Thermal Control Approach Research Articles

Multilayer thermal control for high-altitude vertical imaging aerial cameras.

Aerial cameras play an important role in obtaining ground information. However, the complex and changeable aviation environment limits its application. Thermal control is vital in improving the environmental adaptability of the camera to obtain high-quality images. Conventional thermal control of aerial cameras is to directly implement active thermal control on the optical system, which is a single layer thermal control method. Such a method cannot isolate the optical system from the external environment. It results in a sharp increase in thermal control power consumption and in temperature gradient, which increases the difficulty of thermal control. Here, we propose a multilayer system-level thermal control approach by partitioning the aerial camera into two parts, i.e., the imaging system and the outline cabin. Two parts are connected by materials with poor thermal conductivity, and an air insulation interlayer is formed in between. Theoretical analysis is carried out to model the internal and external thermal environment of the aerial camera in a complex high-altitude environment. We study passive thermal control of the thermal insulation layer of the outline cabin, the optical window, the imaging optics, the CCD device, and the phase change material, and active thermal control of the thermal convection and heating film. Numerical modeling on the multilayer thermal control of the system is carried out and verified by the thermal equilibrium test and actual field flight test. The total power consumption of the thermal control system is 270 W. High-quality images are obtained when the temperature gradient of the optical lens is less than 5°C and the temperature of the CCD is lower than 30°C. Our technology is simple, accurate, low cost, and easy to implement compared to the conventional thermal control method. It effectively lowers the power consumption and reduces the difficulty of thermal control.

Battery High Temperature Sensitive Optimization-Based Calibration of Energy and Thermal Management for a Parallel-through-the-Road Plug-in Hybrid Electric Vehicle

Preserving high-voltage battery pack lifetime represents a key issue in hybrid electric vehicles (HEVs). Temperature has remarkably major impacts on battery lifetime and implementing HEV thermal and energy management approaches to enhance fuel economy while preserving battery lifetime at various temperatures still represents an open challenge. This paper introduces an optimization driven methodology to tune the parameters of thermal and energy on-board rule-based control approaches of a parallel through-the-road plug-in HEV. Particle swarm optimization is implemented to this end and the calibration objective involves minimizing HEV operative costs concerning energy consumption and battery degradation over the entire vehicle lifetime for various ambient temperatures, driving conditions, payload conditions, and cabin conditioning system states. Numerical models are implemented that can estimate the evolution over time of the state of charge, state of health, and temperature of HEV high-voltage battery packs. Obtained results suggest that the calibrated thermal and energy management strategy tends to reduce pure electric operation as the ambient temperature progressively increases beyond 30 °C. The consequent longer internal combustion engine operation entails a gradual increase in the overall vehicle energy demand. At a 36 °C ambient temperature, the HEV consumes 2.3 times more energy compared with the 15 °C reference value. Moreover, activating the cabin conditioning system seems beneficial for overall plug-in HEV energy consumption at high ambient temperatures. The presented methodology can contribute to easing and accelerating the development process for energy and thermal management systems of HEVs.

Regional temperature control in ceramic injection moulding: An approach based on cooling rate optimisation

The injection moulding of ceramic components with uneven wall thickness presents challenges due to differential cooling rates developing in the injected parts, which cause premature solidification of the feedstock at thin features and lead to detrimental defects, worsening in components from green to sintered states. To cope with this, suitable mould thermal control approaches have to be selected and validated, as current control methods are based on the achievement of a uniform cavity surface temperature, which is not tailored to such complex geometries. In this work, a novel thermal control system is proposed, based on regional mould temperatures, implemented with the use of Peltier modules, which locally and independently heat and cool different cavity features according to their thickness. The regional temperature profiles are optimised over time with the use of a coupled Finite Element - Particle Swarm Optimisation (FE-PSO), to achieve uniform cooling rates throughout the moulded components. The performance of this approach is compared to both constant ambient mould temperature and Rapid Heat Cycle Moulding (RHCM) techniques, which instead aim at achieving uniform temperatures throughout the mould cavity surface. Results show that the novel proposed method, based on regional temperature control and uniform cooling rates, promotes the simultaneous solidification of features with a 10-times difference in surface-to-volume ratio. Due to this, in terms of components quality, the novel method brings the advantages of higher dimensional control and reduction of differential shrinkage compared to the other analysed approaches, thus increasing the capability to use injection moulding to manufacture ceramic components characterised by non-uniform wall thickness.

Near-field radiation assisted smart skin for spacecraft thermal control

Thermal control is of critical importance for normal operation of spacecraft. Given thermal radiation is the only means of heat dissipation in space, an efficient thermal control approach for spacecraft is to coat the radiator with a tunable-emittance “skin” that can tune its heat dissipation according to various thermal conditions. The existing schemes solely relying on far-field thermal radiation, which are based on mechanical, electrochromic or thermochromic working principles, are difficult to combine the advantages of all-solid-state structure, actively and accurate tuning, and large tuning range of heat flux. In this work, we propose a near-field radiation assisted (NFRA) smart skin for thermal control which can tune the heat rejection accurately and in a large range. It contains a metal-insulator-semiconductor (MIS) structure, where the carrier distribution in the semiconductor layer can be electrically altered. In this way, the near-field heat flux, and ultimately the skin emission power expressed using effective emittance, can be controlled as a function of the applied voltage. The variation range of the effective emittance can exceed 0.7 when adjusting the applied voltage from −10 V to 100 V with our preliminary design. This work opens a new way of smart skin design for active spacecraft thermal control.

