Loop Thermal Control Research Articles

Dynamic verification of an optimisation algorithm for power dispatch of integrated energy systems

The urgent need to achieve net-zero carbon emissions by 2050 has led to a growing focus on innovative approaches to producing, storing, and consuming energy. Integrated energy systems (IES) have emerged as a promising solution, capitalising on synergies between energy networks and enhancing efficiency. Such a holistic approach enables the integration of renewable energy sources and flexibility provision from one energy network to another, reducing emissions while facilitating strategies for operational optimisation of energy systems. However, emphasis has been mostly made on steady-state methodologies, with a dynamic verification of the optimal solutions not given sufficient attention. To contribute towards bridging this research gap, a methodology to verify the outcomes of an optimisation algorithm is presented in this paper. The methodology has been applied to assess the operation of a civic building in the UK dedicated to health services. This has been done making use of real energy demand data. Optimisation is aimed at improving power dispatch of the energy system by minimising operational costs and carbon emissions. To quantify potential discrepancies in power flows and operational costs obtained from the optimisation, a dynamic model of the IES that better captures real-world system operation is employed. By incorporating slow transients of thermal systems, control loops, and non-linearity of components in the dynamic model, often overlooked in traditional optimisation modules, the methodology provides a more accurate assessment of energy consumption and operational costs. The effectiveness of the methodology is assessed through model-in-the-loop co-simulations between MATLAB/Simulink and Apros alongside a series of scenarios. Results indicate significant discrepancies in power flows and operational costs between the optimisation and the dynamic model. These findings illustrate potential limitations of conventional operational optimisation modules in addressing real-world complexities, emphasising the significance of dynamic verification methods for informed energy management and decision-planning.

Numerical investigation on thermal performance of thermoelectric-cooler integrated cold plate of thermal control liquid loop in spacecraft

The traditional single-phase fluid loop (SFL) and traditioanl thermal control algorithm can barely control the temperature rapidly. Thermoelectric cooler (TEC) has been proved to be a good thermal controller because of its high reliability, liquid-free characteristics, and fast response. This paper proposes a TEC-based precooling module that resides in front of the cold plate (CP), and consists of a TEC-CP system, manifesting a high compatibility between the novel precooling module and traditional SFL. The TEC-CP system was designed, and a mathematical model of heat and mass transfer was developed to numerically investigate the effects of the geometric parameters, TEC operating conditions, and liquid cooling states of the precooling module upon payload thermal performance. Through analysis, an optimal TEC-based precooling module with optimal geometric dimensions was attained, where the coolant temperature was decreased by 13.04 K, resulting in a 28.98% reduction compared to that without the precooling module. Transient results also demonstrate that the temperature response time can be within 3 min, indicating a fast response system for temperature control. Results outlined in this paper provide structural and data references for future designs of scientific rack-level thermal control loops in space stations.

Study on Limit Margin of Rising and Cooling Rate in Primary Circuit of CPR1000 Unit

The thermal conductivity of waste heat removal system of CPR1000 unit is analyzed, and the rate margin of primary circuit is studied. In this study, the design parameters of a domestic CPR1000 residual heat removal system are used to study the primary loop temperature margin according to the different core states, and the primary loop temperature margin according to the different valve openings of the residual heat removal system (RRA) . The results show that the CPR1000 unit has a large margin in cooling down, but there is no room for improvement in the process of heating up. Therefore, it is necessary for CPR1000 unit to enhance the effect of primary loop heating and cooling rate on primary loop thermal stress, material and control operation of system equipment.

4 × 25 Gb/s PAM4 optical transmitter for micro‐ring modulator with thermal control

AbstractThe explosive growth of bandwidth demands of data center and super‐computing systems spur the appliance and development of optoelectronic‐based solutions such as micro‐ring modulator (MRM) transmitters, and advanced modulation schemes such as four‐level pulse‐amplitude modulation (PAM4). In this paper, a 4 × 25 Gb/s PAM4 MRM transmitter fabricated in 0.13 μm SiGe BiCMOS technology is presented. It consists of four‐channel MRM driver and thermal control loop. Capacitor and resistor degeneration techniques and inductor peaking techniques are adopted to expand channel bandwidth. Meanwhile, the predistortion technique is utilized to compensate for MRM nonlinearity, and auto gain control (AGC) circuits to enable the MRM driver to realize a fixed differential output swing of 3.5 Vpp. Furthermore, a thermal control method based on analog to digital converter, digital to analog converter, and logic control circuits is proposed to compensate for the temperature sensitivity of MRM. The measurement results show that the 25 Gb/s nonreturn‐to‐zero optical eye achieves an extinction ratio of 5.63 dB, and the PAM4 eye can be observed up to 40 Gb/s.

