Browsing by Author "Nagai, Hiroki"

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A Two-Phase Mechanically Pumped Fluid Loop for Thermal Control of Deep Space Science Missions
(46th International Conference on Environmental Systems, 2016-07-10) Sunada, Eric; Bhandari, Pradeep; Carroll, Brian; Hendricks, Terry; Furst, Benjamin; Kempenaar, Joshua; Birur, Gajanana; Nagai, Hiroki; Daimaru, Takurou; Sakamoto, Kenichi; Cappucci, Stefano; Mizerak, Jordan
NASA’s planetary science objectives are achieved through mission opportunities and the ability to obtain quality science data. Toward this end, a flight system that requires fewer resources in extreme environments while providing the stability for maximum instrument return is a fundamental goal of the engineering team. Thermal-related challenges represent some of the largest threats toward this goal. These include the ability to deal with disturbances from widely varying environments while allowing for cost-reduction options that include non-nuclear power systems and smaller spacecraft. Such options are enabled through heater power conservation and higher heat flux management, respectively. A thermal management system that can concurrently provide a precision temperature-controlled platform for instruments would further lower instrument noise floors, allowing for better science data return. A two-phase mechanically pumped fluid loop (2-φ MPFL) thermal management system addresses these needs. A reference mission was developed to illustrate savings associated with such an architecture in terms of system resources, while maximizing the range of planetary science consistent with the Planetary Science Decadal Survey. Thermal/fluid architecture and system configuration tradeoffs highlighted key component and system sensitivities and critical environmental drivers. Results from the corresponding flight system model highlight the benefits of a 2-φ MPFL, such as efficient waste heat reclamation to address the precarious energy balance associated with deep-space, solar-powered missions. The specific loop architecture was derived based on a set of underlying performance requirements and included the development of a system thermal-hydraulic/thermodynamic model for performance trade studies, including working fluid selection. It was determined that a key component of the loop, which influenced the overall architecture, was the heat-acquiring and isothermalizing evaporator. Results from this specific study are also presented, which include early test data on a subscale prototype. Finally, a path forward highlighting 2-φ MPFL challenges and system recommendations is presented.
Backlight Measurement of Low Mass Flux Nitrogen Condensate Flow Inside a Cryogenic Loop Heat Pipe
(2024 International Conference on Environmnetal Systems, 2024-07-21) Gomi, Atsuhiro; Odagiri, Kimihide; Ogawa, Hiroyuki; Nagai, Hiroki
Recently, the demand for cryogenic cooling technology has increased, driven by the need to improve the sensitivity, response time, and noise reduction of space telescopes. Cryogenic Loop Heat Pipes (CLHP) are effective heat transport devices for such demand. To estimate the performance of a CLHP, it is necessary to predict the flow patterns in the condenser. Flow patterns are generally estimated from flow regime maps, but they are constructed based on visualization results of room-temperature fluids. In cryogenic fluids such as nitrogen and hydrogen, there is no visualization example of condensate flow because of the difficulty of experimentation. Therefore, there are challenges in applying previous flow regime maps on pattern estimation in CLHP steady-state models. To investigate transition conditions of flow patterns and modify previous flow regime maps for cryogenic condense flow, backlight measurement of the condenser was conducted in the nitrogen-charged CLHP. The experiment was conducted in an 80K cryogenic vacuum chamber. The evaporator has a porous wick made of SUS316L with a pore radius of 1.0 ?m. The heat transport distance was 2000 mm. 300 mm length visualization condenser was installed upstream of the main condenser. The CLHP started operation at a low heat load of 2 W on the evaporator and operated steadily until 8 W. At all heat load conditions, dark films considered to be vapor-liquid interfaces were seen on top and bottom surfaces of the channel. At 2–6 W heat load, the bottom dark film was thicker than the top. Although the flow patterns were estimated to be stratified at 2 W and wavy at 4 – 8 W from the steady-state model calculation, wavy flow was not observed. For the next experiment, it is planned to add another condenser upstream of the visualization condenser to understand the overall picture of flow pattern transitions.
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.
