Thermal Control System Research Articles

Design and test of a compact capacitor-based energy storage pulsed power module with high repetitive discharge frequency

Advance in electromagnetic launch have put forward higher requirements for the pulsed power supply(PPS). A capacitive PPS for electromagnetic launcher has been constructed in NJUST recently with a basic cell of 220kJ energy storage, which has a good scalability. Design of integrated 220kJ pulsed power unit (PFU) was demonstrated in the paper. To meet the requirement of compact structure of PPS, the device design and system layout are considered and combined with simulation to optimize the magnetic field distribution in the constrained space. In order to achieve the function of continuous discharge, the reliability of thermal management system, control system and safety protection system are focused on. System description was presented in the paper. A series of experiments were conducted to verify the performance of the module. The results show that the PFU shows good reliability in 10 consecutive burst-shot tests. Due to the modular setup of this pulse formation network, it can be extended to a larger-scale pulse forming network. Flexible current pulse shapes can be formed by controlling the charging voltage and the trigger time of the PFU.

The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment

Present as well as future challenges of space exploration point to the need for improved thermal control systems. The “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” experiment, which is approved by ESA for execution on board the International Space Station, aims to contribute directly to current knowledge and basic understanding of heat and mass transport in phase change materials (PCMs) that incorporate a free surface in reduced gravity. The experiment will apply fixed temperatures to opposite ends of PCM samples held in cuboidal and cylindrical containers in order to drive controlled melting and solidification cycles that will be observed by means of optical cameras. The recorded images will be complemented by thermal measurements at key positions along the samples, which will allow different thermocapillary flow regimes to be distinguished according to their temporal dynamics. It is anticipated that thermal Marangoni (thermocapillary) convection will increase the heat transfer rate in these PCM devices by a significant factor (on the order of two or more) compared to melting governed by thermal diffusion (conduction). If the PCM designs prove robust, the experiment results can be expected to lead to substantial improvements in future designs for passive PCM applications in space missions.

Continuous Photothermal and Radiative Cooling Energy Harvesting by VO2 Smart Coatings with Switchable Broadband Infrared Emission

Extensive use of renewable and clean energy is one of the promising ways to solve energy/environmental problems and promote the sustainable development of our society. As inexhaustible energy sources, the photothermal (PT) and radiative cooling (RC) energy from the sun and outer space have recently attracted tremendous interest. However, these two kinds of energy utilization have distinctly opposite spectral properties, especially in the infrared range, making it extremely difficult to integrate these two energy harvesting modes within a fixed device for continuous energy collection. Thus, in the current study, we have proposed a spectrally self-adaptive broadband absorber/emitter (SSBA/E) based on vanadium dioxide (VO2), a typical phase transition material, to achieve continuous energy harvesting via collecting solar thermal energy in PT mode during the day and obtaining cool energy in wide-band RC mode at night. Experimental results show that owing to the phase transition property of the VO2 layer, these two energy collection modes can be adaptively switched. Specifically, the VO2-based device shows a broadband infrared emissivity modulation from 0.21 to 0.75 and low critical temperatures (58.4 and 49.2 °C) during the phase transition, leading to continuous energy harvesting with high efficiency. Due to the broadband infrared emission, the RC maximum power of the SSBA/E device was estimated to be 58 W m-2. The proposed VO2 smart coatings are also applicable for many other applications such as thermal management of spacecraft, infrared camouflage, or adaptive optical devices.

Tunable thermal transport in 4D printed mechanical metamaterials

Here the authors present an active thermal control system using 4Dprinted shape memory polymers and demonstrate how distinct deformation mechanisms lead to unique, tunable thermal properties using stretching- and bending-dominated architectures. Infrared thermography measurements with varying temperature and compression settings show that at low strains, radiation drives the effective conductance increase as the view factors among the struts increase with increasing strain, and at higher strains, conduction drives the effective conductance increase as the strut-to-strut contact areas increase. The effective thermal conductance increases from 4.41mW/K to 14.52mW/K and from 3.23mW/K to 10.48mW/K for the Kelvin foam and octet-truss microlattices, respectively, as strain increases from 0% to approximately 70%. As the strain is adjusted, the stretching-dominated octet-truss architecture exhibits abrupt changes in shape and conductance due to buckling. The bending-dominated Kelvin foam architecture allows for gradual geometric changes and precise tuning of thermal conductance. These findings provide a new understanding of thermal transport phenomena in 4D-printed metamaterials, which may be a breakthrough in tunable thermal systems.

