Investigation on the Use of Nanofluids to Enhance Heat Pipe Performance

Solar Energy ◽  
2005 ◽  
Author(s):  
Tomer Israeli ◽  
T. Agami Reddy ◽  
Young I. Cho
Keyword(s):  
Thermal Conductivity ◽  
Surface Tension ◽  
Thermal Resistance ◽  
Copper Oxide ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Experimental Studies ◽  
Heat Pipes ◽  
Thermal Network ◽  
Overall Resistance

This paper reports on preliminary experimental results on using nanofluids to enhance the thermal performance of heat pipes. Our experience with preparing copper oxide (CuO) nanofluids is described. Contrary to earlier studies which report infinite shelf life, we found that nanofluid stability lasted for about three weeks only; an issue which merits further study. We have also conducted various experiments to measure the variation of thermal conductivity and surface tension with CuO nanofluid concentration. Actual experiments on nanofluid heat pipes were also performed which indicated an average 12.5% decrease in the overall thermal resistance of the heat pipe using nanofluid of 3% vol concentration. This observed improvement is fairly consistent with our predictions using a simple analytical thermal network model for heat pipe overall resistance and the measured nanofluid conductivity. The results, though encouraging, need more careful and elaborate experimental studies before the evidence can be deemed conclusive.

Study on the Thermal Characteristics of Heat Pipes with Water-Based MWCNT Nanofluids

2011 ◽  
Vol 110-116 ◽  
pp. 1879-1885
Author(s):  
Hyo Jun Ha ◽  
Ji Hun Park ◽  
Seok Pil Jang
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Volume Fraction ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Multiwalled Carbon ◽  
Evaporation Temperature ◽  
Water Based

In this paper, thermal characteristics of miniature heat pipes with grooved wick and water-based multiwalled carbon nanotubes(MWCNT) nanofluids(0.1, 0.2, and 0.5 vol.%) as working fluids are experimentally investigated. The thermal conductivity and thermal resistances are measured and compared with those of DI water. The thermal conductivity of water-based MWCNT nandfluids is enhanced by up to 29% compared with that of DI water. Experiments are performed under the same evaporation temperature condition. The thermal resistance of heat pipe is reduced from 30% to 35.2% as the volume fraction of nanoparticles inceasing from 0.1% to 0.5%. Finally, based on the experimental results, we present the reduction of the thermal resistances of the heat pipes compared with conventional heat pipes cannot be explained by only the thermal conductivity of water-based MWCNT nanofluids.

Heat Transfer Characteristics of Self-Rewetting Fluid and its Application in Heat Pipe

2015 ◽  
Author(s):  
S. F. Wang ◽  
Y. X. Hu ◽  
Y. Zhou ◽  
W. Zhang
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Heat Pipe ◽  
Pure Water ◽  
Experimental Studies ◽  
Heat Pipes ◽  
Research Field ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
High Efficient

Self-rewetting fluids (SRWFs) are non-azeotropic solutions enjoy a particular surface tension behavior — an increase in the surface tension with increasing temperature. Due to the unique property, the SRWF can spontaneously wet hotter region and enhance heat transfer. The interesting behavior makes the SRWF become the research hotspot in phase change heat transfer research field. To clarify the heat transfer characteristics of SRWF, a series of boiling experiments have been carried out by employing dilute heptanol aqueous solution as SRWF. It is found out that, the bubble size of the SRWF is much smaller than that of pure water, and the critical heat flux of SRWF is much higher than that of water, which is beneficial for application in heat pipes. To find out the heat transfer performance of SRWF in heat pipes, experimental studies are performed on oscillating heat pipe (OHP) consisting of 4 meandering turns, with heat transfer length (L) of 150 mm and inner diameter (Di) of 1.3 mm. Compared with the water, the SRWF exhibits much better thermal performance, which indicates that SRWF is a promising and useful working liquid for the application in high efficient cooling devices with micro structure.

Numerical Analysis of Effects of Surface Tension and Viscosity on 3 Dimensional Pulsating Heat Pipe

2018 ◽  
Author(s):  
Durga Bastakoti ◽  
Hongna Zhang ◽  
Weihua Cai ◽  
Fengchen Li
Keyword(s):  
Surface Tension ◽  
Numerical Analysis ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Input ◽  
Lower Surface ◽  
Experimental Results ◽  
Pulsating Heat Pipe ◽  
Lower Surface Tension

Since the development of Pulsating Heat Pipe (PHP), it has gained a lot of attention in the field of thermal management. Flow inside multi-turn PHP is dominated by the capillary action mostly driven by the surface tension and drag force. Cetyltrimethyl ammonium chloride (CTAC) surfactant solution has lower surface tension and higher viscosity values compared to water, its base fluid. Experimental results have proven that the thermal resistance of PHP has increased its thermal performance at higher fill ratios and higher heat input, however the operational mechanism is not yet understood. Vapor formation, its movement and flow pattern of phases of working fluid can be well analyzed by the computational approach. In this paper, results of numerical analysis of 3-D PHP with working fluids that has values of surface tension and viscosity equal to that of 2000 ppm of CTAC are presented to validate the experimental results, thereby explain the thermodynamic reason of decreased thermal resistance. Moreover, the reasons for degraded performance of PHP with CTAC solutions at lower fill ratio and lower heat inputs are explained based on the vapor generation and flow of liquid-vapor inside the capillary tube. The numerical investigation was carried out for the case of 35%, 50% and 65% Fill Ratios (FR) at heat supply of 20, 30, 40 and 50 Watts. Lower surface tension promoted the phase change by rapid formation of vapor from liquid phase. Higher viscosity decreased the velocity of the fluid within the pipe. Influence of surface tension and viscosity on the thermal performance of PHP varied with different fill ratios and heat input.

