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Loop heat pipe (LHP) promises great application potential in electronics cooling. However, the selection of environmentally friendly working fluid remains a big issue, especially in commercial applications. Although R134a is a common refrigerant, the R134a-charged LHP is limited by small heat transfer capacity (HTC). In this work, a LHP with R134a as the working fluid is designed and fabricated. In order to enhance its HTC, the structure optimization has been made based on the theoretical analysis of flow resistance where the smaller wick thickness and larger diameter of the vapor and condenser lines are adopted. Experimental results show that the R134a LHP can reach a high HTC up to 250 W at the horizontal orientation with the condenser cooled by air forced convection. With an adverse elevation of 5 cm, the HTC is reduced to about 230 W. In addition, an extensive experimental study on its startup characteristics with the heat loads ranging from 5 to 30 W is conducted. The influence of the initial liquid/vapor distribution in the evaporator on the startup performance is investigated. This work proposes an effective method to enhance the HTC of the R134a LHP, which contributes greatly to its structure optimization and future commercial applications.

Flat-plate loop heat pipe (FLHP) is a passive two-phase heat transfer device. Comparing with traditional LHP with a cylindrical evaporator, it can be directly connected to a flat heat source without the employment of a saddle, which can effectively reduce the system thermal resistance and enhance the temperature uniformity. In this work, a stainless steel-ammonia FLHP was developed, and extensive experiments have been conducted to investigate its startup characteristics with the evaporator in the horizontal and vertical positions. Experimental results show that the FLHP exhibits excellent startup performance. It can successfully start up at a small heat load as low as 2 W with no obvious temperature overshoot. In a wide power range of 5–35 W, the FLHP generally starts up in only one situation, much simpler than the startup of a LHP with a cylindrical evaporator. For this rectangular evaporator, the heat leak from the evaporator to the compensation chamber (CC) becomes very small. As a result, the vapor can easily exit the condenser in most cases in the power range of 5–35 W, leading to a 100% utilization efficiency of the condenser and the resultant satisfactory thermal performance of the FLHP. In addition, the startup performance and the system thermal resistance of the FLHP are insensitive to the evaporator orientation, promising great application potential in future electronics cooling.

Thermal storage technology is becoming more and more significant with the increase of high-power equipment in space applications. In this paper, 3D printing technology and Phase Change Material (PCM) were combined into a Thermal Energy Storage (TES) system, which could fulfill the requirements of light weight and high thermal conductivity. A 3D-printed lattice-structure TES plate with N-tetradecane as the PCM and aluminum alloy as the thermal conductivity enhancer was manufactured, and experimentally tested in a thermal vacuum chamber. In addition, a simplified simulation model of the lattice cell was established to clearly analyze the heat transfer process of the TES plate. The effects of initial temperature distribution and heat load gradient on the thermal storage performances were investigated experimentally and theoretically. The equivalent thermal conductivity of the 3D-printed lattice-structure TES plate turns out to be 13 times of the pure PCM thanks to the aluminum skeleton. The heat transfer enhancement appears at the end of the phase change stage due to the sudden mixture of the PCM with different temperature. The simulation results agree well with the experimental data. The equivalent thermal conductivity obtained by the phase change simulations are a little higher than those of the experiments, which is mainly caused by the initial uneven temperature distribution in the tests. Additionally, the effects of non-uniform heat load and the presence of the PCM in the TES plate are studied. This work successfully validates the feasibility and effectiveness of 3D printing technology and TES technology for the temperature control in space applications.

In this paper, systematic characterization of the dual probe, which is designed for the near field simultaneous measurement of both electric and magnetic field, is investigated with a microstrip line as the device under test (DUT). The characterization includes frequency response, transmission performance, symmetry, reflection, the intrusion of probe to the DUT, isolation of electric and magnetic field responses, field profile and spatial resolution, and differential electric field suppression. The dual probes with different design are adopted to demonstrate the systematic characterization.

