Novel Fluorescent Visualization Method to Characterize Transport Properties in Micro/Nano Heat Pipe Wick Structures

2009 ◽  
Author(s):  
Pramod Chamarthy ◽  
H. Peter J. de Bock ◽  
Boris Russ ◽  
Shakti Chauhan ◽  
Brian Rush ◽  
...  
Keyword(s):  
Heat Pipe ◽  
High Performance ◽  
Gravitational Force ◽  
Driving Forces ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
High Permeability ◽  
Permeability Characteristics ◽  
Wick Structure ◽  
Initial Results

Heat pipes have been gaining a lot of popularity in electronics cooling applications due to their ease of operation, reliability, and high effective thermal conductivity. An important component of a heat pipe is the wick structure, which transports the condensate from condenser to evaporator. The design of wick structures is complicated by competing requirements to create high capillary driving forces and maintain high permeability. While generating large pore sizes will help achieve high permeability, it will significantly reduce the wick’s capillary performance. This study presents a novel experimental method to simultaneously measure capillary and permeability characteristics of the wick structures using fluorescent visualization. This technique will be used to study the effects of pore size and gravitational force on the flow-related properties of the wick structures. Initial results are presented on wick samples visually characterized from zero to nine g acceleration on a centrifuge. These results will provide a tool to understand the physics involved in transport through porous structures and help in the design of high performance heat pipes.

Hot Spot Elimination by Thin and Smart Heat Spreader

2015 ◽  
Author(s):  
Mohammad Shahed Ahamed ◽  
Yuji Saito ◽  
Masataka Mochizuki ◽  
Koichi Mashiko
Keyword(s):  
Heat Pipe ◽  
Hot Spot ◽  
Electronic Devices ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Metal Plate ◽  
Confined Space ◽  
Heat Spreader ◽  
Clock Speed ◽  
Wick Structure

Heat pipes are recognized as an excellent heat transport devices and extensively investigated for applications in electronic cooling. Different types of heat pipes have been developed such as micro/miniature heat pipes, loop heat pipes and so on, and these heat pipes have been widely applied in the field of electronics cooling such as notebook, desktop, data center; as well as aerospace, industrial cooling field. However, in recent years the application of heat pipe is widening to the filed of hand held mobile electronic devices such as smart phone, tablet pc, digital camera etc. With the development in technology these devices have different user friendly functions and capabilities, which requires the highest processor clock speed. In general, high clock speed of processor generates lot of heat which need to be spread or removed to eliminate the hot spot. It becomes a challenging task to cool such electronic devices as mentioned above with a very confined space and concentrated heat sources. Regarding to this challenge, ultra thin flat heat pipe is developed; this newly developed heat pipe consists of a special fiber wick structure which can ensure vapor spaces on the two sides of the wick structure. In this paper a novel thin spreader is proposed to eliminate the hot spot; generally the proposed heat spreader consists of 0.20mm thick metal plate and ultra thin heat pipe of 0.40mm thickness soldered in its body. Maximum thickness of this spreader is 0.63mm. Metal plate is 60mm × 110mm in size; and the ultra thin heat pipe can be fabricated from different original diameter ranges from 2.0mm to 3.0mm Cu tube. Theoretical and experimental analysis have been done to evaluate this thin spreader. In addition, some real application of this spreader will be introduced in this paper.

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 on Applied Thin Vapor Chamber and Embedded Heat Pipe Heat Sinks

2009 ◽  
Author(s):  
Garrett A. Glover ◽  
Yongguo Chen ◽  
Annie Luo ◽  
Herman Chu
Keyword(s):  
Heat Pipe ◽  
Heat Sink ◽  
High Performance ◽  
Structural Integrity ◽  
Heat Pipes ◽  
Electronic Cooling ◽  
Working Fluid ◽  
Vapor Chamber ◽  
Trade Offs ◽  
Pipe Heat

The current work is a survey of applied applications of passive 2-phase technologies, such as heat pipe and vapor chamber, in heat sink designs with thin base for electronic cooling. The latest improvements of the technologies and manufacturing processes allow achievable heat sink base thickness of 3 mm as compared to around 5 mm previously. The key technical challenge has been on maintaining structural integrity for adequate hollow space for the working fluid vapor in order to retain high performance while reducing the thickness of the overall vapor chamber or flattened heat pipe. Several designs of thin vapor chamber base heat sink and embedded heat pipe heat sink from different vendors are presented for a moderate power density application of a 60 W, 13.2 mm square heat source. Numerous works have been published by both academia and commercial applications in studying the fundamental science of passive 2-phase flow technologies; their performance has been compared to solid materials, like aluminum and copper. These works have established the merits of using heat pipes and vapor chambers in electronic cooling. The intent of this paper is to provide a methodical approach to help to accelerate the process in evaluating the arrays of different commercial designs of these devices in our product design cycle. In this paper, the trade-offs between the different types of technologies are discussed for parameters such as performance advantages, physical attributes, and some cost considerations. This is a bake-off evaluation of the complete heat sink solutions from the various vendors and not a fundamental research of vapor chambers and heat pipes — for that, it is best left to the vendors and universities.

