Effect of Sintering Temperature and Time in Nickel Wick for Loop Heat Pipe with Flat Evaporator

2014 ◽  
Vol 602-605 ◽  
pp. 528-532
Author(s):  
Shen Chun Wu ◽  
Chang Yu Wu ◽  
Weie Jhih Lin ◽  
Jia Ruei Chen ◽  
Yau Ming Chen
Keyword(s):  
Heat Pipe ◽  
Constant Temperature ◽  
Heat Load ◽  
Sintering Temperature ◽  
Performance Testing ◽  
Effective Porosity ◽  
Temperature Curve ◽  
Loop Heat Pipe ◽  
Maximum Heat ◽  
Load Increase

This paper specifically addresses the effect of changing the constant temperature region of the sintering temperature curve in manufacturing nickel powder capillary structure (wick) on the performance of a flat loop heat pipe (FLHP). The sintering temperature curve is composed of three regions: a region of increasing temperature, a region of constant temperature, and a region of decreasing temperature, with the sintering time and temperature in the region of constant temperature having significant effect on the permeability of the wick. In this study, for wick manufacturing the temperatures in this region tested range from 550°C to 650°C and the time from 30 minutes to 60 minutes. The properties and internal parameters of the wick are measured, and the wick is placed into FLHP for performance testing. Experimental results show that at sintering temperature of 550°C and lasting about 45 minutes, maximum heat load is 200W, minimum thermal resistance is 0.32°C/W, permeability is , porosity is 66%, effective porosity is 3.8and heat flux is around 21W/cm2; related literatures have only reported maximum heat load increase of 25%.

Effect of Sintering Temperature Curve in Wick Manufactured for Loop Heat Pipe with Flat Evaporator

2014 ◽  
Vol 595 ◽  
pp. 24-29 ◽  
Author(s):  
Shen Chun Wu ◽  
Kuei Chi Lo ◽  
Jia Ruei Chen ◽  
Chen Yu Chung ◽  
Weie Jhih Lin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Sintering Temperature ◽  
Temperature Curve ◽  
Loop Heat Pipe ◽  
Transfer Performance ◽  
Total Thermal Resistance ◽  
Flat Evaporator ◽  
Increasing Temperature

This paper specifically addresses the effect of the sintering temperature curve in manufacturing nickel powder capillary structure (wick) for a loop heat pipe (LHP) with flat evaporator. The sintering temperature curve is composed of three regions: a region of increasing temperature, a region of constant temperature, and a region of decreasing temperature. The most important region is the increasing temperature region, as the rate of temperature increase directly affects the performance of the wick.When the slope of the region of increasing temperature is 0.8 (equivalent to 8 OC/min), the structure of the manufactured wick is complete, with the best heat transfer performance result. Experimental resultsshowed that the optimal heat transfer performance is 160W, the minimal total thermal resistance is approximately 0.43OC/W, and the heat flux is 17W/cm2; the optimal wick manufactured has an effective pore radius of 5.2 μm, a permeability of 5.9×10-13m2, and a porosity of 64%.

Experimental Investigation of Heat Transfer Performance of a Miniature Loop Heat Pipe with Flat Evaporator

2011 ◽  
Vol 71-78 ◽  
pp. 3806-3809
Author(s):  
Xian Feng Zhang ◽  
Shuang Feng Wang
Keyword(s):  
Heat Pipe ◽  
Heat Load ◽  
Temperature Oscillation ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Operating Characteristics ◽  
Maximum Heat ◽  
Power Cycle ◽  
Flat Evaporator ◽  
Compensation Chamber

The present work experimentally investigated the operating characteristics of a miniature loop heat pipe (LHP) under different power cycle. The miniature LHP with flat evaporator of 8mm thick is made of copper. The evaporator with sintered copper power wick is in series structure with compensation chamber. Water is working fluid. It is found that the LHP can start up at heat load of 15W with temperature oscillation and the maximum heat load is 160W with Rl=0.068°C/W. The LHP operates unstably under low heat load. The oscillating frequency of temperature rises with heat load increased. The operating performance of the LHP is affected by the power cycle.

scholarly journals Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

2021 ◽  
pp. 199-199
Author(s):  
Lakshmi Reddy ◽  
Srinivasa Bayyapureddy Reddy ◽  
Kakumani Govindarajulu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Tilt Angle ◽  
Heat Load ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

Analysis of Vapor Blanket Formation in the Porous Wick of a Loop Heat Pipe With High Heat Load

2013 ◽  
Author(s):  
X. M. Huang ◽  
X. Jin ◽  
B. B. Chen ◽  
W. Liu
Keyword(s):  
Mass Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
High Heat ◽  
Loop Heat Pipe ◽  
Porous Wick ◽  
High Heat Load ◽  
Theoretical Results

A loop heat pipe has different transport mechanisms depending on heat flux. The interface of liquid and vapor cannot maintain at the surface of the wick when heat flux is high, and a vapor blanket will form in the wick. To investigate when the vapor blanket appears and how it affects heat and mass transfer in the system is very import to minimize the device. A mathematical model of heat and mass transfer in the evaporator, coupled with analysis of fluid flow in the loop, is developed in the paper. The model is applied to calculate the critical heat load that the vapor blanket forms, and to analyze how the blanket delays. A comparison of theoretical results and experimental measurements is further presented. The consistence of the results validates the model and the mechanisms.

Improvement of Heat Transfer Performance of Loop Heat Pipe for Electronic Devices

2011 ◽  
Author(s):  
Tomonao Takamatsu ◽  
Katsumi Hisano ◽  
Hideo Iwasaki
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Thermal Energy ◽  
Heat Load ◽  
Cooling System ◽  
Electronic Devices ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Reserve Area ◽  
Heat Transport Capability

In this paper is presented the results on performance of the cooling model using Loop Heat Pipe (LHP) system. In recent years, ever-ending demand of high performance CPU led to a rapid increase in the amount of heat dissipation. Consequently, thermal designing of electronic devices need to consider some suitable approach to achieve high cooling performance in limited space. Heat Pipe concept is expected to serve as an effective cooling system for laptop PC, however, it suffered from some problems as follows. The heat transport capability of conventional Heat Pipe decreases with the reduction in its diameter or increase in its length. Therefore, in order to use it as cooling system for future electronic devices, the above-mentioned limitations need to be removed. Because of the operating principle, the LHP system is capable of transferring larger amount of heat than conventional heat pipes. However, most of the LHP systems suffered from some problems like the necessity of installing check valves and reservoirs to avoid occurrence of counter flow. Therefore, we developed a simple LHP system to install it on electronic devices. Under the present experimental condition (the working fluid was water), by keeping the inside diameter of liquid and vapor line equal to 2mm, and the distance between evaporator and condenser equal to 200mm, it was possible to transport more than 85W of thermal energy. The thickness of evaporator was about 5mm although it included a structure to serve the purpose of controlling vapor flow direction inside it. Successful operation of this system at inclined position and its restart capability are confirmed experimentally. In order to make the internal water location visible, the present LHP system is reconstructed using transparent material. In addition, to estimate the limit of heat transport capability of the present LHP system using this thin evaporator, the air cooling system is replaced by liquid cooling one for condensing device. Then this transparent LHP system could transport more than 100W of thermal energy. However, the growth of bubbles in the reserve area with the increase in heat load observed experimentally led to an understanding that in order to achieve stable operation of the LHP system under high heat load condition, it is very much essential to keep enough water in the reserve area and avoid blocking the inlet with bubbles formation.

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