Innovative Nanostructured Wicks for Heat Pipes

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Bohan Tian ◽  
Corey Wilson ◽  
H. B. Ma
Keyword(s):  
Substrate Surface ◽  
Heat Pipes ◽  
Two Phase ◽  
Evaporation And Condensation ◽  
Oxide Nanostructures ◽  
Anodization Process ◽  
Conical Structure ◽  
Two Phase Heat Transfer ◽  
Hexagonal Columnar ◽  
Scanning Electron

A good wicking structure is necessary for the design of a highly efficient heat pipe. Several unique aluminum oxide nanostructures were developed as wicks for heat pipes. The wicks were manufactured via an anodization process at various anodization voltages and etching times. This allows for the manufacture of spatially variable wicking structures that can be tuned for specific applications. The resulting nanostructures were characterized with a scanning electron microscope. Six distinct wicking structures are shown in Fig. 1. The honeycomb nanostructure is a self-ordered, hexagonal columnar array. The clumped nanotube structure is composed of bundles of nanotubes separated by deep grooves. The teepee nanostructure has a honeycomb bottom covered with a conical structure top. The horizontal nanofiber structure consists of nanofibers laying parallel to the substrate surface. The ridge network nanostructure is a multiscaled structure with nanoporous ridges. The clumped nanofiber structure is formed from long tangled fibers that meet in a thin ridge. Each of these structures has features useful for nucleation, evaporation, and condensation. These wicks will have many applications in the fields of heat pipes and two-phase heat transfer.

Development and Experimental Validation of a Micro/Nano Thermal Ground Plane

2011 ◽  
Author(s):  
H. Peter J. de Bock ◽  
Shakti Chauhan ◽  
Pramod Chamarthy ◽  
Chris Eastman ◽  
Stanton Weaver ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Ground Plane ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Working Fluid ◽  
Heat Sources ◽  
Two Phase ◽  
Evaporation And Condensation ◽  
Two Phase Heat Transfer ◽  
Thermal Ground Plane

Heat pipes are commonly used in electronics cooling applications to spread heat from a concentrated heat source to a larger heat sink. Heat pipes work on the principles of two-phase heat transfer by evaporation and condensation of a working fluid. The amount of heat that can be transported is limited by the capillary and hydrostatic forces in the wicking structure of the device. Thermal ground planes are two-dimensional high conductivity heat pipes that can serve as thermal ground to which heat can be rejected by a multitude of heat sources. As hydrostatic forces are dependent on gravity, it is commonly known that heat pipe and thermal ground plane performance is orientation dependent. The effect of variation of gravity force on performance is discussed and the development of a miniaturized thermal ground plane for high g operation is described. In addition, experimental results are presented from zero to −10g acceleration. The study shows and discusses that minimal orientation or g-force dependence can be achieved if pore dimensions in the wicking structure can be designed at micro/nano-scale dimensions.

scholarly journals Skeletal heat conductivity of porous metal fiber materials

2021 ◽  
Vol 27 (2) ◽  
pp. 70-77
Author(s):  
A.G. Kostornov ◽  
◽  
A.A. Shapoval ◽  
I.V. Shapoval ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Materials ◽  
Porous Metal ◽  
Heat Pipes ◽  
Metal Fiber ◽  
Two Phase ◽  
Research Results ◽  
Fiber Materials ◽  
Two Phase Heat Transfer

The influence of a number of physical characteristics and parameters of metallic fiber materials on their thermal conductivity is studied in this work. Such porous materials are intended, among other things, for their effective use in two-phase heat transfer devices (heat pipes). The use of heat pipes in aircraft and space vehicles provides a number of thermophysical advantages. In particular, heat pipes significantly expand the possibilities of air cooling of heat-loaded technical devices. The thermal conductivity of capillary-porous materials-structures, which are important elements of heat pipes, significantly affects the intensity of two-phase heat transfer inside heat pipes. Frame thermal conductivity is equivalent to the thermal conductivity of materials that are conditionally continuous medium. Studies of the influence of structural characteristics of porous materials, such as porosity and parameters (dimensions) of discrete particles-fibers (fractions of the studied materials), were performed using special experimental equipment created at the I.M. Frantsevich Institute for Problems of Materials Science of the National Academy of Sciences of Ukraine (Kyiv). Porous metal structures (coatings) made of copper, nickel, and steel fibers (MPM) were investigated under conditions similar to those for space heat pipes. The porosity values ​​of the prototypes of materials were in the range of 40 to 93%. The research results showed that the following physical characteristics of capillary structures, such as values ​​of thermal conductivity of metallic materials (fiber fractions), the porosity of capillary-porous metal materials (structures), significantly affect the value of thermal conductivity of porous materials. The dimensions of discrete particles-fibers also affect in a certain way the value of the MBM thermal conductivity but to a lesser degree. The results obtained in this work are summarized in the form of empirical dependencies – formulas, providing engineering calculations of the thermal conductivity values ​​of metal fiber materials. The research results are intended for practical application in aviation and spacecraft apparatus engineering. In particular, the presented results are necessary for the development and creation of effective heat pipes with metal fiber capillary structures.

