Thermal Control System Research Articles

Hydraulic Performance Comparison of Centrifugal Closed Impellers Fabricated by Means of Additive Manufacturing and Classical Machining for Space Active Thermal Control Systems of Satellites

Hydraulic Performance Comparison of Centrifugal Closed Impellers Fabricated by Means of Additive Manufacturing and Classical Machining for Space Active Thermal Control Systems of Satellites

Molecularly and Structurally Designed Polyimide Nanofiber Radiative Cooling Films for Spacecraft Thermal Management

AbstractRadiative cooling films (RCFs) are crucial for spacecraft thermal management, but their optical performance is currently limited by their structures and intrinsic high absorption at short wavelengths. In this study, a novel RCF using electrospun polyimide nanofibers optimized at both the molecular and microscale levels is developed. The newly designed polyimide molecules significantly decrease visible and ultraviolet (UV) light absorption while maintaining excellent thermal radiation properties in the infrared spectrum. By optimizing the diameter and orientation of the nanofibers using Monte Carlo simulations, the resulting film achieves a solar reflectivity of 99.6% and a mid‐infrared emissivity of 0.93. Its physical structures and optical properties remain stable under exposure to UV light, atomic oxygen, and extreme temperature changes. Further vacuum radiative cooling tests reveal that the thermal equilibrium temperature of this film is approximately 28 °C lower than that of Kapton‐based RCFs currently used in spacecraft. These results provide a new approach for creating efficient thermal management materials for space applications, with potential for broader use in architecture, electronic devices, and outdoor equipment.

Electric Vehicle Energy Management via Traffic Light Detection and Segmental Velocity Forecasting

Abstract Predictive-based power control has been widely recognized as a promising approach to boost driving range and improve system-level energy efficiency for electric vehicles (EVs), in which vehicle velocity forecasting generally serves as a preliminary input to optimally schedule the operations of varying on-board electrical and thermal systems. A segment-based velocity forecasting approach for individual commuting vehicles developed in this study reveals that it is challenging to forecast the velocity at intersection segments only using the velocity data. To address this challenge, this study seeks to develop a YOLO-V2-based object detection deep network to recognize the traffic lights in advance, and leverage the detected signals to establish a forecasting model that integrates with the probability-based hybrid forecasting approach. The case study results show that the traffic light detection-based forecasting model can significantly improve the forecasting accuracy for intersection segments. Based on the forecasting velocity 5-15 seconds ahead, the effectiveness of model predictive control-based energy management strategy is further evaluated with a liquid-based battery thermal control system. The proposed Battery Thermal Management System (BTMS) model shows promising results in maintaining battery temperature within an appropriate range, thus improving the overall energy efficiency of the EV. Moreover, a traffic light-based real-time energy management framework is developed to directly control the power demand from the Air Conditioning (AC) system.

Towards Explainable Anomaly Detection in Safety-critical Systems

Ensuring the reliability and safety of space missions necessitates advanced anomaly detection systems capable of not only identifying deviations but also providing clear, understandable insights into their causes. This paper introduces a novel methodology for the detection of systemic anomalies in the telemetry data of the International Space Station (ISS), leveraging the synergistic application of the Functional Resonance Analysis Method (FRAM) and the Specification Tools and Requirement Methodology-Requirement Language (SpecTRM-RL). Integrated with machine learning-based normal behavior prediction model, this approach significantly enhances the explanatory of anomaly detection mechanisms. The methodology is verified and validated through its application to the thermal control system within the ISS's Japanese Experimental Module (JEM), illustrating its capacity to augment diagnostic capabilities and assist flight controllers and specialists in preserving the ISS's functional integrity. The findings underscore the importance of explainability in the machine learning-based anomaly detection of safety-critical systems and suggest a promising avenue for future explorations aimed at bolstering space system health management through improved explainability and operational efficiency.

Comparative Study of Active and Passive Thermal Control Systems: A Case Study of Terra Satellite

Comparative Study of Active and Passive Thermal Control Systems: A Case Study of Terra Satellite

A Data-Driven Online Prediction Model for Battery Charging Efficiency Accounting for Entropic Heat

This study proposes a charging efficiency calculation model based on an equivalent internal resistance framework. A data-driven neural network model is developed to predict the charging efficiency of lithium titanate (LTO) batteries for 5% state of charge (SOC) segments under various charging conditions. By considering the impact of entropy change on the open-circuit voltage (OCV) during the charging process, the accuracy of energy efficiency calculations is improved. Incorporating battery data under various charging conditions, and comparing the predictive accuracy and computational complexity of different hyperparameter configurations, we establish a backpropagation neural network model designed for implementation in embedded systems. The model predicts the energy efficiency of subsequent 5% SOC segments based on the current SOC and operating conditions. The results indicate that the model achieves a prediction error of only 0.29% under unknown charging conditions while also facilitating the deployment of the neural network model in embedded systems. In future applications, the relevant predictive data can be transmitted in real time to the cooling system for thermal generation forecasting and predictive control of battery systems, thereby enhancing temperature control precision and improving cooling system efficiency.

