A Mathematical Model for Predicting the Thermal Resistance of a Flat Micro Heat Pipe with Fiber Wick

2012 ◽  
Vol 7 (1) ◽  
pp. 202-204
Author(s):  
Han Tian ◽  
Liu Xiaowei
Keyword(s):  
Mathematical Model ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Micro Heat Pipe

A Mathematical Model for Optimizing the Structure of a Flat Micro Heat Pipe with Fiber Wick

2011 ◽  
Vol 187 ◽  
pp. 261-265
Author(s):  
Tian Han ◽  
Xiao Wei Liu ◽  
Rui Zhang ◽  
Chao Wang
Keyword(s):  
Mathematical Model ◽  
Contact Angle ◽  
Heat Pipe ◽  
Control Volume ◽  
Three Dimensional ◽  
Heat Conducting ◽  
Governing Equations ◽  
Micro Heat Pipe ◽  
Changing Rate

A three-dimensional mathematical model is developed for a kind of micro heat pipe with fiber wick. The effects of phase changing, the contact angle, gravity, and heat conducting between the fibers are accounted in the model. The governing equations are formulated in the control volume and calculated by iteration. The calculated results of the model present the velocity of the working material and the phase changing rate of the liquid. The structure of the micro heat pipe is optimized by the calculated results of the model and the two levels of fibers are enough for this kind of flat micro heat pipe.

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.

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.

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.

NUMERICAL AND EXPERIMENTAL INVESTIGATION ON A NEW TYPE ELECTRICAL HEAT STORAGE BASED ON FLAT MICRO HEAT PIPE

2018 ◽  
Author(s):  
Zeyu Wang ◽  
Yanhua Diao ◽  
Yaohua Zhao ◽  
Chuanqi Chen ◽  
Lin Liang ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Heat Pipe ◽  
Heat Storage ◽  
Micro Heat Pipe ◽  
New Type

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%.

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