scholarly journals Experimental and analytical study of dual compensation chamber loop heat pipe under acceleration force assisted condition

2020 ◽  
Vol 153 ◽  
pp. 119615
Author(s):  
Longzhu Han ◽  
Yongqi Xie ◽  
Jianqin Zhu ◽  
Hongwei Wu ◽  
Hongxing Zhang
Keyword(s):  
Heat Pipe ◽  
Analytical Study ◽  
Loop Heat Pipe ◽  
Acceleration Force ◽  
Compensation Chamber

Investigation of Loop Heat Pipe Startup Using Liquid Core Visualization

2008 ◽  
Author(s):  
B. P. d’Entremont ◽  
J. M. Ochterbeck
Keyword(s):  
Heat Pipe ◽  
Liquid Core ◽  
High Heat ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Buoyancy Driven Flows ◽  
Compensation Chamber ◽  
Fill Level ◽  
Heat Loads

In this investigation, a Loop Heat Pipe (LHP) evaporator has been studied using a borescope inserted through the compensation chamber into the liquid core. This minimally intrusive technique allows liquid/vapor interactions to be observed throughout the liquid core and compensation chamber. A low conductivity ceramic was used for the wick and ammonia as the working fluid. Results indicate that buoyancy driven flows, both two-phase and single-phase, play essential roles in evacuating excess heat from the core, which explains the several differences in performance between horizontal and vertical orientations of the evaporator. This study also found no discernable effect of the pre-start fill level of the compensation chamber on thermal performance during startup at moderate and high heat loads.

Effect of Sink Temperature on the Stability of the Pressure-Controlled Loop Heat Pipe

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Wukchul Joung ◽  
Joohyun Lee
Keyword(s):  
Heat Pipe ◽  
Temperature Control ◽  
Control Technique ◽  
Loop Heat Pipe ◽  
Heat Leak ◽  
Start Up ◽  
Recent Emergence ◽  
Compensation Chamber ◽  
The Stability ◽  
Pressure Controlled

Recently, a novel temperature control technique utilizing the unique thermohydraulic operating principles of the pressure-controlled loop heat pipes (PCLHPs) was proposed and proved its effectiveness, by which a faster and more stable temperature control was possible by means of the pressure control. However, due to its recent emergence, the proposed hydraulic temperature control technique has not been fully characterized in terms of the various operating parameters including the sink temperature. In this work, the effect of the sink temperature on the loop heat pipe (LHP)-based hydraulic temperature control was investigated to improve the stability of the proposed technique. Start-up characteristics and transient responses of the operating temperatures to different pressure steps and sink temperatures were examined. From the test results, it was found that there was a minimum sink temperature, which ensured a steady-state operation after the start-up and a stable hydraulic temperature control with the increasing pressure steps, due to the unstable balance between the heat leak and the liquid subcooling in the compensation chamber at low sink temperatures. In addition, the range of the stable hydraulic temperature control was extended with the increasing coolant temperature due to the decreased heat leak, which resulted in the increased pressure difference between the evaporator and the compensation chamber. Therefore, it was found and suggested that for a stable hydraulic temperature control in an extended range, it was necessary to operate the PCLHP at higher sink temperatures than the low limit.

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.

Effect of Vibrations on Thermal Performance of Miniature Loop Heat Pipe for Avionics Cooling: An Experimental Analysis

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Prem Kumar ◽  
Sameer Khandekar ◽  
Yuri F. Maydanik ◽  
Bishakh Bhattacharya
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Longitudinal Vibration ◽  
Decisive Role ◽  
Fluid Distribution ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Horizontal Orientation ◽  
Acceleration Rate ◽  
Compensation Chamber

Abstract A loop heat pipe (LHP) is an efficient passive, two-phase heat transfer device which can transport heat up to large distances (over ∼ 5 m) even in the anti-gravity mode. It is necessary to miniaturize the LHPs to make them suitable for space-constrained avionics applications. However, before incorporating these devices under high-vibrational environmental conditions such as those encountered in avionics applications, it is imperative to study their thermal performance under such loads. With the aim of understanding the effect of acceleration and frequency of imposed vibration on thermal performance of miniature LHP (mLHP), a contextual experimental study has been reported here using an ammonia charged mLHP (8 mm evaporator diameter; titanium wick) in the horizontal orientation for two cases: (a) without vibration and (b) with the transverse and longitudinal harmonic vibrations (1–4g, frequencies 15–45 Hz, and sine sweep 15–45 Hz in 1 s). With start-up loads between 5 W and 8 W, the LHP can transfer heat load of about 120 W at safe evaporation temperature of 70 °C. Results show that for the transverse vibration, acceleration rate and frequency of imposed vibrations do not affect the thermal performance of mLHP. For the longitudinal vibration, the device performance gets noticeably enhanced with increased acceleration. The decisive role of heat leak (from evaporator to the compensation chamber (CC)) with imposed vibrations is clearly observed, and its link to the internal fluid distribution can be discerned from data trends.

scholarly journals Experimental study on a dual compensation chamber loop heat pipe with dual bayonet tubes

2020 ◽  
Vol 180 ◽  
pp. 115821
Author(s):  
Lizhan Bai ◽  
Jingwei Fu ◽  
Liping Pang ◽  
Yongbo Tao ◽  
Guiping Lin ◽  
...  
Keyword(s):  
Experimental Study ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Compensation Chamber

Numerical study on thermohydraulic behavior in compensation chamber of a loop heat pipe with flat evaporator

2020 ◽  
Vol 171 ◽  
pp. 115073 ◽  
Author(s):  
Zikang Zhang ◽  
Hao Zhang ◽  
Xiaotian Lai ◽  
Zhichun Liu ◽  
Wei Liu
Keyword(s):  
Heat Pipe ◽  
Numerical Study ◽  
Loop Heat Pipe ◽  
Flat Evaporator ◽  
Compensation Chamber

scholarly journals One-dimensional steady-state mathematical model of a novel loop heat pipe with liquid line capillary wick

2019 ◽  
Vol 38 (1) ◽  
pp. 253-273 ◽  
Author(s):  
Meng Fanxi ◽  
Quan Zhang ◽  
Sheng Du ◽  
Chang Yue ◽  
Xiaowei Ma
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Heat Pipe ◽  
Characteristic Point ◽  
Loop Heat Pipe ◽  
One Dimensional ◽  
Liquid Line ◽  
Working Medium ◽  
Compensation Chamber ◽  
Relative Errors

A novel loop heat pipe used for data center with a liquid line wick is designed, and its one-dimensional steady-state mathematical model is developed based on the energy and thermodynamic equilibrium of each component and the simulation results were validated by comparing with the experimental data in this work. The compensation chamber of the loop heat pipe was removed, and a section of capillary wick was added in the end of liquid line in order to reduce heat leakage and vapor backflow and increase working medium circulation power. The mathematical model of the novel loop heat pipe can be used to predict the operating temperature of each characteristic point with small relative errors of <13%. A parametric study of the steady-state performance characteristics including the effects of material, diameter, length, and porosity of liquid line wick are conducted, which provides a powerful basis for the design of novel loop heat pipe experiment.

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