Laser-assisted grinding of reaction-bonded SiC

The article presents the development of a novel laser-assisted grinding (LAG) process to reduce surface roughness and subsurface damage in grinding reaction-bonded silicon carbide (RB-SiC). A thermal control approach is proposed to facilitate the process development, in which a two-temperature model (TTM) is applied to control the required laser power to thermal softening of RB-SiC prior to the grinding operation without melting the workpiece or leaving undesirable microstructural alteration. Fourier’s law is adopted to obtain the thermal gradient for verification. An experimental comparison of conventional grinding and LAG shows significant reduction of machined surface roughness (37%–40%) and depth of subsurface damage layer (22%–50.6%) using the thermal control approach under the same grinding conditions. It also shows high specific grinding energy 1.5 times that in conventional grinding at the same depth of cut, which accounts for the reduction of subsurface damage as it provides enough energy to promote ductile-regime material removal.

Self-adapting J-type air-based battery thermal management system via model predictive control

Battery thermal control plays an indispensable role in terms of the safety and performance for electric vehicles. For air-based cooling technologies, one of the most pressing challenges is to balance the temperature uniformity and constrain the maximum temperature simultaneously under varying driving conditions. This paper proposes a self-adaptive intelligent neural network-based model predictive control strategy for a J-type air-based battery thermal management system. The J-type structure is first optimized through surrogate-based optimization to improve the temperature uniformity before control. Based on the optimized J-type configuration, an operation mode switching module is developed to mitigate the temperature unbalance. The thermal control approach is tested using an integrated driving cycle, and its evaluations are threefold: (i) the neural network-based control without mode switching fails to meet the thermal requirements; (ii) the control with mode switching succeeds in constraining the maximum temperature and maintaining the temperature uniformity within 1.33 K; (iii) the added model predictive control approach slightly enhances the thermal performance but improves the energy efficiency significantly by 15.8%. The results show that the J-type structure with its appropriate control strategy is a promising solution for light-duty electric vehicles using an air-cooling technology.

Analysis on thermal control approach for a bare shaft of rudder in a hypersonic vehicle

A 5 mm-wide gap of a shaft connected to the rudder in a hypersonic vehicle is exposed without any heat insulation bearing serious aerodynamic heating. A new thermal control approach combining CO2 flow forced convection in the central inner channel with copper-plating on the outer surface is proposed to prevent the temperature of the gap from exceeding the material’s highest tolerance temperature. Based on the integrated thermal management, CO2 first cools the electronic equipment after being gasified from a high-pressure cylinder, and then moves into the shaft for active thermal control. The thermal control performance is simulated, and the results show the proposed method could satisfy with the thermal control requirements, however, the thermal control requirements could not be fulfilled if the forced CO2 flow convection or the copper-plating was used alone. The mass penalty was estimated within a weight of 11 kg which is quite feasible for engineering applications.

Thermal effects of planar high temperature heat pipes in solid oxide cell stacks operated with internal methane reforming

The presented paper contributes to developing a new thermal control approach for solid oxide cell (SOC) stacks and systems. Integrating planar liquid metal heat pipes to the interconnector structure of the stacks targets a reduction of internal temperature gradients and an enhanced heat extraction from the stack. This work applies 3-D CFD-modelling to discuss the thermal effects of integrated heat pipes in solid oxide cell stacks, in order to evaluate the possible benefits in terms of temperature gradient reduction and heat removal as well as the resulting benefits for stacks and systems. The stack model set-up is described and its functioning is validated with experimental results from thermal short stack measurements with integrated heat pipe interconnectors. The simulation results are discussed with respect to the possible benefits for full-scale stacks of different cell size, in particular regarding internal heat recycling and the beneficial reduction of air ratios.

Hardware-in-the-Loop Validation of Advanced Fuel Thermal Management Control

As a result of increasing aircraft electrification and power density requirements, the development of advanced aircraft thermal management strategies has been identified as a critical research area to support next-generation platforms. To facilitate the validation and evaluation of thermal management strategies, this paper presents results from an experimental testbed that is representative of an aircraft fuel thermal management system. Validation of physics-based models with experimental data demonstrates the ability to accurately capture relevant system dynamics via first-principles modeling. These models can be used to represent the plant in simulation for rapid system analysis and control evaluation and can be embedded in model-based control designs. Two thermal management control approaches are experimentally applied on the testbed: one that is purely reactive, and one that uses knowledge of the vehicle mission to proactively prepare for upcoming disturbances. The proactive approach is applied both with exact knowledge of the upcoming mission loads and with errors in timing and magnitude between the predicted and true loads. Hardware-in-the-loop implementation of these control approaches demonstrates that the proactive approach exhibits superior performance in maintaining temperature constraints as compared to the reactive approach.