Conductive paths generation using topology optimization for worst-case thermal design in space systems

Designing thermal systems for space platforms is a challenging task due to the wide variability in thermal conditions during the orbit and the strict constraints imposed by other subsystems. Several strategies have been developed to address these challenges while minimizing the thermal control subsystem’s signature, encompassing different algorithms optimize components positions in the platform. When relocation is not possible, thermal couplings between components can be modified to enhance heat transfer and achieve more uniform temperature distribution. To design optimal thermal paths in 2D space structures, in this paper a topology optimization framework based on the Heaviside Projection Method is introduced, using the Lumped Parameter Method (LPM) and taking the radiation heat transfer into account. The algorithm’s performance is tested on a Printed Circuit Board (PCB) by designing an optimal copper layer to meet specific thermal requirements under both extreme hot and cold conditions. Results show a significant improvement in thermal compliance for all components with the addition of this high-conductivity layer. Additionally, a reduction method is introduced to transfer the material distribution from the optimization to a coarser mesh of any size, which is useful to facilitate its implementation in existing software, where a large number of degrees of freedom can be a limitation.

Design and Verification of Thermal Control System of Communication Satellite

The multiple working modes, complex working conditions, frequent changes in external heat flux, and high power consumption of communication satellites all pose great difficulties to their thermal design. This paper mainly describes the design of a thermal control system for high-power communication satellites. Firstly, new efficient heat transfer technologies and thermal control materials for spacecraft are introduced. Secondly, the structure and internal heat source of the satellite are introduced. Thirdly, the external heat fluxes are analyzed, and the position of the heat dissipation surface and extreme conditions are confirmed. Then, a thermal control system is designed around the difficulties of thermal control. With heat pipes, the temperature uniformity of +Y deck, −Y deck, and +Z deck increased by 8 °C, 9.9 °C, and 34.2 °C, respectively. Furthermore, the maximum temperature of the power controller, secondary power supply, bidirectional frequency converter, and solid discharge decreased by 32.5 °C, 22.0 °C, 14.0 °C, and 164 °C, respectively. Finally, a thermal balance test is performed. The test results show that the temperatures of the solid-state power amplifier, on-board computer, power controller, secondary power supply, and bidirectional frequency converter meet the requirements of the thermal control indices. In addition, the temperature of thermal-sensitive components such as batteries and the storage tank also meets the requirements. The thermal design scheme is reasonable and feasible, and the thermal balance test verifies the correctness of the thermal design.

Design and experimental analysis of a novel thermal diode with asymmetric heat transfer inspired by feather

To overcome the limitation of isotropic heat transfer of traditional heat pipes, a novel thermal diode with asymmetric flow resistance vapor channel inspired by the goose feather fibers is proposed in this study. The thermal performance of novel thermal diode is experimentally investigated. Results show that under the wide range of operating conditions, the thermal resistance of one end surpasses the thermal resistance of the other end, indicating its excellent thermal rectification capability. Under the filling ratio of 10 % and heating power of 7.5 W, the maximum thermal resistance of the thermal diode is 5.23 times the minimum thermal resistance, demonstrating excellent asymmetric heat transfer performance. Experimental results demonstrate that the novel thermal diode proposed in this study can easily change its unidirectional heat transfer direction by simply adjusting the internal filling ratio, showing significant application potential in the fields of thermal control system.

In situ growth of graphene on carbon fibers to enhance the mechanical and thermal conductivity of epoxy composites

High-strength and high-thermal-conductivity composite materials have become crucial requirements for thermal control systems in various field. Carbon fiber-reinforced polymer (CFRP) has demonstrated potential superior performance. However, the application of CFRP is limited by the chemical inertness of the carbon fiber surface and the shortness of low surface energy. Therefore, surface modification of carbon fibers is necessary. This research employs a pulse plasma discharge method, to in-situ grow graphene on the surface of carbon fibers by disrupting some polymer structures on the carbon fiber surface in a “bottom-up” approach. This method offers advantages such as rapid, simple, convenient, economical, and environmentally friendly preparation process., the modified carbon fibers used in CFRP exhibit superior mechanical and thermal conductivity properties. The flexural strength increased by 218 % to reach 109.5 MPa, and the thermal conductivity increased by 251 % to achieve 1.153 W/(m*K).

