Effects of Gravity on Start-up and Heat Load Sharing of a Miniature Loop Heat Pipe

2007 ◽  
Author(s):  
Jentung Ku ◽  
Hosei Nagano
Keyword(s):  
Heat Pipe ◽  
Heat Load ◽  
Load Sharing ◽  
Loop Heat Pipe ◽  
Start Up

Thermal Vacuum Testing of a Miniature Loop Heat Pipe With Multiple Evaporators and Multiple Condensers

2007 ◽  
Author(s):  
Jentung Ku ◽  
Laura Ottenstein ◽  
Hosei Nagano
Keyword(s):  
Low Power ◽  
Heat Pipe ◽  
Temperature Control ◽  
Heat Load ◽  
Operating Temperature ◽  
Loop Heat Pipe ◽  
Thermal Vacuum ◽  
Heater Power ◽  
Start Up ◽  
Vacuum Testing

This paper describes thermal vacuum testing of a miniature loop heat pipe (MLHP) with two evaporators and two condensers designed for future small systems applications requiring low mass, low power and compactness. Each evaporator contains a wick with an outer diameter of 6.4 mm, and each has its own integral compensation chamber (CC). Multiple evaporators provide flexibility for placement of instruments that need to be maintained at the same temperature, and facilitate heat load sharing among instruments, resulting in a reduced auxiliary heater power requirement. A flow regulator is used to regulate heat dissipations among all condensers, thus providing flexibility for placement of radiators on the spacecraft. A thermoelectric converter (TEC) is attached to each CC for operating temperature control and enhancement of start-up success. Tests performed include start-up, power cycle, sink temperature cycle, high power and low power operation, heat load sharing, and operating temperature control. The MLHP demonstrated excellent performance in the thermal vacuum environment. The loop started successfully and operated stably under various evaporator heat loads and condenser sink temperatures. The TECs were able to maintain the loop operating temperature within ±0.5K of the desired set point temperature at all power levels and all sink temperatures. The un-powered evaporator would automatically share heat from the other powered evaporator. The CC control heater power was reduced by more than 50 percent when a TEC was used instead of conventional electrical heaters. The flow regulator was able to regulate the heat dissipation among the radiators and prevent vapor from flowing into the liquid line.

scholarly journals Experimental analysis of a Vapour-Liquid Separated Flat Loop Heat Pipe Evaporator System

2020 ◽  
Vol 307 ◽  
pp. 01055
Author(s):  
Yang Yang ◽  
Zhu Kai ◽  
Wang Yabo ◽  
Wei Jie ◽  
Sarula Chen
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Load ◽  
Experimental System ◽  
Base Plate ◽  
Loop Heat Pipe ◽  
Operation Performance ◽  
Total Thermal Resistance ◽  
Variable Heat ◽  
Start Up

In this paper, a unique operation mechanism of loop heat pipe (LHP) was proposed. To test the performance of LHP under this new mechanism, a visual flat LHP evaporator prototype and an open experimental system were designed and assembled, and start-up experiment and variable heat load experiment were done respectively to obtain the actual operation characteristics, such as the evaporator thermal resistance (Re), total thermal resistance (Rt), start-up time and temperature of base plate. The proposed LHP had better overall performance during the start-up tests when He value of EC was set to 0.5mm, and its corresponding Re and Rt value were 0.035 K/W and 0.451 K/W when the heating power was 208w. Meanwhile, as per the heat load applied to the base plate, the whole variable heat load experiment could be divided into three distinct stages: low heat load stage, efficiency operation stage and dry-out stage. Moreover, the results also showed that the circulation driven head formed inside of the EC played an important role in promoting the operation performance, especially when the wick, the vapour-liquid interface and the bottom of the evaporator arrived at a reasonable situation.

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%.

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 ◽  
Start Up

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.

scholarly journals Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1616
Author(s):  
Jaehwan Lee ◽  
Dongmin Kim ◽  
Jeongmin Mun ◽  
Seokho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Infrared Detectors ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Zero Gravity ◽  
Heat Transfer Characteristics ◽  
Space Applications ◽  
Transfer Characteristics ◽  
Start Up

Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

Start-Up Behavior of Double-Condenser Loop Heat Pipe

2005 ◽  
Author(s):  
Hiroki Nagai ◽  
M Muto ◽  
M Murakami ◽  
S Ueno
Keyword(s):  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Start Up
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