Electrostatic discharge (ESD)-induced soft failures are a critical issue for electronic systems as the failures are mostly found after the hardware design is completed. Any changes applied to the hardware may delay the project. Diagnostic tools capable of identifying soft failure-induced malfunctions in an early stage of product design help to reduce the risk of late stage ESD-induced project delays. In many cases, soft failures can be directly observed by the user interface, system crash, or other obvious indicators. However, in an early product design stage the operation system may be marginal and applications may not be available. To improve the ability to detect soft failure critical design choices, this paper presents several methods to identify ESD-induced changes which may not be observable via direct observation. These methods include the observation of ac or dc currents, monitoring dc voltages, capturing near fields and processing them via short-term fast fourier transform (FFT), wavelet transformation, down mixing to audible range, and monitoring for latch-up via thermal imaging. The paper introduces the basis of each method, shows examples, and compares them for their detection ability.

To solve the heat dissipation problem of high heat flux components on spacecraft, experiments were carried out to investigate the flow boiling heat transfer characteristics of ammonia in a microchannel heat sink. Verified by gravity-independent criteria, the experimental results can be used to predict the performance of flow boiling heat transfer in microgravity environment. The heat sink consisted of 37 V-shaped microchannels with hydraulic diameters of 280 μm and channel lengths of 45 mm. Saturated flow boiling experiments were conducted with heat fluxes of 60.2~134.3 W/cm2, mass fluxes of 165~883 kg/m2s and saturation temperatures of 25 and 35 °C, as well as subcooled flow boiling experiments with inlet subcooling of 5 °C as a comparison. According to the experimental results, the following conclusions can be drawn. (1) As the mass flow rate increases, higher wall superheat is needed to trigger nucleate boiling. (2) In a lower mass flux range, the heat transfer coefficient changes drastically with mass flux, showing convective boiling characteristics, while the value varies slightly in a higher mass flux range, indicating that the nucleate boiling mechanism is dominant. (3) Under the experimental conditions in this work, the average heat transfer coefficient of ammonia reaches its peak when the outlet vapor quality is between 0.21 and 0.31. (4) A subcooled inlet condition has a suppression effect on the average heat transfer capacity of the working fluid at high mass flux, and increasing the saturation temperature reduces the average heat transfer coefficient. In addition, a comparison between the experimental results and existing correlations demonstrated that the correlation proposed by Fang predicted the experimental results well, and then a modified Fang correlation was proposed based on the experimental data obtained in this study. The results could provide references for the prediction of flow boiling heat transfer performance in aerospace environments and the design of heat dissipation systems.

Intelligent manufacturing is considered among the most important elements of the modern industrial revolution, which includes digitalization, networking, and the development of the intelligent manufacturing industry. With the progressive development of modern information technology, particularly the new generation of artificial intelligence (AI) technology, many new opportunities are coming into existence for intelligent machine tool (IMT) development. Intelligent machine tools offer diverse advantages, including learning and optimizing machining processes, error compensation, energy savings, and failure prevention. The paper focuses on the machine tool market in terms of global production, the leading machine tool-producing countries, and the leading countries’ market share in machine tool production. Moreover, the usage of various artificial intelligence techniques in intelligent machining operations is also considered in this comprehensive review, including machining parameter optimization, tool condition monitoring (TCM), and chatter vibration management of intelligent machine tools. Furthermore, future challenges for the machine tool industry are also highlighted.

In this paper, an accurate high-frequency modeling methodology for a permanent magnet synchronous motor (PMSM) in a vehicular electrical braking system is presented, which is suitable for analyzing various electromagnetic interference problems caused by a motor drive system. The proposed modeling approach is established according to the vector fitting technique and based on the S-parameter measurements of the PMSM. The equivalent circuit model of the PMSM converted from a measured S-parameter matrix can better describe the impedance characteristics of the three-phase PMSM under study compared to the existing equivalent circuit models because the imbalances inside the motor are taken into account in the proposed modeling process. The proposed PMSM model exhibits high accuracy in the range from 100 kHz to 120 MHz in comparison with the common-mode and differential-mode characteristics of the PMSM, which are measured using the conventional setups.

