Intelligent Thermal Control Research Articles

A broadband acoustic metamaterial lens for sub-wavelength imaging based on bandwidth enhancement

Acoustic metamaterials manufactured from natural materials can exhibit exotic characteristics that cannot be found in nature materials through the design of geometric structures and resonance effects, and acoustic metamaterials can be used to achieve sub-wavelength acoustic imaging as the acoustic metamaterial lens (AML). Currently, the AMLs based on the Fabry–Pérot (FP) resonance principle are all with single effective length hole, which is directly related to the thickness of its structure. They can only achieve acoustic imaging in a relatively narrow frequency range, and there is no AML which can achieve broadband sub-wavelength acoustic imaging. In this paper, a kind of broadband acoustic metamaterial lens (BAML) is introduced. While maintaining a constant overall thickness of the AML, a design which is composed of the supercell consisting of a cross distribution of different effective length holes is proposed. This design enables the AML formed by these supercells to encompass multiple operating frequencies corresponding to various holes, thereby broadening the frequency range of acoustic imaging. Finite element simulation and imaging experiments were conducted, and results demonstrated that the BAML consisting of multiple effective length holes has the ability to enhance bandwidth of acoustic imaging. Compared to AML with single effective length hole, it offers a broader range of imaging frequencies, this design offers a general method of bandwidth enhancement. BAML has potential application value in ultrasonic imaging, sound absorption, intelligent thermal control and medical diagnosis.

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.

Intelligent Space Thermal Control Radiator Based on Phase Change Material with Partial Visible Transparency

Coating structures with dynamically adjustable infrared emissivity are crucial in spacecraft components to cope with the transient thermal environments of space. For a long time, thermochromic phase change materials have been widely used in applications requiring emissivity adjustment, and optimizing the range of adjustable infrared emissivity has always been at the forefront of research. However, reducing the absorption of solar radiation has significant implications for the practical application and thermal stability of spacecraft components in space environments. In this paper, we propose a multilayer film structure based on the phase change material VO2 combined with the materials ZnSe and ITO to achieve low solar radiation absorption and adjustable infrared emissivity for intelligent thermal radiators in space. Through finite element simulation analysis of the structure, we achieve a solar radiation absorption rate of 0.3 and an adjustable infrared emissivity of 0.49. According to Stefan–Boltzmann’s law, the structure exhibits strong radiative heat dissipation at high temperatures and weak energy dissipation at low temperatures to maintain the thermal stability of the device and ensure efficient operation. The intelligent thermal radiator operates based on the principles of Fabry–Perot resonance. Therefore, the multilayer structure based on the phase change material VO2 demonstrates excellent performance in both solar radiation absorption and adjustable infrared emissivity, showcasing its tremendous potential in the field of intelligent thermal control in aerospace.

Structural color tunable intelligent mid-infrared thermal control emitter

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of εH = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of εL = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials.

Design of VO2-based spacecraft smart radiator with low solar absorptance

Thermochromic film with the ability to self-adaptively switch emittance is important for spacecraft missions experiencing rapidly increasing demand. Current research on thermochromic films primarily focuses on optimizing emittance tunability, while the solar absorptance of these films remains high, limiting their practical application in spacecraft thermal control. In this work, a VO2-based spacecraft smart radiator with low solar absorptance and high emittance tunability is proposed. The smart radiator is a multilayer structured film composed of a switchable resonator (i.e., a superposed Fabry-Perot cavity) and a solar reflector (i.e., a Distributed Bragg Reflector). The performance of the smart radiator is optimized by combining the Rigorous Coupled Wave Analysis method and Genetic Algorithm, achieving a normal solar absorptance of 0.121 and emittance tunability of 0.825. The solar absorptance and emittance tunability of the smart radiator remain excellent even at large incident angles. The underlying mechanisms involved in the smart radiator are attributed to the combination of superposed Fabry-Perot resonance and multiple solar reflectance. In addition, we provide a numerical example using a geosynchronous orbit satellite to demonstrate that the regulation range of the net heat dissipation flux density can increase from 146.5–463.9 W/m2 by using Optical Solar Reflector to 0–494.6 W/m2 when using the proposed smart radiator within the permissible temperature range (263.15–318.15 K) of spacecraft. This VO2-based spacecraft smart radiator with outstanding properties which outperform the existing thermochromic films reveals the promising potential of thermochromic films for spacecraft intelligent thermal control applications.

