Flat Heat Pipe Cooling Devices for Mobile Computers

2003 ◽  
Author(s):  
Yaxiong Wang ◽  
G. P. Peterson
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Management ◽  
High Efficiency ◽  
Junction Temperature ◽  
Working Fluid ◽  
Closed Chamber ◽  
Maximum Heat ◽  
Micro Heat Pipe ◽  
Mobile Computers

The rapid increases in package density in the high-performance microprocessors utilized in laptop, notebook and other mobile computers has resulted in power-densities that are challenging the existing thermal management technologies. In order to accomodate these challenges within the existing space and volume constraints, a novel, flat, micro heat pipe (MHP) cooling device has been conceptualized, designed, and evaluated analytically. The novel device consists of a flat micro heat pipe heat spreader, fabricated by sintering copper mesh and wires between two thin copper sheets to form a closed chamber. High-efficiency folded fins are then bonded to the condenser to produce a device that is capable of dissipating the high heat loads and reducing the thermal resistance typically present in these packages. Because of its high latent heat and surface tension, water was used as the working fluid. A number of different designs with different CPU mounting positions and fin sets were examined theoretically in an effort to optimize the initial design. The effects of the physical properties of the mesh, wire diameter, and effective thermal conductivity of the capillary structure were then evaluated and optimized. This process resulted in a design optimized on thermal performance, that is an excellent candidate for the thermal management of laptop and/or notebook computers. At a junction temperature of 85 °C, the maximum heat transport capacity and corresponding thermal resistance of an optimized MHP heat sink, 25.4 man wide and 152.4 mm long, were 33 W and 0.80 W/°C, respectively, for an environmental temperature of 45 °C.

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

2020 ◽  
Vol 38 (1A) ◽  
pp. 88-104
Author(s):  
Anwar S. Barrak ◽  
Ahmed A. M. Saleh ◽  
Zainab H. Naji
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Maximum Deviation ◽  
Inlet Temperature ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Vof Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively.  Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input.  The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

Nano Heat Pipe: Nonequilibrium Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Mohammad Moulod ◽  
Gisuk Hwang
Keyword(s):  
Molecular Dynamics ◽  
Heat Flux ◽  
Heat Pipe ◽  
Thermal Management ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Management Systems ◽  
Working Fluid ◽  
Maximum Heat

A heat pipe has been known as a thermal superconductor utilizing a liquid-vapor phase change, and it has drawn significant attentions for advanced thermal management systems. However, a challenge is the size limitation, i.e., the heat pipe cannot be smaller than the evaporator/condenser wick structures, typically an order of micron, and a new operating mechanism is required to meet the needs for the nanoscale thermal management systems. In this study, we design the nanoscale heat pipe employing the gas-filled nanostructure, while transferring heat via ballistic fluid-particle motions with a possible returning working fluid via surface diffusions along the nanostructure. The enhanced heat flux for the nano heat pipe is demonstrated using the nonequilibrium molecular dynamics simulations (NEMDS) for the argon gas confined by the 20 nm-long Pt nanogap with a post wall with the temperature difference between the hot and cold surfaces of 20 K. The predicted results show that the maximum heat flux through the gas-filled nanostructure (heat pipe) nearly doubles that of the nanogap without the post wall at 100 < T < 140 K. The optimal operating conditions/material selections are discussed. The results for the nanogap agree with those obtained from the kinetic theory, and provide insights into the design of advanced thermal management systems.

Investigation of Polymer Based Micro Heat Pipes for a Flexible Spacecraft Radiator

2001 ◽  
Author(s):  
D. McDaniels ◽  
G. P. “Bud” Peterson
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Power Density ◽  
Polymeric Material ◽  
Heat Dissipation ◽  
Effective Conductivity ◽  
Chemical Reactivity ◽  
Working Fluid ◽  
Maximum Heat ◽  
Micro Heat Pipe