Developing renewable energy technologies, especially solar energy-based, is of great importance to secure our energy future. Current solar thermal systems, however, have relatively low utilization efficiencies, limited not only by their low solar energy capture efficiency but also the auxiliary pumping power to circulate the working fluid. Here an innovative nanoparticle enabled pump-free direct absorption solar collector concept is presented, which combines the advantages of volumetric solar harvesting and oscillating heat pipes. Two different flow modes have been observed when the concentration of nanofluid is different. There is an optimum filling ratio when the thermal resistance reaches the minimum. Validation experiments show that the proposed concept can efficiently harvest solar energy and spontaneously transfer the heat into targeted areas, providing a novel approach for efficient solar energy utilization.

Because of the simplicity of design and measurement, as well as the accuracy of results, the 2×-thru de-embedding has replaced the traditional de-embedding algorithms such as thru-reflect-line and short-open-load-thru for printed circuit board (PCB) characterization. In this paper, the theory of [$2^{n}$ -port 2×-Thru de-embedding is derived first. The self-error reduction schemes are introduced to mitigate the de-embedding errors due to non-ideal manufacturing effects that make mode conversion terms non-zero. Both the theory and the self-error reduction schemes are fully validated through simulation and measurement cases.

A near-field scanning is usually time-consuming to map the electromagnetic field along the surface of a device. In this communication, a dual probe is proposed with a U-shaped loop to sense radio frequency (RF) magnetic and electric fields simultaneously, so that the one-time scanning by the dual probe can replace the two-time scanning by single-detector probes. Different from the traditional near-field scanning by using a single-detector probe and spectrum analyzer, the proposed scanning can be achieved by the two-output probe and a two-port vector network analyzer connecting to the probe. The efficient near-field scanning measurements of the electric and magnetic field on a conductor-backed coplanar waveguide transmission line and an RF power divider by using the dual probe are in agreement with those by using two single-detector probes.

Far-end crosstalk (FEXT) can reduce the eye opening and eventually decrease the maximum data rate that can be transmitted through the high-speed interconnections. Therefore, FEXT is an important concern in high-speed digital design. The contributors of stripline FEXT include the dielectric inhomogeneity and the proximity effect. In addition, a characterization technique for the effective relative dielectric constant (Dk) of both core and prepreg has been proposed recently for the analysis of the inhomogeneous medium and induced FEXT. In our study, the FEXT levels of the striplines on various printed circuit boards (PCBs) are measured and compared. It is brought to our attention that for some PCB striplines sharing the same stack-up, same PCB material, and manufactured by the same vendor, the corresponding measured FEXT magnitudes of these coupled single-ended traces could vary drastically, which may bring great challenges to the hardware engineers about FEXT level control during the high-volume PCB production phase. In this paper, the root cause of this issue is investigated and analyzed. The “critical resin content percent” concept is proposed to explain the variations in the Dk values of prepreg that result in the FEXT level variance. The full wave simulations are conducted to identify the “critical glass weave”. A measurement-based statistical analysis is performed to verify the “critical resin content percent” concept. A design guideline for FEXT control strategy in the high-volume PCB manufacturing is presented based upon this investigation.

Optical engines co-packaged with switching Application-Specific Integrated Circuit (ASIC) can offer a solution for advancement in bandwidth requirement and are potentially the ultimate direction for the long-touted "optical integration" era. This paper proposes a novel signal integrity (SI) design methodology for package of co-packaged optics (CPO) by using channel operating margin (COM) as a figure of merit (FOM) for the first time. The conventional design method of SI based on individual criteria, such as masks for loss, crosstalk, jitter, eye width/height, impedance, etc., are no longer able to be satisfied at the same time for current high-speed signals up to 50Gbps and even over 100Gbps. COM, combining most of the individual criteria into a single value of signal to noise ratio, provides the possibility to estimate the quality of the channel and achieve a balance between performance and design complexity in the early design stage. In this work, a design methodology in a format of a visible map using the most two significant factors, loss, and crosstalk, to satisfy the required COM is discussed in detail. With this novel methodology, one can predict the SI performance of a package in the early design stage when the real layout has not generated yet for full-wave simulation and can avoid the costly iteration in the conventional design concept.