Research on flow distribution optimization method of fluid loop system based on generalized Lagrange multiplier method

Abstract With the development of space science in China, the scale of space application payloads continues to increase, and the demand for heat dissipation is also gradually increasing. The fluid loop thermal control is a more efficient way of heat dissipation. In order to optimize the heat dissipation effect of the fluid loop system, this paper establishes a thermal model of the fluid loop system and converts it into a constrained optimization problem. The generalized Lagrange multiplier method is used to calculate the optimal flow distribution strategy, and the influence of the weight is analyzed, which provides a reference for the setting of the weight in practical applications.

Development of a novel probe for measuring emissivity and temperature during Raman spectroscopy

Abstract In this work, an innovative tool to perform real-time measurements of emissivity and temperature of a given material surface under CW laser irradiation was developed. In the radiative energy balance, the emissivity represents the complementary component of the reflectance, thus, its measurement can be exploited to calculate the temperature at the target surface from infrared emission measurements provided by a suitable sensor. A miniaturized photothermal sensing line was designed as an accessory of Raman probes for driving thermal control loops in order to prevent overheating during the spectroscopic acquisition. To demonstrate its effectiveness and reliability, it was integrated with in a home-made Raman instrument (exc. 1064 nm) and associated software to achieve an automated online thermal control. Temperature rise during Raman spectroscopy can induce chemical alterations of the material under analysis and seriously affect its original spectral features. In several applications, such photothermal side effects can represent a serious problem to be carefully controlled in order to safeguard the integrity of the material and its spectral fingerprint. A thorough experimentation of the novel tool was carried out on photothermally sensitive materials such as red lead and massicot powders, traditionally used as pigments since ancient times. Finally, the compactness of the components and the fast response time made this system particularly suitable for nondestructive in-situ investigations.

Supporting Simultaneous Air Revitalization and Thermal Control in a Crewed Habitat With Temperate Chlorella vulgaris and Eurythermic Antarctic Chlorophyta.

Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (C. vulgaris, 9–27°C; Chlorophyta-Ant, 4–14°C) and included a constant temperature control (10°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (C. vulgaris; initial: 0.013 mgO2 L–1, final: 3.15 mgO2 L–1 and Chlorophyta-Ant; initial: 0.653 mgO2 L–1, final: 1.03 mgO2 L–1) and culture growth, suggesting environmental acclimation. Antarctic sample conditions exhibited increases or sustainment of oxygen production rates normalized by biomass dry weight, while both C. vulgaris sample conditions decreased oxygen production per biomass. However, even with the temperature-induced reduction, cycled temperature C. vulgaris had a significantly higher normalized oxygen production rate than Antarctic Chlorophyta. Chlorophyll fluorometry measurements showed that the cycled temperature conditions did not overly stress both sample types (FV/FM: 0.6–0.75), but the Antarctic Chlorophyta sample had significantly higher fluorometry readings than its C. vulgaris counterpart (F = 6.26, P < 0.05). The steady state C. vulgaris condition had significantly lower fluorometry readings than all other conditions (FV/FM: 0.34), suggesting a stressed culture. This study compares the results to similar experiments conducted in steady state or diurnally cycled temperature conditions. Recommendations for surface system implementation are based off the presented results. The preliminary findings imply that both C. vulgaris and Antarctic Chlorophyta can withstand the dynamic temperature environment reflective of a thermal control loop and these data can be used for future design models.

Metabolic response of Chlorella vulgaris to a transient thermal environment for supporting simultaneous air revitalization and thermal control in a crewed habitat

Implementing multifunctional bioregenerative technologies may provide mission carbon loop closure while simultaneously addressing multiple environmental control and life support system requirements. This paper proposes using water-based algal medium for thermal control of the spacecraft cabin, while taking advantage of the algae's photosynthetic activity for air revitalization. Consequently, this could expose the algal culture to transient thermal environments fluctuating between +4 °C and +30 °C, in the span of minutes, reflecting the operation of the International Space Station (ISS) internal thermal control and cabin system. This paper presents an initial investigation of the metabolic response of Chlorella vulgaris to transient environmental temperatures, reflecting temperature ranges and cycling frequency of the ISS cooling loop (+9 °C to +27 °C, 30 min). The constant 19 °C control represented the time-averaged temperature of the cycled condition. Growth and acclimation were observed in both tested conditions through pH, dissolved oxygen, optical density, and photosynthetic quantum yield measurements. However, there was significant reduction in the oxygen production rate, measured pH, and optical density for the cycled temperature condition when compared to the control (cycled temperature = 0.95 gO2 L−1 d−1, pH = 6.75, OD = 0.05; control = 1.17 gO2 L−1 d−1, pH = 8.20, OD = 0.08). No significant reduction in growth rate or photosynthetic quantum yield were recorded between the two tested conditions. Growth rate of the cycled temperature condition reflected those of psychrotolerant algae, suggesting some amount of culture acclimation to the rapidly dynamic environment. Results suggest that while C. vulgaris was viable within the tested temperature environment reflecting the ISS thermal control loop and cabin, there was a measurable reduction in the oxygen production rate.