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.

Analysis of CuO-Water Nanofluid Application on Heat Pipe

2014 ◽  
Vol 590 ◽  
pp. 234-238
Author(s):  
Nandy Putra ◽  
Wayan Nata Septiadi ◽  
Ranggi Sahmura
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Research Area ◽  
Working Fluid ◽  
Research Subject ◽  
High Concentration ◽  
Low Concentration ◽  
The World

Since their first introduction to the world, both heat pipe and nanofluid have caught the interest of many researchers. Heat pipe with its unique and exceptional capability in transferring heat passively and effectively, was studied intensively and developed extensively for many applications. While nanofluid with its higher thermal conductivity and some other upgraded properties compared to conventional fluid rose as appealing research subject especially on fluid and thermal research area. This study analyzes the utilization of CuO-water nanofluid on biomaterial wick heat pipe. Laboratory-developed CuO-water nanofluid was used as working fluid for vertically straight-shaped biomaterial wick heat pipe. From the experiment, it was shown that the application of CuO-water nanofluid reduced the heat pipe thermal resistance up to 83%. It was figured out that this enhancement is due to the combination of higher thermal conductivity and better wettability of the fluid. It was also found that the heat pipe with nanofluid did not show significant degradation though being inactivated for several weeks. However, it was figured out that unlike the application of low concentration nanofluid, application of high concentration nanofluid was insignificant in improving thermal performance of the heat pipe.

Characterizing Bulk Thermal Conductivity and Interface Contact Resistance Effects of Thermal Interface Materials in Electronic Cooling Applications

2003 ◽  
Author(s):  
Vadim Gektin ◽  
Sai Ankireddi ◽  
Jim Jones ◽  
Stan Pecavar ◽  
Paul Hundt
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Performance ◽  
Electronic Cooling ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Contact ◽  
Interface Materials ◽  
Bulk Thermal Conductivity

Thermal Interface Materials (TIMs) are used as thermally conducting media to carry away the heat dissipated by an energy source (e.g. active circuitry on a silicon die). Thermal properties of these interface materials, specified on vendor datasheets, are obtained under conditions that rarely, if at all, represent real life environment. As such, they do not accurately portray the material thermal performance during a field operation. Furthermore, a thermal engineer has no a priori knowledge of how large, in addition to the bulk thermal resistance, the interface contact resistances are, and, hence, how much each influences the cooling strategy. In view of these issues, there exists a need for these materials/interfaces to be characterized experimentally through a series of controlled tests before starting on a thermal design. In this study we present one such characterization for a candidate thermal interface material used in an electronic cooling application. In a controlled test environment, package junction-to-case, Rjc, resistance measurements were obtained for various bondline thicknesses (BLTs) of an interface material over a range of die sizes. These measurements were then curve-fitted to obtain numerical models for the measured thermal resistance for a given die size. Based on the BLT and the associated thermal resistance, the bulk thermal conductivity of the TIM and the interface contact resistance were determined, using the approach described in the paper. The results of this study permit sensitivity analyses of BLT and its effect on thermal performance for future applications, and provide the ability to extrapolate the results obtained for the given die size to a different die size. The suggested methodology presents a readily adaptable approach for the characterization of TIMs and interface/contact resistances in the industry.

scholarly journals Performance improvement of the heat recovery unit with sequential type heat pipes using TiO2 nanofluid

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1755-1764 ◽  
Author(s):  
Ahmet Ozturk ◽  
Mehmet Ozalp ◽  
Adnan Sozen ◽  
Metin Guru
Keyword(s):  
Thermal Performance ◽  
Heat Recovery ◽  
Experimental Studies ◽  
Heat Pipes ◽  
Outer Diameter ◽  
Distilled Water ◽  
Condenser Section ◽  
Recovery System ◽  
Heat Recovery System ◽  
Set Up

This paper deals with the improvement of thermal performance of the heat recovery system in air-to-air unit by using a nanofluid of TiO particles and distilled water. The 2 experimental set-up equipped with 15 copper pipes of a 1000 mm length, 10.5 mm inner diameter, and 12 mm outer diameter was used. The evaporator section consists of 450 mm of heat pipes, the condenser section is 400 mm, and the adiabatic section is 150 mm. In experimental studies, 33% of the evaporator volumes of heat pipes were filled with working fluids. Experiments were carried out at temperatures between 25?C and 90?C by using five different cooling air-flows (40, 42, 45, 61, and 84 g/s), and two different heating powers (3 kW and 6 kW) for the evaporation section, to determine heat removed from the condensation section. Trials were performed for distilled water and nanofluid respectively, and the results were compared with each other. Results revealed that a 50% recovery in the thermal performance of the heat pipe heat recovery system was achieved in the design using TiO nanofluid as the working liquid, at a heating power of 3 kW, air 2 velocity of 2.03 m/s and air-flow of 84 g/s.

Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays

1995 ◽  
Vol 117 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. K. Mallik ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Bottom Surface ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

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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