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.

Reciprocating-Mechanism Driven Heat Loops and Their Applications

2003 ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Evaporator Section ◽  
Two Phase Heat Transfer ◽  
Transfer Device

This paper introduces a novel heat transfer mechanism that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. The heat transfer device is coined as the reciprocating-mechanism driven heat loop (RMDHL), which includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300 W/cm2 in the evaporator section could be handled. The applications of the bellows-type reciprocating heat loop for gas turbine nozzle guide vanes and the leading edges of hypersonic vehicles are also illustrated. The new heat transfer device is expected to advance the current two-phase heat transfer device and open up a new frontier for further research and development.

Charging Station of a Planar Miniature Heat Pipe Thermal Ground Plane

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammed T. Ababneh ◽  
Shakti Chauhan ◽  
Frank M. Gerner ◽  
Doug Hurd ◽  
Peter de Bock ◽  
...  
Keyword(s):  
High Performance ◽  
Ground Plane ◽  
Heat Pipes ◽  
Working Fluid ◽  
Liquid Volume ◽  
Two Phase ◽  
Gravitational Fields ◽  
Charging Station ◽  
Error Characterization ◽  
Key Factor

Thermal ground planes (TGPs) are planar, thin (thickness of 3 mm or less) heat pipes which use two-phase heat transfer. The objective is to utilize TGPs as thermal spreaders in several microelectronic cooling applications. TGPs are innovative high-performance, integrated systems able to operate at a high power density with a reduced weight and temperature gradient. Moreover, being able to dissipate large amounts of heat, they have very high effective axial thermal conductivities and can operate in high adverse gravitational fields due to nanoporous wicks. A key factor in the design of the TGP is evacuation prior to filling and introduction of the proper amount of working fluid (water) into the device. The major challenge of this work is to fill heat pipes with a total liquid volume of less than 1 ml, without being able to see into the device. The current filling station is an improvement over the current state of the art as it allows for accurate filling of microliter sized volumes. Tests were performed to validate performance of the system and to verify that little to no noncondensable gasses were introduced to the system. Careful calibration of the amount of liquid introduced is important. Therefore, calibration of the burettes utilized for a liquid fill range of 0.01 ml to 100 ml was important. The magnitude of the pressure inside the TGP device is also an important factor. Charging station validation demonstrated the capability of charging TGPs with accuracy of ±1.64 μl. Calibration curves for the burettes and error characterization curves for a range of liquid charging volumes will be presented and discussed in this paper.

A Compact Integrated Thermosyphon Heat Sink for Power Electronics Cooling

2019 ◽  
Author(s):  
Ahmed Elkholy ◽  
Roger Kempers
Keyword(s):  
Natural Convection ◽  
Heat Sink ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Heat Sinks ◽  
Working Fluid ◽  
Convection Heat ◽  
Two Phase ◽  
Spreading Resistance

Abstract The trend in miniaturization of power electronic components requires the development of new robust and passive cooling methods to meet increased heat flux demands. Conventional heat sinks encounter inherent shortcomings due to heat spreading resistance of the heat sink baseplate particularly in natural convection heat sinks used to cool small localized heat sources. Heat pipes embedded within the base of heat sinks can be used to improve spreading performance but are limited by the ability to conduct heat into and out of the heat pipes. In the current study, a small, naturally aspirated two-phase thermosyphon heat sink was developed and characterized experimentally. The proposed architecture integrates all thermosyphon components into one compact device, where the evaporator, riser and the downcomer are incorporated at the heat sink base. The downcomer also serves as the condenser within the base of a vertical finned natural convection heat sink. The side-heated evaporator consists of an array mini-channels configuration which can operate in either pool boiling or flow boiling configuration, which allows the thermosyphon heat sink to operate in either reflux mode or looped mode, respectively. Experiments were carried out using HFE 7000 as the working fluid. The effect of the of input power on the thermal performance is examined for both modes for powers ranging from 10 to 80 W. Results demonstrate that this approach significantly reduces the spreading resistance resulting in a net improvement which can be traded-off for a decrease the overall size or weight of the heat sink.

