Search Results (23)

The increasing global demand for oil and gas, together with the depletion of shallow reservoirs, has driven exploration toward deep and ultra-deep formations characterized by high-temperature and high-pressure (HTHP) conditions. In such environments, conventional drill pipes often experience thermal stress, corrosion, and mechanical degradation, which can reduce drilling efficiency and compromise operational reliability. Thermal insulated drilling pipes (TIDPs) have therefore emerged as an effective solution to minimize heat transfer between drilling fluids and the surrounding formation. This review summarizes recent advances in TIDP materials, structural design strategies, fabrication technologies, and critical performance. Relevant studies were collected from major scientific databases, including Web of Science and Google Scholar, with a focus on insulation materials, coating technologies, and thermal management approaches used in drilling systems. The analysis indicates that advanced insulation systems, including polymer-based coatings, silica aerogels, vacuum-insulated layers, and phase-change materials, can significantly enhance thermal management in drilling operations. These technologies can reduce heat loss by approximately 40–60% (i.e., 400–600 W·m⁻²) and maintain drilling-fluid temperature differentials of 10–18 °C under HTHP conditions. In addition, fabrication techniques such as plasma spraying, composite fabrication, and additive manufacturing enable the development of multifunctional insulation systems with improved thermal, mechanical, and corrosion-resistant properties. Hybrid TIDP systems integrating nanocomposites and advanced polymers show strong potential for improving drilling safety and efficiency. However, challenges related to durability, scalability, and cost remain, highlighting the need for further research on multilayer insulation architectures and sustainable materials. Full article

In this study, the influence of residual gas pressure within a vacuum insulation cavity on the insulation performance of a multi-layer insulation (MLI) system was investigated through thermal analysis. Based on an electrical analogy, a thermal resistance network was constructed, considering heat transfer through the insulation system by gas conduction, solid conduction, and surface radiation. Lees’ four-moment model was employed to calculate the gas conduction across a wide range of vacuum conditions, including medium-to-low vacuum situations. The analysis shows that total heat flux and effective thermal conductivity exhibited non-linear increases as the pressure approached atmospheric level. This trend was successfully validated by comparisons with experimental data from the literature, thereby confirming the rationality of the proposed analytical model. Furthermore, the contributions of individual heat-transfer modes to the total heat flux within the insulation system were scrutinized, thereby revealing their redistribution patterns. Under high-vacuum conditions, solid conduction and radiation were the primary modes of heat transfer. However, with increasing pressure, the proportion of gas conduction rose markedly, becoming the primary heat-transfer mode under medium-vacuum and low-vacuum conditions. Finally, a validated analytical technique was utilized to predict heat-transfer characteristics under cryogenic boundary conditions associated with liquid hydrogen storage. Full article

Cryogenic storage systems require precise management of boil-off gas (BOG) to prevent pressure buildup caused by external heat ingress. This study investigates sloshing-induced heat transfer and BOG generation in a double-shell vacuum-insulated cryogenic storage tank subjected to dynamic excitation. Experiments were conducted under dynamic operating conditions, during which BOG generation and boil-off rate (BOR) were measured over a range of vibration frequencies, acceleration levels, and fill ratios. The results reveal a strong frequency-dependent sloshing behavior that significantly influences BOG generation. Under dynamic conditions, the BOR exhibited a non-linear dependence on filling ratio, with a maximum response occurring at 50% filling, reflecting an optimal balance between sloshing-enhanced heat transfer and geometric confinement. Based on the experimental observations, an integrated numerical heat transfer model incorporating multilayer insulation (MLI) performance and vacuum level effects was developed and validated against experimental data. The validated numerical model successfully predicts pressure evolution and BOG generation under operational sloshing conditions, providing valuable insights for optimizing cryogenic tank design and minimizing boil-off losses. Full article

