Experimental Study on a Flat Loop Heat Pipe Coupling the Compensation Chamber and the Condenser

2010 ◽  
Author(s):  
Dong-chuan Mo ◽  
Guan-sheng Zou ◽  
Shu-shen Lu
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Temperature Oscillation ◽  
Large Temperature ◽  
Loop Heat Pipe ◽  
Normal Type ◽  
Operation Temperature ◽  
High Efficient ◽  
New Type ◽  
Compensation Chamber

Loop heat pipes are high efficient heat transfer loops/devices. Compared to the typical loop heat pipe with cylinder evaporator, loop heat pipe with flat evaporator (flat loop heat pipe, FLHP) can reduce the thermal resistance between the evaporator and the heat loads. In order to remove the heat leak from the evaporator to the compensation chamber to reduce the operation temperature, a new type of FLHP coupling the compensation chamber and the condenser has been developed. Experiments have been conducted to compare the heat transfer characteristics between the normal type and the new type of FLHP. Part of the heat lead from the evaporator to the compensation chamber can be removed in the new type of FLHP, so it gives better heat transfer performance than the normal one. Results show that, the temperatures in the loop of the new type of FLHP are much more stable than the normal one. The evaporator temperatures and the total thermal resistances of the new type are much lower than those of the normal type. For the normal type of FLHP, it may be failed to start up under low power, and usually the larger temperature oscillation will happen. With the power increasing, the frequency of the oscillation is increasing. When the applied power is large enough, the loop can keep running in the design way, and the large temperature oscillation will disappear.

Design and Simulation of Visual Miniature Loop Heat Pipe

2012 ◽  
Vol 605-607 ◽  
pp. 346-351
Author(s):  
Yan Chen ◽  
Yan Qu ◽  
Shu Sheng Zhang
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Pipe ◽  
Flow Characteristics ◽  
System Level ◽  
Loop Heat Pipe ◽  
Design Requirements ◽  
Compensation Chamber ◽  
Fluid Flow Characteristics ◽  
Level Performance

A miniature loop heat pipe (MLHP) with a glass condenser was designed and manufactured. Stress analysis on compensation chamber/evaporator and glass condenser is made to confirm strength of loop heat pipe using the software MSC NASTRAN. Results indicate this new structure loop heat pipe can meet the design requirements and secure to work well. A system level performance analysis was made about heat transfer and fluid flow characteristics inside loop heat pipe using the software of SINDA/FLUINT. This miniature loop heat pipe realized visualization research of phase change phenomenon to some extent.

Multilayer Wick Structure of Loop Heat Pipe

2007 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-Lung Chen ◽  
Julie F. Asfia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Transfer Resistance ◽  
Heat Leakage ◽  
Wick Structure ◽  
Operating Temperatures ◽  
Compensation Chamber ◽  
Two Phase Heat Transfer

Loop heat pipe (LHP) is known as a two-phase heat transfer device that utilizes the evaporation and condensation of an operating fluid to transfer heat. At the LHP low operating temperatures, heat leakage induced by saturated temperature differences between the evaporator and compensation chamber is more serious than at high operating temperatures, due to inherent thermophysical properties of the operating liquid. The serious heat leakage at the low operating temperature not only causes high liquid subcooling requirement but also leads to high total temperature difference and degraded heat transfer performance. In this paper, research efforts are placed on reducing the heat leakage by introducing a multilayer wick structure into the LHP. Based on the previous research results of LHP non-metallic wick structures, the multilayer wick LHP combines advantages of both metallic and non-metallic wick structures, retains good heat conduction from the evaporator case to the liquid/vapor interface and inhibits the reverse heat transfer from the interface to compensation chamber. By demonstrating the concept on a methanol LHP, experimental results exhibit a significant enhancement in reducing heat leakage and the total heat transfer resistance.

