
pp. 5854-5860 ◽  
Author(s):  
Yu Wang ◽  
Wei Yi Li
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Input ◽  
Closed Loop ◽  
Research Work ◽  
Design Parameters ◽  
Working Fluid ◽  
High Heat Flux ◽  
Pulsating Heat Pipe

Closed loop pulsating heat pipe (CLPHP) is a relatively new two-phase passive heat transfer device to suit present requirement of high heat flux dissipation in modern electronic components. The operating mechanism of CLPHP is not well understood and the present state of the technology cannot predict required design parameters for a given task. The aim of research work presented in this paper is to better understand thermal performance of CLPHP. A series of experimental investigation were conducted on a multi-turn CLPHP made of copper capillary tube of 2-mm inner diameter. Two kinds of working fluids viz. ethanol and acetone were employed. The influence characterization has been studied for the variation of heat input and filling ratio (FR) of the tested CLPHP. Thermal performance of the CLPHP is evaluated by heat transfer and thermal resistance. The results strongly demonstrate the effect of heat input and FR of the working fluid on thermal performance of the device.

Sign in / Sign up

Export Citation Format

Share Document