scholarly journals Staying Cool

1999 ◽  
Vol 121 (07) ◽  
pp. 64-65
Author(s):  
Calvin C. Silverstein
Keyword(s):  
Heat Pipe ◽  
Thermal Management ◽  
Liquid Flow ◽  
High Performance ◽  
Heat Pipes ◽  
Flow Channel ◽  
Aircraft Engines ◽  
Chemical Milling ◽  
Combination Of Methods ◽  
Half Thickness

This article reviews heat pipes that address thermal management problems inside high-performance aircraft engines. Higher performance engines demand that compressors develop higher pressure ratios which, in turn, result in higher temperatures at the entrance to the combustor. CCS Associates of Bethel Park, PA, proposes tackling the problem by using pipes to distribute heat more effectively throughout the combustor. The heat pipe liner must handle both acceleration and vibration. The heat pipe arrays, including half-thickness webs, can be fabricated into gas-side and air-side halves by extrusion, forging, stamping, chemical milling, or some combination of methods. The liquid flow channel would be formed as an integral part of the gas-side valves.

scholarly journals Experimental and Numerical Analysis of Composite Wick Heat Pipes using Ethanol

2020 ◽  
Vol 9 (3) ◽  
pp. 2360-2363
Keyword(s):  
Heat Pipe ◽  
Heat Load ◽  
Information Sources ◽  
Heat Pipes ◽  
Wide Scope ◽  
Computational Investigation ◽  
Water Stream ◽  
Sintered Copper ◽  
Wick Structure ◽  
Working Liquid

Warmth pipes come convenient now-a-days as they work with most noteworthy warmth conductance contrasted with some other method of warmth move and accessible over wide scope parameters. In the present investigation de-ionized water stream in plain thermo siphon, Sintered Copper wick and Helical scored heat pipes with synchronous vanishing, adiabatic and buildup wonder are contemplated utilizing Heat pipe test gear. In this hardware warmth pipe exposed to foreordain heat load an obstruction radiator at its evaporator end water coat with controlled progression water is utilized disperse warmth vitality at condenser end. Every one temperatures are estimated necessary computations are done get rate efficiencies at different stream rates warmth inputs. The exhibition warmth funnels correlation between their efficiencies is done. The sintered copper wick structure pipe have been found capable when stood out from other two with heat inputs beginning from 50 to 800 watts evaporator 30, condenser 72, adiabatic 110, flate heat pipe width 7.6mm, thickness 3.4 mm, first dia 6mm warmth pipe holder thickness in 0.5mm working liquid ethanol wick in view prevailing Capillarity property. The varieties of evaporator and condenser surface temperatures are plotted for changing warmth information sources and stream rate changes at condenser water coat. ANSYS programming is utilized for computational investigation and exploratory outcomes are in great concurrence with the examination.

A High Performance Semi-Passive Cooling System: The Pulse Thermal Loop

Volume 3 ◽  
2004 ◽  
Author(s):  
Mark M. Weislogel ◽  
Michael A. Bacich
Keyword(s):  
Heat Transport ◽  
High Performance ◽  
Driving Forces ◽  
Cooling System ◽  
Heat Pipes ◽  
Thermal Control ◽  
High Heat ◽  
Transport Systems ◽  
Passive Cooling ◽  
Cooling Systems

Over the past decade, the search for and development of high performance thermal transport systems for a variety of cooling and thermal control applications have intensified. One approach employs a new semi-passive oscillatory heat transport system called the Pulse Thermal Loop (PTL). The PTL, which has only recently begun to be characterized, exploits large pressure differentials from coupled evaporators to force (pulse) fluid through the system. Driving pressures of over 1.8MPa (260psid) have been demonstrated. Other passive cooling systems, such as heat pipes and Loop Heat Pipes, are limited by capillary driving forces, typically less than 70kPa (10psid). Large driving forces can be achieved by a mechanically pumped loop, however, at the expense of increased power consumption, increased total mass, and increased system cost and complexity. The PTL can be configured in either active or semi-passive modes, it can be readily designed for large ∼ O(100kW) or small ∼ O(10W) heat loads, and it has a variety of unique performance characteristics. For low surface tension dielectric fluids such as R-134a, the PTL system has over a 10-fold heat carrying capacity in comparison to high performance heat pipes. Data accumulated thus far demonstrate that the PTL can meet many of the requirements of advanced terrestrial and spacecraft cooling systems: a system that is robust, ‘semi-passive,’ high flux, and offers high heat transport thermal control while remaining flexible in design, potentially lightweight, and cost competitive.