A Comparison of System Architectures for a Mechanically Pumped Two-Phase Thermal Control System
(47th International Conference on Environmental Systems, 2017-07-16) Furst, Benjamin; Sunada, Eric; Cappucci, Stefano; Bhandari, Pradeep; Daimaru, Takurou; Nagai, Hiroki
The NASA Jet Propulsion Laboratory is developing a mechanically pumped two-phase fluid loop thermal control system to enable novel mission designs. Pumped two-phase fluid loops have the potential to provide robust and effective thermal control that combine the best aspects of passive two-phase systems (heat pipes) and mechanically pumped single-phase fluid loops. The current program requirements include the development of a system with multiple 1 m2 evaporators, each of which is capable of remaining spatially and temporally isothermal while accommodating heat loads of up to 500 W and local fluxes of up to 5 W/cm2. The goal is to attain this using less than 5 W of power. Such a system would be able to accommodate the next generation of payload and bus electronics while using minimal resources. This paper compares two different mechanically pumped two-phase fluid loop architectures in the context of these requirements. A mixed flow and separated flow architecture are compared on a theoretical and experimental basis. Test data from sub-scale, single evaporator/single condenser, mixed flow and separated flow testbeds are presented. In addition, a model is introduced to better understand separated flow systems and some expressions for the theoretical performance limits of such systems are developed. To date, the investigation suggests that a separated flow architecture is better suited to the program requirements. Separated flow systems have the potential to accommodate an isothermalizing two-phase evaporator while using lower levels of power than would be required for a mixed flow system. In addition, it is argued that separated flow systems are more robust and amenable to analysis than mixed flow systems, since they significantly reduce the occurrence of two-phase flow by separating phases in the evaporator. Future work will include developing a full-scale testbed that includes multiple evaporators and condensers in a representative flight configuration.
Data Assimilation Applied Thermal Analysis of Mars Airplane for High-altitude Flight Test (MABE2)
(2020 International Conference on Environmental Systems, 2020-07-31) Tanaka, Hiroto; Misaka, Takashi; Nagai, Hiroki
As a new means of Mars exploration method, Mars airplane has been studied for a long time. The Mars airplane enables to bridge the scale and resolution measurement gaps between rovers and orbiters. However, it is not realized yet due to the severe flight conditions. Now, JAXA advances the development of the Mars airplane and plans to make a high altitude flight test called MABE2 (Mars Airplane Balloon Experiment 2). In order to demonstrate a severe condition: atmospheric temperature and pressure on Mars, the flight model will be launched to 35 km in altitude on Earth by High-Altitude Balloon. There, the Mars airplane is released from the balloon, and the flight test is conducted under the Martian-like atmospheric condition. For the high altitude flight test, a thermal mathematical model of the Mars airplane was built on Thermal Desktop©, and thermal analysis was conducted. In the analysis, we introduced a new thermal analysis method using data assimilation to build a reliable thermal mathematical model. The data assimilation is a statistical method to combine physical simulation and observation data obtained from an actual system, and has been used to solve dynamic inverse problems. We employed the Ensemble Kalman Filter, which is one of the data assimilation techniques, to the thermal mathematical model and estimated uncertain parameters, such as thermal conduct conductance. This paper describes the thermal modeling of the Mars airplane for a high-altitude flight test, firstly. Then, the results of the thermal vacuum test and model-test correlation are described. Finally, the result of the thermal conductance estimation and the availability of the new thermal analysis method using data assimilation is discussed.
Design for Large Isothermal Evaporator Mounted on Two-Phase Mechanically Pumped Fluid Loop
(2020 International Conference on Environmental Systems, 2020-07-31) Nagai, Hiroki; Hirata, Takumi; Fujita, Koji; Okazaki, Shun; Okamoto, Atsushi
As the performance of mounted devices in spacecraft improves, heat density increases and accurate temperature control is required. In addition, it is necessary to control the temperature of multiple devices, and the complexity of spacecraft thermal design is a problem. Therefore, a large isothermal evaporator has been developed that can control temperature by freely arranging multiple devices. The large isothermal evaporator is mounted on a Two-Phase Mechanically Pumped Fluid Loop (2PMPFL). 2PMPFL is a heat transport device that transports heat utilizing a phase-change of a working fluid and consists of an evaporator, condenser, pump, and accumulator. The working fluid driven by the pump evaporates in the evaporator and condenses in the condenser. A porous media is arranged in a large isothermal evaporator, and the isothermal surface can be maintained in a large area by maintaining the vapor-liquid interface in the entire evaporator by the capillary force. However, there is no clear design guideline for such an evaporator, and many past studies have been exploratorily designed and tested. In order to show the design guidelines of the large isothermal evaporator, it is necessary to understand the complicated flow inside the evaporator and to evaluate the relationship between the shape inside the different evaporators and the evaporator performance. The purpose of this study is to perform a three-dimensional unsteady analysis using OpenFOAM and provide a design guideline. In the analysis, evaluation focusing on the shape in the vapor channel was performed. From the analysis results, it became clear that the steady-state temperature (convergence temperature) of the evaporator, the flow velocity at the vapor outlet, and the evaporator thermal resistance differed greatly depending on the shape. In the present study, these features are shown and one design guideline is shown.