Abstract In response to the space industry’s pursuit of interplanetary travel and a continuous human presence in space, there is increasing focus on spacecraft that change configuration while in space. Flexible thermal radiators are being developed to accommodate various collapse and deployment mechanisms. An analytical model suggests that a lightweight polymeric material with imbedded micro heat pipe arrays can meet heat dissipation requirements while contributing less mass than competing flexible materials. The capillary pumping limit is evaluated as a function of operating temperature using two candidate working fluids. Using water, the maximum heat transport is 18 mW per channel at 140/160 °C. The maximum heat transport using methanol is 2.2 mW at 120 °C, an order-of magnitude difference. A thermal circuit model translates heat transport per channel into total radiator capacity as a function of source temperature and environmental sink temperature. Using water as the working fluid, the radiator capacity was shown to vary from 6.0 kW to 12.2 kW for source temperatures of 20 °C to 50 °C. For source temperatures of 40 °C and higher, the capacity meets or exceeds the dissipation requirements of a reference spacecraft design. While evaluated, methanol is not recommended as a working fluid because its radiator capacity is two to three times lower than water. Although thermal system constraints place limits on the micro heat pipe operating range, design changes directed at alleviating capillary limitations should increase radiator capacity. Technical issues for further study include effects of film billowing, performance limitations related to vapor viscosity, working fluid diffusion, and chemical reactivity between case and working fluid. Compared to a competing graphite fiber weave, the polymeric material has an effective conductivity over ten times higher. Its area power density (in kW/m2) is 18% to 60% lower than the graphite weave, but its mass power density (in kW/kg) is several times higher. Greater flexibility and lower weight also make it more amenable to structural integration. Recently developed space-stable polymers offer resistance to harsh temperature and radiation environments, helping to clear the path toward a more extensive use of polymers within the space industry.

Thermal Characteristics of a Three-Dimensional Coil Type Pulsating Heat Pipe at Different Heating Modes

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Satyanand Abraham ◽  
Anand Takawale ◽  
Peter Stephan ◽  
Arvind Pattamatta
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
3D Structure ◽  
Three Dimensional ◽  
Working Fluid ◽  
Coolant Temperature ◽  
Pulsating Heat Pipe ◽  
Condenser Section ◽  
Maximum Heat

Abstract The heat transfer performance of a pulsating heat pipe (PHP) configured as a three-dimensional (3D) structure is reported in the present study. The PHP structure resembles an elongated coil and termed “coil type PHP.” Five different heating modes were created by positioning the evaporator at different locations and placing the PHP device in vertical and horizontal orientations. Studies were conducted primarily with de-ionized water as the working fluid. Limited number of experiments were also performed using binary fluids. The filling ratio was varied from 40% to 80%, while the heat input was varied from 20 W to 240 W. The vertical and horizontal orientations show almost 30 and 10 times reduction in the thermal resistance, respectively, compared with bare PHP tubes without the working fluid. This results in an effective thermal conductivity of more than 3000 W/(m K) and 12,000 W/(m K) for horizontal and vertical orientations, respectively. The use of the binary fluid (10 wt% and 20 wt% of ethanol aqueous solution) results in an increase in the maximum heat input at different heating modes. The temperature of the coolant supplied to the condenser section of the PHP was also varied, and the thermal resistance of the system was observed to reduce with an increase in the coolant temperature.

Heat Transfer Characteristic of Flat Trapezoid Grooved Micro Heat Pipes

2014 ◽  
Vol 609-610 ◽  
pp. 1526-1531 ◽  
Author(s):  
Yan Xia Yang ◽  
Xiao Dong Wang ◽  
Yi Luo ◽  
Liang Liang Zou
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Capillary Flow ◽  
Transfer Characteristic ◽  
Fluid Distribution ◽  
Working Fluid ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Micro Heat Pipe

To study the heat transfer performance of micro heat pipe, theoretical analysis of flat plate micro heat pipe with trapezoid cross section are presented in this paper. A one-dimensional stationary mathematical model for micro heat pipe grooved capillary flow using finite volume method (FVM) was established. The micro heat pipe had vapor space connect with each other and the influences of shear stress between vapor and fluid in the working process were described in the model which made the model more precisely. The axial variation of working fluid distribution in the heat pipe, pressure difference between vapor and liquid, and velocity of vapor and liquid were analyzed. In addition, the maximum heat transport capacity of micro heat pipe was calculated. The simulation results showed good agreement with the experiment results, and it could predict the heat transfer performance accurately, which was useful to micro heat pipe structural design.