Hydrogen serves as a key clean-energy carrier, with the main hurdles lying in safe, efficient transport and storage (gas or liquid) and in end-use energy conversion. Liquid hydrogen (LH), as a high-density method of storage and transportation, presents cryogenic insulation as its key technical issues. In LH storage tanks, the performance of high vacuum multilayer insulation (HVMLI) will decline due to hydrogen release and leakage from the microscopic pores of steel, which significantly destroy the vacuum layer. The accumulation of residual gases will accelerate thermal failure, shorten the service life of storage tanks and increase safety risks. Adsorption is the most effective strategy for removing residual gases. This review aims to elucidate materials, methods, and design approaches related to hydrogen storage. First, it summarizes adsorbents used in liquid hydrogen storage tanks, including cryogenic adsorbents, metal oxides, zeolite molecular sieves, and non-volatile compounds. Second, it explores experimental testing methods and applications of hydrogen adsorbents in storage tanks, analyzing key challenges faced in practical applications and corresponding countermeasures. Finally, it proposes research prospects for exploring novel adsorbents and developing integrated systems. Full article

The thermal insulation performance of liquid hydrogen (LH₂) storage tanks is critical for long-distance transportation. The active cooled shield (ACS) technologies, such as the liquid nitrogen cooled shield (LNCS) and the vapor hydrogen cooled shield (VHVCS) are important thermal insulation methods. Many researchers installed the VHVCS inside the multilayer insulation (MLI) and obtained the optimal position. However, the MLI layer is often thinner than the vacuum interlayer between the inner and outer tanks, and there is a large vacuum interlayer between the outermost side of MLI and the inner wall of the outer tank. It is unknown whether the insulation performance can be improved if we install ACS in the mentioned vacuum interlayer and separate a portion of the MLI to be installed on the outer surface of ACS. In this configuration, the number of inner MLI (IMLI) layers and the ACS position are interdependent, a coupling that has not been thoroughly investigated. Therefore, thermodynamic models for MLI, MLI-LNCS, and MLI-VHVCS schemes were developed based on the Layer-by-Layer method. By applying Robin boundary conditions, the temperature distribution and heat leakage of the MLI scheme were predicted. Considering the coupled effects of IMLI layer count and ACS position, a co-optimization strategy was adopted, based on an alternating iterative search algorithm. The results indicate that for the MLI-LNCS scheme, the optimal number of IMLI layers and LNCS position are 36 layers and 49%, respectively. For the MLI-VHVCS scheme, the optimal values are 21 layers and 39%, respectively. Compared to conventional MLI, the MLI-LNCS scheme achieves an 88.09% reduction in heat leakage. However, this improvement involves increased system complexity and higher operational costs from LN₂ circulation. In contrast, the MLI-VHVCS scheme achieves a 62.74% reduction in heat leakage, demonstrating that using sensible heat from cryogenic vapor can significantly improve the thermal insulation performance of LH₂ storage tanks. The work of this paper provides a reference for the design and optimization of the insulation scheme of LH₂ storage tanks. Full article

Hydrogen-powered aircraft constitute a transformative innovation in aviation, motivated by the imperative for sustainable and environmentally friendly transportation solutions. This paper aims to concentrate on the design of hydrogen powertrains employing a system approach to propose representative design models for distribution and propulsion systems. Initially, the requirements for powertrain design are formalized, and a use-case-driven analysis is conducted to determine the functional and physical architectures. Subsequently, for each component pertinent to preliminary design, an analytical model is proposed for multidisciplinary analysis and optimization for powertrain sizing. A double-wall pipe model, incorporating foam and vacuum multi-layer insulation, was developed. The internal and outer pipes sizing were performed in accordance with standards for hydrogen piping design. Valves sizing is also considered in the present study, following current standards and using data available in the literature. Furthermore, models for booster pumps to compensate pressure drop and high-pressure pumps to elevate pressure at the combustion chamber entrance are proposed. Heat exchanger and evaporator models are also included and connected to a burning hydrogen engine in the sizing process. An optimal liner pipe diameter was identified, which minimizes distribution systems weight. We also expect a reduction in engine length and weight while maintaining equivalent thrust. Full article

