Development Of Loop Heat Pipe Research Articles

Effect of PTFE wick thickness on Loop heat pipe performance

Heat leakage has long been a problem in the development of Loop heat pipe (LHP). Among the strategies to suppress heat leakage, the use of low thermal conductivity polymer materials and adjustment of wick thickness are considered as one of the effective methods. However, although there are many recent reports on the effect of metal wick thickness on performance, there are few studies on the effect of polymer wick thickness such as PTFE wick. Therefore, this paper hopes to integrate the two factors and present the best results. This paper investigates the effect of PTFE wick thickness (1 to 2.75 mm) on LHP performance and proposes the thickness effects on both thermal resistance and flow drag. In addition, since PTFE is hydrophobic, water, with its high surface tension, cannot be used as working fluid. Therefore, in this study, a tiny amount of Butanol (6 wt%) is added to water to create self-rewetting fluid to be used as working fluid, overcoming the flow drag of PTFE wick and allowing the system to operate smoothly.Regarding the wick’s porosity and permeability, the best capillary effect and flow drag occurs at wick thickness of 2 mm. The LHP performance result shows, compared to using PTFE wick with water as working fluid where the system was unable to start up, the system using self-rewetting fluid can smoothly operate, overcome heat leakage and enhance performance. The best performance occurs at wick thickness of 2 mm, the maximum heat load reaches 600 W and heat flux 30 W/cm2; the results are all consistent with the performance predictions based on the wick parameters.

RESEARCH AND DEVELOPMENT OF LOOP HEAT PIPE – A REVIEW

RESEARCH AND DEVELOPMENT OF LOOP HEAT PIPE – A REVIEW

Heat Pipe for Aerospace Applications—An Overview

The paper presents an overview of heat pipes, especially those used in different space missions. Historical perspectives, principles of operations, types of heat pipes are discussed. Several factors have contributed to the science and technology of the present state-of-Art heat pipe leading to the development of loop heat pipes, micro and miniature heat pipes and micro loop heat pipes. The paper highlights the advancement of heat pipe for hypersonic cruise vehicles, loop heat pipes with higher conductance in 10 K range, heat pipe switches for temperature control of the spacecraft electronics.

Development of LHPs with ceramic wick

Abstract The ceramic porous wick is proposed as an alternative to wicks made of metal and plastic for Loop Heat Pipes (LHP) applications. Performance tests of two LHPs using acetone and water as working fluids were carried out for power inputs up to 25 W. The evaporators have a stainless steel cylindrical assembly, with 80 mm of length and 10 mm of inner diameter. The ceramic porous wick has 50% of porosity, 1–3 μm of pore radius distribution and a permeability of about 35 × 10 −15 m 2 . The active zone length of the evaporators is 25 mm. For a limited operation temperature of 100 °C, the LHPs were able to transfer up to 25 and 15 W using acetone and water, respectively, at steady state condition. An operation analysis concerning the effects of the LHP inclination, the heat sink temperature and LHP thermal resistances is also presented. Despite the relative good performance of the LHPs, further researches are still required taking into account changes related to properties of the ceramic porous wick in particular and improvements in the whole LHP design in general.

Loop heat pipe for cooling of high-power electronic components

In this paper, we present a new development of loop heat pipe (LHP) technology in its applications to cooling systems for high-power IGBT elements. An advanced method of LHP evaporator wick manufacturing has been proposed. Following this approach, a 16 mm outer diameter and 280 mm-length LHP evaporator was designed and manufactured. Nickel and titanium particles were used as raw material in LHP evaporator wick fabrication. LHP with a nominal capacity as high as 900 W for steady-state condition and more than 900 W for a periodic mode of operation at a temperature level below 100 °C and a heat transfer distance of 1.5 m was designed through the cooling of a high-power electronic module. An experimental program was developed to execute LHP performance tests and monitor its operability over a span of time. An investigation of the effects of LHP performance of parameters such as evaporator and condenser temperatures and LHP orientation in a gravity field was brought about. As regards the results of this initial series of tests, it was found that LHP spatial orientation within the nominal range of heat loads has no drastic effect on overall LHP functioning, whereas condenser temperature does play an important role, especially in the range of heat load close to critical. A 2D nodal model of the evaporator was developed and provides us with confirmation of the suggestion that when high-power dissipation levels are available, low wick conductivity is well adapted for LHP applications.

Capillary heat loop technology: Space applications and recent Canadian activities

Capillary heat loops (CHL) are heat transfer designs with high-effectiveness, high-performance, high-reliability, high-flexibility, and anti-gravitation features of interest to the space community. At the Canadian space agency a project has been initiated since 2002 to develop an understanding of CHL technology. The technology is targeted towards the thermal control systems of miniaturized satellites. This paper presents reviews of CHL modeling and space applications and introduces the recent development of loop heat pipe (LHP) technology in Canada in the hardware development, application, performance testing, analytical prediction and numerical modeling.