PVA-assisted graphene aerogels composite phase change materials with anisotropic porous structure for thermal management

The rapid development of spacecraft thermal control systems necessitates high-performance phase change materials (PCMs) with low density, high thermal conductivity and high enthalpy. Graphene aerogels (GAs) prepared by unidirectional freezing are ideal candidates as thermal conductive networks for PCMs due to the anisotropic porous structures. However, constructing anisotropic thermal conductive composite PCMs with low graphene aerogel loading while employing environmentally friendly cross-linking agents remains challenging. To fulfill the research gap, this study explores the synthesis of poly(vinyl alcohol) (PVA)/graphene aerogels (PGAs) by hydrothermal reaction and conventional freeze-drying. Anisotropic PGAs with oriented porous structures were fabricated by unidirectional freezing. After annealing and impregnation with paraffin wax, composite PCMs with excellent shape stability were obtained. The prepared composite exhibits low density (0.82 g cm−3) and high enthalpy (165 J g−1). The combination of PVA and graphene enables the composite to achieve an ultralow graphene aerogel loading (0.85 wt%) while maintaining high thermal conductivity (1.37 W m−1 K−1), leading to a high specific thermal conductivity enhancement up to 477. This work sheds light on the potential of combing PVA and graphene to construct thermal conductive aerogels, intending to provide feasible means to develop high-performance PCMs for spacecraft thermal management.

Evolution law of flow characteristics for straight pipeline after leaking

Aiming at the leakage problem of the fluid loop system for the thermal control system of spacecraft caused by the impact of micro-meteoroid and orbital debris, we investigate the dependence of the leak rate, pressure drop and flow characteristics before and after leaking on leak position, inlet pressure, and leaking aperture, calculated in a straight pipeline with single leakage, using stationary and transient three-dimensional computational fluid dynamics simulations with commercial software (FLUENT). The working fluid adopts single-phase water without gravity. It is found that the pressure increases obviously near the leak point, which is caused by the local peak of pressure. As the length between the leak point and the inlet becomes larger, the local peak of pressure and the dimensionless leak rate are smaller. When the inlet pressure increases, the leaked mass flow rate increases; however, the ratio of the leaked flow rate to inlet flow rate decreases. Furthermore, it is observed that the dependence of dimensionless leaking rate on dimensionless leaking aperture has a scaling relation with the scaling exponent approximating to 2, which may be related to the proportion of the vortex formed by the backward flow at the leak hole, the amplitude, and the affected length along the pipe of the local peak of pressure. This study is instructive and meaningful to the leak detection and plugging of fluid loop in space.

Usability of personalized thermal control systems by people with intellectual disabilities in energy poverty

This study assessed the usability of three readily available Personalized Thermal Control Systems (PECS)—an electric blanket, a small personal fan, and a large pedestal fan—among individuals with intellectual disabilities living independently in energy poverty conditions in Chile. The research aimed to identify the primary usability challenges that affect the adoption and operational effectiveness of these technologies and, consequently, their potential to enhance thermal comfort. Results indicated that devices with more advanced control features, i.e. the large pedestal fan, presented the most significant usability challenges, followed by the electric blanket and the small personal fan. Key usability issues included poor visibility, inadequate material choice, ineffective communication, bad affordance, and inadequate levels of touch sensitivity of the control interface in these PECS. The study also showed a large variance in the level of adoption of the PECS among participants, thereby indicating that users have different individual attitudes, ranging from passive acceptance to proactive exploration and use. To conclude, this study advocates for the necessity of developing easily operable PECS that cater to the specific needs of individuals with intellectual disabilities, thereby supporting their autonomy and improving their quality of life in thermally comfortable environments.