Enhancing infrared electrochromic properties of the poly(styrene sulfonate) doped polyaniline composite film by morphology regulation

Infrared electrochromic device based on polyaniline (PANI) possesses the ability to regulate infrared radiation, which has a great application prospect in the field of satellite intelligent thermal control. However, it is still challenging to efficiently fabricate uniform and dense PANI functional layer with excellent infrared electrochromic properties. Here, we demonstrate the use of polymer additive to promote deposition of PANI with smooth and dense morphology by inducing uniform electrochemical deposition rate on the electrode surface and inhibiting the growth of PANI in three-dimensional direction through adsorption mechanism. By adding a low concentration of poly(styrene sulfonate) (PSS) to the electrodeposition solution, the PANI film with uniform and compact micromorphology was prepared with excellent infrared electrochromic property, which can realize the modulation of emittance more than 0.4 and 0.45 in the range of 8 ∼ 14 μm and 2.5 ∼ 25 μm, respectively. Furthermore, the infrared electrochromic device that employ the optimized PANI functional film and adsorbing ionic liquid porous gel electrolyte was constructed. Through high and low temperature cycle test (1000 cycles) and vacuum environment test, the device exhibits wonderful durability and can achieve large emissivity modulation in the wavelength range of 2.5 μm ∼ 25 μm (Δε = 0.38). Meanwhile, the transient thermal analysis of the heat dissipating plate attached with the infrared electrochromic device exhibits that the device has an excellent potential for the purposes of efficient thermal management of the satellite.

Spacecraft smart radiation device with near-zero solar absorption based on cascaded photonic crystals

Smart radiation device (SRD) for spacecraft based on thermochromic material vanadium dioxide (VO2) attracts increasing interest due to its ability of self-adaptive emission regulation. However, the spacecraft SRD is constrained by the high solar absorption at a high temperature and low emission tunability in practical applications. In this paper, a SRD is proposed for spacecraft thermal control, which consists of a solar reflector based on cascaded photonic crystals and a thermal emitter (VO2/BaF2/Ag). By cascading four photonic crystals with photonic band gaps for different central wavelengths, the total reflection range of the SRD in the solar radiation band is broadened. It is found that the SRD can realize near-zero solar absorption and high emission modulation depth, simultaneously. Though optimizing the thicknesses of the VO2 and BaF2, the emission modulation depth can reach 0.69, and the solar absorption can reduce to 0.08. In addition, the physical mechanism is studied by the distribution of the electric field. It is proved that the near-zero solar absorption originates from the broadband total reflection of the cascaded photonic crystals. The phase transition properties of VO2 and the difference in inherent losses at high and low temperatures result in high emission modulation depth. Besides, the low solar absorption and high emission modulation depth performances of the SRD can remain excellent when the angle of incidence is small than 46° regardless of the transverse electric wave or transverse magnetic wave. This work not only provides a new idea for designing SRDs, but also is expected to accelerate the development of intelligent thermal control of spacecraft.

Application of New Materials in Aerospace Thermal Management

This paper summarizes the mission, scheme and main technology of spacecraft thermal management. The development requirements of new thermal control technologies, especially new thermal control materials, for future spacecraft are analysed. The research progress of new high thermal conductivity materials, new interface filler materials and intelligent thermal control coatings at home and abroad and their applications in the thermal control field of spacecraft are reviewed.