Reduction and reconstruction strategy of active thermal control system based on unsupervised learning and thermo-optics for spaceborne high-resolution remote sensor

The development of small Earth observation satellites with high performance optical remote sensors has received much attention in recent years due to its responsiveness and immediacy. As one of the most resource-intensive subsystems of spacecrafts, the active thermal control system (ATCS) should be optimized; however, manual thermal design does not guarantee an optimal solution and requires months. For this purpose, we presented a ATCS’s reduction and reconstruction strategy based on an unsupervised learning framework, in which factor loadings are applied to combine kernel-based principal component analysis and Gaussian mixture model clustering. This strategy was implemented on a spaceborne high-resolution remote sensor (HRS) with 0.5 m ground sample distance. As a result, with the cumulative variance contribution rate > 90 % and 10 Gaussian distributions, the reconstructed ATCS of HRS had a 78.6 % reduction rate and took only 3 h, which suggests the high efficiency and low computational cost of the proposed strategy. Finally, the performed orbital thermal and thermo-optical integrated analyses indicated that temperature fluctuations were within ± 0.02–0.6 °C and optical surface errors were within the tolerance. The average modulation transfer function in the tangential and sagittal directions decreased by only 2 % and 2.5 %, respectively, and the radius of the spot root mean square was considerably smaller than the size of one pixel (8.75 μm). These results prove the feasibility and validity of the proposed strategy. This study solved the problem of identifying the optimal ATCS for optical remote sensors and significantly reducing the ATCS’s resource occupancy, which provided a reliable research basis for the development of high-performance small Earth observation satellites. Additionally, the proposed strategy is versatile and can be used in thermal engineering applications of various complex spacecrafts and payloads.

Thermal control system design and analysis for a micro-nano satellite stays on target satellite

Aiming at the future satellites on-orbit service requirements, this paper researched the thermal control system for a micro-nano satellite. The micro-nano satellite can be attached on target satellite. The extreme temperature conditions of the micro-nano satellite has been determined by analyzing the complex space heat environment and power consumption, the thermal control system of micro-nano satellite has been designed, the finite element model (FEM) of the satellite is established, and the temperature fields about the extreme temperature conditions are calculated. The simulation results proves the feasibility of the thermal control system.

Feedback control of the mechanical spindle thermal error based on thermal simulation with bearing heat sources analysis

The thermal error stability (STE) of the spindle seriously affects the machining accuracy of a machine tool, however existing empirical heating model-based active cooling strategies mainly focus on suppressing the spindle’s overall thermal deformation and cannot effectively stabilize the thermal error. This study regards the “active cooling-spindle” system as a feedback control system and employs a data-driven thermal error model to provide feedback. Thus, the spindle thermal error can be stabilized for a long time owing to the homeostasis of the feedback control system under disturbance. A mechanical spindle with an external cooling scheme is taken as the study object. Bearings are the primary heat sources of the mechanical spindle; thus, the angular contact ball-bearing heat generation is precisely modeled based on local heat sources analysis of bearing components, elastohydrodynamic lubrication, and micro-contact theory. Thermal simulation of the spindle under varying-coolant temperature cooling is conducted to pre-validate the thermal error suppression and variation trend influencing effect, and obtain the Reference Input of Thermal Error (RITE) for the feedback control under different work conditions. Subsequently, a spindle thermal error feedback control system is developed, including computation, cooling, and real-time monitoring modules with inter-communication. Finally, the thermal error feedback control strategy is applied on the mechanical spindle, and experimental comparisons with constant coolant temperature cooling show that the thermal equilibrium time is advanced by 61.46%, 59.16%, 40.51%, and 58.08%. The thermal error variation range (TEVR) after the preheating stage is reduced to1.92, 1.52, 1.91, and 1.69 μm, respectively. The significant reduction in TEVR validated the effectiveness of the proposed strategy for spindle thermal error stabilization.

