Shield Temperature Research Articles

Thermomechanical optimization of actively cooled thermal shield in PIP II Cryogenic Distribution System

The PIP-II Cryogenic Distribution System (CDS) connects the cryogenic plant to the superconducting linac consisting of 23 modules. The helium stream flow through the PIP-II CDS is regulated by means of control valves located in the Distribution Valve Box. The cryomodules are supplied with helium from individual Bayonet Cans. The entire CDS process lines are shielded from the thermal radiation from the ambient vacuum jacket by actively cooled thermal shields. High efficiency of the thermal shield has been achieved by state-of-the-art optimization of its thermalization system consisting of thermal bridges connecting the shield to the high temperature helium return pipe nominally at 80 K. The temperature and stress analyses of the thermal shield have been performed numerically. The results obtained for the thermal shield of the PIP-II CDS Distribution Valve Box are compared with the solutions applied in other large science machines.

Low-noise thermal shielding around the cryogenic payloads in the Einstein Telescope

The Einstein Telescope (ET) is a planned third-generation gravitational-wave detector that includes a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF is imperative for exploiting the full scientific potential of ET, with mirrors operated at temperatures of 10 K to 20 K in order to reduce the thermal noise. Thermal shielding around the optics is essential to support the cooldown process and to decrease the heat load. Additionally in steady-state operation, mechanical vibrations must be kept to an absolute minimum in order to limit noise contributions from scattered light.We present a cooling concept for a thermal shield surrounding the cryogenic optics of ET-LF, which considers rapid cooldown and low vibration in steady-state operation. During cooldown, cooling tubes enable the flow of supercritical helium, driving the shield temperature decrease by forced convection. For steady-state operation, the shield cooling mechanism is converted to static heat conduction in He-II within the same tubes. A first mechanical model is presented that fulfills the thermal and vibrational requirements. Thermal characteristics of the shield are demonstrated by means of analytical and numerical modeling results. Modal and dynamic analyses are performed to obtain natural frequencies and transfer functions.

Numerical study on the influence of turbine swirl on exhaust system

This article employed numerical methods to investigate the aerodynamic, thermal, and infrared characteristics of last-stage turbine swirl on a two-dimensional convergent divergent (2D-CD) exhaust system with an afterburner under varying bypass ratios. The research results indicate that the swirl diminishes the thrust coefficient and flow coefficient of the 2D-CD exhaust system with an afterburner. At a bypass ratio of 0.2, the thrust coefficient and flow coefficient decrease by 0.65% and 1.07%, respectively. When the bypass ratio is relatively small, the swirl flow leads to a decrease in the temperature of the afterburner heat shield. Conversely, when the bypass ratio is relatively large, the opposite occurs. The maximum temperature of the heat shield increases by up to 7.2% (bypass ratio = 0.35), while the average temperature decreases by up to 7.1% (bypass ratio = 0.2). The swirl causes an increase in the temperature of the divergent section heat shield, with the most significant deterioration observed at a bypass ratio of 0.25, resulting in a maximum temperature increase in 12.2%. Swirling flow shortens the length of the jet flow, and as the bypass ratio reduces, this attenuation effect becomes more pronounced. When the bypass ratio is 0.2, the length of the core area decreases by 40.3%, and the infrared intensity of the narrow-side jet flow decreases by 12.5%. Overall, on the XOY detection plane, the maximum decrease in infrared intensity is 11.5%, and the maximum increase is 11.7%. On the XOZ detection plane, the maximum decrease in infrared intensity is 15.9%, and the maximum increase is 5.7%.

