Browsing by Author "Ando, Makiko"

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Comparison between Numerical Simulation and On-orbit Experiment of Oscillating Heat Pipes
(46th International Conference on Environmental Systems, 2016-07-10) Daimaru, Takurou; Yoshida, Shuhei; Nagai, Hiroki; Tanaka, Kosuke; Ando, Makiko; Okamoto, Atsushi; Sugita, Hiroyuki
With current complexity and diversity of space missions, on-board devices of spacecraft must be highly performing and densely mounted. These facts lead a remarkable increase in heat generation density. Therefore, the next generation of heat transfer devices are required to have higher heat transport capabilities and be more flexible. Recently, a new concept of heat pipe known as Oscillating Heat Pipes (OHPs) has attracted attention. OHPs consist only of narrow bended tubes containing a working fluid. The working fluid exists as vapor plugs and liquid slugs due to capillary force in OHPs. As heat is applied to the heating section, oscillation/circulation is driven by the pressure difference between vapor plugs. This way, the working fluid transports heat from the heating section to the cooling section by a combination of sensible and latent heat transfer. Since very thin pipes can be used, OHPs can transport heat from very narrow spaces with high efficiency. In Japan, JAXA has conducted on-orbit experiments of OHPs with check valves on a small satellite named SDS-4 since 2012, and the effectiveness has been verified. However, the operating characteristics of OHPs are not yet fully understood, and it has not yet been taken into practical use. The critical issue for the practical use is startup characteristics under some conditions, as noticed during the on-orbit experiments. The objective is to investigate the startup behavior of OHPs. In this paper, a one-dimensional mathematical OHP-model with check valves was developed. The model was validated by using laboratory experimental results and compared with on-orbit experiments. In a simulation, the initial vapor-liquid distribution, and the timing of heating regarding eclipse were varied. As results, the mathematical model showed good agreement with experimental results. Also, it was found that initial vapor-liquid distribution and the timing of heating affect the startup behavior of OHPs.
Development of Mechanical Heat Switch for Future Space Missions
(44th International Conference on Environmental Systems, 2014-07-13) Ando, Makiko; Shinozaki, Keisuke; Okamoto, Atsushi; Sugita, Hiroyuki; Nohara, Takehiro
The heat switch provides appropriate thermal switching (high or low thermal conductance) depending on the thermal environment around spacecraft. It has an advantage in terms of thermal control of spacecraft such as a lunar rover and planetary exploration spacecraft which have difficulty securing sufficient heater power to keep the spacecraft within its allowable temperature range. The authors have developed a paraffin-actuated heat switch. The required thermal performance is 1W/K as ON thermal conductance and 100 as ON/OFF thermal conductance ratio. The test model was fabricated and some activities to improve thermal performance were conducted, such as Au coating on the contact surfaces. A breadboard model (BBM) with the improved design was fabricated and its performance evaluated. Consequently, BBM achieved 1.6W/K as ON thermal conductance and 127 as ON/OFF ratio.
An Experimental Attempt to Improve Start-up Characteristics of Oscillating Heat Pipe with Check Valves
(49th International Conference on Environmental Systems, 2019-07-07) Ando, Makiko; Okamoto, Atsushi; Tanaka, Kousuke; Matsutomo, Rui; Inoue, Nao; Nagasawa, Hiroki; Nagai, Hiroki
An oscillating heat pipe consists of a meandering capillary tube and working fluid in it. It has high heat transport capability due to the use of both sensible and latent heat and has an advantage of simple structure. Moreover, it enables heat transfer from narrow space, compared to the conventional heat pipes with wicks or grooves. Therefore, an OHP is one of the desired thermal control devices for future space spacecraft with larger heat dissipation. We have developed an OHP with check valves (CVOHP) for space application. The check valves make the fluid flow one-directional rather than oscillatory, resulting in the enhancement of the effective thermal conductivity and operational limit of the CVOHP. The on-orbit experiment of the CVOHP was conducted from 2012 to 2016 as one of the missions of Small Demonstration Satellite-4 (SDS-4) by JAXA. The CVOHP had successfully operated on orbit for four years without any degradation of heat transfer performance, however, the start-up difficulty was observed under the certain initial conditions. The most severe initial condition for start-up is the liquid-vapor distribution where most of the liquid localizes in the cooling section of the CVOHP. There are two approaches to improve the start-up characteristics; one is to prevent the liquid localization, the other is to make the CVOHP start up at any initial liquid-vapor distributions. This paper describes the experimental attempt to improve of the start-up characteristics.
Experimental Study of Heat Transfer Characteristics of Oscillating Heat Pipe with Different Numbers and Orientations of Check Valves.
(2024 International Conference on Environmnetal Systems, 2024-07-21) Kawaguchi, Ayumu; Sasaoka, Yuzen; Ando, Makiko; Okamoto, Atsushi; Ikami, Tsubasa; Nagai, Hiroki
An Oscillating Heat Pipe with Check Valves (CVOHP) is a two-phase thermal control device that is thin thickness, lightweight and has a large heat-receiving surface. In addition, a CVOHP has high heat transfer performance because it transfers heat using latent heat and sensible heat. Therefore, a CVOHP is attracting attention as a novel thermal control device for spacecraft. This study aims to clarify the optimal number and orientation of check valves to maximize the heat transfer performance of the CVOHP. The experiments were conducted using four types of 15-turn CVOHP with different numbers of check valves: every turn, every two turns, every five turns, and no check valves. The effect of the orientation of the check valves was also investigated in two cases. One was a case where the check valves allowed flow from the cooling section to the heating section (forward orientation), and the other was the opposite (backward orientation). The result showed that in the forward case, the thermal resistance decreased as the number of check valves increased. On the other hand, in the case of the backward case, the thermal resistance increased as the number of check valves increased, and the maximum heat transfer capability deteriorated significantly compared to the forward orientation. Based on the results of this study, it is recommended to install check valves at each turn in the forward orientation to maximize the heat transfer performance.