Development of an advanced thermal mathematical model construction method for spacecraft using artificial neural networks
(50th International Conference on Environmental Systems, 7/12/2021) Tanaka, Hiroto; Nagai, Hiroki; Fujita, Koji
Thermal analysis of spacecraft is one of the most critical processes for the flight model, and the number of missions that need severe thermal requirements is increasing these days. Hence, constructing an accurate thermal mathematical model (TMM) is indispensable to enable the operation to be safe and stable. However, the model has many uncertain parameters, such as thermal contact conductance. In general, these unknown parameters are tuned up by model-test correlation spending much cost with engineer�s know-how. This is because the TMM is too complex to tune up by hand. Then, the automatic correlation method for TMM of spacecraft is required. Here, we propose a technique to estimate thermal conductance based on machine learning for the TMM of spacecraft systems. We especially focused on a deep neural network that has inputs of temperature data and outputs of thermal conductance. In this study, a fully-connected feed-forward neural network and a TMM of a spacecraft were installed, and numerical experiments were conducted to evaluate the new method. Then, their network architecture, calculation condition, and estimation results are shown. Also, we discuss the benefits and problems of the model-test correlation based on a deep neural network.
Development of cryogenic loop heat pipe for deep space mission
(50th International Conference on Environmental Systems, 7/12/2021) Chang, Xinyu; Adachi, Takuya; Odagiri, Kimihide; Ogawa, Hiroyuki; Nagai, Hiroki
Cryogenic loop heat pipe (CLHP) is an efficient two-phase heat transfer device for cooling electronic components with cryogenic operating temperature range (2-240 K), such as an infrared detector. Compared to connecting an electronic component directly to a cryocooler, CLHP results in a higher flexible arrangement of the heat sources and the cryocooler, less disturbance from the cryocooler�s vibration. The final goal of this research is to realize the future space application of CLHP. In this research, a CLHP was developed to demonstrate the fabrication technology, and the detailed design method is shown. Nitrogen was selected as the working fluid. The CLHP was designed with more than 10 W heat transfer capability for a 2 m heat transport distance in the operating temperature range of 80-110 K. A liquid nitrogen tank was used for cooling condensing line. To assist the startup from a supercritical state, the CLHP was tested in a gravity-assisted attitude: The condenser was located at a higher position than that of the evaporator so that the evaporator and the compensation chamber was filled with liquid nitrogen at the startup. A 300 ml gas reservoir was installed in the CLHP. The inventory of nitrogen in the CLHP was 11.5 g, and the charged pressure was 3.26 MPa at 300 K. A sintered stainless steel wick was inserted into the evaporator with a shrink fitting method. To reduce the heat leak to the ambient, the CLHP was covered by insulation with high infrared reflectance and tested in a vacuum chamber. A mathematical model was proposed to predict the operating performance of CLHP. The numerical results will be evaluated with experiments.
Development of Two-Phase Mechanically Pumped Fluid Loop with Large Isothermal Evaporator using Porous Wick Structure
(47th International Conference on Environmental Systems, 2017-07-16) Sakamoto, Kenichi; Adachi, Takuya; Daimaru, Takurou; Nagai, Hiroki; Sunada, Eric; Bhandari, Pradeep; Furst, Benjamin; Cappucci, Stefano; Okazaki, Shun; Ogawa, Hiroyuki
"In recent years, space exploration is improving. Therefore, requirements for the thermal control system of the electric devices on spacecraft are getting higher. The requirements are accommodating high heat generation, keeping science instruments isothermal, and so on. For the easy installing and the cost reduction of the spacecraft, the free arrangement of on-board devices is also necessary. Therefore, the large isothermal evaporator has been proposed. The present state of the technology of thermal control systems is mainly Single-Phase Mechanically Pumped Fluid Loop (SPMPFL) and Loop Heat Pipe (LHP). The merit of SPMPFL is the long heat transport distance. The demerit of SPMPFL is the large temperature difference on the evaporator because heat transport is carried out by sensible heat of working fluid. For this reason, the heat transport capability is small. The merit of LHP is capillary force-driven without the electrical power, whereas the heat transport distance and capability are limited by the wick capillary force. Then, Two-Phase Mechanically Pumped Fluid Loop (2PMPFL) which has pumped driving force and two-phase flow is remarkable. The 2PMPFL enables the long heat transport distance, the high heat transport capability and the large isothermal area. We developed the Two-Phase Mechanically Pumped Fluid Loop with large isothermal evaporator using porous wick structure. This evaporator consists of a liquid channel, a vapor channel and a wick.　The vapor channel has a lot of pillars which conduct heat for the wick. The wick holds the working fluid on the whole area of the evaporator. Then, the working fluid evaporates and two-phase state is held. Therefore, the temperature on the evaporator surface can be kept isothermal. In the present study, we investigated the thermal performance of the 2PMPFL and verified the temperature uniformity on the evaporator surface."