Thermal analysis of multifunctional structural battery for satellite applications

Multifunctional structures combine multiple functionalities in a single structural part in order to increase performance while limiting mass and volume. Conventional satellite batteries are designed separately as a stand-alone subsystem then added to satellite host structure in the last assembly, bringing assistant containers and connectors etc. that often cause undesirable mass loading effects and consume valuable space. Power subsystem and then the whole satellite can benefit from the introduction of multi-functionality as a means of improving overall system efficiency. This paper presents the investigation of a new multifunctional structural battery (MFSB) consisting of energy storage, energy supply, and load bearing ability in a single composite structural panel for satellite applications. Thermal vacuum testing (TVT) was carried out and transient thermal analysis was performed, and the results demonstrated that the current material formula and workmanship are viable in the space. When mounted within satellites as an equipment-panel, the designed MFSB panel can keep itself retaining the required operational temperature without supplementary thermal control approaches.

An equivalent ground thermal test method for single-phase fluid loop space radiator

Thermal vacuum test is widely used for the ground validation of spacecraft thermal control system. However, the conduction and convection can be simulated in normal ground pressure environment completely. By the employment of pumped fluid loops’ thermal control technology on spacecraft, conduction and convection become the main heat transfer behavior between radiator and inside cabin. As long as the heat transfer behavior between radiator and outer space can be equivalently simulated in normal pressure, the thermal vacuum test can be substituted by the normal ground pressure thermal test. In this paper, an equivalent normal pressure thermal test method for the spacecraft single-phase fluid loop radiator is proposed. The heat radiation between radiator and outer space has been equivalently simulated by combination of a group of refrigerators and thermal electrical cooler (TEC) array. By adjusting the heat rejection of each device, the relationship between heat flux and surface temperature of the radiator can be maintained. To verify this method, a validating system has been built up and the experiments have been carried out. The results indicate that the proposed equivalent ground thermal test method can simulate the heat rejection performance of radiator correctly and the temperature error between in-orbit theory value and experiment result of the radiator is less than 0.5°C, except for the equipment startup period. This provides a potential method for the thermal test of space systems especially for extra-large spacecraft which employs single-phase fluid loop radiator as thermal control approach.

Online thermal control methods for multiprocessor systems

With technological advances, the number of cores integrated on a chip is increasing. This in turn is leading to thermal constraints and thermal design challenges. Temperature gradients and hotspots not only affect the performance of the system but also lead to unreliable circuit operation and affect the lifetime of the chip. Meeting temperature constraints and reducing hotspots are critical for achieving reliable and efficient operation of complex multi-core systems. In this article, we analyze the use of four of the most promising families of online control techniques for thermal management of multiprocessors system-on-chip (MPSoC). In particular, in our exploration, we aim at achieving an online smooth thermal control action that minimizes the performance loss as well as the computational and hardware overhead of embedding a thermal management system inside the MPSoC. The definition of the optimization problem to tackle in this work considers the thermal profile of the system, its evolution over time, and current time-varying workload requirements. Thus, this problem is formulated as a finite-horizon optimal control problem, and we analyze the control features of different online thermal control approaches. In addition, we implemented the policies on an MPSoC hardware simulation platform and performed experiments on a cycle-accurate model of the eight-core Niagara multi-core architecture using benchmarks ranging from Web-accessing to playing multimedia. Results show different trade-offs among the analyzed techniques regarding the thermal profile, the frequency setting, the power consumption, and the implementation complexity.

Thermal control of shape memory alloy artificial anal sphincters for completeimplantation

This paper presents an approach for the thermal control of an artificial anal sphincterusing shape memory alloys. An artificial anal sphincter has been proposed by theauthors to resolve problems of severe fecal incontinence in patients. The basicdesign of the artificial sphincter consists of two all-round shape memory alloyplates as the main functional parts, and heaters that are attached to the SMAplates for generating the thermal cycles required for the phase transformationaccompanied shape changes of the plates. The SMA artificial sphincter could be fittedaround intestines, performing an occlusion function at body temperature and arelease function upon heating. Thermal compatibility of such prostheses is mostimportant and is critical for practical use. Since a temperature rise of approximately20 °C from body temperature is needed to activate a complete transformation of SMA plates, anearlier model of ours allowed only a short period of heating, resulting in incompleteevacuation. In this work, a thermal control approach using a temperature-responsive reedswitch has been incorporated into the device to prevent the SMA plates fromoverheating. Then, with thermal insulation the artificial anal sphincter is expected toallow a long enough opening period for fecal continence; without any thermalimpact to the surrounding tissues that would be in contact with the artificialsphincter. Thermal control was confirmed in both in vitro and in vivo experiments,suggesting the effectiveness of the present approach. The modified SMA artificialanal sphincter has been implanted into animal models for chronic experimentsof up to 4 weeks, and has exhibited good performance by maintaining occlusionand release functions. At autopsy, no anomaly due to thermal impact was foundon the surfaces of intestines that had been in contact with the artificial analsphincter.