Far-end crosstalk (FEXT) noise is a critical factor that affects signal integrity performance in high-speed systems. The FEXT level is sensitive to the dielectric inhomogeneity of the stripline in fabricated printed circuit boards (PCB). Stripline is typically modeled as a 2-layer model with core and prepreg layers. However, in reality, the stripline is laminated by multiple inhomogeneous dielectric layers (IDL). The dielectric layers of the stripline are laminated with epoxy resin and glass bundles. The dielectric permittivity (e r ) of the epoxy resin and glass bundles are different, which causes the inhomogeneity of the dielectric layers while also increasing the FEXT magnitude. Therefore, a typical 2-layer structure is inaccurate to model the FEXT. In this paper, the stripline model is constructed with the core, prepreg, and resin pocket layers. To analyze the stripline with three IDL, a practical superposition method is proposed. A design guideline to mitigate the FEXT level in the stripline design is proposed based on the method.

This paper presents a method for the reduction of mode conversion from differential-mode (DM) noise to common-mode (CM) noise in an unbalanced EMI filter. The unbalanced nature in the EMI filter is a result of not incorporating all the required filter components due to space and cost constraints or due to the parasitic impedances of a printed circuit board (PCB). It is demonstrated that the reduction of mode conversion from DM noise to CM noise can be achieved by modifying the current path on the ground (GND) layer of the PCB of the unbalanced EMI filter. The currents on the GND layer are guided to take a longer route by introducing a "cutout" to the ground plane in the PCB, which increases the impedance of the current path on the GND layer. This approach does not require additional components to the EMI filter for the reduction of CM noise due to the mode conversion. Simulations show that the cutout decreases the CM noise converted from the DM noise by at least 4 dB in the AM radio frequency band (530 kHz – 1.8 MHz).

High-speed PCB design for signal integrity (SI) is about feasible material selection, trace geometry determination and optimization of discontinuities, where the accurate PCB material characterization is essential since incorrect material properties may lead to misleading results and wrong design descisions. The previous studies have revealed that the simulated time-domain reflectometry (TDR) impedance in material characterization, which is based upon the transmission-line-based methods, is erroneous when compared to the measured value, although a good agreement between simulation and measurement in the frequency domain can always be reached. In addition, it is also shown that achieving a satisfactory correlation in both transmission phase and trace impedance is a challenge for SI engineers. This implies that the transmission-line-based approaches, which are widely used in industries, are not perfect and that the extracted PCB material properties are not accurate enough. In this paper, a step-by-step investigation is performed and demonstrated to disclose the root causes of the TDR impedance discrepancy. It is found that the disagreement in TDR impedance is contributed by multiple factors which need to be taken into consideration during material characterization. The improved simulation result exhibits excellent consistency with the measured trace impedance. The suggestions to hardware designers on how more accurate PCB dielectric properties can be obtained are given by addressing the TDR impedance discrepancy issue.

Water droplet changes its movement direction and velocity when it bypasses an aircraft component with the surrounding airflow or gets blown by air injection from the inner part. When the deflected droplet impacts on the downstream surface, its impingement characteristics would be different from those without the frontal effects. In this article, a Lagrangian method was developed to include those upstream effects on the droplet collection efficiency. Validation cases were carried out for a cylinder and an MS (1)-0317 airfoil, whereas a multielement airfoil and an engine cone with a hot air film-heating anti-icing system were computed to investigate the effects of the upstream component and air injection on the impingement characteristics of downstream surfaces. It is found that the present collection efficiencies are in good agreement with the experimental data and the simulation results obtained by the Eulerian and traditional Lagrangian methods when not affected by those upstream factors. The droplet deflections and trajectory crossings are observed clearly under the influence of the upstream component, and the Lagrangian results of downstream surfaces differ from those of the Eulerian method. In addition, due to the air injection from the inner engine cone, the peak collection efficiency on the cone surface increases with the decrease of the droplet diameter and the value even exceeds one when the droplet is small. This work is helpful for the understanding of the droplet motion and the accuracy of aircraft icing simulation.

