THERMAL ANALYSIS AND FLOW VISUALIZATION OF A FLAT LOOP HEAT PIPE

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.

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On Application of Looped Pulsating Heat-Pipe in High-Power LED for Street Light

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.732-733.265 ◽

2013 ◽

Vol 732-733 ◽

pp. 265-269 ◽

Cited By ~ 1

Author(s):

Wen Wu Tang ◽

Guang Xiao Kou ◽

Liang Liang Hu ◽

Hui Wen Zhou ◽

Bo Feng

Keyword(s):

Thermal Analysis ◽

Heat Pipe ◽

High Power ◽

Thermal Condition ◽

Experimental Results ◽

Maximum Temperature ◽

Loop Heat Pipe ◽

Pulsating Heat Pipe ◽

Temperature Distributions ◽

Simulation Results

The ANSYS-ICEPAK is used to establish and analyze the thermal condition of the cooling modular of the looped pulsating heat pipe in the street light, the reliability is proved by experimental results of thermal analysis. The experimental results show that: the temperature distributions on the surface of the lamp shell and loop heat pipe are uniform, and the average temperatures of them are about 40°Cand 43°C; while the maximum temperature of the chip base reaches 67.5°C. Through comparison, the simulation results are close to the actual measured results.

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Thermal analysis of loop heat pipe used for high-power LED

Thermochimica Acta ◽

10.1016/j.tca.2009.03.016 ◽

2009 ◽

Vol 493 (1-2) ◽

pp. 25-29 ◽

Cited By ~ 77

Author(s):

Xiang-you Lu ◽

Tse-Chao Hua ◽

Mei-jing Liu ◽

Yuan-xia Cheng

Keyword(s):

Thermal Analysis ◽

Heat Pipe ◽

High Power ◽

Loop Heat Pipe ◽

High Power Led

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Theoretical and Experimental Study of a Loop Heat Pipe at Positive Elevation

Heat Transfer, Volume 2 ◽

10.1115/imece2004-60925 ◽

2004 ◽

Author(s):

Po-Ya Abel Chuang ◽

John M. Cimbala ◽

Jack S. Brenizer ◽

C. Thomas Conroy

Keyword(s):

Steady State ◽

Flow Visualization ◽

Heat Pipe ◽

Neutron Radiography ◽

Loop Heat Pipe ◽

Operating Characteristics ◽

Two Phase ◽

State Behavior ◽

Wide Range ◽

Two Phase Heat Transfer

A loop heat pipe (LHP), which is a two-phase heat transfer device, was studied experimentally and theoretically. The steady-state operating characteristics of a LHP when it is operated at adverse (the condenser is below the evaporator) and zero elevations (the evaporator and the condenser are at the same level) had been studied intensively in the past. However, study of a LHP when it is operated at positive elevation (the condenser is above the evaporator) is still lacking. This paper presents detailed theoretical analysis of the steady-state behavior of a LHP operated at positive elevation. The present analysis agrees with experimental results, and is confirmed by flow visualization images. Testing was performed for a wide range of heat loads (20 W-600 W) at three positive elevations: 25.4mm, 76.2mm, and 127mm. Flow visualization images were taken by neutron radiography when the LHP was operated at 102mm positive elevation.

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