Experimental Study of Effect Factors on Performance of Heat Dissipation of HP Heat Exchanger for LED Cooling System

2012 ◽  
Vol 490-495 ◽  
pp. 2530-2533
Author(s):  
Yun Jun Gou ◽  
Zhong Liang Liu ◽  
Chun Min Wang ◽  
Xiao Hui Zhong
Keyword(s):  
Heat Exchanger ◽  
High Power ◽  
Heat Dissipation ◽  
Environmental Temperature ◽  
Cooling System ◽  
Heat Pipes ◽  
Two Phase ◽  
High Power Led ◽  
Street Lamp ◽  
Two Phase Heat Transfer

A new cooling concept for high power LED street lamp by combining the heat release of high power LED with two-phase heat transfer heat pipes was proposed, and in this paper we study the effect of heat pipe numbers, fins structure and ambient temperature on the performance of heat dissipation of HP heat exchanger. Through experimental results, we found the heat pipes number plays a more importent role on the performance of heat dissipation than the fins material and the final surface temperature will increase with the environmental temperature.

Experimental Investigation of Micro/Nano Heat Pipe Wick Structures

2008 ◽  
Author(s):  
H. Peter J. de Bock ◽  
Kripa Varanasi ◽  
Pramod Chamarthy ◽  
Tao Deng ◽  
Ambarish Kulkarni ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
High Performance ◽  
Heat Pipes ◽  
High Heat ◽  
Two Phase ◽  
Wick Structure ◽  
Two Phase Heat Transfer ◽  
Heat Transport Capability ◽  
Transfer Device

The performance of electronic devices is limited by the capability to remove heat from these devices. A heat pipe is a device to facilitate heat transport that has seen increased usage to address this challenge. A heat pipe is a two-phase heat transfer device capable of transporting heat with minimal temperature gradient. An important component of a heat pipe is the wick structure, which transports the condensate from the condenser to the evaporator. The requirements for high heat transport capability and high resilience to external accelerations leads to the necessity of a design trade off in the wick geometry. This makes the wick performance a critical parameter in the design of heat pipes. The present study investigates experimental methods of testing capillary performance of wick structures ranging from micro- to nano-scales. These techniques will facilitate a pathway to the development of nano-engineered wick structures for high performance heat pipes.

Experimental Study of Heat Pipe Exchanger for High Power LED Cooling System

2012 ◽  
Vol 490-495 ◽  
pp. 2278-2281
Author(s):  
Yun Jun Gou ◽  
Xiao Hui Zhong
Keyword(s):  
Heat Pipe ◽  
High Power ◽  
Heat Exchangers ◽  
Heat Dissipation ◽  
Cooling System ◽  
Heat Pipes ◽  
Two Phase ◽  
High Power Led ◽  
Two Phase Heat Transfer ◽  
Pipe Heat

A new cooling concept for high power LED street lamp by combining the heat release of high power LED with two-phase heat transfer heat pipes was proposed, and in this study a series of heat pipes with specific fins structure were developed. Through experimental results, we found the new heat pipe heat exchangers have the features of higher efficiency of heat dissipation and more compact construction which meets the demand of heat dissipation for high power LED than the traditional heat pipe heat exchangers and the new exchanger with outwards-radiate structure has the best heat dissipation performance.

MICROSCALE TWO PHASE HEAT TRANSFER ENHANCEMENT IN POROUS STRUCTURES

Equipment ◽  
2006 ◽  
Author(s):  
Leonid L. Vasiliev ◽  
A. Zhuravlyov ◽  
A. Shapovalov ◽  
L. L. Vasiliev, Jr
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Porous Structures ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Two Phase Heat Transfer

scholarly journals Effects of Long Durations of RF–Magnetron Sputtering Deposition of Hydroxyapatite on Titanium Dental Implants

2021 ◽  
Author(s):  
Ihab Nabeel Safi ◽  
Basima Mohammed Ali Hussein ◽  
Hikmat J. Aljudy ◽  
Mustafa S. Tukmachi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Magnetron Sputtering ◽  
Dental Implants ◽  
Substrate Surface ◽  
Rf Magnetron Sputtering ◽  
P Value ◽  
Edx Analysis ◽  
Significant Difference ◽  
Scanning Electron

Abstract Objectives Dental implant is a revolution in dentistry; some shortages are still a focus of research. This study use long duration of radiofrequency (RF)–magnetron sputtering to coat titanium (Ti) implant with hydroxyapatite (HA) to obtain a uniform, strongly adhered in a few micrometers in thickness. Materials and Methods Two types of substrates: discs and root form cylinders were prepared using a grade 1 commercially pure (CP) Ti rod. A RF–magnetron sputtering device was used to coat specimens with HA. Magnetron sputtering was set at 150 W for 22 hours at 100°C under continuous argon gas flow and substrate rotation at 10 rpm. Coat properties were evaluated via field emission scanning electron microscopy (FESEM), scanning electron microscopy–energy dispersive X-ray (EDX) analysis, atomic force microscopy, and Vickers hardness (VH). Student’s t-test was used. Results All FESEM images showed a homogeneous, continuous, and crack-free HA coat with a rough surface. EDX analysis revealed inclusion of HA particles within the substrate surface in a calcium (Ca)/phosphorus (P) ratio (16.58/11.31) close to that of HA. Elemental and EDX analyses showed Ca, Ti, P, and oxygen within Ti. The FESEM views at a cross-section of the substrate showed an average of 7 µm coat thickness. Moreover, these images revealed a dense, compact, and uniform continuous adhesion between the coat layer and the substrate. Roughness result indicated highly significant difference between uncoated Ti and HA coat (p-value < 0.05). A significant improvement in the VH value was observed when coat hardness was compared with the Ti substrate hardness (p-value < 0.05). Conclusion Prolonged magnetron sputtering successfully coat Ti dental implants with HA in micrometers thickness which is well adhered essentially in excellent osseointegration.

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