Signal integrity (SI) issue is a critical concern as the data rate continues to increase and SI analysis is heavily dependent on simulations. Inaccurate simulation data may result in inadequate design decisions influencing high-speed digital design and optimization. The surface impedance boundary condition (SIBC) concept is generally utilized in commercial electromagnetic (EM) solvers, which is considered to be an efficient technique as the interior region of the conductor of interest does not need to be included in the numerical procedure. The first-order SIBC has been incorporated into many EM simulation tools widely used in industries. In this paper, the limitations of the first-order SIBC in 2D simulations for PCB transmission lines are analyzed and demonstarted for the first time. Different PCB transmission lines with various cross-sectional geometries are simulated in a commercial 2D EM solver with and without the implementation of the first-order SIBC to reveal the effect on the simulated transmission line behaviors. It is found that the accuracy of the simulations with the first-order SIBC decreases as the edge of the signal conductor in the cross-section becomes narrower. The possible solutions are proposed to overcome the issue.

The increasingly growth of the traffic in data centers demands for high-speed data transition and high bandwidth density. Optical communication is a promising way for the propagation of high-speed signals with less distortions. The quad small form-factor pluggable (QSFP) transceiver module is an essential component converting an electrical signal into an optical signal for point-to-point data transition. Considerable attentions have been paid to the signal integrity (SI) optimization for the optical QSFP transceiver modules with different data rates, where the receiver sensitivity is generally considered to be critical. In this paper, the receiver sensitivity problem of a typical QSFP transceiver module with 10 Gbit/s data rate is studied. It is the first time to demonstrate that the receiver sensitivity improvement is not only related with the SI design, but also connected with the electromagnetic interference (EMI) mitigation inside the DUT. The convential simulation model used for SI analysis with important metal configurations excluded is limited in the ability to identify the coupling between the radiating structures. It is found that the EMI noise induced by the unbalanced PCB routing and the interconnect between the PCB and flexible printed circuit (FPC) has significant contribution to the total noise at the receiver end. The generation of the antenna-mode current is verified and further studied using the full wave simulations. The mitigation method is proposed and confirmed through the measurements to improve the receiver sensitivity.

A cryogenic integrated system, consisting of a neon loop heat pipe, two pulse tube cryocoolers and other components, was designed and tested in the terrestrial environment. This paper presents the test results of the pre-flight thermal performance of the cryogenic integrated system, such as supercritical characteristics, steady-state operating characteristics and critical heat transfer capacity. The integrated system could achieve supercritical startup under auxiliary heat load of 0.4 W and obtain maximum heat transfer capacity of 1.3 W under anti-gravity attitude. The results show that both the function and the thermal performance are in concordance with the expectations, which validates the design of this cryogenic integrated system. Radiator temperature play an important role in the operation of the integrated system, where a temperature increment of 5 °C would lead the supercritical startup to fail.

As a highly efficient cryogenic heat transfer device, cryogenic loop heat pipe (CLHP) promises great application potential in the thermal control of future space infrared detection system. In this work, a CLHP using methane as working fluid operating at 100–190 K was developed, and its thermal performance including the supercritical startup, heat transport capacity under different heat sink, power cycling characteristics, temperature hysteresis phenomenon and thermal resistance variation, was experimentally investigated. Experimental results showed that the CLHP could successfully realize the supercritical startup under various auxiliary heat loads applied to secondary evaporator, reach a various heat transfer capacity under different heat sink temperature over a 0.6 m distance, and manifest good response characteristics to the cycle of heat load applied to the primary evaporator. The temperature hysteresis phenomenon was detected and thermal resistance of the CLHP varied with increasing heat load applied to the primary evaporator, but not the same with that in heat load reverse motion.