Performance Analysis of a 300 MW Coal-Fired Power Unit during the Transient Processes for Peak Shaving

A simulation model based on Dymola modelling was developed to investigate the dynamic characteristics of automatic generation control (AGC) for variable-load thermal power units in this study. Specifically, a 300 MW unit from a power plant in northern China was used to verify the model’s validity in steady-state processes and to analyze the behavior of the main thermal parameters under different rates of load changes. The economic performance of the unit under different rates of load changes is also analyzed by combining the economic indexes of “two regulations” in the power grid. Results indicate that as the rate of load changes increases, boiler output, main steam temperature, reheat steam temperature, main steam pressure, and working temperatures of various equipment fluctuate more intensely. Specifically, at a rate of load reduction of 2.0% Pe MW/min, the maximum deviation of the main steam temperature can reach 7.6 °C, with the screen-type superheater experiencing the largest heat exchange. To achieve a balance between safety and economics for the unit, the rate of load raising should not exceed 1.2% Pe MW/min, and the rate of load reduction should not exceed 0.8% Pe MW/min. This paper applies the covariance index and AGC assessment index of the thermal power unit load control system to the established dynamic simulation model to supplement the AGC assessment index in the “two regulations”, and to provide a flexible and reasonable system evaluation result for field operators to refer to, so as to improve the economics of the system on the basis of safety.

Optimization of novel flat serial single-phase radiators for spacecraft thermal control

Space thermal radiators play a significant role in the thermal management of spacecraft. With the increase in heat dissipation requirement, the heat pipe radiators are being replaced by mechanically pumped fluid loop radiators. In recent years, authors proved that optimum serpentine serial radiators are advantageous over conventional optimum parallel radiators in terms of the mass and pressure drop. The spiral radiators, inspired by spiral plate heat exchangers, are proposed and analyzed as a replacement for the serpentine serial radiators. Performance analysis of radiators is carried out using conjugate heat transfer analysis. Conjugate heat transfer results are validated with the experimental results obtained from the literature. The performance analysis indicated that the circular spiral radiator performs better than the other two types due to their lower mass and pressure drop. Optimization of radiators is carried out using Taguchi Signal to Noise ratio analysis. Analysis of Variance is conducted to determine the percentage contribution of each variable to the performance of the radiator. When lower pressure drop requirement is prominent, the contribution of the diameter of the tube is 79.3%, whereas the contribution of fin thickness and pitch of the tubes are only 6.1% and 8.2%, respectively. The contribution of the fin thickness is 57.39%, the diameter of the tube is 37.71%, and the pitch of the tubes is 1.89% when the lower mass of the radiator is the prime requirement. The high-performance spiral radiators may find their application in the thermal management of human space flights and high-power GEO satellites.

Evaluation and analysis of the improvement in charging time for the high-power fast charging module using phase change material

The advancement of charging time for the fast charging piles facilitates the full adoption of EVs. The benefits of adding the suitable phase change material (PCM) to the thermal control system of the high-power fast charging power module are demonstrated in this experimental study. The effects of different PCM's melting temperature, thermal conductivity, and filling thickness on the improvement of charging time are explored, and the PCM melting rate is visualized to reveal the mechanism of PCM in improving the charging time. The results show that the extension in charging time of 2370 s is found for the charging power module coupled with PCM at the heat generating power of 15 W, and it is extended by 54% and 39% at heat generating power of 25 W and 35 W, respectively. The benefit of applying the PCM in the improvement of charging time for the charging power module is lessened with increasing the air velocity. The optimal PCM melting temperature is 47.5 °C, and it achieves the maximum charging time of 1540 s. The maximum available charging time is 1620 s at the filling PCM thickness of 5.5 mm. Also, the charging time is extended by 510 s when the thermal conductivity of PCM increases from 0.2 W/(m K) to 5 W/(m K). Increasing the heat generating power or decreasing the air velocity will shorten the completed melting time of the used PCM, and the initial melting time is also ahead. A faster PCM melting rate is observed at the lower PCM melting temperature and filling thickness, and this shortens the PCM latent heat role in the thermal control for the charging power module.