Improved Surface Temperature Identification Method for Remote Observations of Sample Return Capsules

A new method for the identification of the peak temperature of the heat shield based on remote spectral irradiance measurements is proposed and tested through the analysis of results from the Hayabusa sample return capsule. To identify the peak temperature of the heat shield, a parameterized empirical model for the surface temperature distribution on the geometry is developed, and it is then used to simulate spectra for optimized fitting with a measured spectral radiance. This new peak temperature identification method is shown to be insensitive to the wavelengths resolved, the view of the geometry, and measurement noise. The peak temperature of the Hayabusa capsule geometry at the representative condition considered (3330 K) was resolved to within 20 K for the three instruments investigated, while the effective temperature varied by around 600 K depending on which instrument was used. The error in the peak temperature model is also shown to be an order of magnitude less sensitive to measurement noise than the effective temperature approach. The new peak temperature method facilitates the direct comparison of results from instruments with different bandwidths and/or different view angles of the capsule, which was previously not possible.

Numerical study of an infrared suppression (IRS) device with cooling hole configuration on the mixing tube

Hot walls of the infrared suppression (IRS) device intensify the infrared signature of warships, which is detrimental for attaining infrared stealth. In this work, to effectively reduce the wall temperature, hole cooling technology is innovatively adopted on a marine IRS device. Circular holes are arranged on the mixing tube of the device. Numerical simulations are conducted to predict the temperature and flow distribution. The current research comprehensively analyzes the effects of hole position, number of hole rows, and number of holes on the wall temperature of the mixing tube and heat shield. The air suction rate and the exit temperature of the whole device are considered as well. The results indicate that the air suction and exit temperature of the device do not significantly change with the hole arrangement parameters. As the hole position moves towards the mixing tube outlet, the average temperature of the mixing tube continuously increases, while the maximum temperature of the mixing tube exhibits a peak-and-valley pattern. When the holes with large diameters are located near the mixing tube inlet, a backflow occurs between the mixing tube and the heat shield, causing the heat shield temperature to rise appreciably. Increasing the number of hole rows can reduce the mixing tube temperature, but excessive hole rows lead to an elevation in the heat shield temperature. The optimal configuration for the number of hole rows is found to be 2 with a hole diameter of 80 mm. With the increment in hole number, the average temperature of the mixing tube rises due to the accelerated disappearance of the streamwise vortices behind the holes; however, the maximum temperature of the mixing tube shows a decreasing-then-increasing trend owing to that more streamwise vortices are created. This study paves the way for the practical application of hole cooling technology on marine IRS devices. The findings can provide instructive suggestions for the arrangement of cooling holes.

Stress relaxation and thermal management in highly filled flexible styrene butadiene styrene copolymer‐tungsten composites for high‐energy radiation attenuation

AbstractA high loading of high‐density and high‐atomic‐number fillers are necessary to obtain desirable X‐ray attenuation characteristics from radiation shields. However, at high filler loadings, the mechanical and viscoelastic properties of polymers are severely impaired, posing a long‐term threat to the mechanical integrity and radiation protection, and the radiation shield temperature may increase after prolonged exposure to ionizing radiation, accelerating the aging of the polymer matrix. In addition, inadequate thermal conduction can make the user uncomfortable while using radiation shields for personal protection. Unfortunately, little attention has been paid to the viscoelastic, stress relaxation, and thermal conductivity‐related features of these densely loaded systems, despite the significant effect of these parameters on long‐term applications and user compliance. In the present work, two different styrene butadiene styrene (SBS) copolymers were used to develop SBS‐tungsten (W) composites. At 500 phr W loading, significant attenuation of X‐rays was achieved along with good tensile strength and elongation at break. The results indicate that the concentration of styrene in the SBS and W loading substantially affected the attenuation, mechanical and rheological properties, and tensile stress relaxation rates. The thermal conductivity increased by >100%, and after gamma irradiation, faster cooling was observed in the W‐loaded composites beyond 300 phr of W loading. The 40% styrene composite demonstrated superior heat transfer at high W loadings owing to the better dispersion and distribution of the W filler in the SBS matrix. Rheological results showed that SBS‐W composites with 30% styrene had a more pronounced Payne effect than those with 40% styrene. Stress relaxation and morphological analyses also revealed changes in the W dispersion in the SBS matrix depending on the styrene content.