Effects of a Secondary Wick on the Thermal Performance of a Loop Heat Pipe
(44th International Conference on Environmental Systems, 2014-07-13) Taketani, Masahiko; Nagai, Hiroki
A Loop Heat Pipe (LHP) is a heat transfer device utilizing the phase change of fluid. It has high heat transfer performance and robustness to changes in the ambient temperature. However, LHPs have problematic startup behavoir in certain situations. One of the proposed solutions for this problem is the use of secondary wick. However, it has not yet been verified that a secondary wick can actually improve the startup process of an LHP. In this study, we manufactured a miniature LHP and studied the effects of a secondary wick on the thermal performance of the LHP. We find that (1) using a secondary wick improves the startup process and (2) certain types of secondary wicks have an adverse effect on the maximum heat inputs.
Evaluation of temperature estimation accuracy using Physics-Informed Neural Network for small satellite model
(51st International Conference on Environmental Systems, 7/10/2022) Tanaka, Hiroto; Fujita, Koji; Nagai, Hiroki
Thermal analysis of spacecraft is one of the most critical processes for the flight model, and the number of missions that need severe thermal requirements is increasing these days. However, the thermal mathematical model has many uncertain parameters, such as thermal contact conductance; hence, it is impossible to predict the true value of temperature distribution. On the other hand, the number of temperature sensors on the small satellites is limited, and it is difficult to predict the temperature distribution accurately. In this study, we propose a method to estimate the temperature distribution of the entire spacecraft system based on a small amount of temperature data. To realize the temperature estimation, we use the Physics-Informed Neural Network, which is a neural network that uses the physical conservation law and the observation error as evaluation functions. Specifically, the actual value of the temperature distribution is estimated using the conservation law of the thermal mathematical model, the difference between the operational temperature data and the estimated value, and the boundary conditions as the evaluation function of the neural network. As a result, the temperature distribution of the system can be reproduced from a small amount of temperature data. In this presentation, the temperature estimation accuracy of the proposed method will be shown by numerical experiments using a thermal mathematical model of a pseudo small satellite.
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.
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 Simulation of Heat Transport Characteristics of CFRP embedded Oscillating Heat Pipes for Space Applications
(50th International Conference on Environmental Systems, 7/12/2021) Matsubara, Kosei; Sone, Kohei; Fujita, Koji; Nagai, Hiroki
An oscillating heat pipe (OHP) has attracted attention because it is lightweight and thin and does not require additional power to operate. Therefore, it is expected to be applied to spacecraft as a new heat transfer device, and we are aiming to develop a satellite structure panel in which OHP is embedded in CFRP. There are many previous studies on the thermal transport performance of OHP, but most of those have dealt with the OHP, which is made of metal. On the other hand, CFRP is lightweight and has high thermal conductivity, but has anisotropy in thermal conductivity. The thermal conductivity of CFRP is high in the carbon fiber direction whereas it is low in the perpendicular to the fibers. Therefore, it is assumed that the performance of OHP will change significantly depending on the anisotropy of thermal conductivity. Thus, it is necessary to predict the heat transport performance of OHP using CFRP. In this study, we constructed a numerical model of OHP, considering the anisotropy of the thermal conductivity of CFRP. The flow paths were made of stainless steel, and the spaces between the flow paths are filled with CFRP. Using this numerical model, we investigated the heat transport performance by varying heat input, number of turns, and carbon fiber orientation. In the paper, we show the effects of CFRP orientation on the thermal performance of OHP based on the results of numerical simulation.
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.