Thermal and Humidity Control System in Interior as Climate Responsive Design (Case Study: Rectorate Building of Widya Mandira University in Kupang, East Nusa Tenggara)

Design of an interior space is user centered. The controlled thermal and humidity of a room by a data according to standards can meet the needs and comfort of users. The interior of the room is designed as a response to the environmental conditions in which the room designed. The study was conducted to examine how the implementation of thermal and humidity control system in the interior can maximize the comfort aspect of the user. Descriptive qualitative method with an experimental approach used in the study. Data was collected through previous literacy studies and field visit of object of study case, which is Rectorate Building of Widya Mandira University in Kupang, East Nusa Tenggara. This research aims to indicate how an implementation of system in interior design can be an answer to the state of the surrounding environment and becomes a climate responsive design. The results of this study can be used as future approach of smart building in responsive climate design.

Calculation of environmental loads for a CubeSat using MATLAB

From 2011 to 2022, around 1,663 CubeSats between 1.1 kg and 10 kg were launched worldwide. These satellites were used for sensing, technology development, communications, and scientific applications. To develop these satellites, it is necessary to determine the thermal loads for the calculation of the internal temperature distribution of the components, which allows us to design the thermal control system. In this work, the mathematical formulations are presented to be able to obtain the thermal loads. Simulations were carried out with STK which assisted in obtaining the thermal loads and another simulation was carried out with MATLAB where the results were later compared, the values to be studied being solar radiation, albedo, and planetary radiation. When comparing the results, an error of 9.32% was obtained, which is discussed in the conclusions. The importance of developing a tool that allows obtaining the thermal loads and that said tool be open source was discussed.

Thermal control performance of phase change material combined with ultra-light hollow metallic microlattice for microsatellites

Phase change materials (PCMs) have been utilized to realize the passive thermal control of the large spacecrafts. To date, there have been few reports on the use of PCMs for the development of thermal control systems in microsatellites with small size and lightweight. Herein, we report a method of the fabrication of the microlattice phase change material (MPCM), which is a lightweight heat storage material using a combination of PCMs and hollow metallic microlattice materials. The thermal control performance of the MPCM is studied using a combination of theoretical analysis, experimental tests and numerical simulations. Parametric analysis reveals that the thermal control performance of MPCM is quite sensitive to the micro-structure of the microlattice. The equivalent heat flux is determined to realize the homogenization of the thermal properties of MPCM. Results obtained from the numerical simulation results reveal that as the macroscopic dimensions of MPCM are 10.3 cm × 10.3 cm × 1.9 cm with the weight of 59.4 g, the microsatellite can be operated over a period of 10000 s at temperatures ≤ 35 °C under conditions of heat load cycles and the temperature range can be controlled within 10.3 ℃. The properties of the developed MPCM can be tuned, and the material can be efficiently used to realize the thermal control of microsatellites.

DETERMINATION OF THE TEMPERATURE FIELD DISTRIBUTION IN THE WINDING RODS OF THE STATOR OF TURBOGENERATORS OF TYPE TVV FOR PURPOSES OF CONTROL AND DIAGNOSTICS

Turbogenerators were and remain the most unreliable element at nuclear power plants in Ukraine. The most dangerous disturbances in the operation of turbogenerators of the TVV type is complete or partial blockage of the hollow conductors of the stator winding. The systems of operational control and technical diagnostics today, in a number of cases, cannot cope with the identification of these phenomena. The complex application of adequate mathematical models, indications of the standard thermal control system and new diagnostic features give the opportunity with sufficient accuracy for practical purposes to detect blockages in the hollow conductors of the stator windings of these turbogenerators. The aim of the work is to develop a program for calculating the three-dimensional temperature field in the rods of the stator winding of a turbogenerator of the TVV-1000-2U3 type, taking into account the temperature field of the stator core, to carry out a test calculation and to compare the experimental and to calculated data. The problem is solved with the help of the finite difference method using the integro-interpolation method.