Valve for two-phase fluid loop

Improvement of heat transfer efficiency of the spacecraft thermal control subsystem constitutes a relevant problem for today space industry. Two phase thermal control system presents the most suitable solution for this problem. Implementation of reliable thermal control loop elements constitutes one the major prerequisites for reliability of thermal control systems featuring the operating pressure of 4.8 MPa and ammonia as heat fluid. This paper presents the design and test results of manual valve and fill and drain valve to be operated within the spacecraft two phase thermal control subsystem. The paper provides considerations and detailed description of the technical solutions adopted to ensure compliance with the specification requirements such as operating pressure and plug seat leak tightness under the operating pressure and 160 open/close cycles. Valve plug torque selection criteria are described. The employed design and technical solutions as well as qualification test results have proven that the units designed feature outstanding combination of performances such as leak tightness, life cycle with ammonia as heat fluid.

Electro-thermal therapy: Microsecond duration pulsed electric field tissue ablation with dynamic temperature control algorithms

Electro-thermal therapy (ETT) is a new cancer treatment modality which combines the use of high voltage pulsed electric fields, dynamic energy delivery rates, and closed loop thermal control algorithms to rapidly and reproducibly create focal ablations. This study examines the ablative potential and profile of pulsed electric field treatments delivered in conjunction with precise temperature control algorithms. An ex vivo perfused liver model was utilized to demonstrate the capability of 5000 V 2 μs duration bipolar electrical pulses and dynamic temperature control algorithms to produce ablations. Using a three applicator array, 4 cm ablation zones were created in under 27 min. In this configuration, the algorithms were able to rapidly achieve and maintain temperatures of 80 °C at the tissue-electrode interface. A simplified single applicator and grounding pad approach was used to correlate the measured ablation zones to electric field isocontours in order to determine lethal electric field thresholds of 708 V/cm and 867 V/cm for 45 °C and 60 °C treatments, respectively. These results establish ETT as a viable method for hepatic tumor treatment with ablation profiles equivalent to other energy based techniques. The single applicator and multi-applicator approaches demonstrated may enable the treatment of complex tumor geometries. The flexibility of ETT temperature control yields a malleable intervention which gives clinicians robust control over the ablation modality, treatment time, and safety profile.

Towards a multi-sensor monitoring methodology for AM metallic processes

Additive Manufacturing (AM) is a promising manufacturing technology as compared to subtractive processes, in terms of cost and freedom of manufacturing. Among the AM techniques, Direct Energy Deposition (DED) processes are dedicated to functional metallic parts manufacturing. The energy input can be provided either by laser or electric arc, and having its deposited material as wire or powder form. DED processes incur drawbacks from lack of reproducibility and important production losses, mainly because they are operated in open-loop. Consequently, process monitoring is investigated to control the manufacturing state in real-time and ensure acceptable final parts. Presently, lots of papers have designed single closed-loop controls for DED processes, controlling either thermal, geometrical, or material delivery aspects. Multi-sensors monitoring strategies are also increasingly proposed, as controlling only one criterion has shown some limitations. Nevertheless, the developed multi-sensor strategies still focused on one type of phenomenon—mainly geometry—and have been implemented for only one DED process. This paper presents a new methodology of multi-sensor and multi-physics monitoring dedicated to at least two DED processes. The first investigations focus on a coupling between thermal and geometrical control loops, considering global part’s temperature and layer height for thermal and geometrical aspects respectively. At the end of this paper, perspectives are given for closed-loop corrections according to the precited descriptors. These perspectives will be implemented in further works.