Cryogenic loop heat pipes (CLHP) hold significant potential for applications in the thermal control of advanced, space based infrared exploration systems. In the current investigation, a neon CLHP operating in the 30–40 K temperature range was developed and evaluated. The thermal performance characteristics, included assessment of the supercritical startup, matching characteristics of heat loads applied to the primary and secondary evaporators, power cycling, heat transfer limit and thermal resistance variations, all of which were explored and evaluated experimentally. The longitudinal temperature and pressure variations were measured simultaneously at several locations along the loop. The experimental results indicated that the CLHP could successfully achieve the supercritical startup with an input power of 1.5 W applied to the secondary evaporator, and reach a heat transfer limit of approximately 4.0 W over a 0.6 m distance. The CLHP exhibited good response characteristics to step changes in the heat load applied to the primary evaporator, resulting in smooth temperature transitions in the primary evaporator. The thermal resistance of the CLHP was found to decrease monotonically with increasing heat load applied to the primary evaporator, with values as low as 0.4 K/W.

This paper presents an experimental investigation of the influence of multiple parameters on the thermal performance of variable conductance heat pipes (VCHPs) according to theoretical design and analysis. The operating characteristics of four VCHPs, such as the steady-state temperature, thermal resistance, and degree of self-control, were systematically analysed and compared. The design principles were examined considering the structural matching design, thermal-physical properties, and charging mass of the fluids. The examined types included the cold-gas reservoir VCHP (CGR-VCHP) and the hot-gas reservoir VCHP (HGR-VCHP), whose steady-state operating temperatures and thermal resistances were compared. The HGR-VCHP attained a higher degree of self-control than the CGR-VCHP for the same heat pipe (HP) structure size. The effects of the reservoir volume of the CGR-VCHP were experimentally and theoretically assessed. Compared to a small volume of 33.66 mL, a large volume of 43.27 mL increased the self-control, with d T v a / d Q dropping from 0.272 K/J to 0.042 K/J. Moreover, the temperature difference decreased from 13.6 to 2.09 ℃ under the same heat load increase of 50 W. Both R22 and ammonia were chosen as working fluids due to their similar sensitivity factors. The self-control ability of the ammonia CGR-VCHP was higher than that of the R22 CGR-VCHP based on the obtained experimental and theoretically calculated results. This research provides valuable insights into VCHP multiparameter analysis, which are of great significance for the practical application of VCHPs in self-control thermal.

Next generation space infrared sensor and detector have pressing requirement for cryogenic heat transport technology in the temperature range of 30–40 K. Cryogenic loop heat pipe (CLHP) has excellent thermal performance and particular characteristics such as high flexibility transport lines and no moving parts, thus it is regarded as an ideal thermal control solution. A neon CLHP referring to infrared point-to-point heat transfer element in future space application has been designed and experimented. And it could realize supercritical startup successfully. Experimental results show that the supercritical startup were realized successfully at cases of 1.5 W secondary evaporator power, but the startup was failed when 0.5 and 1 W heat load applied to secondary evaporator. The maximum heat transport capability of primary evaporator is between 4.5 and 5 W with proper auxiliary heat load. Before startup, even the heat sink temperature decreased to 35 K, the primary evaporator can still maintain at almost 290 K; and the primary evaporator temperature increased at once when the powers were cut off, which indicated the CLHP has a perfect function of thermal switch. The CLHP could adapt to sudden changes of the primary evaporator power, and reach a new steady-state quickly. Besides, some failure phenomena were observed during the test, which indicated that proper secondary evaporator power and heat sink temperature play important roles on the normal operation.