On-orbit demonstration of Advanced Thermal Control Devices using JAXA Rapid Innovative payload demonstration SatellitE-2 (RAISE-2)
(50th International Conference on Environmental Systems, 7/12/2021) Nagai, Hiroki; Tanaka, Hiroto; Kajiyama, Satoshi; Mizutani, Takuji; Nagano, Hosei; Sawada, Kenichiro; Matsumoto, Kan
In recent years, advances in thermal control technology have become essential for deep space exploration to achieve exploration goals. For missions that explore an outer planet, the limited power resources available from solar panels must be used to maintain the temperature of the spacecraft. Therefore, there is an urgent need to develop lightweight thermal control technology that does not use power resources. ?We have conducted research and development of original thermal control devices such as flexible deployable radiators, thermal straps, self-excited oscillating heat pipes, and heat storage devices, and their effectiveness has been confirmed in ground tests, but there has been no opportunity for on-orbit technical demonstrations, and there has been no path to practical application. However, we were selected in 2018 to participate in the Innovative Satellite Technology Demonstration Program proposed by JAXA, and we have the opportunity to conduct on-orbit experiments with the RApid Innovative payload demonstration SatellitE-2 (RAISE-2) in 2021. However, we were selected in 2018 to participate in the Innovative Satellite Technology Demonstration Program proposed by JAXA, and we have the opportunity to conduct on-orbit experiments with the Innovative Satellite Technology Demonstration Satellite 2 in 2021. This program provides opportunities for private companies and universities to acquire and accumulate new knowledge using nano-satellites, to create future mission projects, and to conduct on-orbit demonstrations of key components and new element technologies for space systems.
Operating Characteristics of Cryogenic Loop Heat Pipes at Different Filling Pressures
(2023 International Conference on Environmental Systems, 2023-07-16) Yokouchi, Takeshi; Chang, Xinyu; Nagai, Hiroki; Odagiri, Kimihide; Ogawa, Hiroyuki; Nagano, Hosei
A cryogenic loop heat pipe (CLHP) is a two-phase heat transport device for cooling equipment in cryogenic operating temperature regions, such as infrared detectors. Long-distance heat transport using a CLHP can decouple the heat source from the cryocooler, reducing the effects of vibration from the cryocooler. It is expected to improve the attitude control of the satellite and enable high-precision observations using optical instruments. In this study, a gravity-assisted CLHP has been designed, and its operational characteristics have been determined. The transport distance of the CLHP was 2m. In this report, we investigate the operating characteristics of the CLHP by changing the filling pressure of the CLHP. In addition, a one-dimensional thermal-mathematical model simulating the gas reservoir specific to the CLHP was constructed to investigate the effect of the filling pressure on the operating characteristics. In this study, the filling pressure was varied between 2.9 MPa and 3.4 MPa in 0.1 MPa increments. As a result, the maximum heat transport capacity was 25 W at 2.9 MPa-3.2 MPa and 30 W at 3.3 MPa-3.4 MPa, indicating that the heat transport capacity tends to increase as the filling pressure increases. The operating temperature increased with increasing filling pressure, with a maximum difference of 4.2 K. The effect on the operating characteristics was confirmed.
Operation Characteristics of Loop Heat Pipes with PTEF and SUS wicks
(44th International Conference on Environmental Systems, 2014-07-13) Okazaki, Shun; Ogawa, Hiroyuki; Nagano, Hosei; Nagai, Hiroki
A loop heat pipe (LHP) is a two-phase heat transfer device. Recently, small LHPs on the order of a few hundred watts have been investigated. We have developed a new primary wick made of stainless steel (SUS). In this study, the two types of the primary wick are investigated. One is the PTFE wick with a pore radius of 1.2 micron and the other is stainless steel wick which is made of stainless steel material with a pore radius of 1 micron. Using these 2 types of primary wick, a 100W class small LHPs are designed and fabricated for laboratory test. The LHP in which this stainless steel wick is installed can transfer the heat from the evaporator to the condenser and shows the high heat transfer performance. By comparison with these two types of wick, the stainless steel wick has high heat transport capability and low operating temperature. From these results, we can confirm that developed stainless steel wick and LHP has high performance.
Parametric Study for Vapor-Liquid Separation in Evaporator of Two-Phase Mechanical pump Fluid Loop System for Lunar and Planetary Exploration
(50th International Conference on Environmental Systems, 7/12/2021) Asato, Rin; Adachi, Takuya; Okazaki, Shun; Okamoto, Atsushi; Nagai, Hiroki
In recent years, the number of spacecraft components requiring accurate temperature control has increased, and the complexity of thermal design has become a problem. A thermal control system that can accurately control the temperature of multiple devices with a single evaporator is required to simplify the thermal design. We are developing a vapor-liquid two-phase fluid mechanical pump loop system with a large-area isothermal evaporator using a porous wick to meet this requirement. In previous studies, reliable vapor-liquid separation in the evaporator has been an issue. In this study, we improved our previous system and conducted parametric tests. Also, a one-dimensional steady-state model was developed and compared with experiments. As a result, it was shown that vapor-liquid separation could be achieved in the evaporator by positioning the accumulator just before the mechanical pump, reducing the differential pressure in the bypass flow channel installed just before the evaporator, lowering the accumulator temperature below the evaporator outlet temperature.