Different ion-based electrolytes for electrochromic devices: A review

Initially, electrochromic (EC) technology was an attractive research topic aiming at the development of green buildings and smart displays. Nowadays, EC technology has been extended in various fields of energy storage systems, wearable devices, military camouflage, intelligent thermal control, etc. Electrochromic devices (ECDs) have been considered promising candidates for next-generation multi-functional devices due to their prominent advantages in integrated intelligence, low energy consumption, flexibility, displayable, and adjustable features. Electrochromism refers to the reversible change in color, transmittance, or reflectance of materials via a low voltage. Generally, the EC process lies in the dual adjustment of electrons and ions, so the transmission kinetics of electrolyte ions plays an extremely key role in EC performance. Although Li-ion-based ECDs are still mainstream, the emerging ion-based ECDs (such as Na + , K + , Ca 2+ , Mg 2+ , Zn 2+ , Al 3+ , etc) with improved performance have been reported one after another in recent years. This review summarized existing studies about advanced EC design by driving different electrolyte ions and analyzed their positive influence and side effect on EC performance. Meanwhile, the corresponding preparation method, structure design, and ions transport mechanism were discussed in detail. Finally, the facing challenges and development direction of related filed in the future were proposed. Hopefully, this review can provide useful help for the suitable selection of electrolyte cations for different EC systems and the promotion of diverse ion-based ECDs in practical application.

Passive and Dynamic Phase-Change-Based Radiative Cooling in Outdoor Weather.

Radiative cooling has attracted considerable attention due to its tremendous potential in exploiting the cold reservoir of deep sky. However, overcooling always occurs in the conventional static radiative coolers because they operate only in the cooling mode in both hot and cold. Therefore, a dynamic radiative cooler based on phase change materials is highly desired. Nevertheless, the practical outdoor phase-change-based dynamic radiative cooling has not yet been experimentally demonstrated. To satisfy the stringent requirement of the phase-change-based radiative cooler in outdoor weather conditions, we engineered the phase-change material (VO2) to possess the room-temperature phase-transition capability for typical weather conditions. Second, the reconfigurable cavity consists of the lossless spacer to ensure the magnitude of thermal modulation and suppress the solar absorption simultaneously. Third, the practical selective-filtering method is devised to shield the solar irradiance while permitting the thermal emission. Our experiment demonstrates that these materials and photonic measures can work together to realize the dynamic radiative cooling in actual weather conditions, which shows a self-adaptive switch between the ON-cooling state in hot daytime and the OFF-cooling state in cold nighttime. The study pushes the radiative cooler toward multifunctionality and provides beneficial guidance for the phase-change-based intelligent thermal control.

VO2-based intelligent thermal control coating for spacecraft by regulating infrared emittance

Intelligent thermal control coating (ITCC) for the thermal management of the spacecraft needs a high emittance on the sunny side to consume the energy absorbed from the sun and a low emittance on the night side to reduce the energy radiated to the space. Because of the thermochromic phase transition from the semiconducting state to the metallic state at 68 °C, the VO2 with dynamic emittance is a viable option as an intelligent thermal control coating. In this work, a simple three layers Ag/SiO2/VO2 ITCC has been demonstrated, and the ITCC shows a low emittance εL of 0.07 at temperature of 293 K, and a high emittance εH of 0.59 at temperature of 353 K. The VO2 based ITCC designed with the near-field effect provides a new energy-efficient and cost-effective way in the thermal management system for the spacecraft.