A Flow Visualization Study on the Temperature Oscillations Inside a Loop Heat Pipe With Flat Evaporator

2013 ◽  
Author(s):  
Dongchuan Mo ◽  
Guansheng Zou ◽  
Shushen Lu ◽  
L. Winston Zhang
Keyword(s):  
Flow Visualization ◽  
Heat Pipe ◽  
Temperature Oscillation ◽  
Heating Power ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Interface Motion ◽  
Temperature Oscillations ◽  
Flat Evaporator ◽  
Compensation Chamber

This paper presents a flow visualization study on the temperature oscillations inside a loop heat pipe in order to gain a better understanding of its heat transfer characteristics. A flat loop heat pipe (FLHP) with a flat evaporator instead of a typical cylindrical evaporator was built using copper as the shell and water as the working fluid. An experimental setup was designed by using the transparent material instead of copper in some parts of the FLHP. The experiment results showed that there were at least three different flow patterns in the vapor line as the heating power increased. The temperatures in different locations of the loop oscillated even when the heating power was kept constant. The largest amplitude of the temperature oscillation in the loop was located at the condenser outlet. It was found that the temperature oscillation at the condenser outlet could be divided into two types, one with smaller amplitudes and the other with larger amplitudes. The smaller amplitude temperature oscillations were always there when the heating power was increased step by step, while the larger amplitude temperature oscillations would disappear initially and show up later. Finally, the location of the vapor/liquid interface inside the condenser varied with the temperature oscillations, resulting in liquid/vapor interface motion in the compensation chamber.

scholarly journals Modeling of Loop Heat Pipe Thermal Performance

2021 ◽  
Vol 81 (1) ◽  
pp. 41-72
Author(s):  
Inès Gabsi ◽  
Samah Maalej ◽  
Mohamed Chaker Zaghdoudi
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Conductive Heat ◽  
Steady State Operation ◽  
Evaporation Heat ◽  
Compensation Chamber ◽  
Heat Loads ◽  
Good Agreement

The present work deals with the heat transfer performance of a copper-water loop heat pipe (LHP) with a flat oval evaporator in steady-state operation. Modeling the heat transfer in the evaporator was particularly studied, and the evaporation heat transfer coefficient was determined from a dimensionless correlation developed based on experimental data from the literature. The model was based on steady-state energy balance equations for each LHP component. The model results were compared to the experimental ones for various heat loads, cooling temperatures, and elevations, and a good agreement was obtained. Finally, a parametric study was conducted to show the effects of different key parameters, such as the axial conductive heat leaks between the evaporator and the compensation chamber cases, the capillary structure porosity and material, and the groove dimensions.

Temperature oscillation of a dual compensation chamber loop heat pipe under acceleration conditions

2021 ◽  
Vol 198 ◽  
pp. 117450
Author(s):  
Xiaochen Lv ◽  
Yongqi Xie ◽  
Hongxing Zhang ◽  
Yanmeng Xu ◽  
Hongwei Wu ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Temperature Oscillation ◽  
Loop Heat Pipe ◽  
Compensation Chamber

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.

Nucleate Boiling Inside the Evaporator of the Planar Loop Heat Pipe

2004 ◽  
Author(s):  
Junwoo Suh ◽  
Ahmed Shuja ◽  
Frank M. Gerner ◽  
H. Thurman Henderson
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Input Energy ◽  
Cooling Devices ◽  
Compensation Chamber ◽  
Dry Out ◽  
Transfer Device

The Loop Heat Pipe (LHP) under development is a next generation micro heat transfer device that utilizes the latent heat of a working fluid and has excellent transfer capacity compared with that of standard metallic cooling devices. A typical LHP consists of an evaporator, a reservoir (also called the compensation chamber), vapor and liquid lines, a subcooler, and a condenser. As heat is applied to the evaporator, all of the input energy goes into the evaporation of the liquid in the pores of the primary CPS wick or leak to the bottom. The nucleate boiling, which occurs beneath the primary wick in the evaporator, is a very significant phenomena. It affects critical operating issues, such as dry out of the primary wick. Using a clear evaporator machined from Pyrex glass, the nucleation, which occurred in the evaporator, was studied. De-ionized water was utilized as the working fluid.

Experimental study of heat transfer and start-up of loop heat pipe with multiscale porous wicks

2017 ◽  
Vol 117 ◽  
pp. 782-798 ◽  
Author(s):  
Xianbing Ji ◽  
Ye Wang ◽  
Jinliang Xu ◽  
Yanping Huang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
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