In electric vehicles, the pulse width modulation scheme is widely used in three-phase motor drive systems for its high performance. However, the fast switching of semiconductor devices may induce excessively high dv/dt and di/dt, which can cause electromagnetic interference (EMI) issues, making it difficult to satisfy electromagnetic compatibility standards. In this paper, the current conducted emission test for a three-phase motor drive system is performed based on CISPR 25 component-level testing setup for AM radio frequency band, which is from 530 kHz to 1.8 MHz. Under these conditions, common-mode (CM) noise generation mechanisms of the motor drive system are identified through measurements. It is found that the dominant mechanism is the mode conversion from differential mode (DM) switching current of the three-phase PWM inverter to CM current through the cable harness due to the imbalances in the PCB structure and EMI filter network which are at the dc input side of the three-phase inverter. Based on this finding, ground (GND) bridges are added between the digital signal and power GND nets to reduce the CM noise. The GND bridge effect on the reduction of CM noise in AM band is experimentally verified and further studied using circuit simulations.

Surface roughness of the conductor in transmission lines will introduce extra losses. The recently proposed Huray model is quite accurate for modeling these additional losses by changing R terms in RLGC models. However, only focusing on the loss modeling of the transmission line may lead to causality issues in time domain simulations. In this paper, the causality requirements of the RLGC models are theoretically analyzed firstly. Then, two solutions of the causality problems in Huray model-based transmission line with rough conductors modeling were proposed and compared. One of them is based on the numerical Hilbert transform, and the other one is analytically based on a complex-valued roughness factor. The causalities of those two solutions are validated by a time domain pulse through a transmission line. The results comparisons of the received pulse responses after the transfer functions show that both methods can improve the causality of the wave propagation term significantly, whereas the analytical solution has better performances and the numerical method has some limitations.

In this paper I-V method-based impedance measurement of power distribution network (PDN) in printed circuit board (PCB) technique is proposed and compared to the traditional VNA method [1]. A I-V method-based probe is designed and verified by comparing the performance with VNA method. To de-embed the parasitic problems, a special I-V probe calibration method is created according to the characteristics of the probe.

SI engineers usually build PCB test coupons and perform cross-sectioning and material properties extraction, and then do design optimization. But designing transmission lines on PCB with good analysis to measurement correlation is really challenging. Although there are some systematic approaches which can be applied to a broad range of applications for highspeed digital designs, it is found that in the validation process, there is always several-ohm mismatch in the comparison of TDR impedance between simulated and measurement results. This degrades engineers' confidence about high-speed design. Taking a real case as an example, this paper is trying to analyze which factors have influence on the trace impedance correlation and showing step by step how the agreement can be improved.

ANSYS Q3D Extractor is a fast quasi-static 3D solver for extracting lumped RLGC parameters and SPICE models. Although Q3D Extractor is faster than full wave simulation, it results in inaccuracies at high frequency simulation, especially for PCB sructures. This paper proposes a method of improving the accuracy of high frequency simulations by using segmentation. For the convenience of study, a transmission line on PCB is selected as the device under test without sacrificing generality, and HFSS simulation results and measurement data are used as reference. Extensive simulations are performed to investigate the effectiveness of segmentation method. It is found that by dividing the transmission line into a set of electrically small segments, the high frequency simulation accuracy can be effectively enhanced. Some other relevant tips for using Q3D are also presented.

Cryogenic system is important for the infrared detectors, which can increase the ratio of signal-to-noise at low temperature. Long lifetime, high efficiency mechanical cryocoolers and two-phase heat pipes can reduce the energy consumption of the spacecraft and ensure a low weight. A co-designing cryogenic system consisting of two pulse tube cryocoolers (PTCs) and two neon cryogenic loop heat pipes (CLHPs) operating at temperature around 35 K is designed, manufactured, and tested in the present work. A novel integrated multifunctional heat exchanger is proposed to couple the heat exchange between the cold head of PTC and the condenser of CLHP. To our best knowledge, it is the first time to couple these two technologies directly for space application. The thermal design and efficiency analysis of this cryogenic system are presented, which optimize both the structural layout and insulation to reduce the heat load from surroundings. The thermal performance of the PTCs is ground tested and the co-designing cryogenic system is integrated in a vacuum chamber. The no-load temperatures of the PTCs are 25.3 K and 25.7 K, respectively, while both of the cooling capacities are over 2 W@35 K with the input power of 250 W AC. Meanwhile, the thermal performance of supercritical startup and steady-state operation are tested, and the results are discussed and analyzed.