In general, graphene is known to be thermally stable. In this study, we analyzed the Raman spectra of graphene prepared on copper (Cu) and nickel (Ni) by chemical vapor deposition (CVD) as well as monolayer and multilayer graphene transferred onto SiO₂ under vacuum heating. We observed a shift in the position of the graphene G peak due to temperature changes for all substrates. For graphene on insulating substrates, the peak position returned to its original position after heating when the substrate returned to room temperature, indicating the thermal and chemical stability of graphene. In contrast, the Raman spectra of graphene on Cu and Ni, which have different carbon solubilities, showed significant shifts and broadening of the G peak as the temperature increased. We also utilized optical microscopy to observe morphological changes during heating, which complemented the Raman spectroscopy analysis. The optical microscopy images obtained in the previous study revealed morphological changes on the graphene surface that correlate with the shifts observed in the Raman spectra, especially in graphene on metal substrates. These combined findings from Raman spectroscopy and optical microscopy could provide insights for optimizing graphene growth processes. In addition, knowledge of the thermal behavior of graphene on insulating substrates could be useful for device construction. Full article

As environmental pollution has become a global concern, regulations on carbon emissions from maritime activities are being implemented, and interest in using renewable energy as fuel for ships is growing. Hydrogen, which does not release carbon dioxide and has a high energy density, can potentially replace fossil fuels as a renewable energy source. Notably, storage of hydrogen in a liquid state is considered the most efficient. In this study, a 0.7 m³ liquid hydrogen fuel tank suitable for small vessels was designed, and a structural analysis was conducted to assess its structural integrity. The extremely low liquefaction temperature of hydrogen at −253 °C and the need for spatial efficiency in liquid hydrogen fuel tanks make vacuum insulation essential to minimize the heat transfer due to convection. A composite insulation system of sprayed-on foam insulation (SOFI) and multilayer insulation (MLI) was applied in the vacuum annular space between the inner and outer shells, and a tube-shaped supporter made of a G-11 cryogenic (CR) material with low thermal conductivity and high strength was employed. The material selected for the inner and outer layers of the tank was STS 316L, which exhibits sufficient ductility and strength at cryogenic temperatures and has low sensitivity to hydrogen embrittlement. The insulation performance was quantitatively assessed by calculating the boil-off rate (BOR) of the designed fuel tank. Structural integrity evaluations were conducted for nine load cases using heat transfer and structural analyses in accordance with the IGF code. Full article

Cavity silicon on insulator (Cavity-SOI) offers significant design flexibility for microelectromechanical systems (MEMS). Notably, the shape and depth of the cavity can be tailored to specific requirements, facilitating the realization of intricate multi-layer structural designs. The novelty of the proposed fabrication methodology is manifested in its employment of a micromachining process flow, which integrates dry etching, wafer level Au–Si eutectic bonding, and chemical mechanical polishing (CMP) to create Cavity-SOI. This innovative approach substantially mitigates the complexity of fabrication, and the implementation of wafer-level gold–silicon eutectic bonding and vacuum packaging can be achieved, representing a distinct advantage over conventional methods. To evaluate the technical viability, a MEMS resonant pressure sensor (RPS) was designed. Experimental findings demonstrate that during the formation of Cavity-SOI, dry etching can accurately fabricate cavities of predefined dimensions, wafer-level Au–Si eutectic bonding can achieve efficient sealing, and CMP can precisely regulate the depth of cavities, thus validating the feasibility of the Cavity-SOI formation process. Additionally, when implementing Cavity-SOI in the fabrication of MEMS RPS, it enables the spontaneous release of resonators, effectively circumventing the undercut and adhesion issues commonly encountered with hydrofluoric acid (HF) release. The sensors fabricated using Cavity-SOI exhibit a sensitivity of 100.695 Hz/kPa, a working temperature range spanning from −10–60 °C, a pressure range of 1–120 kPa, and a maximum error of less than 0.012% full scale (FS). The developed micromachining process for Cavity-SOI not only streamlines the fabrication process but also addresses several challenges inherent in traditional MEMS fabrication. The successful fabrication and performance validation of the MEMS RPS confirm the effectiveness and practicality of the proposed method. This breakthrough paves the way for the development of high-performance MEMS devices, opening up new possibilities for various applications in different industries. Full article