Toward Intelligent Multizone Thermal Control With Multiagent Deep Reinforcement Learning

Energy usage and thermal comfort are the pillars of smart buildings. Many research works have been proposed to save energy while maintaining a comfortable thermal condition. However, most of them either make the oversimplified assumption on thermal comfort with unsatisfied comfort performance or deal with the single-zone thermal control only with limited practical impact. A few preliminary pieces of research on multizone control are available, but they fail to keep pace with the latest advancements in the deep-learning-based control techniques. In this article, we investigate the multizone thermal control with optimized energy usage and canonical thermal comfort modeling. We adopt the emerging multiagent deep reinforcement learning techniques and propose to model each zone as an agent. A multiagent framework is established to support the information exchange among the agents and enable intelligent thermal control in the heterogeneous zones. Accordingly, we mathematically formulate a problem to optimize both energy and comfort. A multizone thermal control algorithm (MOCA) is proposed to solve the problem by deriving optimal control policies. We validate the performance of MOCA through simulation in professional TRNSYS, configured based on our real-world laboratory. The results are promising with up to 15.4% energy saving as well as satisfied thermal comfort in different zones.

Research progress of infrared electrochromic devices

Infrared electrochromic device is a kind of device whose infrared emissivity can change reversibly under electric field excitation. This kind of device has important applications in the fields of adaptive infrared camouflage and intelligent thermal control, and has become a research frontier and hot spot in the field of infrared radiation control. In this paper, the working principle, research status and progress of infrared electrochromic devices based on metal oxides, conductive polymers, graphene and metals are summarized, and the development trend of infrared electrochromic device is analyzed.

A novel method of enhancing convective heat transfer by dynamic controlling rib

New and efficient mixing heat technology is increasingly demanded for many industrial fields. This paper proposed a novel technique of enhancing convective heat transfer by dynamic controlling rib and investigated several cases of vibration rib controlling flow. The study results of heat transfer coefficient, temperature and turbulent intensity indicate that dynamic flow control is an efficient heat transfer enhancement technique. The dynamic flow control breaks through the current enhancement heat transfer technologies such as general stationary rib and other vortex generators, and achieves a better heat transfer effect. Comparing traditional rib technologies, vibration rib does not only increase heat transfer performance but leads a lower flow resistance. More importantly, it can be dynamically adjusted to achieve better flow turbulence. As a conclusion, the enhancement heat transfer performance can be timely dynamically adjusted to meet the different heat transfer demand by changing timely the frequency and amplitude of vibration rib, which achieves the optimization of whole system thermal protection. New enhancing heat transfer technique effectively improve the comprehensive heat transfer performance, and provides a reference for intelligent thermal control protection system

A wireless intelligent thermal control and management system for piglet in large-scale pig farms

Indoor temperature is a critical environmental factor for piglets that affects the health, welfare, and production efficiency of domesticated pigs. However, there are limited reports about wireless intelligent thermal control and management system for piglets in large-scale pig farms, and evaluation energy saving. This paper presents an Automatic Thermal Control and Management System (ATCMS) of micro-environment for piglets, that could provide a suitable production environment and reduce the energy consumption. ATCMS includes automatic temperature control system (ATCS), multipoint temperature management system (MTMS) and remote access. The infrared heating lamps are chosen in the ATCS for their good performance in heating rate and heating distribution. In order to meet a scientific temperature requirements of piglet growth, the suitable thermal ranges of each growth-stage (STREG) are employed as intelligent control strategies to generate an automatic and precise heating control. MTMS is responsible for communicating with ATCSs and transmitting information to database server for record based on wireless technology. Remote access offers information services for remote administrators by smart phones and clients via Internet. The experiments of ATCMS were carried out both in winter and summer at Binsheng Breeding Piggery Farm, Acheng City, Heilongjiang Province, China. Results showed that the temperature provided by ATCS had been kept in STREG of piglets during the whole winter period. When the indoor temperature during summer period were in or above STREG, heating lamps were turned off by ATCS for a long time. The energy consumption of ATCS were 63.60% in winter and 39.35% in summer with continuous heating system operation. Therefore, ATCMS could take the suitable thermal ranges of each growth-stage as an intelligent control principle to give an automatic and precise control to heating devices in order to meet a scientific temperature requirements of piglet growth.

Bioinspired Microstructured Materials for Optical and Thermal Regulation.