Multiple strategies for evaluating the uncertainty of blackbody radiation frequency shift in an optical clock

The Stark shift due to the blackbody radiation (BBR) is a crucial obstacle limiting the performance of optical clocks. Here five different methods are reported to evaluate an ytterbium (Yb) clock’s BBR shift in the same science chamber for the first time. The intercomparison shows that incorporating in-chamber temperature information can reduce the uncertainty by one order of magnitude. Notably, a simulation model is developed and optimized through calibration with in-chamber sensors, which can suppress the BBR uncertainty close to 1 × 10−18 at room temperature and provide more credible results. Moreover, the 10−19 level uncertainty is further identified by surrounding the atoms in the cryogenic environment. It is worth noting that the above results were obtained without BBR shield and external temperature control. These comprehensive evaluation results provide a valuable reference for different uncertainty requirements or building advanced optical clocks towards total uncertainty in the 10−19 region.

Heat Transfer Performance Analysis of End Structures of Large Synchronous Condenser Based on Deep Forest Prediction Model

This paper presents a three-dimensional fluid-solid coupling heat transfer model of the end domain of a synchronous condenser. The temperature of the end structures and the flow distribution of the cooling medium were analysed. The highest temperature point of the structural part was explored, and the influence rule of the properties of the cooling medium on the temperature of the end structures of the condenser were analysed in detail. Based on the deep forest prediction model (DFPM), an accurate prediction of the temperature of the copper shield, far finger plates, clamping plate and stator end winding insulation was obtained by selecting a cooling medium and a heat-conducting medium with different properties. Comparing the predicted temperature data of the end structural parts with the finite element simulation results, the difference is minor. In addition, by measuring the temperature of the inner edge of the copper shield, the simulation results are in agreement with the measurement results, confirming the accuracy of the proposed model. The presented model can replace the complex simulation and can be considered an interesting reference for selecting the cooling scheme.

Design and Backdrivability Modeling of a Portable High Torque Robotic Knee Prosthesis With Intrinsic Compliance For Agile Activities.

High-performance prostheses are crucial to enable versatile activities like walking, squatting, and running for lower extremity amputees. State-of-the-art prostheses are either not powerful enough to support demanding activities or have low compliance (low backdrivability) due to the use of high speed ratio transmission. Besides speed ratio, gearbox design is also crucial to the compliance of wearable robots, but its role is typically ignored in the design process. This paper proposed an analytical backdrive torque model that accurately estimate the backdrive torque from both motor and transmission to inform the robot design. Following this model, this paper also proposed methods for gear transmission design to improve compliance by reducing inertia of the knee prosthesis. We developed a knee prosthesis using a high torque actuator (built-in 9:1 planetary gear) with a customized 4:1 low-inertia planetary gearbox. Benchtop experiments show the backdrive torque model is accurate and proposed prosthesis can produce 200 Nm high peak torque (shield temperature <60°C), high compliance (2.6 Nm backdrive torque), and high control accuracy (2.7/8.1/1.7 Nm RMS tracking errors for 1.25 m/s walking, 2 m/s running, and 0.25 Hz squatting, that are 5.4%/4.1%/1.4% of desired peak torques). Three able-bodied subject experiments showed our prosthesis could support agile and high-demanding activities.

Study on room-temperature effect of a superconducting gravimeter prototype

PurposeThis study aims to reveal the room-temperature effect of a superconducting gravimeter prototype, which will guide its subsequent optimization to improve its gravimetric measurement accuracy.Design/methodology/approachWithout leveling, the prototype output signal, tilt data and room temperature were measured under steady operating conditions. After analyzing the correlations of the three data sets, the residuals of the prototype’s output signal were compensated using the tilt data and the geodynamic effects (ocean tide loading, atmospheric loading and the gravitational effect of polar motion) were then corrected.FindingsThe remaining residuals after correction may be caused by small tilt variations that are due to the sensor chamber temperature and radiation shield temperature changes. These small tilt variations were submerged in the tilt signal noise. Although the peak-to-peak noise of the tiltmeter does not exceed 15 µrad, it can still produce gravimetric deviations above 60 µGal when the prototype is significantly tilted.Originality/valueThis study analyzes in detail the room-temperature effect of a superconducting gravimeter prototype, introduces the tilt effect of the relative gravimeters to compensate for the gravimetric deviations and emphasizes that the improvement of fine leveling and the accuracy of the tiltmeter are key requirements for the prototype to perform high-accuracy gravity measurement tasks.