Characteristics of Thermal Performance in High Power LED Package with Heat Pipe

2007 ◽  
Vol 124-126 ◽  
pp. 85-88 ◽  
Author(s):  
Woong Joon Hwang ◽  
Hwa Jun Yeo ◽  
Moo Whan Shin
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
High Power ◽  
Pure Water ◽  
Input Power ◽  
Junction Temperature ◽  
Working Fluid ◽  
Sintered Metal ◽  
Forced Cooling

This paper discusses about thermal performance of high power light emitted diode (HPLED) implemented with sintered metal wick type heat pipe(SWHP). The HPLED(2.5 W) samples were surface mounted device(SMD) package used in our experiments. The experiments were made for SWHP with diameters of 6.0 mm. The length of the SWHP is 150 mm. The working fluid in the heat pipes is pure water. The electrical-thermal transient technique was employed for the junction temperature measurement. It was found that the SWHP leads to decreased of thermal resistance by 35 % compared with a simple copper bar in oil bath (forced cooling condition). Employment of copper cap as a LED attachment was more advantageous over the phosphor bronze. After the increase of input power, the thermal resistance of HPLED package has decreased with the increase of effective thermal conductivity of SWHP.

Research on Thermal Resistance of Micro Heat Pipe with Sintered Wick

2013 ◽  
Vol 589-590 ◽  
pp. 552-558
Author(s):  
Xi Bing Li ◽  
Xun Wang ◽  
Yun Shi Ma ◽  
Zhong Liang Cao
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Performance ◽  
Total Thermal Resistance ◽  
Vapor Cavity ◽  
Micro Heat Pipe

As a highly efficient heat dissipation unit, a micro heat pipe is widely used in high heat flux microelectronic chips, and its thermal resistance is crucial to heat transfer capacity. Through analyses of the structure and heat transfer performance of a circular heat pipe with sintered wick, the theoretical model of total thermal resistance was established on heat transfer theory, and then simplified, finally a testing platform was set up to test for total thermal resistance performance. The testing results show that when the micro heat pipe is in optimal heat transfer state, its total thermal resistance conform well with that from the theoretical model, and its actual thermal resistance is much lower than that of the rod made of the material with perfect thermal conductivity and of the same geometric size. With the increment of heat transfer capability, the total thermal resistance of a micro heat pipe with sintered wick decreases first, then increases and reaches the minimum when it is in the optimal heat transfer state. The greater total thermal resistance in low heat transfer performance is mainly caused by too much working fluid accumulating in evaporator and the lower velocity in vapor cavity, and the greater total thermal resistance in high heat transfer performance is mainly due to the working fluid drying up in condenser. Total thermal resistance is related to many factors, such as thermal conductivity of tube-shell material, wall thickness, wick thickness, copper powders grain size and porosity, the lengths of condenser and evaporator, and the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with sintered wick should be reasonably designed according to the specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements.

Research on Thermal Resistance of Micro Heat Pipe with Trapezium-Grooved Wick

2016 ◽  
Vol 693 ◽  
pp. 395-402
Author(s):  
Xi Bing Li ◽  
Ming Jian Li ◽  
Ming Li ◽  
Ying Si Wan
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Performance ◽  
Total Thermal Resistance ◽  
Micro Heat Pipe ◽  
Heat Transfer Capacity

As an efficient heat conducting unit, micro heat pipe is widely used in high heat flux microelectronic chips, and thermal resistance is one of the factors that are crucial to its heat transfer capacity. Based on heat transfer theory, this paper established a theoretical model of total thermal resistance through analyzing the structure and heat transfer performance of circular heat pipe with trapezium-grooved wick, simplified the model and tested the micro heat pipe for its total thermal resistance performance by setting up a testing platform. The testing results show that when the micro heat pipe is in the optimal heat transfer state, its total thermal resistance well coincides with that from the established theoretical model. As for a micro heat pipe with trapezium-grooved wick, its total thermal resistance first decreases, then increases with heat transfer capability increment, and reaches the minimum when it is in the optimal state of heat transfer performance. That too much working fluid accumulates in evaporation section and the vapor velocity is rather low is the main cause for the greater thermal resistance when the pipe is in low heat transfer quantity, yet the greater total thermal resistance when the pipe is in high heat transfer quantity is mainly caused by the working fluid drying up in condensation section. The total thermal resistance is related to many factors, such as the thermal conductivity of tube-shell material, wall thickness, wick thickness, the number of the grooves, the lengths of condensation and evaporation sections, the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with trapezium-grooved wick should be rationally designed according to specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements and be in the optimal state.

Investigation of thermal management of lithium-ion battery based on micro heat pipe array

2021 ◽  
Vol 39 ◽  
pp. 102624
Author(s):  
Lincheng Wang ◽  
Yaohua Zhao ◽  
Zhenhua Quan ◽  
Jianan Liang
Keyword(s):  
Heat Pipe ◽  
Lithium Ion Battery ◽  
Thermal Management ◽  
Lithium Ion ◽  
Micro Heat Pipe
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