Precise optical and thermal regulatory systems are found in nature, specifically in the microstructures on organisms' surfaces. In fact, the interaction between light and matter through these microstructures is of great significance to the evolution and survival of organisms. Furthermore, the optical regulation by these biological microstructures is engineered owing to natural selection. Herein, the role that microstructures play in enhancing optical performance or creating new optical properties in nature is summarized, with a focus on the regulation mechanisms of the solar and infrared spectra emanating from the microstructures and their role in the field of thermal radiation. The causes of the unique optical phenomena are discussed, focusing on prevailing characteristics such as high absorption, high transmission, adjustable reflection, adjustable absorption, and dynamic infrared radiative design. On this basis, the comprehensive control performance of light and heat integrated by this bioinspired microstructure is introduced in detail and a solution strategy for the development of low-energy, environmentally friendly, intelligent thermal control instruments is discussed. In order to develop such an instrument, a microstructural design foundation is provided.

Intelligent Thermal Control Strategy Based on Reinforcement Learning for Space Telescope

In this study, a thermal model of a space telescope is established in Simulink. An intelligent autonomous thermal control strategy based on actor-critic reinforcement learning (RL) for proportional–integral–derivative (PID) parameter adaptive self-tuning, called RL PID, is proposed. This control strategy enables the PID thermal controller to adaptively tune the PID parameters to achieve stable and precise temperature control. A single radial basis function (RBF) neural network is applied to simultaneously approximate the strategy function of the actor and the value function of the critic. The actor maps the system state to PID parameters, and the critic evaluates the output of the actor and generates a temporal difference (TD) error. Based on the architecture of the actor-critic RL algorithm and the TD error performance index, a design flow chart of RL PID is made. Both theoretical and experimental results show that RL PID can achieve a temperature control precision of , and that the steady-state error is reduced by 50 and 75% in the simulation and 50 and 67% in the experiment compared with those of the traditional PID controller and the traditional switch controller, respectively. RL PID has better reliability, more robustness, and a faster response.

Intelligent Thermal Control of Resistance Welding of Fiberglass Laminates for Automated Manufacturing

A novel approach to automate large-scale resistance welding of thermoplastic composite materials, based on real-time temperature control, is presented in this paper. Resistance welding, a kind of fusion bonding, is a widespread alternative process to mechanical fastening and adhesive bonding in joining thermoplastic composites. A second-order linear observer was identified to estimate the online temperature at the weld interface. A fuzzy logic controller (FLC) was designed to control the weld temperature using both process voltage and linear weld speed as the control inputs and using the temperature estimate as the feedback signal. The FLC was implemented in real time with the experimental setup using an industrial robot—KUKA KR 210. The closed-loop controller was capable of successfully controlling the weld temperature within 10% of the desired temperature, resulting in superior weld quality when compared to open-loop results. The results thus affirm the suitability of the control strategy for large-scale automated welding.

Implementation of a heat recovery unit in a proton exchange membrane fuel cell system

A heat recovery unit (HRU) has been developed and implemented in a proton exchange membrane (PEM) fuel cell cogeneration system that generates electricity and hot water efficiently. It consists of a stack coolant circuit, a heat exchanger, and a heat recovery circuit. An intelligent thermal control algorism is proposed as well to manage the cogeneration system. The HRU together with the control scheme has managed the fuel cell cogeneration system properly and efficiently. The stack coolant inlet temperature (SCIT) is well controlled at the preset temperatures (55 °C and 59 °C) under different external loads (0–3 kW). Results also show that the dynamics of the SCIT is closely related to the actions of the secondary fluid pump. Up to 50% fuel energy can be recovered thermally in the present cogeneration system. Examination of the external-load effects reveals that increasing external loads increases the electrical efficiency but decreases the heat recovery efficiency slightly. The maximum efficiency as a combination of heat and power is 82% based on hydrogen's lower heating value.