Perovskite manganese oxide-based superposed multilayer film with high emittance tunability for smart radiation devices

Smart radiation devices (SRDs) with the ability to switch emittance according to the radiator surface’s temperature are significant for spacecraft thermal control on exploration missions with drastic changes in thermal environments. However, it is quite urgent to improve the performance of the intelligent thermal control films in SRDs due to the limitations such as low emittance tunability and inappropriate phase transition temperature. Consequently, a film with self-adaptive infrared emittance based on anti-reflective design is proposed in this paper. The main structure is a superposed multilayer film based on a doped perovskite manganese oxide La0.825Sr0.175MnO3 (LSMO) and BaF2 stacks. The emittances of the designed multilayer film are 0.18 and 0.83 at the temperatures of 100 K and 295 K, and therefore the emittance tunability achieves 0.65. Compared with single-layer LSMO, the emittance tunability has increased 25 % approximately. The enhancement in emittance tunability can be explained by the fact that multilayer films with staggered low and high refractive index dielectric layers may cause destructive interference and suppress the Fresnel reflections at high temperatures. In addition, the thickness of dielectric part is carefully designed to avoid the formation of high emissivity Fabry-Perot (FP) resonance when LSMO switches to metallic state at low temperatures. This perovskite manganese oxide-based multilayer film exhibits remarkable intelligent thermal control properties. It provides a significant opportunity to improve the performance of SRDs and a promising potential for maintaining the optimal operating temperature of the spacecraft.

VO2-Based Spacecraft Smart Radiator with High Emissivity Tunability and Protective Layer.

In the extreme space environment, spacecraft endure dramatic temperature variations that can impair their functionality. A VO2-based smart radiator device (SRD) offers an effective solution by adaptively adjusting its radiative properties. However, current research on VO2-based thermochromic films mainly focuses on optimizing the emissivity tunability (Δε) of single-cycle sandwich structures. Although multi-cycle structures have shown increased Δε compared to single-cycle sandwich structures, there have been few systematic studies to find the optimal cycle structure. This paper theoretically discusses the influence of material properties and cyclic structure on SRD performance using Finite-Difference Time-Domain (FDTD) software, which is a rigorous and powerful tool for modeling nano-scale optical devices. An optimal structural model with maximum emissivity tunability is proposed. The BaF2 obtained through optimization is used as the dielectric material to further optimize the cyclic resonator. The results indicate that the tunability of emissivity can reach as high as 0.7917 when the BaF2/VO2 structure is arranged in three periods. Furthermore, to ensure a longer lifespan for SRD under harsh space conditions, the effects of HfO2 and TiO2 protective layers on the optical performance of composite films are investigated. The results show that when TiO2 is used as the protective layer with a thickness of 0.1 µm, the maximum emissivity tunability reaches 0.7932. Finally, electric field analysis is conducted to prove that the physical mechanism of the smart radiator device is the combination of stacked Fabry-Perot resonance and multiple solar reflections. This work not only validates the effectiveness of the proposed structure in enhancing spacecraft thermal control performance but also provides theoretical guidance for the design and optimization of SRDs for space applications.

Thermal control system of Space Laser Communication Payload

Abstract To ensure the high-quality communication requirements of laser communication payload, the thermal control system is designed. Firstly, the structure and optical system of laser communication payload are introduced. Secondly, the task characteristic is analyzed. Then, the thermal design of laser communication payload is carried out with thermal conduction, thermal insulation, thermal dissipation and heating. Finally, a thermal balance test is performed. The test results show that the temperature of the optical system is 20.9 °C∼22.1 °C, the temperature of the detector is 15.5∼20.7 °C, the temperature of the pointing mechanism is 14.9 ∼ 17.5 °C, the temperature of the star sensor is 9.9 ∼ 18.7 °C, the temperature of the base is 13.9 ∼ 21.8 °C, and the temperature of the electric box is 14.7 ∼ 22.8 °C. The results of the test satisfy the requirements of the temperature indicators, indicating that the thermal design scheme is reasonable and feasible.