Experiment investigation of impingement/effusion cooling on overall cooling effectiveness and temperature gradients of afterburner heat shields in a high-performance aircraft engine

Considering that the jet impingement cooling method applied to the combustion chamber and turbine blade has a beneficial effect on the cooling performance, the impingement/effusion cooling was applied in the afterburner heat shield (DCH) to improve the reliability and durability of the afterburner cylinder. Although the impingement/effusion cooling scheme has been numerously investigated on the internal heat transfer, its investigation of conjugated heat transfer characteristics is limited as applying in the afterburner heat shield. This paper aims to investigate the effects of adding array impingement and area ratio on the conjugate heat transfer of afterburner heat shield. The surface temperatures on the mainstream side of DCH in the upstream (UR), midstream (MR), and downstream (DR) regions were measured using IR thermography under a high-temperature ratio between mainstream and coolant (Tg/Tc = 2). The overall cooling effectiveness (ϕ) and temperature uniformity (RSD) were plenty compared with the single-layer effusion cooling heat shield (ECH) at three momentum flux ratios (I = 0.02,0.22,0.50). Moreover, the area ratio of film to impingement holes (Af/Ai) was enlarged from 1 to 4 to obtain high cooling effectiveness and low-temperature gradient. The results indicate that when I is larger than 0.22, the area-averaged ϕ of DCH compared with ECH can be improved by about 16% over the whole measured regions, and 20% in the UR with the lowest ϕ. In addition, the drop coefficient of the RSD of DCH can reach 18%. In comparison with the DCH at Af/Ai = 1, the DCH with an area ratio of 4 can achieve gains of 80% and 45% on ϕ and RSD, respectively. Therefore, adding array impingement on the coolant side of DCH and increasing Af/Ai cannot only effectively reduce the surface temperature of the heat shield and form efficient cooling in the UR, but also increase the temperature uniformity over the entire heat shield, thereby improving the reliability and durability of the afterburner cylinder. Furthermore, the comprehensive and new database can be used to evaluate the computational fluid dynamics simulations in related coupled and decoupled research.

Evaluation of blackbody radiation shift with 2 × 10−18 uncertainty at room temperature for a transportable 40Ca+ optical clock

Blackbody radiation (BBR) temperature and its uncertainty mainly contribute to the BBR shift uncertainty, which is one of the challenges in most ion optical clocks. Here, an improved BBR temperature evaluation method based on the analysis of the effective solid angle of an ion trapping system using the finite element method is presented. To effectively suppress the BBR temperature uncertainty, the structure of an ion trap was optimized to reduce the effective solid angle of the insulating supports, and a BBR shield was employed to reduce the influence of the surrounding BBR in the newly developed ion trap system. Due to radiofrequency field, it is difficult to evaluate the temperature of BBR shield accurately using contact-temperature-sensors inside the vacuum chamber. We used a well shielded platinum resistance temperature sensor to measure the temperature of the shield from the outside of the vacuum chamber. Through a detailed evaluation, the BBR temperature uncertainty of this newly designed system is 0.17 K, corresponding to a BBR frequency shift uncertainty of 2 × 10−18 for the 40Ca+ optical clock. This improvement of the BBR temperature uncertainty using the active adjustment of the distribution of the effective solid angle of the ion trapping system, without a complicated cryogenic trap, is very suitable for transportable optical clocks operating at room temperature (∼295 K).

