Multilayer Thermal Insulation Research Articles

Research on Algorithm of Sewing Path Generation for Satellite Multi-layer Thermal Insulation

The production mode of hand-sewn for complex shape multi-layer thermal insulation (MLI) of satellite has seriously affected its production efficiency and quality. Automatic sewing technology is an important means to improve MLI production efficiency. First, the problem of automatic creation of sewing patterns and paths needs to be solved, but there is no targeted research on MLI with special sewing requirements. In this paper, the principles of the sewing path are determined by combing the boundary conditions. Based on the chain code histogram and its spatial distribution entropy, the internal opening of MLI can be quickly identified to determine the nodes through which the sewing path passes. Then, the simulated annealing algorithm which can quickly converge to the global optimal solution is used to solve the NP-hard problem and realize the generation of the sewing path. For the special sewing requirements, the Laguerre diagram-based A-Star algorithm is used to realize the avoidance sewing path to the internal opening, and the MLI contour reinforcement sewing path planning is abstracted into the inward quantitative offset line generation problem of the contour. So the problem of automatic generation for sewing path of complex shape MLI can be solved.

Design and Functional Verification of a Robot Motion Sensor

The outer wall of the rocket tank needs to be sprayed with multi-layer and multi-component thermal insulation coating. To ensure the thickness, uniformity and quality of the coating layer and improve the automation level, it is the best choice to use robot to perform the spraying operation. However, the intricate tank spraying conditions lead to high error rate and great difficulty in planning robot path in the complex structures. In order to tackle above-mentioned problems, this paper designs a robot-end target motion sensor, aiming to realize the robotic spraying movement guided by human direct contact, which transforms the human guiding motion into the robot's motion control quantity. Through the motion experiment, the motion sensor can recognize operator’s motion in the process of grasping the sensor and guiding the robot to move, and using the sensor can control the robot to smoothly run along the desired path.

Magnetic and Thermal Design of HTS Quadrupole Magnet for Newly Developed Superconducting Proton Cyclotron Beam Line

A magnetic and thermal design of high-temperature superconducting (HTS) quadrupole magnet for newly developed superconducting proton cyclotron was presented in this research. With superconducting technology, the design can reduce the magnet size and remove the heat loads more efficiently. Calculations are conducted with finite element method (FEM) to study the quadrupole magnet’s magnetic and thermal properties. For the magnet cold-mass and cryostat system, the heat load is mainly generated by conduction and radiation. Multilayer thermal insulation and G10 supports are used to restrict them. The magnetic field distribution in the HTS coils is calculated to consider the critical current degradation of the YBCO tapes. The effects on the field gradient quality in relation to the pole tip profile and end chamfer are analyzed. The sixth multipole component in the integral field can be improved with end chamfer. Finally, a 20 T/m HTS quadrupole magnet with integral field uniformity less than 0.05% out to 75% of the inscribed radius is proposed.

Preparation and properties of the multi-layer aerogel thermal insulation composites

Multi-layer insulation materials possess low radiation thermal conductivity, and excellent thermal insulation property in a vacuum environment. However, the spacers of the traditional multi-layer insulation materials are mostly loose fibers, which lead to more sensitive to the vacuum environmental of serviced. With the vacuum degree declining, gas phases thermal convection increase obviously, and the reflective screen will be severe oxidation, all of these make the thermal insulation property of traditional multi-layer insulation deteriorate, thus limits its application scope. In this paper, traditional multi-layer insulation material is combined with aerogel and obtain a new multi-layer aerogel thermal insulation composite, and the effects of the number, thickness and type of the reflective screens on the thermal insulation properties of the multi-layer composites are also studied. The result is that the thermal insulation property of the new type multi-layer aerogel composites is better than the pure aerogel composites and the traditional multi-layer insulation composites. When the 0.01 mm stainless steel foil as the reflective screen, and the aluminum silicate fiber and silica aerogel as the spacer layer, the layer density of composite with the best thermal insulation property is one layer per millimeter at 1000 °C.

Enhanced RF Behavior Multi-Layer Thermal Insulation

This paper shows that it is possible to exploit the modulated metasurface concept to control the unwanted coupling between antennas that are installed on the same satellite. The metasurface is combined with a Multi-Layer thermal Insulation blanket to reduce its specular reflection by spreading the energy incoherently in the surrounding space. In the design, sub-wavelength radiating elements printed on thin substrate have been used to make the metasurface response azimuthally independent, and to keep the weight of blanket down. The comparison between simulations and measurements confirms the validity of the idea.