Exercise and resting periods: Thermal comfort dynamics in gym environments

Physical exercise spaces emerged as popular facilities due to recognizing the significance of physical well-being. This study investigates the relationship among physiological responses, human body energy transfer modes, and indoor environmental conditions in influencing thermal comfort perception within indoor physical exercise space. Seven male participants engaged in a 30 min constant-work-rate cycling exercise and a 20 min resting period in a climatic chamber. The physiological and environmental responses were recorded during the experiments, and the body’s energy transfer modes were calculated using the collected data. The dataset was prepared using the 2 min averages of the collected data and calculated parameters across the experiment phases, including the features of skin temperature, core temperature, skin relative humidity, heart rate, oxygen consumption, body’s heat transfer rates through convection, radiation, evaporation, and respiration, net metabolic heat production rate (metabolic rate minus external work rate), indoor air temperature, indoor relative humidity, air velocity, and radiant temperature. Gradient boosting regressor (GBR) was selected as the analyzing method to estimate predicted mean vote (PMV) and thermal sensation vote (TSV) indices during exercise and resting periods using features determined in the study. Thus, the four GBR models were defined as PMV-Exercise, PMV-Resting, TSV-Exercise, and TSV-Resting. In order to optimize the models’ performances, the hyperparameter tuning process was executed using the GridSearchCV method. A permutation feature importance analysis was performed, emphasizing the significance of net metabolic heat production rate (24.2%), radiant temperature (17.0%), and evaporative heat transfer rate (13.1%). According to the results, PMV-Exercise, PMV-Resting, and TSV-Resting GBR models performed better, while TSV-Exercise faced challenges in predicting exercise thermal sensations. Critically, this study addresses the need to understanding the interrelationship among physiological responses, environmental conditions, and human body energy transfer modes during both exercise and resting periods to optimize thermal comfort within indoor exercise spaces. The results of this study contribute to the operation of indoor gym environments to refine their indoor environmental parameters to optimize users’ thermal comfort and well-being. The study is limited to a small sample size consisting solely of male participants, which may restrict the generalizability of the findings. Future research could explore personalized thermal comfort control systems and synergies between comfort optimization and energy efficiency in indoor exercise spaces.

Advancing thermal efficiency and entropy management inside decagonal enclosure with and without hot cylindrical insertions

Effective cooling mechanisms are considered advancements in thermal control systems for diverse engineering purposes. Considering this fact, this investigation explores the analysis of natural convection and entropy generation by employing a decagonal enclosure using Galerkin Residual Finite Element method. In this study, influence of Rayleigh number (103 ≤ Ra ≤ 106), Bejan number (Be), Prandtl number (0.71 ≤ Pr ≤ 7), and isothermal boundary condition are considered. The findings reveal that both Ra and Pr significantly impact the characteristics of convection and flow patterns within the system. In cases with and without the circular object, higher values of Pr and Ra lead to a more pronounced cooling effect on the upper heated surface compared to the lower surface. Also, it enhances the overall thermal efficiency of the system by 112.05 % in comparison to the absence of a cylinder enclosure. These findings shed light on thermal control system advancements and contribute to field progress.

Power engineering of the tangential supply device of the microturbine of the thermal control system of a promising spacecraft

This paper presents an overview of the current technical problem related to two-phase spacecraft thermal control systems and possible technical applications of thermal energy recovery in the organic Rankine cycle as an integral part of thermal management systems. The design solution involves the integration of a steam microturbine behind an evaporator radiator. The microturbine is a tangential supply device and a radially centripetal impeller of low speed nst40. In this area, there is no reliable data on the design and energy of both the supply device and the impeller. The energy (loss of enthalpy) of the supply device mainly determines the transport of the swirling flow to the impeller and, as a result, the circumferential operation on the turbine. A prototype of a radial microturbine has been developed and presented in order to evaluate the design of the flow part of both the supply device and the impeller. As a result of the analysis, the main determining hydrodynamic areas necessary for hydrodynamic analysis and mathematical elaboration of the flow calculation algorithm with an assessment of energy losses are identified: the flow of a swirling flow of a radial-annular slit; axial-annular slit and tangential supply device. The first two algorithms assume computational modeling, the model of energy losses in a tangential supply device is not amenable to analytical modeling because it includes a sequence (or compatibility) of flows under boundary conditions defined as “local resistances”: the sudden expansion, reversal of the flow, together with a section of radially circumferential flow, the mutual influence of these boundary conditions assumes only an expe rimental assessment of energy losses in a tangential supply device through the loss coefficient of local resistance in the range of changes in geometric and operating parameters. As a result of experimental studies, a database has been proposed on the loss coefficient of tangential microturbine supply devices in the field of the practical range of the existence of operating and design parameters.

H∞ stabilization of singular networked cascade control systems subject to periodic DoS attack

In this paper, a [Formula: see text] controller with an event-triggered mechanism is designed for a singular networked cascade control system (SNCCS) under periodic denial-of-service (DoS) attacks. The SNCCS is treated as a system of differential-algebraic equations (DAEs) with an index of two and is modeled as a switched system. The paper first establishes sufficient stability conditions, which are formulated as linear matrix inequalities based on multiple Lyapunov functions. These conditions ensure that the system remains regular, free from impulse modes, and stable. Next, state feedback controllers are designed for both the inner loop and the outer loop. However, the outer loop is subjected to periodic DoS cyber-attacks. Finally, the proposed method’s effectiveness is demonstrated through simulation results on a practical thermal cascade control system.