Neon-charged cryogenic loop heat pipe (CLHP) can realize efficient cryogenic heat transport in the temperature range of 30–40 K, and promises great application potential in the thermal control of future space infrared exploration system. In this work, extensive experimental studies on the supercritical startup and heat transport capability of a neon-charged CLHP integrated with a G-M cryocooler were carried out, where the effects of the auxiliary heat load applied to the secondary evaporator and charged pressure of the working fluid were investigated. Experimental results showed that the CLHP could successfully realize the supercritical startup with an auxiliary heat load of 1.5 W, and there existed an optimum auxiliary heat load and charged pressure of the working fluid respectively, to achieve the maximum temperature drop rate of the primary evaporator during the supercritical startup. The CLHP could reach a maximum heat transport capability of 4.5 W over a distance of 0.6 m corresponding to the optimum charged pressure of the working fluid; however, the heat transport capability decreased with the increase of the auxiliary heat load. Furthermore, the inherent mechanisms responsible for the phenomena observed in the experiments were analyzed and discussed, to provide a better understanding from the theoretical view.

Cryogenic loop heat pipe (CLHP) is one of the key components in the future space infrared exploration system, which enables effective and efficient cryogenic heat transport over a long distance with a flexible thermal link. To realize reliable and long life operation, a CLHP-based thermal control system with redundancy design was proposed in this work, where two nitrogen-charged CLHPs were employed to provide cryocooling at 80–100 K. This study focused on the supercritical startup of the CLHPs with redundancy design, and an extensive experimental study under four possible working modes was conducted. Experimental results showed that with 2.5 W applied to the secondary evaporator, each CLHP could realize the supercritical startup successfully in the normal working mode; however, the required time differed a lot because the difference in the transport line diameter significantly affected the cryocooling capacity to the primary evaporator. In the backup conversion mode, instant switch of the two primary evaporators may cause an operation failure, and an auxiliary operation of the secondary evaporator in advance was necessary to make the primary liquid line filled with liquid. In the malfunction conversion mode, the simulated infrared detector had to be first shut down, but the time needed for the backup CLHP to realize the supercritical startup became obviously shorter than that in the normal working mode, because the primary evaporator of the backup CLHP was always in a cryogenic state. In the dual operation mode, the two CLHPs could realize the supercritical startup simultaneously, but a temperature oscillation phenomenon was observed, which can be eliminated by increasing the heat load applied to the secondary evaporator.

Enhancing Critical Heat Flux (CHF) in pool boiling significantly extends the safety limit in the nuclear system, especially under the In-Vessel Retention-Reactor Vessel Cooling (IVR-ERVC) severe accident management strategy to avoid the failure of the lower head reactor pressure vessel. In this work, the lattice Boltzmann method (LBM) is employed to simulate the effect of surface orientation, wettability, geometric size, and subcooling of the downward-facing lower head on the CHF enhancement. It was found that for the downward-facing surface, the CHF increases with increasing surface orientation, while a vertical surface gives a slightly lower CHF compared to a near-vertical surface. Besides, the CHF for a downward facing surface increases with increasing wettability. The CHF performance of the near-vertical and vertical surfaces exhibits the largest improvement with decreasing surface contact angle. Moreover, it reveals that with an increased radius of the lower head, the CHF decreases for all curved surfaces, especially obvious for the inclination angle smaller than 90∘. For a vertical surface, increasing the length of the heated surface has no obvious improvement on the CHF. This study also provides a discussion regarding the effect of subcooling on the CHF enhancement. It was found that the CHF increases with the increase of subcooling and the simulation results agree with the Elkassabgi-Lienhard and Zuber correlations.