Experimental Investigation of Graphene Oxide Nanofluids on Thermal Performance of Heat Pipe

2019 ◽  
Author(s):  
Weilin Zhao ◽  
Jun Xu ◽  
Jinkai Li
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Air Cooling ◽  
Coating Film ◽  
Water Cooling ◽  
Condenser Section ◽  
Wick Structure

Abstract The graphene oxide-deionized water (GO-DW) and graphene oxide-ethylence glycol (GO-EG) nanofluids were synthesized. The better suspension of nanofluids was achieved. The thermal conductivity of both nanofluids was analyzed. It indicates that GO nanoparticles can strengthen the thermal conductivity of DW base fluids by 22.6%–61.7% and EG base fluids by 15.3%–32.8%. Four copper heat pipes charged with GO-DW and GO-EG nanofluids as well as DW and EG base fluids were experimentally researched, it is discovered that the addition of GO nonoparticles in heat pipe can elevate the condenser wall temperature and reduce the temperature difference. Future analysis finds that, with respect to DW and EG fluids heat pipe, the thermal resistances of GO-DW and GO-EG nanofluids heat pipe are respectively decreased 42.6–52.4% and 31.9%–38.4% for air cooling, and 15.5–16.7% and 11.5%–18.9% for water cooling at condenser section. Besides, the wick structure of GO-DW nanofluids heat pipe was examined by Scanning Electron Microscope, and the effective thermal conductivity of fluid-wick combination was evaluated. The outcomes demonstrate that the evaporator wick surface contains about 0375–1.24μm coating film of GO nanoparticles. Assumed the coating film is 0.75μm, the effective thermal conductivity of fluid-wick combination is respectively enhanced by 66.92 % for GO-DW nonofluids heat pipe and 37.32% for GO-EG nonofluids heat pipe at 70 °C.

Characterization of the Performance of Flat Heat Pipes for Electronics Cooling

2000 ◽  
Author(s):  
Unnikrishnan Vadakkan ◽  
Suresh V. Garimella ◽  
Choondal B. Sobhan
Keyword(s):  
Heat Pipe ◽  
Heat Input ◽  
Energy Transport ◽  
Temperature Drop ◽  
Thermal Conductance ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Flow And Heat Transfer ◽  
Parametric Studies ◽  
Axial Heat

Abstract A computational model has been developed to analyze the transient and steady-state performance of flat heat pipes and assess their performance under different operating and geometric parameters, in order to arrive at optimal designs. The model assumes two-dimensional fields for flow and heat transfer and solves the governing differential equations using a finite-difference approach. The wick region of the heat pipe is analyzed using transport equations for a porous medium. The influence of axial heat conduction along the wall, as well as the energy transport in the wick, on the velocity and temperature distributions is examined. The overall performance of the heat pipe is quantified by calculating an effective thermal conductance from the heat input and the temperature drop along the heat pipe wall. Parametric studies are conducted using the model to investigate the dependence of the heat pipe performance on the heat input at the evaporator, the containing wall thickness, and the porosity of the wick.

scholarly journals Performance Assessment of a Three-Dimensional Printed Porous Media Produced by Selective Laser Melting Technology for the Optimization of Loop Heat Pipe Wicks

2019 ◽  
Vol 9 (14) ◽  
pp. 2905 ◽  
Author(s):  
Jesús Esarte ◽  
Jesús M. Blanco ◽  
Angela Bernardini ◽  
Ramón Sancibrián
Keyword(s):  
Heat Pipe ◽  
Selective Laser Melting ◽  
Three Dimensional ◽  
Loop Heat Pipe ◽  
High Permeability ◽  
Laser Melting ◽  
Powder Sintering ◽  
Sintered Copper ◽  
Wick Structure ◽  
Better Than

The primary wick in a loop heat pipe device is a key component that is central to the operation of the device. Both high permeability and capillary pumping capacity, two properties highly dependent on wick structure, are strongly desirable for a satisfactory thermal performance. In this paper, selective laser melting (SLM), a three-dimensional (3D) printing technology, is used to create a primary wick for an 80 W heat transfer application. The permeability and capillarity values of this wick, experimentally measured, are compared with those built with the most widely used technologies nowadays, such as powder sintering and meshes. In this study, the SLM scaffold is shown to satisfy the minimum values required by the application in terms of capillarity and permeability: 0.031 mm/s and 4 × 10−12 m2, respectively. Our comparative study revealed that the wick produced with the SLM technology presented higher values of permeability, by two orders of magnitude, and slightly higher capillary figures than those corresponding to powder sintering for such application. However, it had capillary values well below those of a stainless-steel mesh. The hydraulic behavior of the SLM wick was better than that of the sintered copper powder, because it not only met the above-mentioned specifications, but it also improved its performance.

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