Charging Station of a Planar Miniature Thermal Ground Plane

2011 ◽  
Author(s):  
Mohammed T. Ababneh ◽  
Frank M. Gerner ◽  
Doug Hurd ◽  
Peter de Bock ◽  
Shakti Chauhan ◽  
...  
Keyword(s):  
Ground Plane ◽  
Heat Pipes ◽  
Working Fluid ◽  
Liquid Volume ◽  
Two Phase ◽  
Charging Station ◽  
Filling Station ◽  
Error Characterization ◽  
Wide Range ◽  
Key Factor

Thermal ground planes (TGPs) are flat thin (less than 1 mm thick) heat pipes that can be used as a thermal spreader in a variety of microelectronic cooling applications. Like conventional heat pipes, TGP’s utilize two-phase cooling. Major advantages, include the ability to integrate directly with the microelectronic substrate for a wide range of applications; and the ability to operate in an adverse gravity environment of up to 20g. Other advantages include a very high thermal conductivity, reliability, no moving parts, electrodes, or need for external power. A key factor in the design of the TGP is evacuation prior to filling and introduction of the proper amount of working fluid (water) into the device. The major challenge of this work is to fill heat pipes with a total liquid volume of less than 1 ml, without being able to see into the device. The current filling station is an improvement over the current state of the art as it allows for accurate filling of micro liter sized volumes. Tests were performed to validate performance of the system and to verify that little to no non-condensable gasses were introduced to the system. Careful calibration of the amount of liquid introduced is essential. Therefore, calibration of the burettes utilized for a liquid fill range of 0.1 ml to 100ml was important. The magnitude of the pressure inside the TGP envelope is also an important factor. Calibration curves for the burettes and error characterization curves for a range of liquid charging volumes will be presented and discussed.

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.

Two-Phase Flow in Microchannels

2001 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Sink ◽  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Infrared Radiometry ◽  
Phase Water

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

Experimental Study of Linear and Radial Two-Phase Heat Transport Devices Driven by Electrohydrodynamic Conduction Pumping

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Source ◽  
Capillary Pressure ◽  
Heat Transport ◽  
Radial Direction ◽  
Heat Pipes ◽  
Working Fluid ◽  
Phase Flow ◽  
Transport Capacity ◽  
Two Phase ◽  
Capillary Phenomenon

Heat pipes are well known as simple and effective heat transport devices, utilizing two-phase flow and the capillary phenomenon to remove heat. However, the generation of capillary pressure requires a wicking structure and the overall heat transport capacity of the heat pipe is generally limited by the amount of capillary pressure generation that the wicking structure can achieve. Therefore, to increase the heat transport capacity, the capillary phenomenon must be either augmented or replaced by some other pumping technique. 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. In this study, two two-phase heat transport devices are created. The first device transports the heat in a linear direction. The second device transports the heat in a radial direction from a central heat source. The radial pumping configuration provides several advantages. Most notably, the heat source is wetted with fresh liquid from all directions, thereby reducing the amount of distance that must be travelled by the working fluid. The power required to operate the EHD conduction pumps is a trivial amount relative to the heat that is transported.

scholarly journals An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

2020 ◽  
Vol 21 (3) ◽  
pp. 309
Author(s):  
Maryam Fallah Abbasi ◽  
Hossein Shokouhmand ◽  
Morteza Khayat
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Double Layer ◽  
Electric Double Layer ◽  
Heat Pipes ◽  
The Body ◽  
Working Fluid ◽  
Two Phase ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

Experimental Validation and Design Simulations of a Passive Two-Phase Cooling System for Datacenters

2020 ◽  
Author(s):  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Raffaele L. Amalfi ◽  
Filippo Cataldo
Keyword(s):  
Thermal Performance ◽  
Experimental Validation ◽  
Cooling System ◽  
Electronics Cooling ◽  
Operating Conditions ◽  
Two Phase ◽  
Data Set ◽  
Pressure Drops ◽  
Wide Range ◽  
Important Challenge

Abstract Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling in general, as they provide high thermal performance, reliability and energy efficiency, as well as capture the heat at high temperatures suitable for many heat reuse applications. On the other hand, the design of passive two-phase thermosyphons is extremely challenging because of the complex physics involved in the boiling and condensation processes; in particular, the most important challenge is to accurately predict the flow rate in the thermosyphon and thus the thermal performance. This paper presents an experimental validation to assess the predictive capabilities of JJ Cooling Innovation’s thermosyphon simulator against one independent data set that includes a wide range of operating conditions and system sizes, i.e. thermosyphon data for server-level cooling gathered at Nokia Bell Labs. Comparison between test data and simulated results show good agreement, confirming that the simulator accurately predicts heat transfer performance and pressure drops in each individual component of a thermosyphon cooling system (cold plate, riser, evaporator, downcomer (with no fitting parameters), and eventually a liquid accumulator) coupled with operational characteristics and flow regimes. In addition, the simulator is able to design a single loop thermosyphon (e.g. for cooling a single server’s processor), as shown in this study, but also able to model more complex cooling architectures, where many thermosyphons at server-level and rack-level have to operate in parallel (e.g. for cooling an entire server rack). This task will be performed as future work.

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