This study investigated the heat transfer characteristics of composite multilayer insulation (MLI) materials used for the storage and transport of liquid hydrogen at cryogenic temperatures. This research focused on analyzing the effects of thermal boundary temperature, total layer count, and vacuum level on the heat flux through the insulation material. Based on the layer-by-layer model, a heat transfer model of composite MLI was constructed. This research introduces a novel method for analyzing the heat transfer properties of composite MLI in the liquid hydrogen temperature range. Results indicate that heat flux increases with higher thermal boundary temperatures, with the MLI layers near the cold boundary playing a critical role in overall insulation performance. Additionally, numerical analysis was conducted to examine the impact of different material combinations and variations in vacuum level on heat transfer characteristics. Findings reveal that adding spray-on foam insulation reduces heat flux by 20.76% compared to using MLI alone. Furthermore, increasing the total number of MLI layers effectively mitigates heat flux increase, achieving an optimal heat flux of 0.5377 W/m² with a total of 50 layers. Full article

In this study, a super-insulated pipe incorporating Multi-Layer Insulation (MLI) and vacuum is numerically analyzed to overcome the challenges faced during the transportation of cryogenic fluids like nitrogen. A super-insulated pipe incorporating an inner process pipe of SS 304 L insulated by twenty-four consecutive layers has been used. Each layer consists of aluminized mylar (as a radiation shield) and dacron netting (as a spacer material). High vacuum (10⁻⁹ torr) is applied and numerically analyzed at multiple flow rates, i.e., 250 LPH, 500 LPH and 1000 LPH. The results show a gradual increase in temperature along the flow direction from 77 K to 79 K at the most. Moreover, the temperature increases with the increase in the length of the pipe and decreases with the increase in the flow rate of LN₂. Full article

Efficient insulation technology is one of the key technologies for the development of large LH₂ storage tanks. This paper aimed at a 4000 m³ LH₂ spherical tank, many insulation schemes were designed, including multilayer insulation systems integrated with a vapor-cooled shield (VCS) and liquid-nitrogen-cooled shield (LN2CS). The heat transfer model was developed to predict the insulation performance of a LH₂ spherical tank. The effect of the VCS position on insulation performance was studied, and the different configurations of double VCSs were compared and discussed. The results showed that the daily evaporation rate of MLI, hollow glass microspheres (HGMs) and vacuum was only 2.05 × 10⁻³%, 3.62 × 10⁻³% and 7.94 × 10⁻²% at 1.34 Pa, respectively. MLI was still the optimal insulation scheme for a 4000 m³ LH₂ spherical tank. Meanwhile, it was found that when the single VCS was placed at the 10th layer, the heat leakage was reduced by approximately 40.5% compared with MLI. The heat leakage of parallel VCS(P-VCS) was 76.6% lower than that of MLI. The minimum heat leakage of series VCS(S-VCS) was 83.79%, 72.75% and 37.36% lower than that of MLI, single VCS and P-VCS, respectively. Additionally, the heat leakage of the LH₂ tank could be reduced to less than 10 W when LN2CS was installed. These results provide a design reference for the highly efficient storage of large LH₂ tanks. Full article