Influences of mass flow rate on heat and mass transfer performances of water sublimator combined with fluid loop

For spacecraft working in vacuum environment, sublimator is an effective heat rejection approach to reject system’s peak heat load, and supplement spacecraft radiation heat rejection. For a spacecraft active fluid loop thermal control system combined with sublimator, waste heat generated from multi-point distributed heat sources could be collected by the fluid loop efficiently. However, the heat and mass transfer performances of the sublimator combined with fluid loop have not been adequately studied in previous research, especially for the influences of the heat load. Since work fluid mass flow rate is the main factor affecting heat load of the fluid loop, this context experimentally studied influences of the fluid loop mass flow rate on sublimator start-up transient characteristics, including heat transfer performances, response time, and work stability. Results indicated that the fluid loop mass flow rate affected the sublimator heat and mass transfer performances obviously, but the heat rejection ability is not always increase with the increasing of the fluid loop mass flow rate. In addition, we obtained the condition to judge whether there is a positive correlation between heat rejection ability and fluid loop mass flow rate.

열진공 챔버용 폐회로 열제어시스템 설계 및 성능평가

A closed loop thermal control system simulates space thermal environment to verify the satellites` functionality in extremely cold/hot temperature. It is composed of a cryogenic blower, thermal shroud, heater, cryogenic valves. This paper presents an overview of closed loop thermal control system`s design parameter and test results for control parameter. A capacity of blower is calculated through energy balance equation and an advantage/disadvantage for a shroud material and a type was analysed. The thermal control system is controlled by a constant density of fluid in the system. A requested performance of closed loop thermal control system was verified by measuring a homogeneity and stability of shroud through control parameter such as density and RPM of blower.

A Fully Integrated Oven Controlled Microelectromechanical Oscillator—Part II: Characterization and Measurement

This paper, the second of two parts, reports the measurement and characterization of a fully integrated oven controlled microelectromechanical oscillator (OCMO). The OCMO takes advantage of high thermal isolation and monolithic integration of both aluminum nitride (AlN) micromechanical resonators and electronic circuitry to thermally stabilize or ovenize all the components that comprise an oscillator. Operation at microscale sizes allows implementation of high thermal resistance platform supports that enable thermal stabilization at very low-power levels when compared with the state-of-the-art oven controlled crystal oscillators. A prototype OCMO has been demonstrated with a measured temperature stability of -1.2 ppb/°C, over the commercial temperature range while using tens of milliwatts of supply power and with a volume of 2.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (not including the printed circuit board-based thermal control loop). In addition, due to its small thermal time constant, the thermal compensation loop can maintain stability during fast thermal transients (>10 °C/min). This new technology has resulted in a new paradigm in terms of power, size, and warm up time for high thermal stability oscillators.

열진공 챔버용 극저온 블로워 설계 및 성능평가

위성체의 지상 검증 시험에는 열진공 챔버가 사용되며, 열제어 시스템은 열진공 챔버의 핵심이라고 할 수 있다. 특히, 기체 질소를 이용한 폐회로 열제어 시스템의 성능은 극저온 블로워의 성능에 의해 결정된다. 본 연구의 최종 목표는 설계 요구조건 <TEX>$-150^{\circ}C{\sim}150^{\circ}C$</TEX>의 온도 조건, 유량 150 CFM, 0.5 bara 이상의 차압을 갖는 극저온 블로워를 개발하는 것으로, 1차원 해석툴 및 CFD를 이용한 성능해석을 통해 임펠러를 설계 하였으며, 구동부와 유체부의 열전달 방지를 위한 열장벽, 모터의 과열 방지를 위한 냉각 시스템 등이 설계되었다. 표준대기상태에서 실험을 통해 성능을 검증하였으며, 최종적으로 열진공 챔버내에 설치하여 운영 조건에서 극저온 블로워의 성능을 확인하였다. Thermal vacuum test should be performed prior to launch to verify satellites' functionality in extremely cold/hot temperatures and vacuum conditions. A thermal vacuum chamber used to perform the thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the gaseous nitrogen (GN2) closed loop thermal control system for thermal vacuum chambers. A final goal of this research is development of cryogenic blower. Design requirements of a blower are 150 CFM flow rate, 0.5 bara pressure difference, hot and cold temperatures. This paper describes the performance analysis of impeller by 1D, CFD commercial software, the design of the thermal protection interface between the driving part and the fluid part. The performance of the cryogenic blower is confirmed by test at the standard air condition and is verified by on the thermal vacuum chamber at the real operating condition.

Inhibition of Rayleigh-Bénard convection via oscillatory acceleration

The ability to dynamically stabilize Rayleigh-Bénard convection by imposition of sinusoidal acceleration is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the machine. These performance issues, tentatively attributed to convective instability, have been observed both in traveling wave thermoacoustic refrigerators and in pulse tube cryocoolers. This presentation discusses an ongoing experiment designed to determine the vibratory conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, to test the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135(2), 654–668 (2014)]. Measurement methods developed to determine the onset and inhibition of convection will be discussed. These include the measurement of heat transport employing a feedback thermal control loop and direct optical observation using a lightsheet produced by a laser diode source illuminating seeded particles. Preliminary results in both the static and vibratory conditions will be presented. [Work supported by the ARL Walker Graduate Assistantship, the Office of Naval Research, and ARPA-E.]