An improved unit circuit model for transient heat conduction performance analysis and optimization in multi-layer materials

Transient heat conduction analysis and optimization in multi-layer thermal insulation materials (MLTIMs) requires an effective simplified model with certain accuracy. This paper proposes an improved unit circuit model (IUCM) based on the thermo-electrical analogy, where the interface nodes between every two adjacent layers are considered to describe the rapid variations of temperature gradients and heat fluxes at the interfaces. Then, the IUCM for three-layer materials is solved with jump and sinusoidal temperature boundaries, and the obtained temperatures and the outlet heat fluxes are compared to the solutions obtained by the finite volume method as well as other two existing lumped parameter models. The comparison shows that the IUCM reduces the relative mean outlet heat flux error by more than 50% compared to the other models in the studied cases. Applying the IUCM together with the genetic algorithm offers the optimal geometrical structures of three-layer materials, where the optimal structure reduced the outlet heat per unit area by more than 50% compared to the feasible structures. Meanwhile, arranging the mechanical layer with high thermal conductivity between two thermal insulation materials leads to a decrease of about 35% in the outlet heat during a certain time.

Identification of radiative heat transfer parameters in multilayer thermal insulation of spacecraft

PurposeThe purpose of this study is to optimize multilayer vacuum thermal insulation (MLI) of modern high-weight spacecrafts. An adequate mathematical simulation of heat transfer in the MLI is impossible if there is no available information on the main insulation properties.Design/methodology/approachThe results of experiments in thermo-vacuum facilities are used to re-estimate some radiative properties of metallic foil/metalized polymer foil and spacer on the basis of the inverse problem solution. The experiments were carried out for the sample of real MLI used for the BP-Colombo satellite (ESA). The recently developed theoretical model based on neglecting possible near-field effects in radiative heat transfer between closely spaced aluminum foils was used in theoretical predictions of heat transfer through the MLI.FindingsA comparison of the computational results and the experimental data confirms that there are no significant near-field effects between the neighboring MLI layers. It means that there is no considerable contradiction between the far-field model of radiative transfer in MLI and the experimental estimates.Originality/valueAn identification procedure for mathematical model of the multilayer thermal insulation showed that a modified theoretical model developed recently can be used to estimate thermal properties of the insulation at conditions of space vacuum.

Theoretical and experimental validation study on automotive air-conditioning based on heat pipe and LNG cold energy for LNG-fueled heavy vehicles

As a clean fuel, LNG has been used in heavy vehicles widely in China. Before reaching the engine for combustion, LNG store in a high vacuum multi-layer thermal insulation tank and need to be evaporated from its cryogenic state to natural gas. During the evaporation, the available cold energy of LNG has been calculated. The concept has been proposed that the separated type heat pipe technology is employed to utilize the available cold energy for automotive air-conditioning. The experiment has been conducted to validate the proposal. It is found that it is feasible to use the separated type heat pipe to convey the cold energy from LNG to automotive air-conditioning. And the cooling capacity of the automotive air-conditioning increase with the LNG consumption and air flow rate increasing.

Numerical evaluation of natural vibration frequencies of thermo-modernized apartment buildings subjected to mining tremors

Prefabricated, with load-bearing walls, apartment buildings represent a significant group of objects, especially occurring in the countries of Central and Eastern Europe. They were built in 50’s, 60’s and 70’s of 20th century. Nowadays, the new European Union environmental regulations forced such buildings’ modernization, mainly regarding energy efficiency. Usually, in order to improve their energy properties and, as the result, to reduce the energy losses, the external walls thermal insulation is performed. This is one of the fastest and cheapest method increasing the thermal resistance of walls of buildings constructed using relatively old technology. Extra thermo-modernization layers of the prefabricated walls (consisting of materials such as styrofoam, reinforced mortar, glass fibre textile mesh) bring additional mass to the building and could change its stiffness. The dynamic properties of the structure could be changed as the result. Changes in the natural frequencies of vibrations are the most important among them–calculations of these values are necessary especially in the case of buildings located in paraseismic or seismic areas. In the paper the influence of the additional multilayer thermal insulation of the external walls on the natural vibration frequencies of high (12 storey) actual apartment buildings subjected to mining tremors is investigated. Numerical calculations were carried out using finite element method software. Various approaches to the modelling of prefabricated load bearing walls before and after thermo-modernization were analyzed and discussed. A simple one layer model of walls with equivalent stiffness as well as multi-layer one were taken into consideration. Finally, the simple model reducing multi-layer panel to one layer panel with equivalent (substitute) Young modulus and equivalent (substitute) Poisson’s ratio was recommended for the practical calculations of the dynamic properties of buildings. Numerically evaluated natural vibration frequencies of the buildings before and after thermo-modernization were verified by the experimental data obtained for actual structures.