Thermal analysis of the EAST tokamak

The superconducting magnet of the Experimental Advanced Superconducting Tokamak (EAST) will experience large steady-state and transient heat loads during operation, which is undoubtedly a major challenge for the cryogenic cooling system. The steady-state heat loads are mainly composed of the thermal conduction from the support structure and thermal radiation from the thermal shields. This paper mainly studies the steady-state heat loads of the superconducting magnet system of the EAST tokamak by establishing a dedicated finite element model. The model simulated the influence of thermal shield temperature, emissivity for thermal radiation analysis, and the thermal anchor on the heat transfer of gravity support structure for the heat conduction analysis. The paper presents the analytical results of radiation and conduction heat for the EAST tokamak system. The validation of simplified finite element models compared to the analytical counterparts indicated very small deviations, which demonstrated a high accuracy of the analysis method.

Thermal Effect of Single Loop Shield on High-Voltage Cable Line Capacity

The paper deals with a single-loop shield with an asymmetric magnetic coupling used for a magnetic field mitigation of a high-voltage three-phase cable line. The goal is to evaluate a thermal effect of this shield on a cable line capacity. To calculate the flat cable line capacity in the nonshielded case, we use a standard IEC 60287. To achieve the goal we carry out a numerical simulation of the thermal field when the shield is installed. Wherein, we deal with two specific sections. One is a long section with the shield being distant from the cable line. The other is a relatively short section where the shield is located near the power cables. The thermal field is applied for a long section in a two-dimensional formulation, and a three-dimensional formulation is used for the short section. Hence, we have obtained the dependences of the maximum temperature of the power cables on parameters of the shield and its location height above the cable line. The most significant allowable cross-sections of the shield cable and their location height have been determined, when the thermal effect of the shield does not decrease the cable line capacity. These results have ensured the maximum cable line capacity while shielding. The shield temperature is shown to exceed the allowable level in the short section. To reduce it the thermal backfill has been used. We recommend the values of its thermal resistivity to be used for different parameters of the single-loop shield.

Development and computational fluid dynamics (CFD) simulation of cryostat thermal shielding for a portable high purity germanium (HPGe) gamma spectrometer

The effect of vacuum degradation in cryostat of a gamma spectrometer on the steady-state temperature of thermal shield and its efficiency are analyzed in this study. Considering the thermal load due to radiation, the thermal conductivity of residual gases and shield supports, the steady-state temperature of the shield is determined based on the differential energy balance equation for a simplified thermal model of the cryostat. A more complex model corresponding to the design of a real cryostat is simulated using computational fluid dynamics. The obtained temperature distribution is presented. The simulated results are compared with experimental data measured on an operating cryostat with a cryocooler in the temperature stabilization mode. The same measurements were carried out for a cryostat with and without a thermal shield, as well as with multilayer insulation. The obtained results confirm that the thermal shield provides decreasing heat transfer even for a vacuum degradation in a cryostat.

Performance of Transpiration-Cooled Heat Shields for Reentry Vehicles

This paper presents results of a system study of transpiration-cooled thermal protection systems for Earth reentry. The cooling performance for the sustained hypersonic flight and transient reentry of a blunt cone geometry is assessed. A simplified numerical model is used to calculate the transient temperature of a transpiration-cooled heat shield. The performance of transpiration cooling is assessed by calculating the overall required coolant mass for different steady-state and transient flight scenarios. Spatially and temporally optimized mass injection is presented for various flight conditions. The majority of the injection is required on the spherical nose segment of the blunted cone. Carbon/carbon composite ceramic and the ultra-high-temperature ceramic zirconium diboride are considered as wall materials. Both materials require similar amounts of coolant injection. In continuous hypersonic cruise, transpiration cooling is highly effective for flight conditions with velocities below and altitudes above 40 km. For transient reentry, transpiration cooling is most viable for the trajectories of entry velocities below and ballistic coefficients below .