Mechanical characterisation of Duraform® Flex for FEA hyperelastic material modelling

Laser Sintering (LS) is widely accepted as a leading additive manufacturing process with a proven capability for manufacturing complex lattice structures using a group of specially developed powder based materials. However, to date, very little research has been directed towards achieving greater knowledge of the properties of the elastomeric materials that can be used to produce energy absorbent items such as personalised sports helmets and running shoes via the LS technique. This paper will contribute to addressing this knowledge gap by examining the material properties and characteristics of Duraform® Flex, a commercially available elastomeric material used for such LS applications.A 3D Systems HiQ machine fitted with a closed loop thermal control system was employed, together with a number of the advanced processing options available in the operating software. In order to measure the mechanical properties of this material, sets of ISO standard tensile test specimens were fabricated, employing a range of different manufacturing processing parameters. The result shows that varying key LS processing parameters such as powder bed temperature, laser power and the number of scanning exposures has a significant impact on the mechanical properties of the resulting part, including its ultimate strength and elongation at break. As LS is a layer manufacturing process, part properties are found to vary considerably between the horizontal (X-Y) and vertical (Z) build orientations.The paper demonstrates how the measured tensile stress-strain curve can be transformed into appropriate hyperelastic material models employing the data curve fitting process in PTC Creo 2.0 Simulate software, and how these material models can be used practically to match user requirements for the laser sintered parts, leading to design optimisation for both bulky solid and lightweight lattice components. The paper concludes with a discussion examining the potential future direction of the research.

우주 열환경 모사용 소형 극저온 블로워 설계 및 성능평가

Thermal vacuum test should be performed prior to launch to verify satellites` functionality in a harsh space environment which is represented by extremely cold temperatures and vacuum conditions. A thermal vacuum chamber which consists of a vacuum vessel, a pumping system, and a thermal control system are used to perform thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the closed loop thermal control system for thermal vacuum chambers. This paper describes the fan design of the cryogenic blower, the design of the thermal protection interface between the driving part and the fluid part, which were verified by thermal and structural analyses. The performance of the cryogenic blower is confirmed by similarity test on the test bench.

Dynamic Properties of the Two-phase Loop Thermal Control System for Space Application

针对两种典型的两相环路热控系统——毛细力驱动的平板型环路热管和机械泵驱动的两相环路热控系统(硅微条探测器控温系统, TTCS)展开讨论, 分析其工作原理, 介绍地面测试实验系统, 使用SINDA/FLUINT和Maltab/Simulink软件分别建立其动态模型. 研究结果表明, 平板型环路热管和TTCS均存在启动问题; 平板型环路热管运行时可能有较严重的稳定性问题, 而TTCS的稳定性相对较高; 重力对平板型环路热管的性能有较大影响, TTCS受重力的影响不大; 双通道平板型环路热管可以比单通道环路平板型环路热管有更优异的传热性能, 而TTCS的双辐射器结构可以有良好的流量和热量自调节能力. 在选择两相环路热控系统时, 需考虑热源的分布特点、寿命要求、控温要求以及系统尺寸和质量等因素, 这两种两相热控技术未来可交叉借鉴、优势互补.

Simultaneous thermal and timeliness guarantees in distributed real-time embedded systems

Distributed real-time embedded systems have stringent requirements for key performance properties, such as end-to-end timeliness and reliability, in order to operate properly. In recent years, with the continuously decreasing feature size and increasing demand for computation capabilities, today's real-time embedded systems face an increasing probability of overheating and even thermal failures. As a result, their temperature must be explicitly controlled for improved reliability. While a variety of control algorithms have been proposed for either real-time guarantees or thermal management in an isolated manner, this paper proposes a coordinated control solution that can provide simultaneous thermal and timeliness guarantees for distributed real-time embedded systems running in unpredictable environments. To achieve desired control functions for different generations of processors, our control solution includes two thermal controllers that are designed for processors with and without DVFS support, respectively. In addition, a novel coordination design is proposed to allow the thermal and timeliness control loops to run on their respective desired small timescales for prompt control actions and yet achieve theoretically guaranteed control accuracy and system stability. We implement our control solution in a real system and present empirical results to show that our solution provides dynamic thermal and timeliness guarantees simultaneously. Our simulation results also demonstrate the efficacy of our control solution in large-scale real-time systems.