Fabrication and Evaluation of an Oscillating Heat Pipe with Check Valves by Metal Additive Manufacturing
(2023 International Conference on Environmental Systems, 2023-07-16) Ando, Makiko; Tanaka, Kousuke; Okamoto, Atsushi; Matsushige, Koutaro; Tanaka, Kentaro; Okuma, Shinya
Mathematical Modeling and Experimental Validation of Oscillating Heat Pipes
(44th International Conference on Environmental Systems, 2014-07-13) Daimaru, Takurou; Yoshida, Shuhei; Nagai, Hiroki; Okamoto, Atsushi; Ando, Makiko; Sugita, Hiroyuki
This paper is intended to investigate the startup behavior of Oscillating Heat Pipes (OHPs). First, a mathematical model of OHPs is presented. The model is a one-dimensional slug flow model in which the movement of liquid slugs is governed by pressure differences between each vapor plug and pressure drops in the tubes. The positions of liquid slugs, pressure of the working fluid, temperature of the tube wall, and momentum of the liquid slugs are calculated at each time step. The model is experimentally validated by using a closed loop OHP with 16 turns. A comparison of the calculations and experimental results shows qualitative agreement. Finally, several conditions of initial liquid and vapor distributions are simulated to evaluate the effects on the startup of OHPs. The results show that initial conditions of the working fluid affect the startup behaviors of OHPs.
Numerical Study on Start-up Characteristics of Oscillating Heat Pipes with Check Valves
(47th International Conference on Environmental Systems, 2017-07-16) Daimaru, Takurou; Inoue, Nao; Nagai, Hiroki; Ando, Makiko; Tanaka, Kosuke; Okamoto, Atsushi; Sugita, Hiroyuki; Isohata, Daichi
An oscillating heat pipe (OHP) is a two-phase heat transfer device using self-existed oscillation. An OHP consists of a bended capillary tube with a heating section at one side and a cooling section at the other. Because of the capillary force, the working fluid is distributed as vapor plugs and liquid slugs in the tube. As heat is applied to the heating section, the working fluid is driven by the pressure difference between each channel. In the OHP, heat is transported by the oscillation and/or circulation of liquid slugs and vapor plugs which go back and forward between the heating section and cooling section by a combination of sensible and latent heat transfer. Experimental studies have shown that the OHP has a higher thermal performance than conventional heat pipes. It has also shown that oscillating heat pipe with check valves (CVOHP) has much higher heat transfer capability than OHP without check valves. In the CVOHP, check valves regulate the flow direction, and the oscillatory amplitude of the waves is increased. For that reason, the local dry-out phenomenon is prevented in CVOHPs, and heat transfer efficiency becomes higher than the OHP. Because of its high performance and simple structure, CVOHP is attractive for a thermal control system for spacecraft. However, the experimental study shows that there is a considerable difference in the resistance between individual check valves, and estimating the value of resistance is difficult because the configuration of check valves is complicated. Furthermore, it is suggested that the start-up characteristics of the OHP changes by the different configuration/flow resistance of the check valve. This paper describes the start-up characteristics of CVOHPs using numerical simulation.
Thermal Performance of Additively Manufactured Three-dimensional Oscillating Heat Pipe with Check Valves in Various Orientations
(2024 International Conference on Environmnetal Systems, 2024-07-21) Ando, Makiko; Okamoto, Atsushi
An oscillating heat pipe (OHP) is an attractive thermal control device, which has high heat transport capability and enables heat transfer from narrow space. The Japan Aerospace Exploration Agency (JAXA) has developed an OHP with check valves (CVOHP) for space applications. CVOHPs are assumed to be used in three-dimensional shapes, such as L shape, U shape, or more complex ones in practical applications. Recently, metal additive manufacturing has been focused as a promising solution to fabricating CVOHPs with complex three-dimensional shapes. In this study, we evaluated the thermal performance of the additively manufactured CVOHP (AM-CVOHP) with a U-shape in various orientations: horizontal, bottom heat, top heat, and orientation where the middle section of the U-shape comes to the top and bottom. The test results showed that the AM-CVOHP operated stably at the orientations except for top heat orientation. In horizontal, bottom heat, and orientation where the middle section of the U-shape comes to the bottom, the AM-CVOHP could transport heat up to 200 W, and its effective thermal conductivity was in the range from 3000 to 7000 W/mK. As for the top heat orientation, the maximum heat transport decreased to 100 W, and the effective thermal conductivity was lower than the other orientations. Also, when the AM-CVOHP was heated after being kept at the top heat orientation for a long time, startup failure was observed. As described above, the U-shaped AM-CVOHP operated well in most orientations except for top heat orientation. We need further investigation to improve the operating characteristics in top heat orientation.