Thermodynamic optimization of composite insulation system with cold shield for liquid hydrogen zero-boil-off storage

The study of zero-boil-off (ZBO) storage is of great significance for the long-term storage of liquid hydrogen (LH2). Preliminary experimental research on the utilization of cryocooler to achieve ZBO storage has been reported, but the optimization of the total power consumption has barely been considered. This paper will fully consider the working characteristics of the cryocooler, that is, refrigerator efficiency increases with the increase of its working temperature. A novel method to realize the cascade utilization of the cooling power of cryocooler is proposed, which can effectively reduce the total power consumption of ZBO system. A thermodynamic model has been developed to optimize the input power of cryocooler in LH2 ZBO storage with cold shied and multilayer insulation (MLI). Thermal coupling characteristics of cryocooler, cold shield and MLI has been studied at the minimum input power. The mechanism and optimization strategy have been explained quantitatively. By optimizing position and temperature of cold shield, the input power of cryocooler can be reduced by 69.5%–74.4%. In addition, the effects of MLI thickness and boundary temperature on the optimization of the cold shield have been studied. The influence of LH2 pressure in tank on cryocooler input power has also analyzed.

Data Logging Implementation on Web-Based Communication on Arduino Devices

Arduino is one of the microcontroller devices commonly used on the Internet of Things. This research designed and objectified web-based data logging system that aimed to record communication and sensir data in iot devices, so it could monitor log data in iot. Devices from this data logging system was created using arduino uno r3 with adding ethernet shield modul and temperature sensor DHT 11. in iot devices, there is an important parameter, that is date time as a history in data logging sistem using an actual time. Website was functioned as system for showing data from log data and could be monitored realtime. This system could record communication brtween arduino device and NTP server using internet network. Beside that?this system could record important parameters in the system such as IP source address, ip destination address, ip address in each node, device time, and room temperature information. Parameters that had been recorded would be stored to database, then would be showed in web data logging.

Comparison of Conductor-Temperature Calculations Based on Different Radial-Position-Temperature Detections for High-Voltage Power Cable

In this paper, the calculation of the conductor temperature is related to the temperature sensor position in high-voltage power cables and four thermal circuits—based on the temperatures of insulation shield, the center of waterproof compound, the aluminum sheath, and the jacket surface are established to calculate the conductor temperature. To examine the effectiveness of conductor temperature calculations, simulation models based on flow characteristics of the air gap between the waterproof compound and the aluminum are built up, and thermocouples are placed at the four radial positions in a 110 kV cross-linked polyethylene (XLPE) insulated power cable to measure the temperatures of four positions. In measurements, six cases of current heating test under three laying environments, such as duct, water, and backfilled soil were carried out. Both errors of the conductor temperature calculation and the simulation based on the temperature of insulation shield were significantly smaller than others under all laying environments. It is the uncertainty of the thermal resistivity, together with the difference of the initial temperature of each radial position by the solar radiation, which led to the above results. The thermal capacitance of the air has little impact on errors. The thermal resistance of the air gap is the largest error source. Compromising the temperature-estimation accuracy and the insulation-damage risk, the waterproof compound is the recommended sensor position to improve the accuracy of conductor-temperature calculation. When the thermal resistances were calculated correctly, the aluminum sheath is also the recommended sensor position besides the waterproof compound.

Cold Test and Performance Evaluation of Prototype Cryoline-X

The multi-process pipe vacuum jacketed cryolines for the ITER project are probably world’s most complex cryolines in terms of layout, load cases, quality, safety and regulatory requirements. As a risk mitigation plan, design, manufacturing and testing of prototype cryoline (PTCL) was planned before the approval of final design of ITER cryolines. The 29 meter long PTCL consist of 6 process pipes encased by thermal shield inside Outer Vacuum Jacket of DN 600 size and carries cold helium at 4.5 K and 80 K. The global heat load limit was defined as 1.2 W/m at 4.5 K and 4.5 W/m at 80 K. The PTCL-X (PTCL for Group-X cryolines) was specified in detail by ITER-India and designed as well as manufactured by Air Liquide. PTCL-X was installed and tested at cryogenic temperature at ITER-India Cryogenic Laboratory in 2016. The heat load at 4.5 K and 80 K, estimated using enthalpy difference method, was found to be approximately 0.8 W/m at 4.5 K, 4.2 W/m at 80 K, which is well within the defined limits. Thermal shield temperature profile was also found to be satisfactory. Paper summarizes the cold test results of PTCL-X