A novel methodology for evaluating high temperature gas corrosion of oxide-C refractories

A new experimental setup to evaluate the corrosion behavior of oxide-C refractories under gaseous reactive atmospheres is presented. Firstly, the paper focuses on the oxidation by oxygen of MgO–C bricks used in the steelmaking industry. The main innovation of the proposed methodology involves simultaneously monitoring and tracking the variations in the sample’s mass and the concentrations of oxygen surrounding it during the test. In addition, the composition of the reactive atmosphere can be changed by mixing different gases. The main components of the equipment (the thermal control system and the data collector system) as well as the sample’s conditioning, the test itself, and the post-test evaluation are described. As an example of how it can be applied, the proposed methodology is used to test MgO–C and MgO–C–Al bricks in contact with atmospheres with different O2 content at 1000°C. The reliable reproducibility of the test is confirmed, and the obtention of valuable information which has not been previously considered, such as the oxygen consumption, is shown.

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.

Concurrent Static and Dynamic State Monitoring Using a Global-Local Model for the Fluid Loop in Space Stations

The fluid loop is the core of thermal control system in the space station. Owing to the complex and changeable operating conditions and long time in orbit, the fault rate and performance degradation rate increase. Therefore, it is of practical significance to timely and accurately monitor the operating state of the fluid loop. This article proposed a combined strategy of canonical variate analysis and slow feature analysis to concurrently monitor the static deviation and process dynamics for the operating state. First, multiple sensors are used to measure the data in all condition of the space station, and typical faults are simulated by fault seeding to obtain fault data. Following that, the serially correlated canonical subspaces for each normal operating condition are modeled, and they are further explored to extract slow features to establish the multiple local static monitoring models. Besides, a global model is built using differential slow features in all condition to detect the dynamic anomalies by monitoring the temporal variations. To illustrate the feasibility and efficacy, the proposed monitoring strategy is applied to monitor the test data consisting of normal samples and fault samples.

Methodology of Analysis of Thermal Vision Parameters of NPP Standby Diesel Together with Standard Instrument Readings

Analytical studies of the results of thermal imaging control using IAS TIK together with the corresponding values of the temperature control results obtained in the standard DGS condition monitoring system were carried out within the framework of R&D for the development of an integrated automated system for thermal imaging control (IAS TIK). Approbation of IAS TIK in NPP conditions was carried out by thermography of standby diesel generator sets of NPP type 12zv40/48+S2445-12. At the same time, the parameters of the diesel engine and the generator were measured using the standard control system. The methodology is proposed that provides an analysis of the uniformity of the operation of diesel cylinders, the condition of the crankshaft bearings, the condition and quality of the generated electricity of the generator, as well as the analysis of the operation of lubrication and cooling systems. The practical application of the technique demonstrates the correspondence between the temperatures measured by the standard system and the IAS TIK. A joint analysis of the results obtained by the standard and developed systems provides an increase in the depth of the diagnostic examination and confirms the information content of the thermographic parameters and the quality of the measurement channels of the standard systems. The parameter values obtained from the analysis of the indicators of the standard control system, recorded at a steady power value, will be used in subsequent diagnostics to establish trends in these parameters

Passive thermal control systems in spacecrafts

Passive thermal control systems in spacecrafts

Ammonia void fraction in smooth tubes at different gravity orientation

Ammonia is an environment-friendly natural refrigerant and working fluid with negligible global warming and ozone depletion. Nowadays, ammonia is widely used in industrial refrigeration systems, heat pumps and thermal control systems, including heat pipes, loop heat pipes and two-phase mechanically pumped loops. In perspective, “green” ammonia is considered an energy carrier and carbon-free fuel. In two-phase systems, the void fraction is one of the critical factors determining the frictional and local pressure losses, boiling and condensation heat transfer and phase separation. The experimental study of ammonia void fraction in tubes with inner diameters of 8.5 mm and 15 mm is proposed in this paper. The quick-closing valve method has been chosen. Three flow configurations are considered: vertical downward, vertical upward and horizontal. The tests were provided for the two-phase ammonia at a mass velocity of 50…500 kg·m−2s−1, saturation pressure of 15…30 bar, and vapour quality of 0.05…0.30. One hundred and five points have been tested. No existing single correlation predicts the ammonia void fraction well at the considered boundary conditions for at least two orientations in the gravity field. A new single correlation has been proposed based on the Rouhani drift model with the tube inclination angle-dependent distribution parameter allowing the adequate prediction of void fraction in a tube with ammonia flow at horizontal, upward and downward orientations.