Analysis of insulation performance of multilayer thermal insulation doped with phase change material

The transient heat transfer characteristics of a new kind of combined multilayer thermal insulation material (MTIM) were numerically investigated in this paper. This new kind of multilayer thermal insulation is composed by silica aerogel and alumina aerogel doping with erythritol and stearic acid phase change materials. Finite Volume method combined with Enthalpy method as well as the Discrete Ordinate method is used to consider the combined conduction and radiation heat transfer with phase change problems. Based on the constructed numerical model, the transient heat transfer characteristics of the MTIM with two kinds of different arrangements were calculated and analyzed in detail. The results indicated that: (1) putting the PCMs at the bottom of the MTIM fails to enhance the thermal insulation performance of the MTIM; (2) in contrast, putting the PCMs at the middle of the MTIM can enhance the thermal insulation performance of the MTIM successfully; (3) there is an optimum doping content of the PCMs that can lead to the lowest of the temperature of the MTIM which makes the thermal insulation performance of the MTIM to be the best.

Heat transfer analysis of compound multi-layer insulation for cryogenic tank under different service conditions

Future space missions require efficient delivery of large payloads over great distances, necessitating the use of high-energy cryogenic propellant. Therefore, reliable compound multi-layer insulation on cryogenic tank is a crucial part of future space exploration. Compound multi-layer insulation is composed of double-aluminized radiation shielding and separated by a combination of netting and bumper strips, with a foam substrate. Considering conduction, convection, and radiation in heat transfer, the thermal field of multi-layer insulation is analysis by theoretical analysis with different thickness of foam substrate and MLI. Based on the formerly theoretical analysis, the heat flux and apparent thermal conductivity are discussed under the different thickness of foam substrate and MLI. Finally, the optimum design of multi-layer thermal insulation is present in consideration of the thickness and insulation performance of multi-layer insulation.

Analysis of sandwich plates with compressible core using layerwise refined plate theory and interface stress continuity

Lightweight sandwich materials are essential in construction in aircraft, spacecraft, and marine applications. Foam core sandwich materials are not only lightweight but extremely good in thermal insulation purposes. In construction of marine vehicles (i.e., boats, yachts), some sport goods (i.e., surf board), and in the packaging industry soft foam core (i.e., polyvinyl chloride (PVC), polyurethane, polystyrene) sandwiches are used. Polymeric or organic foam core sandwiches are being used in National Aeronautics and Space Administration spacecraft for shock absorption under impact from meteoroid and multilayer thermal insulation. High fidelity analysis tools for sandwich materials are in demand by the engineering community. An attempt has been made here to analyze a sandwich plate considering a three-layer approach using refined higher order plate theory for all the three layers. Moreover, the compressibility (i.e., thickness strain) of the central thick core layer has been considered in the analysis. The continuity of displacements and stresses at each layer interface has also been taken into account in the formulation using Lagrangian multiplier approach. The aforementioned theory has been implemented in an in-house Fortran code. Using this approach, various polymer composite and sandwich plates have been analyzed and the results are compared with other reliable published results. The correlations are found to be good for plates with various aspect ratios and ply orientations.

Calculation of high-temperature insulation parameters and heat transfer behaviors of multilayer insulation by inverse problems method

In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities (ECTs) which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation (MTI) is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.

Heat transfer analysis of insulation materials with flexible multilayers

A new flexible multilayer thermal insulation material is presented for applications at harsh environment as high as 433 K or as low as 123 K. A heat transfer model is established and solved to study heat transfer through the material, including radiation, solid heat transfer and gas heat transfer. Comparison between the experimental results and the theoretical prediction shows that the model is feasible to be applied in engineering. The temperature distribution of samples with 10, 15, 20, 25, 30 layers, respectively, the radiation, solid and gas heat transfer of a sample with 10 layers are analyzed at harsh conditions (123 K and 433 K) and the normal condition as well. The theoretical thermal analysis provides an active instruction to an optimal design of such protective materials.

The effective thermal conductivity of insulation materials reinforced with aluminium foil at low temperatures

The effective thermal conductivity (ETC) of multilayer thermal insulation materials was experimentally investigated as a function of temperature (0–25 °C). The materials consisted of binary/ternary glass wools or ternary expanded polystyrene foams reinforced with aluminium foil. The experimental measurements were performed using a guarded hot plate with temperature differences of 5, 10 and 15 °C. The results indicated that significant correlations exist between ETC and the characteristics of the materials with decreasing temperature. The ETC decreases with reinforcement with aluminium foil at the same temperature or with temperature differences of 5 and 15 °C. In addition, it was clearly observed that the ETC decreases sharply with decreased temperature. Consequently, reflective materials may reduce the ETC at low temperatures.

