Browsing by Author "Machida, Yoshihiro"

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Design, Fabrication and Testing of an Ultra-Thin Multi-evaporator Loop Heat Pipe
(2020 International Conference on Environmental Systems, 2020-07-31) Sugimoto, Kenya; Nagano, Hosei; Machida, Yoshihiro
"A Loop Heat Pipe (LHP) is a two-phase heat transfer device that utilizes the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in fine porous wicks to circulate the fluid. Since the LHP can transport large amount of heat with no electric power under various gravity environment, the LHP is attracting attention as thermal management device for both space and terrestrial applications, and various studies on LHP have been conducted. Recently, with the miniaturization and high performance of devices, the integration of equipment is remarkably advanced, and thermal management for multiple heat sources is urgently required. In this study, an ultra-thin LHP with two evaporators (UTMLHP) which can applied to small electric device and/or micro satellite has been proposed. First, the UTMLHP was designed by using a steady-state MLHP model. Based on the thermal requirement, the size of UTMLHP was determined. Secondly, the UTMLHP was fabricated. The case and the wick of UTMLHP was made of copper and pure water was used as a working fluid. The size of each evaporator is 15×15×t0.6mm. The heat transport length is about 380mm. Next, the comprehensive test was conducted under atmospheric condition by changing orientation (horizontal, top-heat, bottom-heat, and sideways), charge amount of the working fluid, heating pattern on the evaporators (both sides, and one side only). The stable operation of the MLHP up to 12W was demonstrated. Finally, the test results are compared with the mathematical model of UTMLHP. The effects of test conditions on thermal performance is discussed with these results. The details of the UTMLHP specification and test results will be presented in the full paper."
Testing and Evaluation of Ultra-Thin Loop Heat Pipe as Lightweight Flexible Thermal Strap for Spacecraft
(51st International Conference on Environmental Systems, 2022-07-10) Nagano, Hosei; Mizutani, Takuji; Kajiyama, Satoshi; Akizuki, Yuki; Machida, Yoshihiro
Thermal strap with high thermal conductance are required. Usually, thermal strap is made of high thermal conductive materials such as copper, aluminum, and graphite sheet. In order to obtain high thermal conductance, the thickness of the materials is increasing, and, as a result, the weight of the strap is increasing. To avoid this problem, this work proposes to apply an ultrathin loop heat pipe (UTLHP) as a thermal strap because the LHP has characteristics of high effective thermal conductivity more than several thousand W/mK even the thickness of the LHP is below 1mm. The thickness of the UTLHP in this work is only 0.6mm, and can operate even bending condition. The UTLHP is made of six layers of pure copper foils. The wick of the UTLHP is made by etching process. Pure water with the freezing point of 0 ? is used as a working fluid. In order to apply the UTLHP to the spacecraft, following factors should be guaranteed. -The UTLHP can operate with no degradation even after the working fluid has melted. -The UTLHP can operate with no degradation even in a vibrating environment. -The UTLHP can operate without leakage under a vacuum condition. In this paper, following evaluations were conducted for the UTLHP to evaluate a potential of this UTLHP as a thermal strap for spacecraft; -Thermal performance of the UTLHP before and after freezing. -Thermal performance of the UTLHP begore and after vibration testing. -Thermal performance of the UTLHP under the vacuum condition. The details of the experimental results will be presented in the full paper.
Thermal Vacuum Testing of Advanced Thermal Control Devices for Flight Demonstration
(51st International Conference on Environmental Systems, 2022-07-10) Kajiyama, Satoshi; Mizutani, Takuji; Ishizaki, Takuya; Tomioka, Kota; Tanaka, Hiroto; Nagai, Hiroki; Matsumoto, Kan; Sawada, Kenichiro; Machida, Yoshihiro; Matsumoto, Kazuaki; Nagano, Hosei
In Japan, several unique thermal control technologies have been developed. However, there are no opportunity to demonstrate in orbit. Therefore, we have proposed to apply our thermal control devices named advanced thermal control devices (ATCD) to the Innovative Satellite Technology Demonstration Program conducted by JAXA, and accepted to apply to the Rapid Innovative payload demonstration SatellitE-2. In this paper, the test results of the thermal vacuum testing of ATCD are presented. ATCD consists of two types of flexible thermal straps: one is made of high-thermal-conductive material, and the other is made of a fluid-loop, and a re-deployable radiator. The conductive-type thermal-strap (CTS) is made of high-thermal-conductive graphite-sheets and aluminum blocks. The fluid-type thermal-strap (FTS) is made of a ultrathin loop-heat-pipe. The re-deployable radiator named reversible-thermal-panel (RTP) is made of high-thermal-conductive graphite-sheets as a flexible fin, and a shape-memory-alloy as a passive re-deployable actuator. As a result, it was confirmed that the thermal conductance between the two ends of CTS was 0.50-0.55 W/K. As for FTS, it was confirmed that it could operate even after recovering from the freezing condition of the working fluid, and that there was no leakage of the working fluid and no performance degradation under vacuum environment. As the heat load increased, the thermal conductance between the evaporator and condenser increased, and finally a thermal conductance value of 4.1 W/K (at 5 W heat load) was confirmed. For RTP, it was confirmed that the radiator fins were fully expanded to 130 when the SMA actuator reached 30 ? during heating. On the other hand, during cooling, the temperature of the SMA actuator dropped only to -15?, and the fins retracted only to 40 . Furthermore, the temperature hysteresis of the SMA actuator was estimated to be about 40? based on the experimental results.