Revealing the interlayer pressure distribution in multilayer insulation (MLI) for cryogen (e.g., liquid hydrogen) containers is very important to improve the insulation-performance-predicting quality. This paper proposed an inversion method to reconstruct the interlayer pressure of multilayer insulations on the basis of experimentally measuring the reflectors’ temperatures. The layer-by-layer (LBL) model was modified by considering the interlayer pressure distribution in MLIs to calculate the reflectors’ temperatures. Groups of pre-given interlayer pressure distributions and the corresponding temperature distributions calculated by the LBL model were used to train an extreme learning machine (ELM) algorithm. Finally, the interlayer pressure distribution of the MLI was reconstructed by the trained ELM algorithm based on the measured reflectors’ temperatures. The method was validated by four additional testing cases. The results showed that the proposed algorithm was accurate in reconstructing the interlayer pressures. Published experimentally measured temperature distributions of a 60-layer MLI were used as input data. The abovementioned inversion method was adopted, and a reasonable interlayer pressure distribution was obtained. Moreover, the thermal insulation performance of the MLI was calculated by the LBL model considering the reconstructed interlayer pressure distribution. We found that the predicted heat flux of the MLI deviated from the experimental results by only 2.77%, while the error of the classical LBL model ignoring the non-ideal vacuum condition was as high as 89%. Meanwhile, the predicted corresponding temperature distribution deviated from the tested value by less than 1.13 K. The proposed method can be applied to assess the interlayer pressure distribution of industrial cryogen containers and precisely predict the thermal insulation performance of a practical multilayer insulation structure. Full article

The utilization of Fiber Bragg Grating (FBG) sensors in innovative optical sensor networks has displayed remarkable potential in providing precise and dependable thermal measurements in hostile environments on Earth. Multi-Layer Insulation (MLI) blankets serve as critical components of spacecraft and are employed to regulate the temperature of sensitive components by reflecting or absorbing thermal radiation. To enable accurate and continuous monitoring of temperature along the length of the insulative barrier without compromising its flexibility and low weight, FBG sensors can be embedded within the thermal blanket, thereby enabling distributed temperature sensing. This capability can aid in optimizing the thermal regulation of the spacecraft and ensuring the reliable and safe operation of vital components. Furthermore, FBG sensors offer sev eral advantages over traditional temperature sensors, including high sensitivity, immunity to electromagnetic interference, and the ability to operate in harsh environments. These properties make FBG sensors an excellent option for thermal blankets in space applications, where precise temperature regulation is crucial for mission success. Nevertheless, the calibration of temperature sensors in vacuum conditions poses a significant challenge due to the lack of an appropriate calibration reference. Therefore, this paper aimed to investigate innovative solutions for calibrating temperature sensors in vacuum conditions. The proposed solutions have the potential to enhance the accuracy and reliability of temperature measurements in space applications, which can enable engineers to develop more resilient and dependable spacecraft systems. Full article

Nonstoichiometric GeSi_xO_y glass films and many-layer structures based on them were obtained by high-vacuum electron beam vapor deposition (EBVD). Using EBVD, the GeO₂, SiO, SiO₂, or Ge powders were co-evaporated and deposited onto a cold (100 °C) p⁺-Si(001) substrate with resistivity ρ = 0.0016 ± 0.0001 Ohm·cm. The as-deposited samples were studied by Fourier-transformed infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. A transparent indium–tin–oxide (ITO) contact was deposited as the top electrode, and memristor metal–insulator–semiconductor (MIS) structures were fabricated. The current–voltage characteristics (I–V), as well as the resistive switching cycles of the MIS, have been studied. Reversible resistive switching (memristor effect) was observed for one-layer GeSi_0.9O_2.8, two-layer GeSi_0.9O_1.8/GeSi_0.9O_2.8 and GeSi_0.9O_1.8/SiO, and three-layer SiO₂/a–Ge/GeSi_0.9O_2.8 MIS structures. For a one-layer MIS structure, the number of rewriting cycles reached several thousand, while the memory window (the ratio of currents in the ON and OFF states) remained at 1–2 orders of magnitude. Intermediate resistance states were observed in many-layer structures. These states may be promising for use in multi-bit memristors and for simulating neural networks. In the three-layer MIS structure, resistive switching took place quite smoothly, and hysteresis was observed in the I–V characteristics; such a structure can be used as an “analog” memristor. Full article