Numerical estimation of time lags and decrement factors for wall complexes including Multilayer Thermal Insulation, in two different climatic zones

In the current contribution, time lags and decrement factors for a building wall including different Multilayer Thermal Insulation (MTI) configurations have been calculated numerically. For this investigation purpose, a numerical model which can take care of composite walls was developed. The combined conduction, radiation and convection heat transfer equation was solved explicitly via a control volume discretization. In order to investigate the thermal behavior of a wall under certain outdoor climates, meteorological data that served as boundary conditions were applied to the outer surface of this wall. The outdoor air temperatures were averaged over a number of years after been obtained from hourly measurements in both locations under study. Regarding the solar radiation, it was calculated using a clear-sky model during the summer period. The influence of geographic coordinates’ location on the insulating performance of MTI applications was investigated while the wall configurations were supposed to be located in two different climatic zones. The selection of a particular wall configuration involved not only the outdoor climate, but also the whole building characteristics, orientation, etc. The results of the present study are useful for further development in order to conceive and design the optimum MTI configuration, adjusted in specific geographic coordinates and orientations.

Method to Have Multilayer Thermal Insulation Provide Damage Detection

Method to Have Multilayer Thermal Insulation Provide Damage Detection

Structure Designing and Property Investigation of Flexible Multilayer Thermal Insulation Materials

In this paper, a method of designing flexible multilayer insulation is analyzed and discussed, with focus on reducing the three basic modes of heat transfer (thermal radiation, solid spacer and residual gas conduction). The foundation for designing the new flexible thermal insulation material is provided. The insulation performances of different types (by choosing different reflection shields and spacers) of flexible multilayer insulation materials are obtained through measurements using a KES-F7 Thermal Labo II apparatus. The thermal performance of flexible multilayer insulation materials at different layers are also presented, and the best is about 20∼25 layers. To improve the thermal performance of multilayer insulation materials, treble spacers between double aluminized shields are applied. Aluminized shields with air, meshes, wool fibres, etc. are compared with each other. The aluminized shields with meshes fixed with down can reduce thermal contact, which reduces the radiation heat transfer more fully and can be more steady than the other spacers in the project applications. With the same layers and spacers, the thermal conductivity of crinkled aluminized shields is lower than that of the smooth aluminized shields. The effects of compressive loads on layer density and thermal performance are also investigated.

Application of Sol-Gel Derived Conductive Oxide LaNiO<sub>3</sub> in Pyroelectric Detector

Conductive LaNiO3(LNO) thin films are grown on Si(100) substrates by a sol-gel method and their application as the bottom electrode for the growth of sol-gel derived Pb(Zr,Ti)O3(PZT) thin films are studied. Morphology and electrical properties of the multilayer films are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), electrical measurements. Experiment results show LNO thin films get highly (110)-oriented perovskite-type structure. Smooth and dense surfaces are observed on LNO thin films. The dielectric properties of PZT films show that PZT/LNO films exhibit worse dielectric properties than those of the PZT/Pt thin films. And LNO thin films prepared by sol-gel methods are not suitable as bottom electrode to deposit PZT thin films. On the other hand, FTIR spectrum and pyroelectric results of LNO thin films reveal that LNO can be used as absorber layer of PT thin films infrared detector with multi-layer thin film thermal insulation structure. At 10Hz, the detectivity (D*) and the voltage response (Rv) of PT thin films are 1.11×107cm·Hz1/2/W, 1.46×103V/W respectively.

Study on transient heat transfer through multilayer thermal insulation: Numerical analysis and experimental investigation

This paper reports on a numerical and experimental study of heat transfer phenomena through two different multilayer fibrous insulations for building applications. The investigated samples were composed of different layers of fibrous materials and aluminium foils, placed between one or two air gaps in the vertical dimension. An experimental apparatus (a guarded hot box) has been used to measure heat transfer through the samples, while a finite volume numerical model combined radiation/conduction heat transfer was developed to predict the temperature distribution and heat transfer in such insulation systems comprised of the materials separated by multiple reflective foils. The model takes into account the coupling between the solid conduction of the fibrous system and the gaseous conduction and radiation. The radiation heat transfer through the insulation system has been modelled via the two flux approximation. The numerical results were compared with the experimental data from the guarded hot box for model validation, as well as to assess the effectiveness of the reflective foils in changing the resistance of the insulations. The comparative verification of the model showed that the numerical results were consistent with the experimental data through the environmental conditions under examination.